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//

//  W A R N I N G

//  -------------

//

// This file is not part of the Qt API.  It exists purely as an

// implementation detail.  This header file may change from version to

// version without notice, or even be removed.

//

// We mean it.

//

/*

    VERTEX SHADERS

    ==============

    Vertex shaders are specified as multiple (partial) shaders. On desktop,

    this works fine. On ES, QGLShader & QGLShaderProgram will make partial

    shaders work by concatenating the source in each QGLShader and compiling

    it as a single shader. This is abstracted nicely by QGLShaderProgram and

    the GL2 engine doesn't need to worry about it.

    Generally, there's two vertex shader objects. The position shaders are

    the ones which set gl_Position. There's also two "main" vertex shaders,

    one which just calls the position shader and another which also passes

    through some texture coordinates from a vertex attribute array to a

    varying. These texture coordinates are used for mask position in text

    rendering and for the source coordinates in drawImage/drawPixmap. There's

    also a "Simple" vertex shader for rendering a solid colour (used to render

    into the stencil buffer where the actual colour value is discarded).

    The position shaders for brushes look scary. This is because many of the

    calculations which logically belong in the fragment shader have been moved

    into the vertex shader to improve performance. This is why the position

    calculation is in a seperate shader. Not only does it calculate the

    position, but it also calculates some data to be passed to the fragment

    shader as a varying. It is optimal to move as much of the calculation as

    possible into the vertex shader as this is executed less often.

    The varyings passed to the fragment shaders are interpolated (which is

    cheap). Unfortunately, GL will apply perspective correction to the

    interpolation calusing errors. To get around this, the vertex shader must

    apply perspective correction itself and set the w-value of gl_Position to

    zero. That way, GL will be tricked into thinking it doesn't need to apply a

    perspective correction and use linear interpolation instead (which is what

    we want). Of course, if the brush transform is affeine, no perspective

    correction is needed and a simpler vertex shader can be used instead.

    So there are the following "main" vertex shaders:

        qglslMainVertexShader

        qglslMainWithTexCoordsVertexShader

    And the the following position vertex shaders:

        qglslPositionOnlyVertexShader

        qglslPositionWithTextureBrushVertexShader

        qglslPositionWithPatternBrushVertexShader

        qglslPositionWithLinearGradientBrushVertexShader

        qglslPositionWithRadialGradientBrushVertexShader

        qglslPositionWithConicalGradientBrushVertexShader

        qglslAffinePositionWithTextureBrushVertexShader

        qglslAffinePositionWithPatternBrushVertexShader

        qglslAffinePositionWithLinearGradientBrushVertexShader

        qglslAffinePositionWithRadialGradientBrushVertexShader

        qglslAffinePositionWithConicalGradientBrushVertexShader

    Leading to 23 possible vertex shaders

    FRAGMENT SHADERS

    ================

    Fragment shaders are also specified as multiple (partial) shaders. The

    different fragment shaders represent the different stages in Qt's fragment

    pipeline. There are 1-3 stages in this pipeline: First stage is to get the

    fragment's colour value. The next stage is to get the fragment's mask value

    (coverage value for anti-aliasing) and the final stage is to blend the

    incoming fragment with the background (for composition modes not supported

    by GL).

    Of these, the first stage will always be present. If Qt doesn't need to

    apply anti-aliasing (because it's off or handled by multisampling) then

    the coverage value doesn't need to be applied. (Note: There are two types

    of mask, one for regular anti-aliasing and one for sub-pixel anti-

    aliasing.) If the composition mode is one which GL supports natively then

    the blending stage doesn't need to be applied.

    As eash stage can have multiple implementations, they are abstracted as

    GLSL function calls with the following signatures:

    Brushes & image drawing are implementations of "qcolorp vec4 srcPixel()":

        qglslImageSrcFragShader

        qglslImageSrcWithPatternFragShader

        qglslNonPremultipliedImageSrcFragShader

        qglslSolidBrushSrcFragShader

        qglslTextureBrushSrcFragShader

        qglslTextureBrushWithPatternFragShader

        qglslPatternBrushSrcFragShader

        qglslLinearGradientBrushSrcFragShader

        qglslRadialGradientBrushSrcFragShader

        qglslConicalGradientBrushSrcFragShader

    NOTE: It is assumed the colour returned by srcPixel() is pre-multiplied

    Masks are implementations of "qcolorp vec4 applyMask(qcolorp vec4 src)":

        qglslMaskFragmentShader

        qglslRgbMaskFragmentShaderPass1

        qglslRgbMaskFragmentShaderPass2

        qglslRgbMaskWithGammaFragmentShader

    Composition modes are "qcolorp vec4 compose(qcolorp vec4 src)":

        qglslColorBurnCompositionModeFragmentShader

        qglslColorDodgeCompositionModeFragmentShader

        qglslDarkenCompositionModeFragmentShader

        qglslDifferenceCompositionModeFragmentShader

        qglslExclusionCompositionModeFragmentShader

        qglslHardLightCompositionModeFragmentShader

        qglslLightenCompositionModeFragmentShader

        qglslMultiplyCompositionModeFragmentShader

        qglslOverlayCompositionModeFragmentShader

        qglslScreenCompositionModeFragmentShader

        qglslSoftLightCompositionModeFragmentShader

    Note: In the future, some GLSL compilers will support an extension allowing

          a new 'color' precision specifier. To support this, qcolorp is used for

          all color components so it can be defined to colorp or lowp depending upon

          the implementation.

    So there are differnt frament shader main functions, depending on the

    number & type of pipelines the fragment needs to go through.

    The choice of which main() fragment shader string to use depends on:

        - Use of global opacity

        - Brush style (some brushes apply opacity themselves)

        - Use & type of mask (TODO: Need to support high quality anti-aliasing & text)

        - Use of non-GL Composition mode

    Leading to the following fragment shader main functions:

        gl_FragColor = compose(applyMask(srcPixel()*globalOpacity));

        gl_FragColor = compose(applyMask(srcPixel()));

        gl_FragColor = applyMask(srcPixel()*globalOpacity);

        gl_FragColor = applyMask(srcPixel());

        gl_FragColor = compose(srcPixel()*globalOpacity);

        gl_FragColor = compose(srcPixel());

        gl_FragColor = srcPixel()*globalOpacity;

        gl_FragColor = srcPixel();

    Called:

        qglslMainFragmentShader_CMO

        qglslMainFragmentShader_CM

        qglslMainFragmentShader_MO

        qglslMainFragmentShader_M

        qglslMainFragmentShader_CO

        qglslMainFragmentShader_C

        qglslMainFragmentShader_O

        qglslMainFragmentShader

    Where:

        M = Mask

        C = Composition

        O = Global Opacity

    CUSTOM SHADER CODE

    ==================

    The use of custom shader code is supported by the engine for drawImage and

    drawPixmap calls. This is implemented via hooks in the fragment pipeline.

    The custom shader is passed to the engine as a partial fragment shader

    (QGLCustomShaderStage). The shader will implement a pre-defined method name

    which Qt's fragment pipeline will call:

        lowp vec4 customShader(lowp sampler2d imageTexture, highp vec2 textureCoords)

    The provided src and srcCoords parameters can be used to sample from the

    source image.

    Transformations, clipping, opacity, and composition modes set using QPainter

    will be respected when using the custom shader hook.

*/

#ifndef QGLENGINE_SHADER_MANAGER_H

#define QGLENGINE_SHADER_MANAGER_H

#include <QGLShader>

#include <QGLShaderProgram>

#include <QPainter>

#include <private/qgl_p.h>

#include <private/qglcustomshaderstage_p.h>

QT_BEGIN_HEADER

QT_BEGIN_NAMESPACE

QT_MODULE(OpenGL)

struct QGLEngineShaderProg

{

    QGLShader*          mainVertexShader;

    QGLShader*          positionVertexShader;

    QGLShader*          mainFragShader;

    QGLShader*          srcPixelFragShader;

    QGLShader*          maskFragShader;        // Can be null for no mask

    QGLShader*          compositionFragShader; // Can be null for GL-handled mode

    QGLShaderProgram*   program;

    QVector<uint> uniformLocations;

    bool                useTextureCoords;

    bool                useOpacityAttribute;

    bool operator==(const QGLEngineShaderProg& other) {

        // We don't care about the program

        return ( mainVertexShader      == other.mainVertexShader &&

                 positionVertexShader  == other.positionVertexShader &&

                 mainFragShader        == other.mainFragShader &&

                 srcPixelFragShader    == other.srcPixelFragShader &&

                 maskFragShader        == other.maskFragShader &&

                 compositionFragShader == other.compositionFragShader

               );

    }

};

/*

struct QGLEngineCachedShaderProg

{

    QGLEngineCachedShaderProg(QGLEngineShaderManager::ShaderName vertexMain,

                              QGLEngineShaderManager::ShaderName vertexPosition,

                              QGLEngineShaderManager::ShaderName fragMain,

                              QGLEngineShaderManager::ShaderName pixelSrc,

                              QGLEngineShaderManager::ShaderName mask,

                              QGLEngineShaderManager::ShaderName composition);

    int cacheKey;

    QGLShaderProgram* program;

}

*/

static const GLuint QT_VERTEX_COORDS_ATTR  = 0;

static const GLuint QT_TEXTURE_COORDS_ATTR = 1;

static const GLuint QT_OPACITY_ATTR = 2;

class QGLEngineSharedShaders : public QObject

{

    Q_OBJECT

public:

    enum ShaderName {

        MainVertexShader,

        MainWithTexCoordsVertexShader,

        MainWithTexCoordsAndOpacityVertexShader,

        UntransformedPositionVertexShader,

        PositionOnlyVertexShader,

        PositionWithPatternBrushVertexShader,

        PositionWithLinearGradientBrushVertexShader,

        PositionWithConicalGradientBrushVertexShader,

        PositionWithRadialGradientBrushVertexShader,

        PositionWithTextureBrushVertexShader,

        AffinePositionWithPatternBrushVertexShader,

        AffinePositionWithLinearGradientBrushVertexShader,

        AffinePositionWithConicalGradientBrushVertexShader,

        AffinePositionWithRadialGradientBrushVertexShader,

        AffinePositionWithTextureBrushVertexShader,

        MainFragmentShader_CMO,

        MainFragmentShader_CM,

        MainFragmentShader_MO,

        MainFragmentShader_M,

        MainFragmentShader_CO,

        MainFragmentShader_C,

        MainFragmentShader_O,

        MainFragmentShader,

        MainFragmentShader_ImageArrays,

        ImageSrcFragmentShader,

        ImageSrcWithPatternFragmentShader,

        NonPremultipliedImageSrcFragmentShader,

        CustomImageSrcFragmentShader,

        SolidBrushSrcFragmentShader,

        TextureBrushSrcFragmentShader,

        TextureBrushSrcWithPatternFragmentShader,

        PatternBrushSrcFragmentShader,

        LinearGradientBrushSrcFragmentShader,

        RadialGradientBrushSrcFragmentShader,

        ConicalGradientBrushSrcFragmentShader,

        ShockingPinkSrcFragmentShader,

        MaskFragmentShader,

        RgbMaskFragmentShaderPass1,

        RgbMaskFragmentShaderPass2,

        RgbMaskWithGammaFragmentShader,

        MultiplyCompositionModeFragmentShader,

        ScreenCompositionModeFragmentShader,

        OverlayCompositionModeFragmentShader,

        DarkenCompositionModeFragmentShader,

        LightenCompositionModeFragmentShader,

        ColorDodgeCompositionModeFragmentShader,

        ColorBurnCompositionModeFragmentShader,

        HardLightCompositionModeFragmentShader,

        SoftLightCompositionModeFragmentShader,

        DifferenceCompositionModeFragmentShader,

        ExclusionCompositionModeFragmentShader,

        TotalShaderCount, InvalidShaderName

    };

    QGLEngineSharedShaders(const QGLContext *context);

    QGLShader *compileNamedShader(ShaderName name, QGLShader::ShaderType type);

    QGLShaderProgram *simpleProgram() { return simpleShaderProg; }

    QGLShaderProgram *blitProgram() { return blitShaderProg; }

    // Compile the program if it's not already in the cache, return the item in the cache.

    QGLEngineShaderProg *findProgramInCache(const QGLEngineShaderProg &prog);

    // Compile the custom shader if it's not already in the cache, return the item in the cache.

    QGLShader *compileCustomShader(QGLCustomShaderStage *stage, QGLShader::ShaderType type);

    static QGLEngineSharedShaders *shadersForContext(const QGLContext *context);

signals:

    void shaderProgNeedsChanging();

private slots:

    void shaderDestroyed(QObject *shader);

private:

    QGLSharedResourceGuard ctxGuard;

    QGLShaderProgram *blitShaderProg;

    QGLShaderProgram *simpleShaderProg;

    QList<QGLEngineShaderProg> cachedPrograms;

    QCache<QByteArray, QGLShader> customShaderCache;

    QGLShader* compiledShaders[TotalShaderCount];

    static const char* qglEngineShaderSourceCode[TotalShaderCount];

};

class Q_OPENGL_EXPORT QGLEngineShaderManager : public QObject

{

    Q_OBJECT

public:

    QGLEngineShaderManager(QGLContext* context);

    ~QGLEngineShaderManager();

    enum MaskType {NoMask, PixelMask, SubPixelMaskPass1, SubPixelMaskPass2, SubPixelWithGammaMask};

    enum PixelSrcType {

        ImageSrc = Qt::TexturePattern+1,

        NonPremultipliedImageSrc = Qt::TexturePattern+2,

        PatternSrc = Qt::TexturePattern+3,

        TextureSrcWithPattern = Qt::TexturePattern+4

    };

    enum Uniform {

        ImageTexture,

        PatternColor,

        GlobalOpacity,

        Depth,

        PmvMatrix,

        MaskTexture,

        FragmentColor,

        LinearData,

        Angle,

        HalfViewportSize,

        Fmp,

        Fmp2MRadius2,

        Inverse2Fmp2MRadius2,

        InvertedTextureSize,

        BrushTransform,

        BrushTexture,

        NumUniforms

    };

    enum OpacityMode {

        NoOpacity,

        UniformOpacity,

        AttributeOpacity

    };

    // There are optimisations we can do, depending on the brush transform:

    //    1) May not have to apply perspective-correction

    //    2) Can use lower precision for matrix

    void optimiseForBrushTransform(const QTransform &transform);

    void setSrcPixelType(Qt::BrushStyle);

    void setSrcPixelType(PixelSrcType); // For non-brush sources, like pixmaps & images

    void setOpacityMode(OpacityMode);

    void setMaskType(MaskType);

    void setCompositionMode(QPainter::CompositionMode);

    void setCustomStage(QGLCustomShaderStage* stage);

    void removeCustomStage(QGLCustomShaderStage* stage);

    uint getUniformLocation(Uniform id);

    void setDirty(); // someone has manually changed the current shader program

    bool useCorrectShaderProg(); // returns true if the shader program needed to be changed

    QGLShaderProgram* currentProgram(); // Returns pointer to the shader the manager has chosen

    QGLShaderProgram* simpleProgram(); // Used to draw into e.g. stencil buffers

    QGLShaderProgram* blitProgram(); // Used to blit a texture into the framebuffer

/*

    // These allow the ShaderName enum to be used as a cache key

    const int mainVertexOffset = 0;

    const int positionVertexOffset = (1<<2) - PositionOnlyVertexShader;

    const int mainFragOffset = (1<<6) - MainFragmentShader_CMO;

    const int srcPixelOffset = (1<<10) - ImageSrcFragmentShader;

    const int maskOffset = (1<<14) - NoMaskShader;

    const int compositionOffset = (1 << 16) - MultiplyCompositionModeFragmentShader;

*/

#if defined (QT_DEBUG)

    Q_ENUMS(ShaderName)

#endif

private slots:

    void shaderProgNeedsChangingSlot() { shaderProgNeedsChanging = true; }

private:

    QGLContext*     ctx;

    bool            shaderProgNeedsChanging;

    // Current state variables which influence the choice of shader:

    QTransform                  brushTransform;

    int                         srcPixelType;

    OpacityMode                 opacityMode;

    MaskType                    maskType;

    QPainter::CompositionMode   compositionMode;

    QGLCustomShaderStage*       customSrcStage;

    QGLEngineShaderProg*  currentShaderProg;

    QGLEngineSharedShaders *sharedShaders;

    QGLShader *customShader;

};

QT_END_NAMESPACE

QT_END_HEADER

#endif //QGLENGINE_SHADER_MANAGER_H