Docs for QSGimpleMaterialShader

Change-Id: I769eb68a1703a2cc7379af702fb888d3e9697300
Reviewed-by: Geir Vattekar <geir.vattekar@nokia.com>

3 files changed, 215 insertions, 2 deletions

diff --git a/src/quick/scenegraph/coreapi/qsgmaterial.cpp b/src/quick/scenegraph/coreapi/qsgmaterial.cpp
index 9f0def4706..850db69948 100644
--- a/src/quick/scenegraph/coreapi/qsgmaterial.cpp
+++ b/src/quick/scenegraph/coreapi/qsgmaterial.cpp
@@ -47,7 +47,12 @@ QT_BEGIN_NAMESPACE
 
 /*!
     \class QSGMaterialShader
-    \brief The QSGMaterialShader class implements a material renders geometry.
+    \brief The QSGMaterialShader class represents an OpenGL shader program
+    in the renderer.
+
+    The QSGMaterialShader API is very low-level. A more convenient API, which
+    provides almost all the same features, is available through
+    QSGSimpleMaterialShader.
 
     The QSGMaterial and QSGMaterialShader form a tight relationship. For one
     scene graph (including nested graphs), there is one unique QSGMaterialShader
@@ -437,6 +442,10 @@ static void qt_print_material_count()
     \class QSGMaterial
     \brief The QSGMaterial class encapsulates rendering state for a shader program.
 
+    The QSGMaterial API is very low-level. A more convenient API, which
+    provides almost all the same features, is available through
+    QSGSimpleMaterialShader.
+
     The QSGMaterial and QSGMaterialShader subclasses form a tight relationship. For
     one scene graph (including nested graphs), there is one unique QSGMaterialShader
     instance which encapsulates the QOpenGLShaderProgram the scene graph uses
diff --git a/src/quick/scenegraph/scenegraph.pri b/src/quick/scenegraph/scenegraph.pri
index 4391ccb553..a58e9b46ad 100644
--- a/src/quick/scenegraph/scenegraph.pri
+++ b/src/quick/scenegraph/scenegraph.pri
@@ -18,7 +18,8 @@ SOURCES += \
     $$PWD/coreapi/qsgnode.cpp \
     $$PWD/coreapi/qsgnodeupdater.cpp \
     $$PWD/coreapi/qsgrenderer.cpp \
-    $$PWD/coreapi/qsgrendernode.cpp
+    $$PWD/coreapi/qsgrendernode.cpp \
+    scenegraph/util/qsgsimplematerial.cpp
 
 # Util API
 HEADERS += \
@@ -85,3 +86,4 @@ SOURCES += \
 
 
 
+
diff --git a/src/quick/scenegraph/util/qsgsimplematerial.cpp b/src/quick/scenegraph/util/qsgsimplematerial.cpp
new file mode 100644
index 0000000000..38758b433a
--- /dev/null
+++ b/src/quick/scenegraph/util/qsgsimplematerial.cpp
@@ -0,0 +1,202 @@
+/****************************************************************************
+**
+** Copyright (C) 2012 Nokia Corporation and/or its subsidiary(-ies).
+** Contact: http://www.qt-project.org/
+**
+** This file is part of the QtQml module of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** GNU Lesser General Public License Usage
+** 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.
+**
+** 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.
+**
+** Other Usage
+** Alternatively, this file may be used in accordance with the terms and
+** conditions contained in a signed written agreement between you and Nokia.
+**
+**
+**
+**
+**
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+/*!
+    \class QSGSimpleMaterialShader
+
+    \brief The QSGSimpleMaterialShader provides a convenient way of
+    building custom materials for the scene graph.
+
+    \inmodule QtQuick
+
+    Where the QSGMaterial and QSGMaterialShader API requires a bit of
+    boilerplate code to create a functioning material, the
+    QSGSimpleMaterialShader tries to hide some of this through the use
+    of templates.
+
+    QSGSimpleMaterialShader::vertexShader() and
+    QSGSimpleMaterialShader::fragmentShader() are used to specify the
+    actual shader source code. The names of the vertex attributes
+    should be listed in the QSGSimpleMaterialShader::attributes()
+
+    QSGSimpleMaterialShader::updateState() is used to push the material
+    state to the OpenGL shader program.
+
+    The actual OpenGL shader program is accessible through the
+    QSGSimpleMaterialShader::program() function.
+
+    Each QSGSimpleMaterialShader implementation operates on a unique
+    state struct. The state struct must be declared using the
+    \c {QSG_DECLARE_SIMPLE_SHADER} macro.
+
+    Here is a simple example of a custom solid-color:
+
+    \code
+    struct Color
+    {
+        float r, g, b, a;
+    };
+
+    class MinimalShader : public QSGSimpleMaterialShader<Color>
+    {
+        QSG_DECLARE_SIMPLE_SHADER(MinimalShader, Color)
+    public:
+
+        const char *vertexShader() const {
+            return
+            "attribute highp vec4 vertex;               \n"
+            "uniform highp mat4 qt_Matrix;              \n"
+            "void main() {                              \n"
+            "    gl_Position = qt_Matrix * vertex;      \n"
+            "}";
+        }
+
+        const char *fragmentShader() const {
+            return
+            "uniform lowp float qt_Opacity;             \n"
+            "uniform lowp vec4 color;                   \n"
+            "void main() {                              \n"
+            "    gl_FragColor = color * qt_Opacity;     \n"
+            "}";
+        }
+
+        QList<QByteArray> attributes() const {
+            return QList<QByteArray>() << "vertex";
+        }
+
+        void updateState(const Color *color, const Color *) {
+            program()->setUniformValue("color", color->r, color->g, color->b, color->a);
+        }
+
+    };
+    \endcode
+
+    Instances of materials using this shader can be created using the
+    createMaterial() function which will be defined by the
+    QSG_DECLARE_SIMPLE_SHADER macro.
+
+    \code
+        QSGSimpleMaterial<Color> *material = MinimalShader::createMaterial();
+        material->state()->r = 1;
+        material->state()->g = 0;
+        material->state()->b = 0;
+        material->state()->a = 1;
+
+        node->setMaterial(material);
+    \endcode
+
+    The scene graph will often try to find materials that have the
+    same or at least similar state so that these can be batched
+    together inside the renderer, which gives better performance. To
+    specify sortable material states, use
+    QSG_DECLARE_SIMPLE_COMPARABLE_SHADER instead of
+    QSG_DECLARE_SIMPLE_SHADER. The state struct must then also define
+    the function:
+
+    \code
+    int compare(const Type *other) const;
+    \endcode
+
+    \warning The QSGSimpleMaterialShader relies on template
+    instantiation to create a QSGMaterialType which the scene graph
+    renderer internally uses to identify this shader. For this reason,
+    the unique QSGSimpleMaterialShader implemenation must be
+    instantiated with a unique C++ type.
+
+ */
+
+/*!
+    \fn QList<QByteArray> QSGSimpleMaterialShader::attributes() const
+
+    Returns a list of names, declaring the vertex attributes in the
+    vertex shader.
+*/
+
+/*!
+    \fn void QSGSimpleMaterialShader::updateState(const State *newState, const State *oldState)
+
+    Called whenever the state of this shader should be updated,
+    typical for each new set of geometries being drawn.
+
+    Both the old and the new state are passed in so that the
+    implementation can compare and minimize the state changes when
+    applicable.
+*/
+
+/*!
+    \fn const char *QSGSimpleMaterialShader::vertexShader() const
+
+    Called when the shader is being initialized to get the vertex
+    shader source code.
+
+    The contents returned from this function should never change.
+*/
+
+
+/*!
+    \fn const char *QSGSimpleMaterialShader::fragmentShader() const
+
+    Called when the shader is being initialized to get the vertex
+    shader source code.
+
+    The contents returned from this function should never change.
+*/
+
+/*!
+    \class QSGSimpleMaterial
+
+    \brief The QSGSimpleMaterial class is a template generated class
+    used to store the state used with a QSGSimpleMateralShader.
+
+    The state of the material is accessible through the template
+    generated state() function.
+
+    \inmodule QtQuick
+
+    \sa QSGSimpleMaterialShader
+*/
+
+
+
+
+
+
+