OP/OP_InputChangeHelper.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.
 *
 * Produced by:
 *      Edward Lam
 *      Side Effects Software Inc
 *      123 Front Street West, Suite 1401
 *      Toronto, Ontario
 *      Canada   M5J 2M2
 *      416-504-9876
 *
 * NAME:        OP_InputChangeHelper.h (OP Library, C++)
 *
 * COMMENTS:    Helper class for keeping track of whether node inputs have
 *              changed.
 *
 * HOW TO USE THIS CLASS
 * =====================
 *
 * SETUP:
 *      - Override OP_Node::inputConnectChanged() to call
 *        OP_InputChangeHelper::inputConnectChanged() as well. Don't forget to
 *        delegate to the base class.
 *      - In the OP_Node::deleteCookedData() and OP_Node::bypassMe() overrides,
 *        call OP_InputChangeHelper::resetChangedSourceFlags(). Any other calls
 *        to delete the node's data should also call resetChangedSourceFlags().
 * 
 * Now, when you want to mark an input as being used, call useInput(). To query
 * if an input is dirty without clearing it, use checkChangedSourceFlags().
 */

#ifndef __OP_INPUTCHANGEHELPER_H__
#define __OP_INPUTCHANGEHELPER_H__

#include "OP_API.h"
#include <UT/UT_Assert.h>
#include <UT/UT_IntArray.h>
#include "OP_Node.h"

class OP_API OP_InputChangeHelper
{
public:

    /// Mark all inputs as dirty. This is the default.
    void resetChangedSourceFlags()
    {
         myDuplicateCounts.resize(0);
    }

    /// Mark the given input as dirty.
    /// NOTE: Users of this class should override
    ///       OP_Node::inputConnectChanged() to call this.
    void inputConnectChanged(const OP_Node &node, int which_input)
    {
        if (which_input >= 0)
            setDuplicateCount(which_input, -1, node.maxInputs());
        else
            resetChangedSourceFlags();
    }

    /// Use the given input on the node. This updates source flags to mark the
    /// input as now clean, returning whether the input changes.
    /// If force is true, then we treat the input as always dirty.
    /// Returns false if input has errors and we'll add an input error in that
    /// case.
    bool useInput(const OP_Node &node, unsigned idx, bool &changed, bool force)
    {
        // checkChangedSourceFlags() returns if input has an error, "changed"
        // is updated.
        if (!checkChangedSourceFlags(node, idx, changed))
            return false;

        if (force || changed)
        {
            OP_Node *   src = node.getInput(idx);

            setDuplicateCount(idx, src->getCookCount(), node.maxInputs());

            changed = true; // we may have entered with (force == true)
        }
        // else not forced, and not changed

        return true;
    }

    /// Similar to useInput() except it doesn't affect the flags. It's used to
    /// simply query whether the given input has changed. Returns false if
    /// there's errors on the input. "changed" is updated.
    bool checkChangedSourceFlags(const OP_Node &node, unsigned idx,
                                 bool &changed)
    {
        OP_Node *   src;

        src = node.getInput(idx);
        if (!src || src->error() >= UT_ERROR_ABORT)
        {
            changed = true;
            return false;
        }

        changed = (src->getCookCount() != getDuplicateCount(idx));
        return true;
    }

private:
    int getDuplicateCount(int idx)
    {
        if (idx >= 0 && idx < myDuplicateCounts.entries())
            return myDuplicateCounts(idx);
        return -1;
    }
    void setDuplicateCount(int idx, int count, int max_inputs)
    {
        if (idx >= 0 && idx < max_inputs)
        {
            while (idx >= myDuplicateCounts.entries())
                myDuplicateCounts.append(-1);
            myDuplicateCounts(idx) = count;
        }
        else    // clear all duplicate counts
        {
            UT_ASSERT(!"Untested code path");
            myDuplicateCounts.entries(0);
        }
    }

private:
    UT_IntArray     myDuplicateCounts;
};

#endif // __OP_INPUTCHANGEHELPER_H__

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