Add a QQuickWidget - QQuickView comparison example

Besides serving as a side-by-side test tool for QQuickView and
QQuickWidget (including multisampling), it also demonstrates some
useful practices for rendering 3D content via QQuickFramebufferObject.

Done-with: Paul Olav Tvete <paul.tvete@digia.com>
Change-Id: Ie73e998ee91e32ef1535dd6f0f65c8a69addcc5e
Reviewed-by: Paul Olav Tvete <paul.tvete@digia.com>

1 files changed, 273 insertions, 0 deletions

diff --git a/examples/quick/quickwidgets/qquickviewcomparison/fbitem.cpp b/examples/quick/quickwidgets/qquickviewcomparison/fbitem.cpp
new file mode 100644
index 0000000000..3b9f2e97f3
--- /dev/null
+++ b/examples/quick/quickwidgets/qquickviewcomparison/fbitem.cpp
@@ -0,0 +1,273 @@
+/****************************************************************************
+**
+** Copyright (C) 2014 Digia Plc and/or its subsidiary(-ies).
+** Contact: http://www.qt-project.org/legal
+**
+** 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 Digia Plc and its Subsidiary(-ies) 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 "fbitem.h"
+#include <QOpenGLFramebufferObject>
+#include <QOpenGLFunctions>
+#include <QMatrix4x4>
+
+FbItem::FbItem(QQuickItem *parent)
+    : QQuickFramebufferObject(parent),
+      m_target(0, 0, -1),
+      m_syncState(AllNeedsSync),
+      m_multisample(false)
+{
+}
+
+QQuickFramebufferObject::Renderer *FbItem::createRenderer() const
+{
+    return new FbItemRenderer(m_multisample);
+}
+
+void FbItem::setEye(const QVector3D &v)
+{
+    if (m_eye != v) {
+        m_eye = v;
+        m_syncState |= CameraNeedsSync;
+        update();
+    }
+}
+
+void FbItem::setTarget(const QVector3D &v)
+{
+    if (m_target != v) {
+        m_target = v;
+        m_syncState |= CameraNeedsSync;
+        update();
+    }
+}
+
+void FbItem::setRotation(const QVector3D &v)
+{
+    if (m_rotation != v) {
+        m_rotation = v;
+        m_syncState |= RotationNeedsSync;
+        update();
+    }
+}
+
+int FbItem::swapSyncState()
+{
+    int s = m_syncState;
+    m_syncState = 0;
+    return s;
+}
+
+FbItemRenderer::FbItemRenderer(bool multisample)
+    : m_inited(false),
+      m_multisample(multisample),
+      m_dirty(DirtyAll)
+{
+    m_camera.setToIdentity();
+    m_baseWorld.setToIdentity();
+    m_baseWorld.translate(0, 0, -1);
+    m_world = m_baseWorld;
+}
+
+void FbItemRenderer::synchronize(QQuickFramebufferObject *qfbitem)
+{
+    FbItem *item = static_cast<FbItem *>(qfbitem);
+    int syncState = item->swapSyncState();
+    if (syncState & FbItem::CameraNeedsSync) {
+        m_camera.setToIdentity();
+        m_camera.lookAt(item->eye(), item->eye() + item->target(), QVector3D(0, 1, 0));
+        m_dirty |= DirtyCamera;
+    }
+    if (syncState & FbItem::RotationNeedsSync) {
+        m_rotation = item->rotation();
+        m_dirty |= DirtyWorld;
+    }
+}
+
+struct StateBinder
+{
+    StateBinder(FbItemRenderer *r)
+        : m_r(r) {
+        QOpenGLFunctions *f = QOpenGLContext::currentContext()->functions();
+        f->glEnable(GL_DEPTH_TEST);
+        f->glEnable(GL_CULL_FACE);
+        f->glDepthMask(GL_TRUE);
+        f->glDepthFunc(GL_LESS);
+        f->glFrontFace(GL_CCW);
+        f->glCullFace(GL_BACK);
+        m_r->m_program->bind();
+    }
+    ~StateBinder() {
+        QOpenGLFunctions *f = QOpenGLContext::currentContext()->functions();
+        m_r->m_program->release();
+        f->glDisable(GL_CULL_FACE);
+        f->glDisable(GL_DEPTH_TEST);
+    }
+    FbItemRenderer *m_r;
+};
+
+void FbItemRenderer::updateDirtyUniforms()
+{
+    if (m_dirty & DirtyProjection)
+        m_program->setUniformValue(m_projMatrixLoc, m_proj);
+
+    if (m_dirty & DirtyCamera)
+        m_program->setUniformValue(m_camMatrixLoc, m_camera);
+
+    if (m_dirty & DirtyWorld) {
+        m_program->setUniformValue(m_worldMatrixLoc, m_world);
+        QMatrix3x3 normalMatrix = m_world.normalMatrix();
+        m_program->setUniformValue(m_normalMatrixLoc, normalMatrix);
+    }
+
+    if (m_dirty & DirtyLight)
+        m_program->setUniformValue(m_lightPosLoc, QVector3D(0, 0, 70));
+
+    m_dirty = 0;
+}
+
+void FbItemRenderer::render()
+{
+    ensureInit();
+
+    QOpenGLVertexArrayObject::Binder vaoBinder(&m_vao);
+    if (!m_vao.isCreated())
+        setupVertexAttribs();
+
+    StateBinder state(this);
+
+    QOpenGLFunctions *f = QOpenGLContext::currentContext()->functions();
+    f->glClearColor(0, 0, 0, 0);
+    f->glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
+
+    if (m_dirty & DirtyWorld) {
+        m_world = m_baseWorld;
+        m_world.rotate(m_rotation.x(), 1, 0, 0);
+        m_world.rotate(m_rotation.y(), 0, 1, 0);
+        m_world.rotate(m_rotation.z(), 0, 0, 1);
+    }
+
+    updateDirtyUniforms();
+
+    f->glDrawArrays(GL_TRIANGLES, 0, m_logo.vertexCount());
+}
+
+QOpenGLFramebufferObject *FbItemRenderer::createFramebufferObject(const QSize &size)
+{
+    m_dirty |= DirtyProjection;
+    m_proj.setToIdentity();
+    m_proj.perspective(45.0f, GLfloat(size.width()) / size.height(), 0.01f, 100.0f);
+
+    QOpenGLFramebufferObjectFormat format;
+    format.setAttachment(QOpenGLFramebufferObject::CombinedDepthStencil);
+    format.setSamples(m_multisample ? 4 : 0);
+    return new QOpenGLFramebufferObject(size, format);
+}
+
+void FbItemRenderer::ensureInit()
+{
+    if (m_inited)
+        return;
+
+    m_inited = true;
+
+    initBuf();
+    initProgram();
+}
+
+void FbItemRenderer::initBuf()
+{
+    m_vao.create();
+    QOpenGLVertexArrayObject::Binder vaoBinder(&m_vao);
+
+    m_logoVbo.create();
+    m_logoVbo.bind();
+    m_logoVbo.allocate(m_logo.constData(), m_logo.count() * sizeof(GLfloat));
+
+    setupVertexAttribs();
+}
+
+void FbItemRenderer::setupVertexAttribs()
+{
+    m_logoVbo.bind();
+    QOpenGLFunctions *f = QOpenGLContext::currentContext()->functions();
+    f->glEnableVertexAttribArray(0);
+    f->glEnableVertexAttribArray(1);
+    f->glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 6 * sizeof(GLfloat), 0);
+    f->glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 6 * sizeof(GLfloat), reinterpret_cast<void *>(3 * sizeof(GLfloat)));
+    m_logoVbo.release();
+}
+
+static const char *vertexShaderSource =
+    "attribute vec4 vertex;\n"
+    "attribute vec3 normal;\n"
+    "varying vec3 vert;\n"
+    "varying vec3 vertNormal;\n"
+    "uniform mat4 projMatrix;\n"
+    "uniform mat4 camMatrix;\n"
+    "uniform mat4 worldMatrix;\n"
+    "uniform mat3 normalMatrix;\n"
+    "void main() {\n"
+    "   vert = vertex.xyz;\n"
+    "   vertNormal = normalMatrix * normal;\n"
+    "   gl_Position = projMatrix * camMatrix * worldMatrix * vertex;\n"
+    "}\n";
+
+static const char *fragmentShaderSource =
+    "varying highp vec3 vert;\n"
+    "varying highp vec3 vertNormal;\n"
+    "uniform highp vec3 lightPos;\n"
+    "void main() {\n"
+    "   highp vec3 L = normalize(lightPos - vert);\n"
+    "   highp float NL = max(dot(normalize(vertNormal), L), 0.0);\n"
+    "   highp vec3 color = vec3(0.39, 1.0, 0.0);\n"
+    "   highp vec3 col = clamp(color * 0.2 + color * 0.8 * NL, 0.0, 1.0);\n"
+    "   gl_FragColor = vec4(col, 1.0);\n"
+    "}\n";
+
+void FbItemRenderer::initProgram()
+{
+    m_program.reset(new QOpenGLShaderProgram);
+    m_program->addShaderFromSourceCode(QOpenGLShader::Vertex, vertexShaderSource);
+    m_program->addShaderFromSourceCode(QOpenGLShader::Fragment, fragmentShaderSource);
+    m_program->bindAttributeLocation("vertex", 0);
+    m_program->bindAttributeLocation("normal", 1);
+    m_program->link();
+    m_projMatrixLoc = m_program->uniformLocation("projMatrix");
+    m_camMatrixLoc = m_program->uniformLocation("camMatrix");
+    m_worldMatrixLoc = m_program->uniformLocation("worldMatrix");
+    m_normalMatrixLoc = m_program->uniformLocation("normalMatrix");
+    m_lightPosLoc = m_program->uniformLocation("lightPos");
+}