Modernize rasterwindow/openglwindow examples to use requestUpdate()

Change-Id: Ib8d0c42db7343247d0431ea008eb17da9ee98f4d
Reviewed-by: Laszlo Agocs <laszlo.agocs@qt.io>

examples/gui/doc/src/openglwindow.qdoc

@@ -34,6 +34,9 @@
 
     \image openglwindow-example.png Screenshot of the OpenGLWindow example
 
+    \note This is a low level example of how to use QWindow with OpenGL.
+    In practice you should consider using the higher level QOpenGLWindow class.
+
     \section1 OpenGLWindow Super Class
 
     Our OpenGLWindow class acts as an API which is then subclassed to do the
@@ -70,9 +73,8 @@
 
     \snippet openglwindow/openglwindow.cpp 2
 
-    The renderLater() function simply puts an update request event on
+    The renderLater() function simply calls QWindow::requestUpdate() to schedule
-    the event loop, which leads to renderNow() being called once the event
+    an update for when the system is ready to repaint.
-    gets processed.
 
     We also call renderNow() when we get an expose event. The exposeEvent() is
     the notification to the window that its exposure, meaning visibility, on
@@ -109,11 +111,11 @@
     \l {http://www.khronos.org/registry/gles/}{Khronos OpenGL ES API Registry}.
 
     If animation has been enabled with OpenGLWindow::setAnimating(true), we
-    call renderLater() to put another update request on the event loop.
+    call renderLater() to schedule another update request.
 
     \snippet openglwindow/openglwindow.cpp 4
 
-    Enabling animation also triggers an update request as shown in the
+    Enabling animation also schedules an update request as shown in the
     following code snippet.
 
     \snippet openglwindow/openglwindow.cpp 5

examples/gui/doc/src/rasterwindow.qdoc

@@ -143,19 +143,16 @@
     \snippet rasterwindow/rasterwindow.cpp 6
 
     We went through a few places where the window needed to repainted
-    immediately. There are some cases where this is not desierable,
+    immediately. There are some cases where this is not desirable,
     but rather let the application return to the event loop and
-    later. We acheive this by posting an even to ourself which will
+    schedule the repaint for later. We achieve this by requesting
-    then be delivered when the application returns to the \l
+    an update, using QWindow::requestUpdate(), which will then be
-    QGuiApplication event loop. To avoid posting new requests when one
+    delivered when the system is ready to repaint.
-    is already pending, we store this state in the \c m_update_pending
-    variable.
 
     \snippet rasterwindow/rasterwindow.cpp 7
 
     We reimplement the virtual \l QObject::event() function to handle
-    the update event we posted to ourselves. When the event comes in
+    the update event. When the event comes in we call renderNow() to
-    we reset the pending update flag and call renderNow() to render
+    render the window right away.
-    the window right away.
 
   */

examples/gui/openglwindow/openglwindow.cpp

@@ -59,7 +59,6 @@
 //! [1]
 OpenGLWindow::OpenGLWindow(QWindow *parent)
     : QWindow(parent)
-    , m_update_pending(false)
     , m_animating(false)
     , m_context(0)
     , m_device(0)
@@ -99,17 +98,13 @@ void OpenGLWindow::render()
 //! [3]
 void OpenGLWindow::renderLater()
 {
-    if (!m_update_pending) {
+    requestUpdate();
-        m_update_pending = true;
-        QCoreApplication::postEvent(this, new QEvent(QEvent::UpdateRequest));
-    }
 }
 
 bool OpenGLWindow::event(QEvent *event)
 {
     switch (event->type()) {
     case QEvent::UpdateRequest:
-        m_update_pending = false;
         renderNow();
         return true;
     default:

examples/gui/openglwindow/openglwindow.h

@@ -82,7 +82,6 @@ protected:
     void exposeEvent(QExposeEvent *event) override;
 
 private:
-    bool m_update_pending;
     bool m_animating;
 
     QOpenGLContext *m_context;

examples/gui/rasterwindow/rasterwindow.cpp

@@ -53,7 +53,6 @@
 //! [1]
 RasterWindow::RasterWindow(QWindow *parent)
     : QWindow(parent)
-    , m_update_pending(false)
 {
     create();
     m_backingStore = new QBackingStore(this);
@@ -68,7 +67,6 @@ RasterWindow::RasterWindow(QWindow *parent)
 bool RasterWindow::event(QEvent *event)
 {
     if (event->type() == QEvent::UpdateRequest) {
-        m_update_pending = false;
         renderNow();
         return true;
     }
@@ -79,10 +77,7 @@ bool RasterWindow::event(QEvent *event)
 //! [6]
 void RasterWindow::renderLater()
 {
-    if (!m_update_pending) {
+    requestUpdate();
-        m_update_pending = true;
-        QCoreApplication::postEvent(this, new QEvent(QEvent::UpdateRequest));
-    }
 }
 //! [6]
 
@@ -99,9 +94,8 @@ void RasterWindow::resizeEvent(QResizeEvent *resizeEvent)
 //! [2]
 void RasterWindow::exposeEvent(QExposeEvent *)
 {
-    if (isExposed()) {
+    if (isExposed())
         renderNow();
-    }
 }
 //! [2]
 

examples/gui/rasterwindow/rasterwindow.h

@@ -74,7 +74,6 @@ protected:
 
 private:
     QBackingStore *m_backingStore;
-    bool m_update_pending;
 };
 //! [1]
 #endif // RASTERWINDOW_H

src/gui/kernel/qwindow.cpp

@@ -2175,11 +2175,14 @@ void QWindowPrivate::deliverUpdateRequest()
     Schedules a QEvent::UpdateRequest event to be delivered to this window.
 
     The event is delivered in sync with the display vsync on platforms
-    where this is possible. When driving animations, this function should
+    where this is possible. Otherwise, the event is delivered after a
-    be called once after drawing has completed.
+    delay of 5 ms. The additional time is there to give the event loop
+    a bit of idle time to gather system events, and can be overridden
+    using the QT_QPA_UPDATE_IDLE_TIME environment variable.
 
-    Calling this function multiple times will result in a single event
+    When driving animations, this function should be called once after drawing
-    being delivered to the window.
+    has completed. Calling this function multiple times will result in a single
+    event being delivered to the window.
 
     Subclasses of QWindow should reimplement event(), intercept the event and
     call the application's rendering code, then call the base class