VOP_Node.h

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/*
 * PROPRIETARY INFORMATION.  This software is proprietary to
 * Side Effects Software Inc., and is not to be reproduced,
 * transmitted, or disclosed in any way without written permission.
 *
 * NAME:        VOP Library (C++)
 *
 * COMMENTS:    The base class for all VOP operators
 *
 */

#ifndef __VOP_Node_h__
#define __VOP_Node_h__

#include <set>
#include <map>
#include <iosfwd>

#include "VOP_API.h"
#include "VOP_DataMicroNode.h"
#include "VOP_Error.h"
#include "VOP_Language.h"
#include "VOP_TypeInfo.h"
#include "VOP_OperatorInfo.h"
#include "VOP_OutputInfoManager.h"
#include <OP/OP_Director.h>
#include <OP/OP_Network.h>
#include <UT/UT_UniquePtr.h>
#include <UT/UT_BitArray.h>
#include <UT/UT_ValArray.h>
#include <UT/UT_SymbolTable.h>
#include <UT/UT_Array.h>
#include <UT/UT_Map.h>
#include <SYS/SYS_Types.h>
#include <utility>
#include <vector>

class UT_StringRef;

#define VOP_OPT_LOW_FLAG        'L'
#define VOP_OPT_MEDIUM_FLAG     'M'
#define VOP_OPT_HIGH_FLAG       'H'
#define VOP_DEBUG_FLAG          'D'
#define VOP_MATERIAL_FLAG       'E'

// The name of the parameter that contains the ordering of the
// VOPNET Parameters.
#define VOP_PARMORDER_NAME              "parmorder"
#define VOP_BIND_NAME                   "bind"
#define VOP_GLOBAL_NODE_NAME            "global"
#define VOP_ILLUM_NODE_NAME             "illuminance"
#define VOP_PARM_NODE_NAME              "parameter"
#define VOP_CONST_NODE_NAME             "constant"
#define VOP_PARMRAMP_NODE_NAME          "rampparm"
#define VOP_INLINE_CODE_NODE_NAME       "inline"
#define VOP_SNIPPET_NODE_NAME           "snippet"
#define VOP_MATERIAL_BUILDER_NODE_NAME  "materialbuilder"
#define VOP_RSL_PREFIX                  "rsl_"
#define VOP_VARIABLE_INOUT_MAX          2048

/// Prefix given to the subnet input variables.
#define VOP_SUBNET_VARIABLE_PREFIX      "_"

enum VOP_UIChangeType
{
    VOP_UICHANGE_DEFINER = OP_UICHANGE_OPTYPE_VOP
};

class TIL_Thumbnail;
class VCC_DiagnosticInfo;
class VOP_Node;
class VOP_GlobalVarData;
class VOP_ParmGenerator;
class VOP_OutputVar;
class VOP_Bind;
class VOP_Block;
class VOP_AutoNode;
class VOP_CodeGenContext;
class VOP_ExportedParmList;
class VOP_ExtraVarRequests;
class VOP_VariableTags;
class VOP_SubnetBase;
using VOP_VariableTagsHandle    = UT_SharedPtr<const VOP_VariableTags>;

extern "C" {
    SYS_VISIBILITY_EXPORT extern void       newVopOperator(OP_OperatorTable *table);
};

typedef UT_ValArray<VOP_Node *>          VOP_NodeList;
typedef UT_ValArray<VOP_GlobalVarData *> VOP_GlobalVarList;
typedef UT_ValArray<VOP_ParmGenerator *> VOP_ParmGeneratorList;

typedef UT_SymbolMap<VOP_GlobalVarData *> VOP_GlobalVarMap;
typedef UT_SymbolMap<VOP_ParmGenerator *> VOP_ParmGeneratorMap;
typedef UT_SymbolMap<VOP_ParmGeneratorList *> VOP_LocalChannelMap;

struct VOP_AutoNodeInfo
{
    VOP_AutoNode*   myAutoVopNode;  // Auto-node that provides VEX code to adjust VOP's code.
    int             myIndex;        // Index of the input on the node the auto-node connects to. 
};
typedef UT_Array< VOP_AutoNodeInfo > VOP_AutoNodeInfoList;

//============================================================================= 
class VOP_API VOP_VarInfo
{
public:
    UT_StringHolder     myName;             // variable name
    UT_StringHolder     myDescription;      // variable description
    VOP_ContextType     myContextType;      // context type in which var exists
    int                 myVarIndex;         // index in the context's var table
    VOP_TypeInfo        myTypeInfo;         // variable type (int, float, etc)
    bool                myReadable;         // can read from variable?
    bool                myWritable;         // can write to variable?
    bool                myIlluminanceVar;   // is illuminance?
};

//============================================================================= 
class VOP_API VOP_GlobalVarData
{
public:
     VOP_GlobalVarData( const char * name, const VOP_VarInfo & info );
    ~VOP_GlobalVarData();
    void                        appendInfo( const VOP_VarInfo & info );

    const UT_StringHolder &     getName() const 
                                { return myName; }

    const UT_StringHolder &     getDescription( VOP_ContextType type ) const;
    const VOP_TypeInfo &        getTypeInfo( VOP_ContextType type ) const;
    int                         getVarIndex( VOP_ContextType type ) const;
    bool                        isReadable( VOP_ContextType type ) const;
    bool                        isWriteable( VOP_ContextType type ) const;
    bool                        isIlluminance( VOP_ContextType type ) const;
    bool                        isValidInContext( VOP_ContextType type ) const;

    const VOP_TypeInfo &        getAnyTypeInfo() const
    {
        return myInfos(0).myTypeInfo;
    }

private:
    template<typename T> T          getInfoMember( VOP_ContextType ctx_type, 
                                               T VOP_VarInfo::*member, 
                                               T default_val ) const;
    template<typename T> const T    &getInfoMemberRef( VOP_ContextType ctx_type,
                                               T VOP_VarInfo::*member, 
                                               const T & default_val ) const;
    int                     getIndexForContextType( VOP_ContextType type) const;

private:
    UT_StringHolder             myName;         // variable name
    UT_Array<VOP_VarInfo>       myInfos;        // infos for applicable contexts
};

//============================================================================= 
class VOP_API VOP_OutputNameEditorSource
{
public:
    virtual             ~VOP_OutputNameEditorSource();
    virtual int          getNumInputsFromParent() const = 0;
    virtual void         NAMEFROMPARM(UT_String &str, int idx) const = 0;
    virtual void         LABELFROMPARM(UT_String &str, int idx) const = 0;
    virtual void         setNAMEFROMPARM(UT_String &str, int idx) = 0;
    virtual void         setLABELFROMPARM(UT_String &str, int idx) = 0;
};

// ============================================================================ 
/// Abstracts information about shader function parameters/arguments.
/// It has two use cases: when declaring and defining a shader function, and
/// when calling a shader function. It always stores shader parameter type and 
/// name, but may not store some of the other information for some use cases.
class VOP_API VOP_FunctionArgInfo
{
public:
                            VOP_FunctionArgInfo();

    /// Argument type.
    void                    setTypeInfo( const VOP_TypeInfo &type_info );
    const VOP_TypeInfo &    getTypeInfo() const
                                { return myTypeInfo; }

    /// Argument name.
    void                    setName( const char *name );
    const UT_StringHolder & getName() const
                                { return myName; }

    /// Local variable name to use when calling the function.
    void                    setVarName( const char *var_name );
    const UT_StringHolder & getVarName() const;

    /// Expression (ie, RHS of the assignment) to use for initialization 
    /// of the argument when calling the shader function.
    void                    setInitCodeStr( const char *init_code );
    const UT_StringHolder & getInitCodeStr() const
                                { return myInitCodeStr; }

    /// Node input index, if argument corresponds to an input; otherwise -1.
    void                    setInputIndex( int input_index );
    int                     getInputIndex() const 
                                { return myInputIdx; }

    /// Node output index, if argument corresponds to an input; otherwise -1.
    void                    setOutputIndex( int output_index );
    int                     getOutputIndex() const
                                { return myOutputIdx; }

    /// True if it's an export (output) shader function parameter.
    void                    setExported( bool exported );
    bool                    isExported() const
                                { return myIsExported; }

private:
    VOP_TypeInfo    myTypeInfo;     // Argument type
    UT_StringHolder myName;         // Argument name
    UT_StringHolder myVarName;      // Variable name to use in function call
    UT_StringHolder myInitCodeStr;  // Expression code to init an arg to.
    int             myInputIdx;     // Input index this variable corresponds to
    int             myOutputIdx;    // Output index this var corresponds to
    bool            myIsExported;   // Is an output argument
};

//============================================================================= 
class VOP_API vop_Connector
{
public:
    vop_Connector(int groups_above,
            int index = -1)
        : myIndex(index),
          myGroupsAbove(groups_above),
          myIsExpanded(false),
          myIsGroup(false)
    { }
    vop_Connector(int groups_above,
            const UT_StringHolder &group_name,
            int index,
            bool expanded)
        : myGroupName(group_name),
          myIndex(index),
          myGroupsAbove(groups_above),
          myIsExpanded(expanded),
          myIsGroup(true)
    { }
    ~vop_Connector()
    { }

    int                  myIndex;
    int                  myGroupsAbove;
    UT_StringHolder      myGroupName;
    bool                 myIsExpanded;
    bool                 myIsGroup;
};
typedef UT_Array<vop_Connector>  vop_ConnectorArray;

//============================================================================= 
/// The allowed name formats when asking for shader name.
enum class VOP_ShaderNameStyle
{
    PLAIN,              // Straight forward name only.
    ALLOW_HDA_SECTION,  // Allow paths to HDA sections in name.
    RELAXED_AUTO        // For potential auto shaders, Parm & Const
                        //          input VOPs don't trigger auto-wrapping.
                        //          Note, this implies allowing HDA sections.
};

//============================================================================= 
class VOP_API VOP_Node : public OP_Network
{
public:
    static const char   *theChildTableName;
    const char          *getChildType() const override;
    const char          *getOpType() const override;

    OP_OpTypeId          getChildTypeID() const override;
    OP_OpTypeId          getOpTypeID() const override;

    ///  Nobody should have to override this, but it's public for other people
    OP_DataType          getCookedDataType() const override;

    /// Whenever a variable type parm changes, we have to send out an event
    /// to get our tile to update.
    void                 opChanged(OP_EventType reason, void *data=0) override;
    void                 referencedParmChanged(int pi) override;
    
    static void          buildOperatorTable(OP_OperatorTable &table);

    /// Get the parm block information that will go in the dialog script
    /// for our VOPNET. The shader_contexts argument is a list of
    /// contexts, in which the parameter is a shader argument.
    virtual void         getParameterBlock(UT_String &parmstr,
                                           const char *shader_contexts);

    /// The parameter variable declaration using the syntax of a given language.
    virtual void         getParameterDeclaration(UT_String &parmdecl,
                                            const VOP_Language *language,
                                            const VOP_CodeGenContext &context);

    /// Obtains the parameter declaration code comment, which is appended
    /// after the declaration in the generated source code.
    virtual void         getParameterComment(UT_String &parm_comment,
                                            const VOP_Language *language,
                                            const VOP_CodeGenContext &context);

    /// If false, getShaderExtraParameters is not invoked as it is assumed
    /// to return an empty list
    virtual bool         definesShaderExtraParameters() const;

    /// Returns a list of the attributes that we want to bind or export.  
    /// These are added to the vex functions parameter list, but not to the
    /// UI as they are only expected to be overridden.  If they match
    /// an existing value, they do not replace.
    /// The shader type is used only in a very specific cases of material
    /// builder, when extra parameters may depend on a shader type.
    virtual int          getShaderExtraParameters(UT_Array<VOP_Type> &types, 
                                UT_IntArray &doexport, UT_StringArray &names,
                                UT_StringArray &def,
                                VOP_Type shader_type = VOP_TYPE_UNDEF ) const;

    /// Get compiler pragmas for thi snode.
    virtual void         getPragmas(UT_String &pragmastr,
                                const VOP_CodeGenContext &context);

    /// If the node generates a shader call, get the modules names to import.
    virtual void         getModulesToImport(UT_StringArray &modules,
                                const VOP_CodeGenContext &context);

    /// Get the code fragment to be included in the outer code,
    /// before the main shader code.
    virtual void         getOuterCode(UT_String &codestr,
                                const VOP_CodeGenContext &context);

    /// Get the code fragment to be included in the shader code.
    virtual void         getCode(UT_String &codestr,
                                const VOP_CodeGenContext &context);

    /// Get the constant code that encodes the value of the node parameter.
    virtual bool         getParmConstantString(const char *parmname,
                                               const VOP_TypeInfo &type_info,
                                               UT_String &str,
                                               bool expand_string,
                                               const VOP_Language *l=0);
    /// Returns the code name of the type, such as "float" from VOP_TYPE_FLOAT
    /// Threadsafe but not re-entrant.
    static const char   *getTypeNameFromType(const VOP_TypeInfo &type_info,
                                                const VOP_Language *lang);
    /// Returns a UI friendly version of the string, with NiceNumber
    /// type effects embedded.
    bool                 getParmPrintableString(const char *parmname,
                                               VOP_Type type,
                                               UT_String &str,
                                               bool expand_string) const;



    /// Returns true if this VOP is a VOP_ParmGenerator or subclass.
    virtual bool         getIsParmGenerator() const;

    /// @{
    /// Virtual methods to avoid dynamic_casts
#define VOP_IMPLEMENT_CASTS(NAME) \
        static const VOP_##NAME *castTo##NAME(const OP_Node *node) { \
            const VOP_Node *vop = CAST_VOPNODE(node); \
            return vop ? vop->castTo##NAME() : nullptr; } \
        static VOP_##NAME *castTo##NAME(OP_Node *node) { \
            VOP_Node *vop = CAST_VOPNODE(node); \
            return vop ? vop->castTo##NAME() : nullptr; } \
        virtual const VOP_##NAME *castTo##NAME() const { return nullptr; } \
        virtual VOP_##NAME *castTo##NAME() { return nullptr; }

    VOP_IMPLEMENT_CASTS(ParmGenerator)
    VOP_IMPLEMENT_CASTS(SubnetBase)
    VOP_IMPLEMENT_CASTS(OutputVar)
    VOP_IMPLEMENT_CASTS(Bind)
    VOP_IMPLEMENT_CASTS(Block)
#undef VOP_IMPLEMENT_CASTS
    /// @}

    /// Moves a visualizer into our output list.
    bool                 addOrMoveVisualizerToOutput(int outputidx) override;

    /// Creates a code generator for the VOP, if it needs one.
    /// When a VOP is placed in a non-shaer container node that does not have
    /// an overarching code generator, this method may be called to create one 
    /// for a VOP to act as a stand-alone shader.
    void                 createAutoCodeGenerator();

    /// Utility method to create explicit children inside that node.
    /// The children correspond to the epilogue in auto-generated shader.
    void                 createAutoShaderChildren();

    /// @{ Obtains a code generator that provides shader code associated
    /// with a node. Usually, vopnet shader VOPs have their own dedicated
    /// code generator for shader constructed fom their children. 
    /// However, also, all VOP nodes inside a Shader Network container node
    /// have their own auto-generator for automatically constructing temporary 
    /// shader from their inputs (siblings).
    VOP_CodeGenerator   *getVopCodeGenerator() override;
    VOP_CodeGenerator   *getVopAutoCodeGenerator() override;
    /// @}

    /// Gives the node a chance to initialize itself when it is first created.
    /// This is only used for VOP_ParmGenerator nodes.
    virtual void         initializeNode();

    /// Called by VOP_CodeGenerator::afterAddNode to ensure that nodes
    /// have been properly initialized. Some nodes weren't calling their
    /// base class' initializeNode() resulting in only partial initialization.
    bool                 isInitialized() const { return myInitialized; }

    /// Make sure that our parmname parameter (if we have one) doesn't
    /// conflict with any other parmname parameter values.
    virtual void         ensureParametersAreValid();
    static void          incrementVariableName(UT_String &varname);

    /// @{ Some variable names may contain characters that are illegal in 
    /// C-style variable names. Eg, Snippet VOP may allow colons to indicate 
    /// namespaced attributes which get bound to VEX parameters/variables.
    /// To ensure the variable name is valid, such characters are encoded
    /// using only alphanumeric (and underscore) characters.
    /// The decode function reverses such encoding.
    static UT_StringHolder       ensureValidVarName(const UT_StringHolder &var);
    static UT_StringHolder       decodeVarName(const UT_StringHolder &var);
    /// @}

    /// Functions to get information about our operator outputs.
    /// These just call the getOutputXXXSubclass functions.
    void                 getOutputName(UT_String &out, int idx) const override;
    void                 getOutputName(UT_StringHolder &out, int idx) const
    { UT_String tmp; getOutputName(tmp, idx); out.adoptFromString(tmp); }
    int                  getOutputFromName(const UT_String &out) const override;
    VOP_Type             getOutputType(int idx);
    void                 getOutputTypeInfo(VOP_TypeInfo &type_info,
                                           int idx) const;
    VOP_Type             getNamedOutputType(const OP_ConnectorId& output_name);
    void                 getNamedOutputTypeInfo(VOP_TypeInfo &type_info,
                                            const OP_ConnectorId& output_name);
    /// Obtains annotations (tags) for the variable value pushed out on
    /// the given output connector. The tags are arbitrary, but are primarily
    /// used to denote the contents of arrays (ie, export name for the value).
    VOP_VariableTagsHandle  getOutputVariableTags(int idx, 
                                VOP_Type shader_type) const;
    VOP_VariableTagsHandle  getNamedOutputVariableTags(
                                const OP_ConnectorId& output_name,
                                VOP_Type shader_type) const;

    /// Returns variable tags provided by an input node on the given input idx.
    VOP_VariableTagsHandle  getVariableTagsFromInputNode( int idx, 
                                VOP_Type shader_type) const;

    /// @{ Virtuals for obtaining inputs from which to copy shader layer
    /// exports variable tags and which exports to add, for a given output.
    virtual UT_IntArray     getShaderLayerExportsInputsToCopy(int out_idx,
                                VOP_Type shader_type);
    virtual UT_StringHolder getShaderLayerExportsToAdd(int out_idx,
                                VOP_Type shader_type);
    /// @}


    /// Returns the variable name associated with a given input number.
    /// These just call the getInputXXXSubclass functions.
    void                 getInputName(UT_String &in, int idx) const override;
    void                 getInputName(UT_StringHolder &in, int idx) const
    { UT_String tmp; getInputName(tmp, idx); in.adoptFromString(tmp); }
    int                  getInputFromName(const UT_String &in) const override;

    /// will_autoconvert_out, if not null, is set to true if autoconversion
    /// will be needed, to false otherwise.
    VOP_Type             getInputType(int idx) const;
    void                 getInputTypeInfo(VOP_TypeInfo &type_info,
                                          int idx) const;
    VOP_Type             getNamedInputType(const OP_ConnectorId& input_name);
    void                 getNamedInputTypeInfo(VOP_TypeInfo &type_info,
                                           const OP_ConnectorId& input_name);

    //  Whether the visibility flag has been set in the operator type property.
    //  This is not the same flag as the one in OP_Input.
    bool                 getIsInputVisibleDefault(int idx) override;

    /// Returns currently allowed input types for a given input, regardless 
    /// of what is connected to that input at the moment. 
    /// These do not include types to which autoconversion is possible. 
    virtual void         getAllowedInputTypeInfos(unsigned idx,
                                              VOP_VopTypeInfoArray &typeinfos);
    virtual void         getAllowedInputTypes(unsigned idx,
                                              VOP_VopTypeArray &voptypes);

    /// Returns all allowed types for a given input, regardless of what is 
    /// currently wired to that input *and* regardless of what subset of all 
    /// these types is currently legal due to pruning of invalid signatures
    /// (input types) on a script node (etc).
    /// This is similar to getAllowedInputTypeInfos(), but unlike it, this 
    /// method returns types belonging to invalid signatures.
    void                 getAllAllowedInputTypeInfos(unsigned idx,
                                              VOP_VopTypeInfoArray &typeinfos);
    
    /// Get the nuber of signatures that the node has, and obtain the i-th
    /// signature name.
    /// The VOP signatures apply mostly to the VOP HDAs,
    /// where a user can define several signatures  for the operator (a
    /// signature is a set of input types, and the user provides a name
    /// associated with each such set). The build-in operators ususally have
    /// only a single signature, and thus don't bother to provide any
    /// distinguishing name for it (but they may).
    virtual int          getSignatureCount() const;
    virtual void         getSignatureName(UT_String &name, int index) const;

    /// Sets the current signature. The name must be a valid signature
    /// recognized by the node. Also it should be possible to switch to that
    /// signature, which may not be possible due to the types of connected
    /// inputs, which limit the aplicability of some signatures.
    virtual void         setCurrentSignature(const char *name);
    /// Obtains the current signature name.
    virtual bool         getCurrentSignatureName(UT_String &name);

    /// Some variables associated with vop inputs can be overriden or set
    /// without an explicit wire to that input. 
    /// The override comes from an output connector of another node,
    /// encoded as <node, output index> pair.
    using InputVariableOverride = std::pair<VOP_Node*, int>;
    void                 setInputVariableOverride(int input_index,
                                const InputVariableOverride &var_override);
    InputVariableOverride getInputVariableOverride(int input_index) const;

    /// Returns true if the output variables of this node should not be
    /// renamed in the code (in an attempt to avoid name collisions);
    /// it usually applies to the shader output parameters in a given context.
    /// If so, the second function returns the name of this output variable.
    /// The version with VOP_CodeGenContext argument should be used.
    virtual bool         areOutputVariablesFixed(const VOP_CodeGenContext &ctx);
    virtual bool         areOutputVariablesFixed(VOP_ContextType context_type);
    virtual void         getFixedOutputVariable(UT_String &var, int idx);

    /// Returns the variable name (in the generated code) that corresponds to 
    /// the node's idx-th output. Usually it's just the output name.
    virtual void         getOutputVariableName(UT_String &var, int idx) const;

    /// If node explicitly declares variables by itself (eg, subnet), it should 
    /// report such types with this method, in case it uses some custom
    /// data type that needs to be defined in the shader code (eg, struct).
    /// Most nodes don't need to override this, since code generator knows
    /// what types it used for this node's (output connector) variables.
    virtual void         getExtraTypesToDefine( UT_Array<VOP_TypeInfo> &types );

    /// Returns true if the methods below should consider only the inputs
    /// of this node that belong to the given shader context.
    /// Most nodes indiscriminately merge all their inputs, but some (like 
    /// Material Buider VOP) need pick inuts that belong to the given context.
    virtual bool         shouldCheckInputContextForMergeInputNodeList() const;

    /// Recurse through our inputs and add them in order to the given list.
    /// Note this this might create new auto-conversion nodes in this list,
    /// and these will have to be deallocated by the caller (using
    /// the utility function deleteAutoNodesIn())
    void                 mergeInputNodeList(VOP_NodeList &nodes, 
                                const VOP_CodeGenContext *context = nullptr);
    void                 mergeInputNodeListInternal(VOP_NodeList &nodes, 
                                VOP_NodeList &extraterminals,
                                const VOP_CodeGenContext *context = nullptr);

    /// Scans the node list and deletes the auto convert nodes (and replaces
    /// them with NULLs in the list). Also, clears any auto-convert information
    /// for all other nodes in the list. Note, thet the node list is usually
    /// constructed with mergeInputNodeList() method.
    static void          deleteAutoNodesIn(VOP_NodeList& nodes);

    /// Determines if this is a terminal node. Ie, whether this node is a
    /// code sink that culminates (one of) the shader calculations. 
    /// The culmination may be in the form of setting the global variable,
    /// setting an export parameter, or a general reqest by a user to
    /// ensure the node is part of the shader (eg, print vop).
    /// The code code generator determines all the nodes that participate
    /// in the shader definition by by recursively traversing the inputs
    /// starting from this node.
    /// @param check_shader_context Is true when the node should consider
    ///     the shader context name/type contained in the code gen context
    ///     parameter; the node should return true only if it really
    ///     is a terminal node for the given shader type.
    ///     Otherwise, if false, the node can disregard the shader type
    ///     most likely because it lives in a single-context vopnet.
    virtual bool         forceCodeGenerationOfInputs(
                                        const VOP_CodeGenContext &context,
                                        bool check_shader_context) const;

    /// Returns true if the node can and should initiate generation of code 
    /// in the given context. If, if the node is a terminal node.
    bool                forceCodeGenerationInContext( 
                                        const VOP_CodeGenContext &context)const;

    /// Returns true if the given output represents an export variable for
    /// a shader of a type specified by context.
    bool                isInputForShaderType(int input_idx, 
                                        const VOP_CodeGenContext &context)const;
    bool                isOutputForShaderType(int output_idx, 
                                        const VOP_CodeGenContext &context)const;

    /// @ Returns a node that implements or represents the given shader type.
    /// The returned node may be a stand-alone (self-contained) shader node,
    /// or a building-block node from which a shader of a given type can
    /// be generated.
    virtual VOP_Node    *findShader(VOP_Type shader_type, fpreal now);

    /// Returns all applicable shader nodes and their corresponding shader 
    /// types, and if applicable output names.
    /// Output names become important when a VOP node is a subnetwork
    /// containing a few surface shaders, one for different renderer.
    /// Note, some returned output names may correspond to a AOV data (eg, 
    /// the output type may be float or a vector rather than a shader type),
    /// in which case the shader type will be reflect that.
    virtual void         findAllShaders( VOP_NodeList &shader_nodes,
                                        VOP_ShaderTypeList &shader_types,
                                        UT_StringArray &output_names );
    /// @}

    /// Returns true if the VOP can represent a shader. Ie,
    /// whether it can be converted into a shader.
    virtual bool         canDefineShader() const;

    /// Returns true if the VOP is a stand-alone shader (and not
    /// a building-block for a shader).
    /// The VOP may generate the code from its children VOPs, point to 
    /// an external file, or store the code in the HDA section.
    /// But, it represents a self-contained shader code, which can be invoked
    /// for shading an object (surface), used as an encapsulated shader (CVEX
    /// shader for geometry procedurals, like fur), or called from another
    /// shader (as a shader function call).
    virtual bool         isShader() const;

    /// Returns true if the VOP is a stand-alone shader (and not a 
    /// building-block for a shader), and can provide the shader code for 
    /// a shader of the given type. Note, material VOP may return true for 
    /// several shader types, such as both surface and displacement.
    virtual bool         isShader(VOP_Type shader_type) const;

    /// Returns true if the VOP is directly translatable to a USD primitive.
    /// Ie, it is not a shader code building-block VOP. 
    virtual bool         translatesDirectlyToUSD() const;

    /// Returns ture if the node represents a USD NodeGraph, and false
    /// if it is a USD Material.
    virtual bool         isUSDNodeGraph() const;

    /// Returns true if the node has pre-generated shader code and is not
    /// using network to generate it. This mainly applies to digital assets
    /// that store shader code in their sections (whether or not they also
    /// store the network contents).
    virtual bool         isCachedShader() const;

    /// Returns true if the operator represents an externally defined shader
    /// such as a Geometry Shader, or a shader whose code is saved in a file
    /// on disk separately from the operator or HDA definition.
    bool                 isExternalShader() const;

    /// Returns true if this is a subnetwork which generates an encapsulated
    /// shader.  For example the SubnetCVEX VOP.  Parent material passes 
    /// encapsulated shaders as shader string to other shaders (usually,
    /// geometry procedurals) to calculate certain properties dynamically.
    /// And to construct shader string there are some restrictions on
    /// encapsulated shaders (eg, their inputs can be only wired to constants 
    /// and parameter VOPs).
    // TODO: But there is little distinction between them and regular shaders,
    //       so remove this method. The difference is really how they are used
    //       (ie, whether the shader string of the main shader like fur
    //       procedural contains the shader string for this cvex 'encapsulated'
    //       shader. But, to distinguis that, the clerk calls
    //       hou.VopNode.shaderString(as_encapsulated=True)
    virtual bool         isEncapsulatedShader() const;

    /// Material VOP may be able to return a procedural node.
    virtual VOP_Node    *getProcedural(VOP_Type type);

    /// @{ Returns the name, type, and render mask of the VOP shader.
    virtual UT_StringHolder getShaderName(
                                    VOP_ShaderNameStyle style, 
                                    VOP_Type shader_type) const;
    UT_StringHolder         getShaderName(bool forvex, 
                                    VOP_Type shader_type) const;
    virtual UT_StringHolder getShaderNameForSignature(
                                    const UT_StringRef &signature) const;

    virtual VOP_Type        getShaderType() const;
    const char *            getRenderMask() const;
    /// @}

    /// @{ For expanding compiler string used in auto code generator.
    bool                 evalVariableValue(
                                UT_String &v, int index, int thread) override;
    bool                 evalVariableValue(
                                fpreal &v, int i, int thr) override
                         { return OP_Network::evalVariableValue(v,i,thr); }
    /// @}

    /// @{
    /// Obtains a coshader node (or array of nodes) associated with the parm.
    /// Usually, the co-shader computes the value for the parameter, and
    /// is represented as a wired input to the main shader node.
    /// If no coshaders are wired in, the output list is empty.
    void                 getCoShaderNodes(UT_ValArray<VOP_Node *> &coshaders,
                                    const char* parm_name);
    void                 getCoShaderNodesOutputNames(UT_StringArray &outputs,
                                    const char* parm_name);
    /// @}

    /// Writes out the shader code from the cache to the given output stream.
    /// Returns true if successful, otherwise, returns false, if there's no 
    /// cached shader code for this context.
    virtual bool         getCachedShaderCode(std::ostream &os,
                                    VOP_ContextType context_type) const;

    /// @{
    /// To be able to use Cvex VOP in Attribute SOP, etc.
    using VexBuildFn1 = void (*)(VOP_Node*, UT_String&, fpreal, OP_Node*, 
            UT_Map<int,bool>*);
    using VexBuildFn2 = void (*)(VOP_Node*, UT_String&, fpreal, DEP_MicroNode*, 
            UT_Map<int,bool>*);
    static void          setBuildVexScriptCB(VexBuildFn1 fn1, VexBuildFn2 fn2);
    void                 buildVexScript(
                                UT_String &result,
                                fpreal t,
                                OP_Node *parent,
                                UT_Map<int, bool> *visited) override;
    void                 buildVexScript(
                                UT_String &result,
                                fpreal t,
                                DEP_MicroNode *depnode,
                                UT_Map<int, bool> *v) override;
    /// @}


    /// @{ Returns true if the VOP represents a method inside a class.
    virtual bool         isVopMethod() const;
    virtual bool         isVopMethodPublic() const;
    /// @}

    /// @{ If the node represents a function, a method, or a shader,
    /// then these functions return the info (name, return type, args) about 
    /// the function or a shader function as it appears in the source code.
    virtual void         getVopFunctionName(UT_String &function_name) const;
    virtual void         getVopFunctionReturnInfo(VOP_FunctionArgInfo &i) const;
    virtual void         getVopFunctionArgInfos(
                                UT_Array<VOP_FunctionArgInfo> &arg_infos);
    /// @}

    /// Obtains shader parameters information.
    void                 getShaderArgInfos( 
                                UT_Array<VOP_FunctionArgInfo> &arg_infos,
                                VOP_Type shader_type);

    /// Checks whether the given parm belongs to the shader of a given type.
    bool                 isParmForShaderType(const PRM_Parm &parm, 
                                VOP_Type shader_type, bool check_context_tag);

    /// Helper method for getVopFunctionArgInfos() to obtain shader function 
    /// parameter infos based on the node inputs and outputs.
    /// Optionally, the method can prefix function argument names with an 
    /// underscore, which is customary for shaders based on subnets. If so,
    /// the variable name will be also implicitly prefixed (otherwise,
    /// it would most likely be resolved to an input value).
    /// If argument name is not prefixed, the local variable used in a call
    /// may still be optionally prefixed (when needed to avoid var replacement).
    void                getVopFunctionArgInfosFromInputsAndOutputs( 
                                UT_Array<VOP_FunctionArgInfo> &arg_infos, 
                                int first_input, int last_input,
                                int first_output, int last_output,
                                bool prefix_input_arg_and_var_names,
                                bool prefix_input_var_names = false,
                                const VOP_CodeGenContext *context = nullptr);

    /// Helper method to obtain shader function parameter infos based on
    /// the node parameters.
    void                getVopFunctionArgInfosFromNodeParameters( 
                                UT_Array<VOP_FunctionArgInfo> &arg_infos,
                                const VOP_CodeGenContext *context = nullptr);
    void                getVopFunctionArgInfosFromNodeParameters( 
                                UT_Array<VOP_FunctionArgInfo> &arg_infos,
                                VOP_Type shader_type);

    /// Helper method to obtain shader function parameter infos based on
    /// the node inputs, outputs, and parameters.
    void                getVopFunctionArgInfosFromInputsOutputsAndParms( 
                                UT_Array<VOP_FunctionArgInfo> &arg_infos, 
                                int first_input, int last_input,
                                int first_output, int last_output,
                                bool prefix_input_arg_and_var_names,
                                bool prefix_input_var_names = false,
                                const VOP_CodeGenContext *context = nullptr);

    /// Helper method to obtain shader function parameter infos based
    /// on writable global variables in the shader's context.
    /// Used for shader call, that explicitly binds shader parameters
    /// to callee's globals, by listing them as arguments.
    void                getVopFunctionArgInfosFromGlobals( 
                                UT_Array<VOP_FunctionArgInfo> &arg_infos, 
                                VOP_Type shader_type );

    /// Helper method to obtain all known export parameters from a shader node.
    virtual void        getVopFunctionArgInfosFromExports( 
                                UT_Array<VOP_FunctionArgInfo> &arg_infos, 
                                VOP_Type shader_type );

    /// Gives this node a chance to register an interest in a varialbe that
    /// the upstream vop computes, but only optionally when explicitly asked.
    virtual void         registerExtraVarRequests(
                                VOP_ExtraVarRequests &extra_var_requests,
                                const VOP_CodeGenContext &context);

    /// Removes entries that correspond to a shader function parameters
    /// at a default value (or unconnected).
    /// If @p keep_export_args is true, all exports args are kept, even
    /// if they are at default. Otherwise, at-default exports are pruned.
    void                pruneVopFunctionArgInfos(
                                UT_Array<VOP_FunctionArgInfo> &arg_infos,
                                bool keep_all_export_args = false );

    /// Returns true if the parameter of a given name is at default value.
    /// If the parameter template is also given, it is used for default value,
    /// otherwise the parameter's template is used.
    bool                isParmAtDefaultValue( const char *parm, 
                            const PRM_Template *tplate = nullptr ) const;

    /// Writes declarations of variables used as argument to a function call.
    /// @param[out] buffer
    ///         Outgoing argument that is filled with variable declarations.
    /// @parm[in] arg_infos 
    ///         Information about inputs/output variables to write out.
    /// @parm[in] use_defined_input_defaults    
    ///         Flags whether the input variables should be initialized to
    ///         special defaults defined by the owner subnet.  If true, any
    ///         unconnected inputs will be initialized to such specially defined
    ///         defaults (connected inputs will be initialized to incoming
    ///         variables corresponding to the incoming wire).  If false, the
    ///         input defaults defined by owner subnet are not used, and all
    ///         inputs are initialized to incoming variables, which resolve to
    ///         the value if input is connected or to the empty constant or node
    ///         parm value.
    void            outputVopFunctionVariableDeclarations(UT_WorkBuffer &buffer,
                                const UT_Array<VOP_FunctionArgInfo> & arg_infos,
                                bool use_defined_input_defaults);

    /// @{ Constructs a shader call, assuming this node represents a shader.
    UT_StringHolder getVopFunctionCallName(const VOP_CodeGenContext &ctx);
    void            getVopFunctionCallCode(UT_String &codestr, 
                                const VOP_CodeGenContext &ctx);
    void            getVopFunctionCallModules(UT_StringArray &modules, 
                                const VOP_CodeGenContext &ctx);
    void            appendVopFunctionArgument(UT_StringArray &arg_names, 
                                UT_StringArray &arg_vals, 
                                const VOP_FunctionArgInfo &arg_info);
    /// @}

    /// Returns true if the code generator should declare local variables
    /// for this node's outputs. Returns false, if node declares them itself.
    virtual bool    shouldOutputNodeVariableDeclarations() const;

    /// Get or set the table of global or local variables for this context.
    /// The global variables are defined solely by the VEX context. The
    /// data associated with each entry is the VEX_Type of the variable.
    /// The local variables are those defined by Parameter ops. This
    /// table provides a common place to look for variable name conflicts.
    const VOP_GlobalVarMap *getGlobalVariables() const;
    const VOP_ParmGeneratorMap *getLocalVariables() const;
    const VOP_LocalChannelMap *getLocalChannels() const;
    void                 setTables(const VOP_GlobalVarMap *globals,
                                   VOP_ParmGeneratorMap *locals,
                                   VOP_LocalChannelMap *channels);
    void                 setTablesFromVop(VOP_Node *vop);
    void                 addLocalVariable(const UT_StringRef &varname,
                                          VOP_ParmGenerator *definer);
    void                 deleteLocalVariable(const UT_StringRef &varname);
    void                 deleteLocalChannelDefiner( VOP_ParmGenerator *definer);
    void                 getSortedGlobalVariableList(VOP_GlobalVarList &vars,
                                                     VOP_ContextType type,
                                                     bool mustBeReadable,
                                                     bool mustBeWritable);

    /// Similar to getLocalVariables() but it returns a table of Parameter ops
    /// that define subnet inputs rather than shader parameters.
    virtual VOP_ParmGeneratorMap* getSubnetVariables();
    VOP_ParmGeneratorMap*   getParentSubnetVariables() const;
    void                    addParentSubnetVariable(const char *varname,
                                          VOP_ParmGenerator *definer);
    void                    deleteParentSubnetVariable(const char *varname);

    /// Returns true if input variables should be prefixed inside the subnet.
    virtual bool         shouldPrefixInputVariablesInsideSubnet() const;

    /// Returns true if parm nodes that define subnet connectors are treated
    /// as shader parms. This is true for subnet material (or shader) nodes.
    virtual bool         usesSubnetConnectorsAsShaderParms() const;

    /// Returns true if shader parameters should be displayed as node inputs
    /// and outputs. This is true for subnet shader nodes.
    virtual bool         showsShaderParmsAsSubnetConnectors() const;

    /// Informs this node that some descendent (but not immediate child)
    /// was added and it represents a shader input or output.
    virtual void         shaderParmGrandChildAdded(VOP_Node *grand_child);
    virtual void         shaderParmGrandChildChanged(VOP_Node *grand_child);
    virtual void         shaderParmGrandChildDeleted(VOP_Node *grand_child);

    /// Functions for getting and setting the in/out LOD value, using the
    /// OP_NodeFlag mechanism.
    void                 setFlag(char flag, int8 val) override;
    bool                 setInOutLOD(int level, bool inoff);
    bool                 getInOutLOD(int level) const;
    static int          &getLODPref() { return theLODPref; }
    static void          setLODPref(int value);

    /// Override the setInput functions so that we can send notification to
    /// the nodes that are our inputs when we disconnect from them.
    OP_ERROR             setInput(unsigned idx, OP_Node *op,
                                  unsigned outputIdx = 0) override;
    OP_ERROR             setInputReference(
                                unsigned idx,
                                const char *label,
                                int keeppos,
                                unsigned outputIdx = 0) override;

    OP_ERROR             setNamedInput(
                                const OP_ConnectorId &input_name,
                                OP_Node *op,
                                const OP_ConnectorId* output_name = nullptr
                                ) override;
    OP_ERROR             setNamedInputReference(
                                const OP_ConnectorId &input_name, 
                                const char *label, int,
                                const OP_ConnectorId* output_name = nullptr
                                ) override;

    /// For subnet VOPs, when moving an input, we want to go in and
    /// reorganize the connections to our subinput and suboutput nodes
    /// so that the internal connections remain the same.
    void                 moveInput(int srcidx, int dstidx,
                                   bool forcesubnet = false) override;

    /// Return our input node for the give index. If recursive is true and we
    /// are in a subnet and the direct input for inputidx is a subnet input
    /// node, travel up the parent chain until no longer in a subnet or the
    /// input node is not a subnet input node. Basically, we want to know if we
    /// are connected to anything meaningful.
    virtual bool         isConnected(int inputidx, bool recursive);

    /// Returns a pointer used by OPUI_OutputNameEditor to get and set data.
    virtual VOP_OutputNameEditorSource  *getOutputNameEditorSource()
                         { return 0; }


    /// Some material vops cache a list of shader that needs to be dirtied.
    virtual void         dirtyShaderList();

    /// Used by subnet type operators which must always have an output node.
    /// However, some specialty subnets, such as volume sampler, may return
    /// NULL, since its output node is not a regular subnet output node that
    /// determines subnet output connectors (which is for what the subnet base 
    /// class uses the output node returned by this method).
    virtual VOP_Node    *getSubnetOutputNode() const;

    /// Returns true if this node is immediatly inside a non-shader subnet.
    bool                 isInNonShaderSubNetwork() const;

    /// Returns true if the node is considered a subnet's input node.
    virtual bool         isSubnetInput() const
                            { return false; }

    /// Returns the node from which to transfer information about local 
    /// variables used in source code generated by this node.
    virtual VOP_Node *  getPreResolveVariableSrc() const
                            { return nullptr; }

    /// Returns true if code generator should attempt to copy info about
    /// a variable corresponding to the i-th output connector.
    virtual bool        shouldPreResolveOutput(int output_index) const
                            { return true; }

    /// Returns true if the node is consdered an output node that represents
    /// a shader or a function that connects to a Collect node.
    virtual bool         isOutputVopNode() const
                            { return false; }

    /// Retruns true if the node is an internal auto node used only during
    /// code generation.
    virtual bool         isAutoVopNode() const
                            { return false; }

    /// Retruns true if the node is an internal auto-convert node.
    virtual bool         isAutoConvertNode() const
                            { return false; }

    /// Defines the different nodes that can be created and automatically
    /// connected to a VOP node's input.
    enum InputParmGenType
    {
        // Create a const VOP to connect to the input.
        INPUT_TYPE_CONST,
        // Create a parm VOP to connect to the input.
        INPUT_TYPE_PARM,
        // Create a subnet-scoped parm VOP to connect to the input.
        INPUT_TYPE_SUBNET_INPUT,
    };

    /// Create a Parameter or Constant VOP that matches the type, name and
    /// value of one of our inputs, and connect it to that input. 'parm'
    /// specifies whether to build a Parameter or a Constant.
    VOP_Node            *insertParmGenerator(int inputidx,
                                InputParmGenType type);
    VOP_Node            *insertNode(int inputidx, const char* nodetype,
                                bool connect_to_input,
                                const char* undo_string = NULL);

    int                  inputParmTypeIndex(int inputidx,
                                const PRM_Parm* parm) const;
    const char          *inputParmTypeString(int inputidx,
                                const PRM_Parm *parm) const;

    /// When inserting a parameter (i.e. Promote Parameter), the source VOP is
    /// allowed to give us a source VOP_ParmGenerator if there's no
    /// corresponding parameter found.  The source parm generator is used to
    /// initialize settings on the new parameter node.
    virtual VOP_ParmGenerator   *getInsertParmGeneratorSource(int inputidx);
    
    /// Create Parameter or Constant VOPs for all inputs of this node. We
    /// don't create nodes for inputs that are already connected.
    /// If `created_vops` is not NULL, then the method will populate the table
    /// with the input names for the keys and the created VOP nodes for the
    /// values.
    void                 insertParmGeneratorsForAllInputs(
                            InputParmGenType type,
                            UT_SymbolMap<VOP_Node *> *created_vops=NULL);

    /// Create Bind Export VOPs for all outputs of this node.
    /// Set `subnet` to true to create subnet-scoped Bind Export VOPs that
    /// produce output connectors on the owner subnetwork.
    void                 insertBindExportsForAllOutputs(bool subnet);
    VOP_Node            *insertBindExport(int outputidx, bool subnet);

    /// Updates the output connections based on the correspondence
    /// between old and new output names.
    void                 rewireOutputConnections( 
                                const UT_StringArray &old_names,
                                const UT_StringArray &new_names );

    /// The following method is needed to obtain the parameter name to be
    /// associated with an input.  It is possible that the parameter name
    /// differs from the input name.
    virtual void         getParmNameFromInput(UT_String &parmname,
                                              int inputidx) const;
    virtual void         getParmNameFromOutput(UT_String &parmname,
                                              int outputidx) const;

    /// Find the parameter associated with an input, if any
    const PRM_Parm      *getParmFromInput(int inputidx) const;
    const PRM_Parm      *getParmFromOutput(int outputidx) const;

    /// Based on the specified input index, output a parm definition block
    /// appropriate for a dialog script. The parm definition provides a
    /// default value for the input if it is not connected. If the input is
    /// VEX_TYPE_UNDEF, we output nothing and return false. Otherwise we return
    /// true.
    bool                 outputDefaultParmDefinition(std::ostream &os, int idx);

    /// Writes out the input and output connector definitions.
    void                 saveNodeInputAndOutputDefinitions(std::ostream &os);

    void                 saveDialogScriptExtraInfo(std::ostream &os) override;

    /// Saves the parameter values to the output stream.
    bool                 saveParmValues(std::ostream &os);
    /// Loads the parameter values to the output stream.
    bool                 loadParmValues(UT_IStream &is);

    /// This virtual is overridden by VOP_ParmGenerator so we can find out
    /// which VOP defines the actual parameter attributes.
    virtual VOP_Node    *getRealDefinition()
                         { return 0; }

    const VOP_Language  *getLanguage() const
                         { return myLanguage; }
    void                 setLanguage(const VOP_Language *language)
                         { myLanguage = language; }

    /// Absolute width
    fpreal               getW() const override;
    /// Absolute height
    fpreal               getH() const override;

    /// Override clearInterrupted so that we don't recook the whole DOP Network
    /// when the user interrupts a cook. The clearInterrupted on the containing
    /// VOP Network willb be enough.
    void                 clearInterrupted() override;

    /// Calls cacheParmName on all VOP_ParmGenerator nodes under root.
    static void          cacheAllParmNames(OP_Node *root);
    /// Calls recalculateParmDefiner on all VOP_ParmGenerator nodes under root.
    static void          recalculateAllParmDefiners(OP_Node *root,
                                bool dive_into_subnets = true,
                                const UT_StringRef &target_parm_name
                                                            = UT_StringRef());

    /// Returns true if the input will be auto-converetd, false otherwise.
    bool                 willAutoconvertInputType(int input_idx) override;

    /// Returns the type to which the input will be auto-convert. This is
    /// necessary because some inputs can take in a range of various types,
    /// and we need to know which one will be converting to. This function
    /// assumes that autoconversion is necessary. If it is not possible, or
    /// not needed, it returns VOP_TYPE_UNDEF.
    VOP_TypeInfo         getAutoConvertTargetTypeInfo(int input_idx);
    VOP_Type             getAutoConvertTargetType(int input_idx);

    // Similar to the getAutoConvertTargetType(), but takes in an input type
    // instead of trying to read it from the connected node. This is useful
    // when one needs to know what the incoming type will be converted to
    // before it is actually connected.
    VOP_TypeInfo         getAutoConvertTypeInfoFromType(int input_idx,
                                const VOP_TypeInfo &source_type);
    VOP_Type             getAutoConvertTypeFromType(int input_idx,
                                VOP_Type source_type);

    /// Do not call this method directly.
    void                 addAutoVopNodePointer(VOP_AutoNode* auto_node,
                                int input_index);
    void                 clearAutoVopNodeInfos();
    VOP_AutoNode        *getAutoVopNode(int input_idx);
    const VOP_AutoNode  *getAutoVopNode(int input_idx) const;
    int                  getAutoVopNodeCount();

    // Returns the output information manager. The manager is responsible for
    // manipulating VOP_OutputInfo objects for each output. These objects
    // dictate how an output behaves when the node is in debug or bypass mode.
    // See VOP_OutputInfo for more information.  Please note that by default,
    // an output info does not exist for any outputs, and is only created when
    // a debug/bypass value is changed.
    VOP_OutputInfoManager* getOutputInfoManager();

    // Appends code which overrides output values if necessary (uses
    // myOutputInfos below to determine this).
    void appendOutputOverrideCode(UT_String& str_code);

    // If this returns false, getCode() will not be called during code
    // generation on this node (appendOutputOverrideCode() still will). This is
    // useful when all outputs of this node are overriden, and no execution is
    // necessary.
    bool needToExecute();

    /// Do not call this method directly.
    void onNodeChange(OP_EventType type);

    OP_ERROR             save(std::ostream &os,
                              const OP_SaveFlags &flags,
                              const char *path_prefix = "",
                              const UT_String &name_override = UT_String()
                              ) override;
    bool                 load(UT_IStream &is, const char *ext="",
                                              const char *path=0) override;

    /// Gets/sets the value of the debug flag on this node.
    bool                 getDebug() const override;
    bool                 setDebug(bool on_off) override;

    /// Gets/sets the value of the material flag on this node.
    bool                 getMaterialFlag() const;
    bool                 setMaterialFlag(bool on_off);
    virtual void         initMaterialFlag();

    void                 getSubOutputAndSubInputs(OP_Node *&outputnode,
                                      OP_NodeList &inputnodes) const;

    void                hideInput(int input_index, bool hide); 
    void                setReferenceTargetDefaults(int input_index,bool do_set);
    bool                getAllowEditingParmDefaults(int input_index);

    /// Determine the VEX context type if the node is single-context type.
    /// For nodes in a multi-context vopnet returns
    /// VEX_INVALID_CONTEXT, because the specific VEX context cannot be 
    /// reliably and unambiguously determined.
    // TODO: remove these methods
    VEX_ContextType      getVexContextType() const;
    RSL_ContextType      getRslContextType() const;
    OSL_ContextType      getOslContextType() const;

    /// Determines if the vop can be interpreted as a single or several RSL/VEX
    /// context types (surface, disp, ..), by looking at code generator.
    /// Returns true if the vop node is multi-type and false if single-type.
    virtual bool        isSingleContextType() const;

    /// Gets the context type (VEX_ContextType or RSL_ContextType) to which
    /// this node subscribes. 
    /// In single-type vopnets, it is equal to the node's VEX/RSL context type.
    /// In multi-type vopnets, the exact type is variable and usually 
    /// depends on the node's parameter value.
    VOP_ContextType      getShaderContextType() const;

    /// Returns a parmmap string array where alternate entries contain key and
    /// value, where key is the vop parameter name and the value is the
    /// parameter name specified by the Parm VOP connected to the input
    /// corresponding to that vop parameter.
    virtual void         getFixedParameterMap(UT_StringArray &parmmap);

    /// Returns an input map string array where alternate entries contain
    /// key and value, where key is the vop parameter name and the value is the
    /// node path specified for that parameter (usually connected into an
    /// input corresponding to that vop parameter).
    virtual void         getShaderInputMap(UT_StringArray &inputmap);

    /// Utility function to check if a parm by a given name is a cvex shader.
    bool                 isCVEXPathParm(const char *parm_name) const;

    /// Obtains the template array for shader parameters.
    const PRM_Template  *getShaderParmTemplates() override;
    static void          refreshShaderParmTemplatesIfNeeded(OP_Node *n);

    /// Returns node parameters that should be authored as input attributes 
    /// (shader parameters) on a USD shader prim.
    UT_ValArray<PRM_Parm *>      getUSDShaderParms();

    /// Returns node parameters used to author a standard USD preview shader.
    UT_ValArray<PRM_Parm *>      getUSDPreviewShaderParms();

    /// Returns true if the given parameter should currently be included 
    /// in the USD shader parameters.
    /// Note, this is a dynamic test, and some nodes will consider a given
    /// parameter to be a USD shader parm under certain conditions but not 
    /// under the others (eg, depending on signature). 
    virtual bool                 allowUSDShaderParm(PRM_Parm &parm);

    /// Returns a set of parm tags relevant to authoring the USD preview shader.
    static const UT_Set<UT_StringHolder> &getUSDPreviewShaderTags();

    /// Deletes the input nodes for a given input (recursively), but
    /// only if none of them depend on anything other than this node.
    /// Returns true if any nodes were deleted, false otherwise.
    bool                 deleteIndependentInputNodes(int input_index);

    void                 getInputsRecursive(OP_NodeList& nodes_out);
    bool                 doesDependOnlyOn(const VOP_Node* other_node, 
                                    int max_connections, bool recurse);

    /// Search through this node's inputs and return a list of parameter VOPs
    /// that appear in the input network.  Recursively search through
    /// subnetworks as well.  If this node is a parameter VOP, then add
    /// it to the list.
    void                 getParmInputs(VOP_ParmGeneratorList &parm_vops);

    /// Returns the node wired to this VOP's 'index' input tracing past
    /// simple VOPs like the Switch or Null VOP.
    VOP_Node            *findSimpleInput(int index);
    /// Virtual helper to findSimpleInput() which returns the simple input
    /// node (ie the final node we look for) based on the request coming
    /// from the node connected to on the output of a given index.
    virtual VOP_Node    *findSimpleInputFromOutput(int output_index) 
                         { return this; }
    /// A method that reports which immediate input connectors are considered
    /// by findSimpleInputFromOutput() method. This is useful when analyzing
    /// the simple input decision tree.
    virtual void         findSimpleInputCandidatesFromOutput(int output_index,
                                            UT_IntArray & input_indices )
                         { input_indices.clear(); }

    /// Gets a default value of an explicitly defined input (applies to subnets)
    virtual void         getInputDefaultValue(UT_String &def, int idx) const;

    /// Gets number of outputs provided by a subnet, in addition to the outputs
    /// defined by wires connected to sub output.
    virtual int          getNumNodeDefinedOutputs() const;

    /// @{ VOP subnets may restrict which inputs should show up in the
    /// Subnet Input and Subnet Output VOPs. These two methods control that.
    /// Gets number of subnet inputs available to subnet input/output children.
    /// Gets the subnet input index corresponding to the given index of
    /// (limited number of) input available to subnet input/output children.
    virtual int     getNumSubnetInputsForChildren() const;
    virtual int     getSubnetInputIndexForChildren(int child_input) const;
    int             getChildConnectorIndexFromParent(int parent_input) const;
    virtual void    getSubnetOutputTerminalChild( 
                                VOP_Node * &output_vop, int &input_idx,
                                int subnet_output_idx ) const;
    /// @}

    /// Obtains additional nodes that should be copied or deleted when this
    /// node is copied or deleted. 
    void                 getExtraNodesForCopyOrDelete(
                                OP_NodeList &extras)const override;

    /// Some clerks add own stuff on creation. Any such action can be
    /// registered with this method.
    static void          setRunCreateScriptCB( void (*)(const char *node_path, 
                                const char*render_mask, VOP_Type shader_type ));

    // Runs the creation script (if there is one). The return value is false
    // if the node was deleted while running the script. In this case
    // obviously the node pointer becomes invalid and should not be used
    // any more. It returns true if the node still exists.
    bool                 runCreateScript() override;

    void                 updateInputFlagsFromOperator(
                                VOP_OperatorInfo *type_info, 
                                bool keep_visible);

    void                onCreated() override;
    void                hideNamedInput(const OP_ConnectorId& connector_name,
                                        bool hide); 

    /// Returns all allowed input types on a given input, regardless of what
    /// is currently connected to that input. These do not include types
    /// to which autoconversion is possible.
    virtual void         getAllowedNamedInputTypeInfos(
                                        const OP_ConnectorId& input_name,
                                        VOP_VopTypeInfoArray &typeinfos);
    virtual void         getAllowedNamedInputTypes(
                                        const OP_ConnectorId& input_name,
                                        VOP_VopTypeArray &voptypes);

    VOP_TypeInfo         getNamedAutoConvertTargetTypeInfo(
                                        const OP_ConnectorId& input_name);
    VOP_Type             getNamedAutoConvertTargetType(
                                        const OP_ConnectorId& input_name);
    VOP_TypeInfo         getNamedAutoConvertTypeInfoFromType(
                                        const OP_ConnectorId& input_name,
                                        const VOP_TypeInfo &source_type);
    VOP_Type             getNamedAutoConvertTypeFromType(
                                        const OP_ConnectorId& input_name,
                                        VOP_Type source_type);

    bool                 willAutoconvertNamedInputType(
                                        const OP_ConnectorId& input_name
                                        ) override;
    VOP_Node            *insertNamedNode(const OP_ConnectorId& input_name,
                                        const char* nodetype,
                                        bool connect_to_input,
                                        const char* undo_string = NULL);

    const OP_DataMicroNode &dataMicroNodeConst() const override
                                { return myVopDataMicroNode; }

    /// Exposes protected method for taking over the errors from global manager.
    /// Should be used only by cerain helpers.
    void                 stealGlobalErrorsForHelper()
                                { stealGlobalErrors(); }

    /// @{ Manipulate cook error dirty state
    void                 setErrorsDirty();
    void                 setErrorsClean(const OP_Context &context);
    bool                 areErrorsDirty(const OP_Context &context);
    /// @}
                
    /// Obtains the idx-th input type info from the connected input node. 
    /// If not connected, type info is set to undefined.
    /// @param  type_info   The type info to fill out.
    /// @parm   idx         The index of the input from where to take the type.
    /// @param  grow_inputs_to_idx 
    ///                     If true and the the requested idx is larger than
    ///                     the input list size, then the list is expanded
    ///                     to make the requested index legal. Otherwise,
    ///                     list is kept constant and input is treated as NULL,
    ///                     resulting in an info for an undefined type.
    /// @return             True if the info was obtained from the vop,
    ///                     otherwise false (info is set to undef, by default).
    bool                 getInputTypeInfoFromInputNode( 
                                    VOP_TypeInfo &type_info, int idx, 
                                    bool grow_inputs_to_idx = false) const;

    /// Obtains the idx-th input name based on a connected input node.
    /// If not connected, the name is "next".
    /// It's ensured that the name is unique even if many input nodes
    /// provide the same name.
    /// If check_output_names is true, the input name is ensured to be unique
    /// and different from the all the output names too.
    void                 getInputNameFromInputNode(UT_String &in, int idx,
                                    bool check_output_names)const;

    /// @{ Virtual overrides for evaluating parameters as render properties,
    /// in case the VOP node is a shader or a material.
    bool                 getParameterOrProperty(
                                const UT_StringRef &name, fpreal now,
                                OP_Node *&op, PRM_Parm *&parm,
                                bool create_missing_multiparms,
                                PRM_ParmList *obsolete = 0) override;
    bool                 getParameterOrPropertyByChannel(
                                const UT_StringRef &chname,
                                fpreal now, OP_Node *&op,
                                PRM_Parm *&parm, int &vector_index,
                                PRM_ParmList *obsolete = 0) override;
    int                  findParametersOrProperties(fpreal now,
                                OP_PropertyLookupList &list) override;
    /// @}

    /// Queries information about visible connectors. This takes into account
    /// grouping of inputs, the current LOD flag, etc.
    int                          getInputVisibleIndex(int idx);
    const vop_ConnectorArray    &getVisibleInputConnectors();
    int                          getOutputVisibleIndex(int idx);
    const vop_ConnectorArray    &getVisibleOutputConnectors();

    /// Get or set the expansion state of an input group for this node.
    /// The information is stored in the user data.
    void                 setInputGroupExpanded(const UT_StringHolder &group,
                                bool expanded);
    void                 setAllInputGroupsExpanded(bool expanded);
    bool                 getInputGroupExpanded(const UT_StringHolder &group);

    /// Fetches grouping information for all inputs whether they
    /// are visible or not. All inputs not in a group will be
    /// returned in the map with an empty string as the key.
    void                 getAllInputsGrouped(UT_StringArray &groups,
                                UT_StringMap<UT_IntArray> &mapping);

    /// Give this VOP ownership of a TIL_Thumbnail object. Deletes any
    /// thumbnail that was already here.
    void                 setThumbnail(TIL_Thumbnail *thumbnail);
    /// Returns a pointer to our thumbnail if we have one.
    TIL_Thumbnail       *getThumbnail() const;
    /// Handle changes to our user data. This may require a redraw.
    void                 userDataChanged(const UT_StringHolder &key) override;

    // Global preferences controlled by the pref dialog.
    static bool          getShowPreviewPref();
    static void          setShowPreviewPref(bool show);
    
protected:
    VOP_Node(OP_Network *parent, const char *name, OP_Operator *entry);
    ~VOP_Node() override;

    void                 getNodeSpecificInfoText(
                                OP_Context &context,
                                OP_NodeInfoParms &iparms) override;
    void                 fillInfoTreeNodeSpecific(
                                UT_InfoTree &tree, 
                                const OP_NodeInfoTreeParms &parms) override;

    void                 deleteCookedData() override;
    int                  saveCookedData(std::ostream &, OP_Context &,
                                        int binary = 0) override;
    int                  saveCookedData(const char *, OP_Context &) override;
    const char          *getFileExtension(int) const override;

    OP_ERROR             cookMe(OP_Context &) override;
    OP_ERROR             bypassMe(OP_Context &, int &) override;

    virtual void         preOpChanged(OP_EventType, void *)
                         { }
    virtual void         postOpChanged(OP_EventType, void *)
                         { }

    /// @{ Helpers for getParameterOrProperty() and 
    /// getParameterOrPropertyByChannel()
    bool                getPropertyFromNode(
                                const UT_StringRef &name, fpreal now,
                                OP_Node *&op, PRM_Parm *&parm,
                                bool add_missing_mparms, PRM_ParmList *obsolet);
    bool                getPropertyFromNode(
                                const UT_StringRef &chname, fpreal now, 
                                OP_Node *&op, PRM_Parm *&parm, int &vec_index,
                                PRM_ParmList *obsolete);
    bool                getPropertyFromCodeGen(
                                const UT_StringRef &name, fpreal now,
                                OP_Node *&op, PRM_Parm *&parm,
                                bool add_missing_mparms, PRM_ParmList *obsolet);
    bool                getPropertyFromCodeGen(
                                const UT_StringRef &chname, fpreal now, 
                                OP_Node *&op, PRM_Parm *&parm, int &vec_index,
                                PRM_ParmList *obsolete);
    bool                getPropertyFromInputs(
                                const UT_StringRef &name, fpreal now,
                                OP_Node *&op, PRM_Parm *&parm,
                                bool add_missing_mparms, PRM_ParmList *obsolet);
    bool                getPropertyFromInputs(
                                const UT_StringRef &chname, fpreal now, 
                                OP_Node *&op, PRM_Parm *&parm, int &vec_index,
                                PRM_ParmList *obsolete);
    /// @}

    /// Gets the shader context type (VEX_ContextType
    /// or RSL_ContextType) to which a node belongs to. 
    ///
    /// This method is meant to be overriden by nodes that can specify a single
    /// concrete context type when they are created in a multi-context vopnet.
    /// This method is invoked by getShaderContextType() to obtain the concrete
    /// type, if possible
    ///
    /// In multi-context vopnets, for nodes that explicitly specify a single
    /// context (such as an output node, usually determined from the node's
    /// parameter), this method returns such explicltly selected context
    /// type. For other nodes that don't explicltly choose a context, this
    /// method returns an invalid type, meaning such nodes don't have control
    /// over a specific type, and they belong to a type specified during code
    /// generation.
    virtual VOP_ContextType     getSpecificShaderContextType() const;

    /// Obtains a list of shading contexts in which this node wants to initiate
    /// the generation of code.
    virtual void                getContextsForCodeGeneration(
                                        UT_StringArray & context_names ) const;

    /// Functions to get information about our operator outputs.
    /// These functions are used for variable name replacement and for
    /// creating output labels on the op tiles.
    virtual void         getOutputNameSubclass(UT_String &out, int idx) const;
    virtual VOP_Type     getOutputTypeSubclass(int idx);
    virtual void         getOutputTypeInfoSubclass(VOP_TypeInfo &type_info, 
                                                   int idx);
    virtual VOP_VariableTagsHandle  getOutputVariableTagsSubclass(int idx,
                                        VOP_Type shader_type);

    /// Clears the cached info (name and type) about output connectors.
    void                 dirtyCachedOutputData();

    /// Returns the variable name associated with a given input number.
    /// Implementers of this function should also implement the reverse
    /// function.
    virtual void         getInputNameSubclass(UT_String &in, int idx) const;
    virtual int          getInputFromNameSubclass(const UT_String &in) const;
    int                  findInputFromInputName(const UT_String &in) const;
    virtual void         getInputTypeInfoSubclass(VOP_TypeInfo &type_info, 
                                                  int idx);
    // Depreciated in favour of getInputTypeInfoSubclass():
    virtual VOP_Type     getInputTypeSubclass(int idx);
    virtual bool         getIsInputVisibleDefaultSubclass(int idx);

    /// @{ One of these two methods should be overriden in most VOP nodes. 
    /// It is preferable to override the one that gets type infos, since
    /// they can encode complex types. 
    /// They should fill in voptypes vector with vop types that are allowed to 
    /// be connected to this node at the input at index idx. 
    /// Note that this method should return valid vop types even when nothing 
    /// is connected to the corresponding input.
    virtual void         getAllowedInputTypeInfosSubclass(unsigned idx, 
                                              VOP_VopTypeInfoArray &infos);
    virtual void         getAllowedInputTypesSubclass(unsigned idx,
                                              VOP_VopTypeArray &voptypes);
    /// @}

    /// If the can only accept parameters as inputs, this method should return
    /// true.  By default, this method checks the operator to see whether the
    /// VOP relies on external code (i.e. geometry procedurals)
    virtual bool         getRequiresInputParameters() const;

    /// Disables parameters whose corresponding inputs are connected.
    bool                 disableConnectedParameters();
    bool                 updateParmsFlags() override;
    bool                 preUpdateParmsFlags() override;
    bool                 updateParmsActiveState(bool active);

    void                 addError(VOP_ErrorCodes code, const char *msg=0,
                                  const UT_SourceLocation *loc=0)
                         { UTaddError("VOP", code, msg, loc); }
    void                 addMessage(VOP_ErrorCodes code, const char *msg=0,
                                    const UT_SourceLocation *loc=0)
                         { UTaddMessage("VOP", code, msg, loc); }
    void                 addWarning(VOP_ErrorCodes code, const char *msg=0,
                                    const UT_SourceLocation *loc=0)
                         { UTaddWarning("VOP", code, msg, loc); }
    void                 addFatal(VOP_ErrorCodes code, const char *msg=0,
                                  const UT_SourceLocation *loc=0)
                         { UTaddFatal("VOP", code, msg, loc); }

    virtual void         addDiagnosticInfo(const VCC_DiagnosticInfo &diag);

    /// This function is used to rewire nodes when we do a moveInput.
    static void          rewireInputs(OP_Network *parent, OP_NodeList &inputs,
                                      int srcidx, int dstidx);

    const VOP_Language  *myLanguage;

    void                getAdditionalUndoNodes(const OP_NodeList& orig_list,
                                OP_NodeList& nodes_for_input_undo) override;

    /// Save and load VOP version numbers
    OP_ERROR             saveIntrinsic(
                                std::ostream &os,
                                const OP_SaveFlags &flags) override;
    bool                 loadPacket(
                                UT_IStream &is,
                                short class_id,
                                short sig,
                                const char *path = 0) override;
    bool                 loadPacket(
                                UT_IStream &is,
                                const char *token,
                                const char *path = 0) override;

    /// If a subclass has VOP versioning, it should return a value greater
    /// than 0 for the latest version.
    virtual int          getLatestVopVersion() const
                         { return 0; }

    void                 getInputsRecursiveHelper(OP_NodeList& nodes_out,
                                UT_Array<int> &array);
    
    bool                 doesDependOnlyOnHelper(const VOP_Node* other_node,
                                int max_connections, 
                                bool recurse,
                                UT_Array<int> &array);

    void                 onInputAllocated(
                                OP_Input* new_input, int index) override;

    void                 finishedLoadingNetwork(
                                bool is_child_call = false) override;
                        
    OP_ERROR             getErrorSeverity() override;
    void                 ensureErrorsAreUpdatedSubclass() override;

    /// Generate the node errors.
    /// Return true if an error was generated and false otherwise.
    /// This method can be overridden to generate errors 
    /// specific to the subclass.
    virtual bool         generateErrorsSubclass();
    
    /// Returns true if the node should attempt testing its parameters
    /// for time dependence during the error generation pass.
    virtual bool         shouldCheckTimeDependence() const;

    int                  myVopVersion;

    /// This returns true if it is okay to modify parms based on input changing
    /// and false otherwise.  The decision is based on things like whether or 
    /// not we are being loaded or running in a creation script.
    bool                 allowedToChangeParms();

    /// @{ Represents this node as a co-shader. Usually it just adds itself
    /// to the list, but some VOPs may represent a co-shader array, in which 
    /// chase, they add a bunch of other VOPs that make up the array.
    virtual void         representAsCoShader(UT_ValArray<VOP_Node*> &coshader);
    virtual void         representAsCoShaderOutputName(UT_StringArray &name,
                                int output_index);
    /// @}

    /// Ensures the given connector name does not have any conflicts
    /// with other connectors and is safe to use.
    /// If check_outputs' is true, the output names are checked for conflicts
    /// too, otherwise only inputs are tested.
    void                 findSafeConnectorNameBase(UT_String &in, 
                                                bool check_outputs ) const;

    /// Returns the name the input connector would prefer to have,
    /// if we did not need to worry about multiple inputs having the same name.
    virtual void         getTentativeInputName(UT_String &in, int idx) const;

    /// Returns the name the output connector would prefer to have,
    /// if we did not need to worry about multiple outputs having the same name.
    virtual void         getTentativeOutputName(UT_String &out, int idx) const;

    /// Flag our visible connector info as dirty so it will be rebuilt the
    /// next time anyone asks for it.
    void                 setVisibleConnectorsDirty();

private:
    /// Generate the node errors.
    void                 generateErrors(const OP_Context &context);

    /// Returns true if this node can access illuminance global variables.
    bool                 getIncludeIllumVars() const;

    /// Helper method for opChanged().
    /// Propagates the node change to the VOP code generator
    /// so that the code is re-generated and the exported parameters
    /// are updated.
    void                 propagateOpChangeToCodeGenerator(
                                OP_EventType reason) const;

    /// Report a recursive loop error.
    void                 reportRecursiveLoopError();
    
    /// Get node type that should be used for promoting input at given index.
    const char          *getParameterOpName(int input_index);
    const char          *getConstantOpName(int input_index);
    bool                 isInputRampRBG(int input_index);

    /// Get the output index that should be used as parameter value.
    virtual int          getParameterOpOutputIndex();

    /// Create Parameter VOPs for all inputs of this node. We
    /// don't create nodes for inputs that are already connected.
    /// If `created_vops` is not NULL, then the method will populate the table
    /// with the input names for the keys and the created VOP nodes for the
    /// values.
    void                 insertParmVOPsForAllInputs(
                                InputParmGenType type,
                                UT_SymbolMap<VOP_Node *> *created_vops);
    
    /// Create Constant VOPs for all inputs of this node. We
    /// don't create nodes for inputs that are already connected.
    /// If `created_vops` is not NULL, then the method will populate the table
    /// with the input names for the keys and the created VOP nodes for the
    /// values.
    void                 insertConstantVOPsForAllInputs(
                                UT_SymbolMap<VOP_Node *> *created_vops);


    /// Add entries to the string array for each struct member. These entries
    /// values come from the given parameter. The values use correct syntax
    /// for the given language.
    void                 getParmConstantStringForStruct(UT_StringArray &values, 
                                const VOP_TypeInfo &type_info,
                                PRM_Parm &parm,
                                const VOP_Language *language);

    /// Update our internal mapping of visible connectors to group names, input
    /// indices, etc.
    void                 updateVisibleConnectorInfo();
    void                 getParameterGroups(UT_StringMap<int> &group_map,
                                UT_StringArray &group_names);

    const VOP_GlobalVarMap      *myGlobalVariables;
    VOP_ParmGeneratorMap        *myLocalVariables;
    VOP_LocalChannelMap         *myLocalChannels;
    UT_UniquePtr<TIL_Thumbnail>  myThumbnail;
    exint                        myLatestOpChangedId;
    unsigned int                 myMakingInputList : 1,
                                 myIsSearchingForParmInputs : 1,
                                 myInitialized : 1;

    static VOP_Node             *theOriginalOpChanged;
    static exint                 theLatestOpChangedId;
    static int                   theLODPref;
    static bool                  theShowPreviewPref;

    using IntPair = std::pair<int, int>;

    VOP_AutoNodeInfoList         myAutoVopNodeInfos;
    VOP_OutputInfoManager        myOutputInfos;
    UT_Array<IntPair>            myInputVariableOverrides;

    mutable UT_Lock                         myCachedDataLock;
    mutable int                             myCachedOutputNodeId;
    mutable UT_SymbolMap<int>               myCachedOutputNames;
    mutable UT_ValArray< VOP_TypeInfo* >    myCachedOutputTypeInfos;

    VOP_DataMicroNode            myVopDataMicroNode;
    VOP_CodeGenerator           *myAutoCodeGenerator;
    UT_Map<int, int>             myVisibleInputIndexMap;
    vop_ConnectorArray           myVisibleInputConnectors;
    UT_Map<int, int>             myVisibleOutputIndexMap;
    vop_ConnectorArray           myVisibleOutputConnectors;
    bool                         myVisibleConnectorsDirty;
};

#endif