/****************************************************************************

**

** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies).

** All rights reserved.

** Contact: Nokia Corporation (qt-info@nokia.com)

**

** This file is part of the QtOpenGL module of the Qt Toolkit.

**

** $QT_BEGIN_LICENSE:LGPL$

** No Commercial Usage

** This file contains pre-release code and may not be distributed.

** You may use this file in accordance with the terms and conditions

** contained in the Technology Preview License Agreement accompanying

** this package.

**

** GNU Lesser General Public License Usage

** Alternatively, this file may be used under the terms of the GNU Lesser

** General Public License version 2.1 as published by the Free Software

** Foundation and appearing in the file LICENSE.LGPL included in the

** packaging of this file.  Please review the following information to

** ensure the GNU Lesser General Public License version 2.1 requirements

** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.

**

** In addition, as a special exception, Nokia gives you certain additional

** rights.  These rights are described in the Nokia Qt LGPL Exception

** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.

**

** If you have questions regarding the use of this file, please contact

** Nokia at qt-info@nokia.com.

**

**

**

**

**

**

**

**

** $QT_END_LICENSE$

**

****************************************************************************/

#include "qgraphicsshadereffect_p.h"

#if !defined(QT_OPENGL_ES_1) && !defined(QT_OPENGL_ES_1_CL)

#include "qglshaderprogram.h"

#include "gl2paintengineex/qglcustomshaderstage_p.h"

#define QGL_HAVE_CUSTOM_SHADERS 1

#endif

#include <QtGui/qpainter.h>

#include <QtGui/qgraphicsitem.h>

#include <QtGui/private/qgraphicseffect_p.h>

QT_BEGIN_NAMESPACE

/*#

    \class QGraphicsShaderEffect

    \brief The QGraphicsShaderEffect class is the base class for creating

    custom GLSL shader effects in a QGraphicsScene.

    \since 4.6

    \ingroup multimedia

    \ingroup graphicsview-api

    The specific effect is defined by a fragment of GLSL source code

    supplied to setPixelShaderFragment().  This source code must define a

    function with the signature

    \c{lowp vec4 customShader(lowp sampler2D imageTexture, highp vec2 textureCoords)}

    that returns the source pixel value

    to use in the paint engine's shader program.  The shader fragment

    is linked with the regular shader code used by the GL2 paint engine

    to construct a complete QGLShaderProgram.

    The following example shader converts the incoming pixmap to

    grayscale and then applies a colorize operation using the

    \c effectColor value:

    \code

    static char const colorizeShaderCode[] =

        "uniform lowp vec4 effectColor;\n"

        "lowp vec4 customShader(lowp sampler2D imageTexture, highp vec2 textureCoords) {\n"

        "    vec4 src = texture2D(imageTexture, textureCoords);\n"

        "    float gray = dot(src.rgb, vec3(0.212671, 0.715160, 0.072169));\n"

        "    vec4 colorize = 1.0-((1.0-gray)*(1.0-effectColor));\n"

        "    return vec4(colorize.rgb, src.a);\n"

        "}";

    \endcode

    To use this shader code, it is necessary to define a subclass

    of QGraphicsShaderEffect as follows:

    \code

    class ColorizeEffect : public QGraphicsShaderEffect

    {

        Q_OBJECT

    public:

        ColorizeEffect(QObject *parent = 0)

            : QGraphicsShaderEffect(parent), color(Qt::black)

        {

            setPixelShaderFragment(colorizeShaderCode);

        }

        QColor effectColor() const { return color; }

        void setEffectColor(const QColor& c)

        {

            color = c;

            setUniformsDirty();

        }

    protected:

        void setUniforms(QGLShaderProgram *program)

        {

            program->setUniformValue("effectColor", color);

        }

    private:

        QColor color;

    };

    \endcode

    The setUniforms() function is called when the effect is about

    to be used for drawing to give the subclass the opportunity to

    set effect-specific uniform variables.

    QGraphicsShaderEffect is only supported when the GL2 paint engine

    is in use.  When any other paint engine is in use (GL1, raster, etc),

    the drawItem() method will draw its item argument directly with

    no effect applied.

    \sa QGraphicsEffect

*/

static const char qglslDefaultImageFragmentShader[] = "\

    lowp vec4 customShader(lowp sampler2D imageTexture, highp vec2 textureCoords) { \

        return texture2D(imageTexture, textureCoords); \

    }\n";

#ifdef QGL_HAVE_CUSTOM_SHADERS

class QGLCustomShaderEffectStage : public QGLCustomShaderStage

{

public:

    QGLCustomShaderEffectStage

            (QGraphicsShaderEffect *e, const QByteArray& source)

        : QGLCustomShaderStage(),

          effect(e)

    {

        setSource(source);

    }

    void setUniforms(QGLShaderProgram *program);

    QGraphicsShaderEffect *effect;

};

void QGLCustomShaderEffectStage::setUniforms(QGLShaderProgram *program)

{

    effect->setUniforms(program);

}

#endif

class QGraphicsShaderEffectPrivate : public QGraphicsEffectPrivate

{

    Q_DECLARE_PUBLIC(QGraphicsShaderEffect)

public:

    QGraphicsShaderEffectPrivate()

        : pixelShaderFragment(qglslDefaultImageFragmentShader)

#ifdef QGL_HAVE_CUSTOM_SHADERS

          , customShaderStage(0)

#endif

    {

    }

    QByteArray pixelShaderFragment;

#ifdef QGL_HAVE_CUSTOM_SHADERS

    QGLCustomShaderEffectStage *customShaderStage;

#endif

};

/*#

    Constructs a shader effect and attaches it to \a parent.

*/

QGraphicsShaderEffect::QGraphicsShaderEffect(QObject *parent)

    : QGraphicsEffect(*new QGraphicsShaderEffectPrivate(), parent)

{

}

/*#

    Destroys this shader effect.

*/

QGraphicsShaderEffect::~QGraphicsShaderEffect()

{

#ifdef QGL_HAVE_CUSTOM_SHADERS

    Q_D(QGraphicsShaderEffect);

    delete d->customShaderStage;

#endif

}

/*#

    Returns the source code for the pixel shader fragment for

    this shader effect.  The default is a shader that copies

    its incoming pixmap directly to the output with no effect

    applied.

    \sa setPixelShaderFragment()

*/

QByteArray QGraphicsShaderEffect::pixelShaderFragment() const

{

    Q_D(const QGraphicsShaderEffect);

    return d->pixelShaderFragment;

}

/*#

    Sets the source code for the pixel shader fragment for

    this shader effect to \a code.

    The \a code must define a GLSL function with the signature

    \c{lowp vec4 customShader(lowp sampler2D imageTexture, highp vec2 textureCoords)}

    that returns the source pixel value to use in the paint engine's

    shader program.  The following is the default pixel shader fragment,

    which draws a pixmap with no effect applied:

    \code

    lowp vec4 customShader(lowp sampler2D imageTexture, highp vec2 textureCoords) {

        return texture2D(imageTexture, textureCoords);

    }

    \endcode

    \sa pixelShaderFragment(), setUniforms()

*/

void QGraphicsShaderEffect::setPixelShaderFragment(const QByteArray& code)

{

    Q_D(QGraphicsShaderEffect);

    if (d->pixelShaderFragment != code) {

        d->pixelShaderFragment = code;

#ifdef QGL_HAVE_CUSTOM_SHADERS

        delete d->customShaderStage;

        d->customShaderStage = 0;

#endif

    }

}

/*#

    \reimp

*/

{

    Q_D(QGraphicsShaderEffect);

#ifdef QGL_HAVE_CUSTOM_SHADERS

    // Set the custom shader on the paint engine.  The setOnPainter()

    // call may fail if the paint engine is not GL2.  In that case,

    // we fall through to drawing the pixmap normally.

    if (!d->customShaderStage) {

        d->customShaderStage = new QGLCustomShaderEffectStage

            (this, d->pixelShaderFragment);

    }

    bool usingShader = d->customShaderStage->setOnPainter(painter);

    QPoint offset;

        // No point in drawing in device coordinates (pixmap will be scaled anyways).

        painter->drawPixmap(offset, pixmap);

    } else {

        // Draw pixmap in device coordinates to avoid pixmap scaling.

        QTransform restoreTransform = painter->worldTransform();

        painter->setWorldTransform(QTransform());

        painter->drawPixmap(offset, pixmap);

        painter->setWorldTransform(restoreTransform);

    }

    // Remove the custom shader to return to normal painting operations.

    if (usingShader)

        d->customShaderStage->removeFromPainter(painter);

#else

#endif

}

/*#

    Sets the custom uniform variables on this shader effect to

    be dirty.  The setUniforms() function will be called the next

    time the shader program corresponding to this effect is used.

    This function is typically called by subclasses when an

    effect-specific parameter is changed by the application.

    \sa setUniforms()

*/

void QGraphicsShaderEffect::setUniformsDirty()

{

#ifdef QGL_HAVE_CUSTOM_SHADERS

    Q_D(QGraphicsShaderEffect);

    if (d->customShaderStage)

        d->customShaderStage->setUniformsDirty();

#endif

}

/*#

    Sets custom uniform variables on the current GL context when

    \a program is about to be used by the paint engine.

    This function should be overridden if the shader set with

    setPixelShaderFragment() has additional parameters beyond

    those that the paint engine normally sets itself.

    \sa setUniformsDirty()

*/

void QGraphicsShaderEffect::setUniforms(QGLShaderProgram *program)

{

    Q_UNUSED(program);

}

QT_END_NAMESPACE