Fix hellowindow example

It seems this example never worked as expected.
It has a 'multiple' option which should show extra
windows with rendering taking place in different
thread, however although render is moved to other thread
render() function was never called in that thread.

Fix following things:
 * make rendering in other thread
 * stop requestUpdate if nothing is exposed
 * add timer so animation works at the same speed despite
   of number of windows (renderer B renders two windows)
 * wait for render to finish before triggering requestUdpate
 * remove mutex where not needed

Pick-to: 5.15
Change-Id: I420436bd28d0357534332dd55b088d634d906c14
Reviewed-by: Laszlo Agocs <laszlo.agocs@qt.io>

1 files changed, 21 insertions, 44 deletions

diff --git a/examples/opengl/hellowindow/hellowindow.cpp b/examples/opengl/hellowindow/hellowindow.cpp
index 1c1259de13..bde763dd70 100644
--- a/examples/opengl/hellowindow/hellowindow.cpp
+++ b/examples/opengl/hellowindow/hellowindow.cpp
@@ -54,11 +54,11 @@
 #include <QOpenGLFunctions>
 #include <QRandomGenerator>
 #include <qmath.h>
+#include <QElapsedTimer>
 
 Renderer::Renderer(const QSurfaceFormat &format, Renderer *share, QScreen *screen)
     : m_initialized(false)
     , m_format(format)
-    , m_currentWindow(0)
 {
     m_context = new QOpenGLContext(this);
     if (screen)
@@ -89,24 +89,33 @@ HelloWindow::HelloWindow(const QSharedPointer<Renderer> &renderer, QScreen *scre
     create();
 
     updateColor();
+
+    connect(renderer.data(), &Renderer::requestUpdate, this, &QWindow::requestUpdate);
 }
 
 void HelloWindow::exposeEvent(QExposeEvent *)
 {
-    m_renderer->setAnimating(this, isExposed());
     if (isExposed())
-        m_renderer->render();
+        render();
 }
 
 bool HelloWindow::event(QEvent *ev)
 {
-    if (ev->type() == QEvent::UpdateRequest) {
-        m_renderer->render();
-        requestUpdate();
-    }
+    if (ev->type() == QEvent::UpdateRequest && isExposed())
+        render();
     return QWindow::event(ev);
 }
 
+void HelloWindow::render()
+{
+    static QElapsedTimer timer;
+    if (!timer.isValid())
+        timer.start();
+    qreal a = (qreal)(((timer.elapsed() * 3) % 36000) / 100.0);
+    auto call = [this, r = m_renderer.data(), a, c = color()]() { r->render(this, a, c); };
+    QMetaObject::invokeMethod(m_renderer.data(), call);
+}
+
 void HelloWindow::mousePressEvent(QMouseEvent *)
 {
     updateColor();
@@ -114,14 +123,11 @@ void HelloWindow::mousePressEvent(QMouseEvent *)
 
 QColor HelloWindow::color() const
 {
-    QMutexLocker locker(&m_colorLock);
     return m_color;
 }
 
 void HelloWindow::updateColor()
 {
-    QMutexLocker locker(&m_colorLock);
-
     QColor colors[] =
     {
         QColor(100, 255, 0),
@@ -132,41 +138,13 @@ void HelloWindow::updateColor()
     m_colorIndex = 1 - m_colorIndex;
 }
 
-void Renderer::setAnimating(HelloWindow *window, bool animating)
-{
-    QMutexLocker locker(&m_windowLock);
-    if (m_windows.contains(window) == animating)
-        return;
-
-    if (animating) {
-        m_windows << window;
-        if (m_windows.size() == 1)
-            window->requestUpdate();
-    } else {
-        m_currentWindow = 0;
-        m_windows.removeOne(window);
-    }
-}
-
-void Renderer::render()
+void Renderer::render(HelloWindow *surface, qreal angle, const QColor &color)
 {
-    QMutexLocker locker(&m_windowLock);
-
-    if (m_windows.isEmpty())
-        return;
-
-    HelloWindow *surface = m_windows.at(m_currentWindow);
-    QColor color = surface->color();
-
-    m_currentWindow = (m_currentWindow + 1) % m_windows.size();
-
     if (!m_context->makeCurrent(surface))
         return;
 
     QSize viewSize = surface->size();
 
-    locker.unlock();
-
     if (!m_initialized) {
         initialize();
         m_initialized = true;
@@ -192,9 +170,9 @@ void Renderer::render()
     m_program->setAttributeBuffer(normalAttr, GL_FLOAT, verticesSize, 3);
 
     QMatrix4x4 modelview;
-    modelview.rotate(m_fAngle, 0.0f, 1.0f, 0.0f);
-    modelview.rotate(m_fAngle, 1.0f, 0.0f, 0.0f);
-    modelview.rotate(m_fAngle, 0.0f, 0.0f, 1.0f);
+    modelview.rotate(angle, 0.0f, 1.0f, 0.0f);
+    modelview.rotate(angle, 1.0f, 0.0f, 0.0f);
+    modelview.rotate(angle, 0.0f, 0.0f, 1.0f);
     modelview.translate(0.0f, -0.2f, 0.0f);
 
     m_program->setUniformValue(matrixUniform, modelview);
@@ -204,7 +182,7 @@ void Renderer::render()
 
     m_context->swapBuffers(surface);
 
-    m_fAngle += 1.0f;
+    emit requestUpdate();
 }
 
 Q_GLOBAL_STATIC(QMutex, initMutex)
@@ -250,7 +228,6 @@ void Renderer::initialize()
     matrixUniform = m_program->uniformLocation("matrix");
     colorUniform = m_program->uniformLocation("sourceColor");
 
-    m_fAngle = 0;
     createGeometry();
 
     m_vbo.create();