Fix issue where revealed widget children do not receive paint event.

When a child of a widget is spontaneously revealed due to a call to
the parent 'resize' method, the child will not receive a paint event
if it has the WA_StaticContents and WA_OpaquePaintEvent flags set.

This is caused by the backing store being pre-emptively resized by the
call to setGeometry_sys, which causes QWidgetBackingStore::sync to skip
the block which handles the static contents.

There doesn't appear to be any reason to preemptively resize the backing
store, since it is always resized as-needed during the the 'sync' method.
This change-set removes the code which preemptively resizes the backing
store.

Task-number: QTBUG-35282
Change-Id: Ie9942854ca5322dfe0f98ed8100810161576be80
Reviewed-by: Jørgen Lind <jorgen.lind@digia.com>
Reviewed-by: Laszlo Agocs <laszlo.agocs@digia.com>

2 files changed, 2 insertions, 13 deletions

diff --git a/src/widgets/kernel/qwidget_qpa.cpp b/src/widgets/kernel/qwidget_qpa.cpp
index acd80afddb..174b7eb5d5 100644
--- a/src/widgets/kernel/qwidget_qpa.cpp
+++ b/src/widgets/kernel/qwidget_qpa.cpp
@@ -549,12 +549,6 @@ void QWidgetPrivate::show_sys()
                 window->resize(geomRect.size());
         }
 
-        if (QBackingStore *store = q->backingStore()) {
-            if (store->size() != geomRect.size()) {
-                store->resize(geomRect.size());
-            }
-        }
-
 #ifndef QT_NO_CURSOR
         qt_qpa_set_cursor(q, false); // Needed in case cursor was set before show
 #endif
@@ -762,11 +756,6 @@ void QWidgetPrivate::setGeometry_sys(int x, int y, int w, int h, bool isMove)
                     QPoint posInNativeParent =  q->mapTo(q->nativeParentWidget(),QPoint());
                     q->windowHandle()->setGeometry(QRect(posInNativeParent,r.size()));
                 }
-                const QWidgetBackingStore *bs = maybeBackingStore();
-                if (bs && bs->store) {
-                    if (isResize)
-                        bs->store->resize(r.size());
-                }
 
                 if (needsShow)
                     show_sys();
diff --git a/src/widgets/kernel/qwidgetbackingstore.cpp b/src/widgets/kernel/qwidgetbackingstore.cpp
index fe877758ef..221e6825ed 100644
--- a/src/widgets/kernel/qwidgetbackingstore.cpp
+++ b/src/widgets/kernel/qwidgetbackingstore.cpp
@@ -940,7 +940,7 @@ void QWidgetBackingStore::sync(QWidget *exposedWidget, const QRegion &exposedReg
     }
 
     // Nothing to repaint.
-    if (!isDirty()) {
+    if (!isDirty() && store->size().isValid()) {
         qt_flush(exposedWidget, exposedRegion, store, tlw, tlwOffset, widgetTextures);
         return;
     }
@@ -1035,7 +1035,7 @@ void QWidgetBackingStore::doSync()
     const QRect tlwRect(topLevelRect());
     const QRect surfaceGeometry(tlwRect.topLeft(), store->size());
     if ((fullUpdatePending || inTopLevelResize || surfaceGeometry.size() != tlwRect.size()) && !updatesDisabled) {
-        if (hasStaticContents()) {
+        if (hasStaticContents() && !store->size().isEmpty() ) {
             // Repaint existing dirty area and newly visible area.
             const QRect clipRect(0, 0, surfaceGeometry.width(), surfaceGeometry.height());
             const QRegion staticRegion(staticContents(0, clipRect));