Make rendernode suitable for public consumption

For non-OpenGL APIs the primary (and likely the only) way to add custom
rendering into the Qt Quick scene is via the render node. Other
approaches,like the before/afterRendering signals,
QQuickFramebufferObject, remain OpenGL-only. (although QQuickFramebufferObject
may get a multi-API replacement based on QSGRenderNode at a later time)

Note that this is not a generic 3D content integration enabler. It targets
creating 2D and 2.5D Quick items with custom rendering via the graphics
API in use.

Make QSGRenderNode public, enhance the docs a bit and add a releaseResources().
Add a QSGRendererInterface with a query function in QQuickWindow and
QSGEngine. The scenegraph adaptation can then return a custom implementation of
the interface. This will be necessary to query API-specific values, f.ex. the
ID3D12Device and ID3D12CommandList when running with the d3d12 backend.

The interface allows querying the API and void* resources. Resources that
we know about in advance are enum-based to prevent the
QPlatformNativeInterface-like ugliness of string keys.

Support is there in the batch renderer already, fix this up according to
the new public API, and implement the corresponding bits for the D3D12
renderer.

For D3D12, fix also an issue with QSGNode destruction where graphics resources
in use were attempted to be final-released without a proper wait.

The semantics of changedStates() in QSGRenderNode is changed so that it can be
called at any time, including before render(). This is very useful since we can
implement some state restoring in a more efficient manner.

Added a new example as well. Documentation for QSGRenderNode is heavily
expanded.

Change-Id: I4c4a261c55791d0e38743a784bc4c05a53b3462d
Reviewed-by: Andy Nichols <andy.nichols@qt.io>

1 files changed, 133 insertions, 0 deletions

diff --git a/examples/quick/scenegraph/rendernode/openglrenderer.cpp b/examples/quick/scenegraph/rendernode/openglrenderer.cpp
new file mode 100644
index 0000000000..e9c1be071c
--- /dev/null
+++ b/examples/quick/scenegraph/rendernode/openglrenderer.cpp
@@ -0,0 +1,133 @@
+/****************************************************************************
+**
+** Copyright (C) 2016 The Qt Company Ltd.
+** Contact: http://www.qt.io/licensing/
+**
+** This file is part of the examples of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:BSD$
+** You may use this file under the terms of the BSD license as follows:
+**
+** "Redistribution and use in source and binary forms, with or without
+** modification, are permitted provided that the following conditions are
+** met:
+**   * Redistributions of source code must retain the above copyright
+**     notice, this list of conditions and the following disclaimer.
+**   * Redistributions in binary form must reproduce the above copyright
+**     notice, this list of conditions and the following disclaimer in
+**     the documentation and/or other materials provided with the
+**     distribution.
+**   * Neither the name of The Qt Company Ltd nor the names of its
+**     contributors may be used to endorse or promote products derived
+**     from this software without specific prior written permission.
+**
+**
+** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include "openglrenderer.h"
+
+#ifndef QT_NO_OPENGL
+
+#include <QOpenGLShaderProgram>
+#include <QOpenGLBuffer>
+#include <QOpenGLFunctions>
+
+OpenGLRenderer::OpenGLRenderer(QQuickItem *item, QSGRenderNode *node)
+    : m_item(item),
+      m_node(node)
+{
+}
+
+void OpenGLRenderer::init()
+{
+    m_program = new QOpenGLShaderProgram;
+
+    static const char *vertexShaderSource =
+        "attribute highp vec4 posAttr;\n"
+        "attribute lowp vec4 colAttr;\n"
+        "varying lowp vec4 col;\n"
+        "uniform highp mat4 matrix;\n"
+        "void main() {\n"
+        "   col = colAttr;\n"
+        "   gl_Position = matrix * posAttr;\n"
+        "}\n";
+
+    static const char *fragmentShaderSource =
+        "varying lowp vec4 col;\n"
+        "void main() {\n"
+        "   gl_FragColor = col;\n"
+        "}\n";
+
+    m_program->addShaderFromSourceCode(QOpenGLShader::Vertex, vertexShaderSource);
+    m_program->addShaderFromSourceCode(QOpenGLShader::Fragment, fragmentShaderSource);
+    m_program->bindAttributeLocation("posAttr", 0);
+    m_program->bindAttributeLocation("colAttr", 1);
+    m_program->link();
+
+    m_matrixUniform = m_program->uniformLocation("matrix");
+
+    const int VERTEX_SIZE = 6 * sizeof(GLfloat);
+
+    // A fully featured renderer should also take inheritedOpacity() into account
+    // and blend, but ignore that for now.
+    static GLfloat colors[] = {
+        1.0f, 0.0f, 0.0f,
+        0.0f, 1.0f, 0.0f,
+        0.0f, 0.0f, 1.0f
+    };
+
+    m_vbo = new QOpenGLBuffer;
+    m_vbo->create();
+    m_vbo->bind();
+    m_vbo->allocate(VERTEX_SIZE + sizeof(colors));
+    m_vbo->write(VERTEX_SIZE, colors, sizeof(colors));
+    m_vbo->release();
+}
+
+OpenGLRenderer::~OpenGLRenderer()
+{
+    delete m_program;
+    delete m_vbo;
+}
+
+void OpenGLRenderer::render(const QSGRenderNode::RenderState *state)
+{
+    QOpenGLFunctions *f = QOpenGLContext::currentContext()->functions();
+
+    m_program->bind();
+    m_program->setUniformValue(m_matrixUniform, *state->projectionMatrix() * *m_node->matrix());
+
+    m_vbo->bind();
+
+    QPointF p0(m_item->width() - 1, m_item->height() - 1);
+    QPointF p1(0, 0);
+    QPointF p2(0, m_item->height() - 1);
+
+    GLfloat vertices[6] = { GLfloat(p0.x()), GLfloat(p0.y()),
+                            GLfloat(p1.x()), GLfloat(p1.y()),
+                            GLfloat(p2.x()), GLfloat(p2.y()) };
+    m_vbo->write(0, vertices, sizeof(vertices));
+
+    m_program->setAttributeBuffer(0, GL_FLOAT, 0, 2);
+    m_program->setAttributeBuffer(1, GL_FLOAT, sizeof(vertices), 3);
+    m_program->enableAttributeArray(0);
+    m_program->enableAttributeArray(1);
+
+    f->glDrawArrays(GL_TRIANGLES, 0, 3);
+}
+
+#endif // QT_NO_OPENGL