From 5786ac12f0a9901b0ddf7ee3c74cd1e87095306c Mon Sep 17 00:00:00 2001
From: Michal Klocek <michal.klocek@qt.io>
Date: Wed, 20 May 2020 11:05:17 +0200
Subject: 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>
---
 examples/opengl/hellowindow/hellowindow.cpp | 65 ++++++++++-------------------
 1 file changed, 21 insertions(+), 44 deletions(-)

(limited to 'examples/opengl/hellowindow/hellowindow.cpp')

diff --git a/examples/opengl/hellowindow/hellowindow.cpp b/examples/opengl/hellowindow/hellowindow.cpp
index 1c1259de137..bde763dd708 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();
-- 
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