Got rid of Map / Unmap events in favor of Expose event.

Since change 2e4d8f67a871f2033 the need for Map and Unmap events has
gone away, as now the Expose event is used to notify the application
about when it can start rendering.

The Map and Unmap events weren't really used except by QWidget to set
the WA_Mapped flag, which we now set based on the expose / unexpose.

Also guarantee that a Resize event is always sent before the first
Expose, by re-introducing an asynchronous expose event handler. Since
an expose is required before rendering to a QWindow, show a warning if
QOpenGLContext::swapBuffers() or QBackingStore::flush() if called on a
window that has not received its first expose.

Change-Id: Ia6b609aa275d5b463b5011a96f2fd9bbe52e9bc4
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@nokia.com>

3 files changed, 19 insertions, 36 deletions

diff --git a/src/widgets/kernel/qwidget_qpa.cpp b/src/widgets/kernel/qwidget_qpa.cpp
index 3d23b04ddf..0f55646958 100644
--- a/src/widgets/kernel/qwidget_qpa.cpp
+++ b/src/widgets/kernel/qwidget_qpa.cpp
@@ -440,9 +440,9 @@ static inline QRect positionTopLevelWindow(QRect geometry, const QScreen *screen
 void QWidgetPrivate::show_sys()
 {
     Q_Q(QWidget);
-    q->setAttribute(Qt::WA_Mapped);
     if (q->testAttribute(Qt::WA_DontShowOnScreen)) {
         invalidateBuffer(q->rect());
+        q->setAttribute(Qt::WA_Mapped);
         return;
     }
 
@@ -483,8 +483,8 @@ void QWidgetPrivate::show_sys()
 void QWidgetPrivate::hide_sys()
 {
     Q_Q(QWidget);
-    q->setAttribute(Qt::WA_Mapped, false);
     deactivateWidgetCleanup();
+
     if (!q->isWindow()) {
         QWidget *p = q->parentWidget();
         if (p &&p->isVisible()) {
@@ -492,7 +492,12 @@ void QWidgetPrivate::hide_sys()
         }
         return;
     }
-    if (QWindow *window = q->windowHandle()) {
+
+    invalidateBuffer(q->rect());
+
+    if (q->testAttribute(Qt::WA_DontShowOnScreen)) {
+        q->setAttribute(Qt::WA_Mapped, false);
+    } else if (QWindow *window = q->windowHandle()) {
          window->setVisible(false);
     }
 }
diff --git a/src/widgets/kernel/qwidgetbackingstore.cpp b/src/widgets/kernel/qwidgetbackingstore.cpp
index b331356e66..2e9f072a0f 100644
--- a/src/widgets/kernel/qwidgetbackingstore.cpp
+++ b/src/widgets/kernel/qwidgetbackingstore.cpp
@@ -914,29 +914,7 @@ void QWidgetPrivate::scrollRect(const QRect &rect, int dx, int dy)
 
 static inline bool discardSyncRequest(QWidget *tlw, QTLWExtra *tlwExtra)
 {
-    if (!tlw || !tlwExtra)
-        return true;
-
-#ifdef Q_WS_X11
-    // Delay the sync until we get an Expose event from X11 (initial show).
-    // Qt::WA_Mapped is set to true, but the actual mapping has not yet occurred.
-    // However, we must repaint immediately regardless of the state if someone calls repaint().
-    if (tlwExtra->waitingForMapNotify && !tlwExtra->inRepaint)
-        return true;
-#endif
-
-    if (!tlw->testAttribute(Qt::WA_Mapped))
-        return true;
-
-    if (!tlw->isVisible()
-#ifndef Q_WS_X11
-        // If we're minimized on X11, WA_Mapped will be false and we
-        // will return in the case above. Some window managers on X11
-        // sends us the PropertyNotify to change the minimized state
-        // *AFTER* we've received the expose event, which is baaad.
-        || tlw->isMinimized()
-#endif
-        )
+    if (!tlw || !tlwExtra || !tlw->testAttribute(Qt::WA_Mapped) || !tlw->isVisible())
         return true;
 
     return false;
@@ -1345,6 +1323,9 @@ void QWidgetPrivate::repaint_sys(const QRegion &rgn)
         return;
 
     Q_Q(QWidget);
+    if (discardSyncRequest(q, maybeTopData()))
+        return;
+
     if (q->testAttribute(Qt::WA_StaticContents)) {
         if (!extra)
             createExtra();
diff --git a/src/widgets/kernel/qwidgetwindow_qpa.cpp b/src/widgets/kernel/qwidgetwindow_qpa.cpp
index f58dddb70f..498908f4db 100644
--- a/src/widgets/kernel/qwidgetwindow_qpa.cpp
+++ b/src/widgets/kernel/qwidgetwindow_qpa.cpp
@@ -137,15 +137,6 @@ bool QWidgetWindow::event(QEvent *event)
         handleDragEvent(event);
         break;
 
-    case QEvent::Map:
-        m_widget->setAttribute(Qt::WA_Mapped);
-        m_widget->d_func()->syncBackingStore();
-        return true;
-
-    case QEvent::Unmap:
-        m_widget->setAttribute(Qt::WA_Mapped, false);
-        return true;
-
     case QEvent::Expose:
         handleExposeEvent(static_cast<QExposeEvent *>(event));
         return true;
@@ -432,7 +423,13 @@ void QWidgetWindow::handleDragEvent(QEvent *event)
 
 void QWidgetWindow::handleExposeEvent(QExposeEvent *event)
 {
-    m_widget->d_func()->syncBackingStore(event->region());
+    if (isExposed()) {
+        m_widget->setAttribute(Qt::WA_Mapped);
+        if (!event->region().isNull())
+            m_widget->d_func()->syncBackingStore(event->region());
+    } else {
+        m_widget->setAttribute(Qt::WA_Mapped, false);
+    }
 }
 
 void QWidgetWindow::handleWindowStateChangedEvent(QWindowStateChangeEvent *event)