QOpenGLTextureBlitter

private api, but useful for 2d gui code that suddenly finds itself
needing to get a set of textures onto some fbo

I didn't want to include ARB_copy_image since it looks like its from
texture/renderbuffer -> texture/renderbuffer while this class implies
texture -> write fbo. We could wrap ARB_copy_image in QOpenGLTexture or
some other class or we can add it later.

I have not added any QOpenGLTexture functions since this class opperates
on the GLuint identifier. We can add overloads later.

Change-Id: I3e565b33466c1c183a249a33c3e82c6786debd55
Reviewed-by: Paul Olav Tvete <paul.tvete@digia.com>

3 files changed, 484 insertions, 2 deletions

diff --git a/src/gui/opengl/opengl.pri b/src/gui/opengl/opengl.pri
index d249b855f5..cadba26797 100644
--- a/src/gui/opengl/opengl.pri
+++ b/src/gui/opengl/opengl.pri
@@ -31,7 +31,8 @@ contains(QT_CONFIG, opengl)|contains(QT_CONFIG, opengles2) {
                opengl/qopenglversionfunctions.h \
                opengl/qopenglversionfunctionsfactory_p.h \
                opengl/qopenglvertexarrayobject.h \
-               opengl/qopengldebug.h
+               opengl/qopengldebug.h \
+               opengl/qopengltextureblitter_p.h
 
     SOURCES += opengl/qopengl.cpp \
                opengl/qopenglfunctions.cpp \
@@ -51,7 +52,8 @@ contains(QT_CONFIG, opengl)|contains(QT_CONFIG, opengles2) {
                opengl/qopenglversionfunctions.cpp \
                opengl/qopenglversionfunctionsfactory.cpp \
                opengl/qopenglvertexarrayobject.cpp \
-               opengl/qopengldebug.cpp
+               opengl/qopengldebug.cpp \
+               opengl/qopengltextureblitter.cpp
 
     !wince* {
         HEADERS += opengl/qopengltexture.h \
diff --git a/src/gui/opengl/qopengltextureblitter.cpp b/src/gui/opengl/qopengltextureblitter.cpp
new file mode 100644
index 0000000000..1fbdd20207
--- /dev/null
+++ b/src/gui/opengl/qopengltextureblitter.cpp
@@ -0,0 +1,394 @@
+/****************************************************************************
+**
+** Copyright (C) 2014 Digia Plc and/or its subsidiary(-ies).
+** Contact: http://www.qt-project.org/legal
+**
+** This file is part of the QtGui module of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and Digia.  For licensing terms and
+** conditions see http://qt.digia.com/licensing.  For further information
+** use the contact form at http://qt.digia.com/contact-us.
+**
+** 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, Digia gives you certain additional
+** rights.  These rights are described in the Digia Qt LGPL Exception
+** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 3.0 as published by the Free Software
+** Foundation and appearing in the file LICENSE.GPL included in the
+** packaging of this file.  Please review the following information to
+** ensure the GNU General Public License version 3.0 requirements will be
+** met: http://www.gnu.org/copyleft/gpl.html.
+**
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include "qopengltextureblitter_p.h"
+
+#include <QtGui/QOpenGLBuffer>
+#include <QtGui/QOpenGLShaderProgram>
+#include <QtGui/QOpenGLVertexArrayObject>
+#include <QtGui/QOpenGLContext>
+
+QT_BEGIN_NAMESPACE
+
+static const char vertex_shader150[] =
+    "#version 150 core\n"
+    "in vec3 vertexCoord;"
+    "in vec2 textureCoord;"
+    "out vec2 uv;"
+    "uniform mat4 vertexTransform;"
+    "uniform mat3 textureTransform;"
+    "void main() {"
+    "   uv = (textureTransform * vec3(textureCoord,1.0)).xy;"
+    "   gl_Position = vertexTransform * vec4(vertexCoord,1.0);"
+    "}";
+
+static const char fragment_shader150[] =
+    "#version 150 core\n"
+    "in vec2 uv;"
+    "out vec4 fragcolor;"
+    "uniform sampler2D textureSampler;"
+    "uniform bool swizzle;"
+    "void main() {"
+    "   if (swizzle) {"
+    "       fragcolor = texture(textureSampler, uv).bgra;"
+    "   } else {"
+    "       fragcolor = texture(textureSampler,uv);"
+    "   }"
+    "}";
+
+static const char vertex_shader[] =
+    "attribute highp vec3 vertexCoord;"
+    "attribute highp vec2 textureCoord;"
+    "varying highp vec2 uv;"
+    "uniform highp mat4 vertexTransform;"
+    "uniform highp mat3 textureTransform;"
+    "void main() {"
+    "   uv = (textureTransform * vec3(textureCoord,1.0)).xy;"
+    "   gl_Position = vertexTransform * vec4(vertexCoord,1.0);"
+    "}";
+
+static const char fragment_shader[] =
+    "varying highp vec2 uv;"
+    "uniform sampler2D textureSampler;"
+    "uniform bool swizzle;"
+    "void main() {"
+    "   if (swizzle) {"
+    "       gl_FragColor = texture2D(textureSampler, uv).bgra;"
+    "   } else {"
+    "       gl_FragColor = texture2D(textureSampler,uv);"
+    "   }"
+    "}";
+
+static const GLfloat vertex_buffer_data[] = {
+        -1,-1, 0,
+        -1, 1, 0,
+         1,-1, 0,
+        -1, 1, 0,
+         1,-1, 0,
+         1, 1, 0
+};
+
+static const GLfloat texture_buffer_data[] = {
+        0, 0,
+        0, 1,
+        1, 0,
+        0, 1,
+        1, 0,
+        1, 1
+};
+
+class TextureBinder
+{
+public:
+    TextureBinder(GLuint textureId)
+    {
+        glBindTexture(GL_TEXTURE_2D, textureId);
+    }
+    ~TextureBinder()
+    {
+        glBindTexture(GL_TEXTURE_2D, 0);
+    }
+};
+
+class QOpenGLTextureBlitterPrivate
+{
+public:
+    enum TextureMatrixUniform {
+        User,
+        Identity,
+        IdentityFlipped
+    };
+
+    QOpenGLTextureBlitterPrivate()
+        : program(0)
+        , vertexCoordAttribPos(0)
+        , vertexTransformUniformPos(0)
+        , textureCoordAttribPos(0)
+        , textureTransformUniformPos(0)
+        , swizzle(false)
+        , swizzleOld(false)
+        , textureMatrixUniformState(User)
+        , vao(new QOpenGLVertexArrayObject())
+    { }
+
+    void blit(GLuint texture, const QMatrix4x4 &vertexTransform, const QMatrix3x3 &textureTransform);
+    void blit(GLuint texture, const QMatrix4x4 &vertexTransform, QOpenGLTextureBlitter::Origin origin);
+
+    void prepareProgram(const QMatrix4x4 &vertexTransform)
+    {
+        vertexBuffer.bind();
+        program->setAttributeBuffer(vertexCoordAttribPos, GL_FLOAT, 0, 3, 0);
+        program->enableAttributeArray(vertexCoordAttribPos);
+        vertexBuffer.release();
+
+        program->setUniformValue(vertexTransformUniformPos, vertexTransform);
+
+        textureBuffer.bind();
+        program->setAttributeBuffer(textureCoordAttribPos, GL_FLOAT, 0, 2, 0);
+        program->enableAttributeArray(textureCoordAttribPos);
+        textureBuffer.release();
+
+        if (swizzle != swizzleOld) {
+            program->setUniformValue(swizzleUniformPos, swizzle);
+            swizzleOld = swizzle;
+        }
+    }
+
+    QOpenGLBuffer vertexBuffer;
+    QOpenGLBuffer textureBuffer;
+    QScopedPointer<QOpenGLShaderProgram> program;
+    GLuint vertexCoordAttribPos;
+    GLuint vertexTransformUniformPos;
+    GLuint textureCoordAttribPos;
+    GLuint textureTransformUniformPos;
+    GLuint swizzleUniformPos;
+    bool swizzle;
+    bool swizzleOld;
+    TextureMatrixUniform textureMatrixUniformState;
+    QScopedPointer<QOpenGLVertexArrayObject> vao;
+};
+
+void QOpenGLTextureBlitterPrivate::blit(GLuint texture,
+                                        const QMatrix4x4 &vertexTransform,
+                                        const QMatrix3x3 &textureTransform)
+{
+    TextureBinder binder(texture);
+    prepareProgram(vertexTransform);
+
+    program->setUniformValue(textureTransformUniformPos, textureTransform);
+    textureMatrixUniformState = User;
+
+    glDrawArrays(GL_TRIANGLES, 0, 6);
+}
+
+void QOpenGLTextureBlitterPrivate::blit(GLuint texture,
+                                        const QMatrix4x4 &vertexTransform,
+                                        QOpenGLTextureBlitter::Origin origin)
+{
+    TextureBinder binder(texture);
+    prepareProgram(vertexTransform);
+
+    if (origin == QOpenGLTextureBlitter::OriginTopLeft) {
+        if (textureMatrixUniformState != IdentityFlipped) {
+            QMatrix3x3 flipped;
+            flipped(1,1) = -1;
+            program->setUniformValue(textureTransformUniformPos, flipped);
+            textureMatrixUniformState = IdentityFlipped;
+        }
+    } else if (textureMatrixUniformState != Identity) {
+        program->setUniformValue(textureTransformUniformPos, QMatrix3x3());
+        textureMatrixUniformState = Identity;
+    }
+
+    glDrawArrays(GL_TRIANGLES, 0, 6);
+}
+
+QOpenGLTextureBlitter::QOpenGLTextureBlitter()
+    : d_ptr(new QOpenGLTextureBlitterPrivate)
+{
+}
+
+QOpenGLTextureBlitter::~QOpenGLTextureBlitter()
+{
+}
+
+bool QOpenGLTextureBlitter::create()
+{
+    QOpenGLContext *currentContext = QOpenGLContext::currentContext();
+    if (!currentContext)
+        return false;
+
+    Q_D(QOpenGLTextureBlitter);
+
+    d->vao->create();
+    d->vao->bind();
+
+    if (d->program)
+        return true;
+
+    d->program.reset(new QOpenGLShaderProgram());
+
+    QSurfaceFormat format = currentContext->format();
+
+    if (format.profile() == QSurfaceFormat::CoreProfile && format.version() >= qMakePair(3,2)) {
+        d->program->addShaderFromSourceCode(QOpenGLShader::Vertex, vertex_shader150);
+        d->program->addShaderFromSourceCode(QOpenGLShader::Fragment, fragment_shader150);
+    } else {
+        d->program->addShaderFromSourceCode(QOpenGLShader::Vertex, vertex_shader);
+        d->program->addShaderFromSourceCode(QOpenGLShader::Fragment, fragment_shader);
+    }
+    d->program->link();
+    if (!d->program->isLinked()) {
+        qWarning() << Q_FUNC_INFO << "Could not link shader program:\n" << d->program->log();
+        return false;
+    }
+
+    d->program->bind();
+
+    d->vertexBuffer.create();
+    d->vertexBuffer.bind();
+    d->vertexBuffer.allocate(vertex_buffer_data, sizeof(vertex_buffer_data) * sizeof(vertex_buffer_data[0]));
+    d->vertexBuffer.release();
+
+    d->textureBuffer.create();
+    d->textureBuffer.bind();
+    d->textureBuffer.allocate(texture_buffer_data, sizeof(texture_buffer_data) * sizeof(texture_buffer_data[0]));
+    d->textureBuffer.release();
+
+    d->vertexCoordAttribPos = d->program->attributeLocation("vertexCoord");
+    d->vertexTransformUniformPos = d->program->uniformLocation("vertexTransform");
+    d->textureCoordAttribPos = d->program->attributeLocation("textureCoord");
+    d->textureTransformUniformPos = d->program->uniformLocation("textureTransform");
+    d->swizzleUniformPos = d->program->uniformLocation("swizzle");
+
+    d->program->setUniformValue(d->swizzleUniformPos,false);
+
+    d->vao->release();
+
+    return true;
+}
+
+void QOpenGLTextureBlitter::destroy()
+{
+    Q_D(QOpenGLTextureBlitter);
+    d->program.reset();
+    d->vertexBuffer.destroy();
+    d->textureBuffer.destroy();
+    d->vao.reset();
+}
+
+void QOpenGLTextureBlitter::bind()
+{
+    Q_D(QOpenGLTextureBlitter);
+
+    d->vao->bind();
+
+    d->program->bind();
+
+    d->vertexBuffer.bind();
+    d->program->setAttributeBuffer(d->vertexCoordAttribPos, GL_FLOAT, 0, 3, 0);
+    d->program->enableAttributeArray(d->vertexCoordAttribPos);
+    d->vertexBuffer.release();
+
+    d->textureBuffer.bind();
+    d->program->setAttributeBuffer(d->textureCoordAttribPos, GL_FLOAT, 0, 2, 0);
+    d->program->enableAttributeArray(d->textureCoordAttribPos);
+    d->textureBuffer.release();
+}
+
+void QOpenGLTextureBlitter::release()
+{
+    Q_D(QOpenGLTextureBlitter);
+    d->program->release();
+    d->vao->release();
+}
+
+void QOpenGLTextureBlitter::setSwizzleRB(bool swizzle)
+{
+    Q_D(QOpenGLTextureBlitter);
+    d->swizzle = swizzle;
+}
+
+void QOpenGLTextureBlitter::blit(GLuint texture,
+                                 const QMatrix4x4 &targetTransform,
+                                 Origin sourceOrigin)
+{
+    Q_D(QOpenGLTextureBlitter);
+    d->blit(texture,targetTransform, sourceOrigin);
+}
+
+void QOpenGLTextureBlitter::blit(GLuint texture,
+                                 const QMatrix4x4 &targetTransform,
+                                 const QMatrix3x3 &sourceTransform)
+{
+    Q_D(QOpenGLTextureBlitter);
+    d->blit(texture, targetTransform, sourceTransform);
+}
+
+QMatrix4x4 QOpenGLTextureBlitter::targetTransform(const QRectF &target,
+                                                  const QRect &viewport,
+                                                  Origin origin)
+{
+    qreal x_scale = target.size().width() / viewport.width();
+    qreal y_scale = target.size().height() / viewport.height();
+
+    const QPointF relative_to_viewport = target.topLeft() - viewport.topLeft();
+    qreal x_translate = ((relative_to_viewport.x() / viewport.width()) + (x_scale / 2)) * 2 - 1;
+    qreal y_translate = ((relative_to_viewport.y() / viewport.height()) + (y_scale / 2)) * 2 - 1;
+
+    if (origin == OriginTopLeft) {
+        y_translate = -y_translate;
+    }
+
+    QMatrix4x4 vertexMatrix;
+
+    vertexMatrix.translate(x_translate, y_translate);
+    vertexMatrix.scale(x_scale, y_scale);
+    return vertexMatrix;
+}
+
+QMatrix3x3 QOpenGLTextureBlitter::sourceTransform(const QRectF &subTexture,
+                                                  const QSize &textureSize,
+                                                  Origin origin)
+{
+    qreal x_scale = subTexture.width() / textureSize.width();
+    qreal y_scale = subTexture.height() / textureSize.height();
+
+    const QPointF topLeft = subTexture.topLeft();
+    qreal x_translate = topLeft.x() / textureSize.width();
+    qreal y_translate = topLeft.y() / textureSize.height();
+
+    if (origin == OriginTopLeft) {
+        y_translate += (y_translate * 2) + y_scale;
+        y_scale = y_scale - 1;
+    }
+
+    QMatrix3x3 matrix;
+    matrix(0,2) = x_translate;
+    matrix(1,2) = y_translate;
+
+    matrix(0,0) = x_scale;
+    matrix(1,1) = y_scale;
+
+    return matrix;
+}
+
+QT_END_NAMESPACE
diff --git a/src/gui/opengl/qopengltextureblitter_p.h b/src/gui/opengl/qopengltextureblitter_p.h
new file mode 100644
index 0000000000..5164d8630e
--- /dev/null
+++ b/src/gui/opengl/qopengltextureblitter_p.h
@@ -0,0 +1,86 @@
+/****************************************************************************
+**
+** Copyright (C) 2014 Digia Plc and/or its subsidiary(-ies).
+** Contact: http://www.qt-project.org/legal
+**
+** This file is part of the QtGui module of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and Digia.  For licensing terms and
+** conditions see http://qt.digia.com/licensing.  For further information
+** use the contact form at http://qt.digia.com/contact-us.
+**
+** 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, Digia gives you certain additional
+** rights.  These rights are described in the Digia Qt LGPL Exception
+** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 3.0 as published by the Free Software
+** Foundation and appearing in the file LICENSE.GPL included in the
+** packaging of this file.  Please review the following information to
+** ensure the GNU General Public License version 3.0 requirements will be
+** met: http://www.gnu.org/copyleft/gpl.html.
+**
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#ifndef QOPENGLTEXTUREBLITTER_P_H
+#define QOPENGLTEXTUREBLITTER_P_H
+
+#include <QtGui/qopengl.h>
+#include <QtGui/QMatrix3x3>
+
+QT_BEGIN_NAMESPACE
+
+class QOpenGLTextureBlitterPrivate;
+
+
+class Q_GUI_EXPORT QOpenGLTextureBlitter
+{
+public:
+    QOpenGLTextureBlitter();
+    ~QOpenGLTextureBlitter();
+
+    enum Origin {
+        OriginBottomLeft,
+        OriginTopLeft
+    };
+
+    bool create();
+    void destroy();
+
+    void bind();
+    void release();
+
+    void setSwizzleRB(bool swizzle);
+
+    void blit(GLuint texture, const QMatrix4x4 &targetTransform, Origin sourceOrigin);
+    void blit(GLuint texture, const QMatrix4x4 &targetTransform, const QMatrix3x3 &sourceTransform);
+
+    static QMatrix4x4 targetTransform(const QRectF &target, const QRect &viewport, Origin origin);
+    static QMatrix3x3 sourceTransform(const QRectF &subTexture, const QSize &textureSize, Origin origin);
+
+private:
+    Q_DISABLE_COPY(QOpenGLTextureBlitter);
+    Q_DECLARE_PRIVATE(QOpenGLTextureBlitter);
+    QScopedPointer<QOpenGLTextureBlitterPrivate> d_ptr;
+};
+
+QT_END_NAMESPACE
+
+#endif //QOPENGLTEXTUREBLITTER_P_H