selection.h

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//
// Copyright 2018 Pixar
//
// Licensed under the terms set forth in the LICENSE.txt file available at
// https://openusd.org/license.
//
#ifndef PXR_IMAGING_HD_SELECTION_H
#define PXR_IMAGING_HD_SELECTION_H

#include "pxr/pxr.h"
#include "pxr/imaging/hd/api.h"
#include "pxr/imaging/hd/version.h"
#include "pxr/usd/sdf/path.h"
#include "pxr/base/gf/vec4f.h"
#include "pxr/base/vt/array.h"

#include <memory>
#include <vector>
#include <unordered_map>

PXR_NAMESPACE_OPEN_SCOPE

using HdSelectionSharedPtr = std::shared_ptr<class HdSelection>;

/// \class HdSelection
///
/// HdSelection holds a collection of selected items per selection mode.
/// The items may be rprims, instances of an rprim and subprimitives of an
/// rprim, such as elements (faces for meshes, individual curves for basis
/// curves), edges & points. Each item is referred to by the render index path.
///
/// It current supports active and rollover selection modes, and may be
/// inherited for customization.
///
class HdSelection
{
public:
    /// Selection modes allow differentiation in selection highlight behavior.
    enum HighlightMode : uint32_t {
        HighlightModeSelect = 0, // Active selection
        HighlightModeLocate,     // Rollover selection
        
        HighlightModeCount
    };

    HD_API
    virtual ~HdSelection();

    /// ------------------------ Population API --------------------------------
    HD_API
    void AddRprim(HighlightMode const &mode,
                  SdfPath const &renderIndexPath);

    HD_API
    void AddInstance(HighlightMode const &mode,
                     SdfPath const &renderIndexPath,
                     VtIntArray const &instanceIndex=VtIntArray());

    HD_API
    void AddElements(HighlightMode const &mode,
                     SdfPath const &renderIndexPath,
                     VtIntArray const &elementIndices);
    
    HD_API
    void AddEdges(HighlightMode const &mode,
                  SdfPath const &renderIndexPath,
                  VtIntArray const &edgeIndices);
    
    HD_API
    void AddPoints(HighlightMode const &mode,
                   SdfPath const &renderIndexPath,
                   VtIntArray const &pointIndices);

    // Special handling for points: we allow a set of selected point indices to
    // also specify a color to use for highlighting in the render's working
    // color space.
    HD_API
    void AddPoints(HighlightMode const &mode,
                   SdfPath const &renderIndexPath,
                   VtIntArray const &pointIndices,
                   GfVec4f const &pointColor);

    // XXX: Ideally, this should be per instance, if we want to support
    // selection of subprims (faces/edges/points) per instance of an rprim.
    // By making this per rprim, all selected instances of the rprim will share
    // the same subprim highlighting.
    struct PrimSelectionState {
        PrimSelectionState() : fullySelected(false) {}

        bool fullySelected;
        // Use a vector of VtIntArray to avoid copying the indices data.
        // This way, we support multiple Add<Subprim> operations without 
        // having to consolidate the indices each time.
        std::vector<VtIntArray> instanceIndices;
        std::vector<VtIntArray> elementIndices;
        std::vector<VtIntArray> edgeIndices;
        std::vector<VtIntArray> pointIndices;
        std::vector<int>        pointColorIndices;
    };

    /// ---------------------------- Query API ---------------------------------

    // Returns a pointer to the selection state for the rprim path if selected.
    // Returns nullptr otherwise.
    HD_API
    PrimSelectionState const *
    GetPrimSelectionState(HighlightMode const &mode,
                          SdfPath const &renderIndexPath) const;

    // Returns the selected rprim render index paths for all the selection
    // modes. The vector returned may contain duplicates. 
    HD_API
    SdfPathVector
    GetAllSelectedPrimPaths() const;

    // Returns the selected rprim render index paths for the given mode.
    HD_API
    SdfPathVector
    GetSelectedPrimPaths(HighlightMode const &mode) const;

    HD_API
    std::vector<GfVec4f> const& GetSelectedPointColors() const;

    // Returns true if nothing is selected.
    HD_API
    bool IsEmpty() const;

    HD_API
    static
    HdSelectionSharedPtr Merge(
        HdSelectionSharedPtr const &,
        HdSelectionSharedPtr const &);

private:
    void _AddPoints(HighlightMode const &mode,
                    SdfPath const &renderIndexPath,
                    VtIntArray const &pointIndices,
                    int pointColorIndex);

    void _GetSelectionPrimPathsForMode(HighlightMode const &mode,
                                       SdfPathVector *paths) const;

protected:
    using _PrimSelectionStateMap =
        std::unordered_map<SdfPath, PrimSelectionState, SdfPath::Hash>;
    // Keep track of selection per selection mode.
    _PrimSelectionStateMap _selMap[HighlightModeCount];

    // Track all colors used for point selection highlighting.
    std::vector<GfVec4f> _selectedPointColors;
};

PXR_NAMESPACE_CLOSE_SCOPE

#endif //PXR_IMAGING_HD_SELECTION_H