Revert "Revert "Introducing QWindow::requestUpdate().""

This reverts commit c141ab0.

src/gui/kernel/qplatformwindow.cpp

@@ -566,6 +566,36 @@ QRect QPlatformWindow::initialGeometry(const QWindow *w,
     return rect;
 }
 
+/*!
+    Requests an QEvent::UpdateRequest event. The event will be
+    delivered to the QWindow.
+
+    QPlatformWindow subclasses can re-implement this function to
+    provide display refresh synchronized updates. The event
+    should be delivered using QWindowPrivate::deliverUpdateRequest()
+    to not get out of sync with the the internal state of QWindow.
+
+    The default implementation posts an UpdateRequest event to the
+    window after 5 ms. The additional time is there to give the event
+    loop a bit of idle time to gather system events.
+
+*/
+void QPlatformWindow::requestUpdate()
+{
+    static int timeout = -1;
+    if (timeout == -1) {
+        bool ok = false;
+        timeout = qgetenv("QT_QPA_UPDATE_IDLE_TIME").toInt(&ok);
+        if (!ok)
+            timeout = 5;
+    }
+
+    QWindow *w = window();
+    QWindowPrivate *wp = (QWindowPrivate *) QObjectPrivate::get(w);
+    Q_ASSERT(wp->updateTimer == 0);
+    wp->updateTimer = w->startTimer(timeout, Qt::PreciseTimer);
+}
+
 /*!
     \class QPlatformWindow
     \since 4.8

src/gui/kernel/qplatformwindow.h

@@ -136,6 +136,7 @@ class Q_GUI_EXPORT QPlatformWindow : public QPlatformSurface
     static QRect initialGeometry(const QWindow *w,
         const QRect &initialGeometry, int defaultWidth, int defaultHeight);
 
+    virtual void requestUpdate();
 protected:
     static QString formatWindowTitle(const QString &title, const QString &separator);
 

src/gui/kernel/qwindow.cpp

@@ -1945,12 +1945,56 @@ bool QWindow::event(QEvent *ev)
         break;
 #endif
 
+    case QEvent::Timer: {
+        Q_D(QWindow);
+        if (static_cast<QTimerEvent *>(ev)->timerId() == d->updateTimer) {
+            killTimer(d->updateTimer);
+            d->updateTimer = 0;
+            d->deliverUpdateRequest();
+        } else {
+            QObject::event(ev);
+        }
+        break;
+    }
+
     default:
         return QObject::event(ev);
     }
     return true;
 }
 
+void QWindowPrivate::deliverUpdateRequest()
+{
+    Q_Q(QWindow);
+    updateRequestPending = false;
+    QEvent request(QEvent::UpdateRequest);
+    QCoreApplication::sendEvent(q, &request);
+}
+
+/*!
+    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
+    be called once after drawing has completed.
+
+    Calling this function multiple times will result in a single event
+    being delivered to the window.
+
+    Subclasses of QWindow should reimplement QWindow::event(), intercept
+    the event and call the application's rendering code, then call the
+    base class implementation.
+*/
+
+void QWindow::requestUpdate()
+{
+    Q_D(QWindow);
+    if (d->updateRequestPending || !d->platformWindow)
+        return;
+    d->updateRequestPending = true;
+    d->platformWindow->requestUpdate();
+}
+
 /*!
     Override this to handle key press events (\a ev).
 

src/gui/kernel/qwindow.h

@@ -293,6 +293,8 @@ public Q_SLOTS:
 
     Q_REVISION(1) void alert(int msec);
 
+    Q_REVISION(3) void requestUpdate();
+
 Q_SIGNALS:
     void screenChanged(QScreen *screen);
     void modalityChanged(Qt::WindowModality modality);

src/gui/kernel/qwindow_p.h

@@ -94,6 +94,8 @@ class Q_GUI_EXPORT QWindowPrivate : public QObjectPrivate
         , maximumSize(QWINDOWSIZE_MAX, QWINDOWSIZE_MAX)
         , modality(Qt::NonModal)
         , blockedByModalWindow(false)
+        , updateRequestPending(false)
+        , updateTimer(0)
         , transientParent(0)
         , screen(0)
 #ifndef QT_NO_CURSOR
@@ -114,6 +116,8 @@ class Q_GUI_EXPORT QWindowPrivate : public QObjectPrivate
     void applyCursor();
 #endif
 
+    void deliverUpdateRequest();
+
     QPoint globalPosition() const {
         Q_Q(const QWindow);
         QPoint offset = q->position();
@@ -160,6 +164,9 @@ class Q_GUI_EXPORT QWindowPrivate : public QObjectPrivate
     Qt::WindowModality modality;
     bool blockedByModalWindow;
 
+    bool updateRequestPending;
+    int updateTimer;
+
     QPointer<QWindow> transientParent;
     QScreen *screen;