Add QPlatformIntegration::BackingStoreStaticContents capability

This was a feature in Qt 4, but the only platform that carried it over
to Qt 5 was Windows, in ab76593f18396e693f24066592244ca95e135ea2, and
that's still the situation.

As a first step in possibly implementing this on more platforms, lets
replace the hard-coded check in QWidgetRepaintManager::hasStaticContents
with a proper QPlatformIntegration capability check in the only call site.

Pick-to: 6.7
Change-Id: I2067109f45116cd8c62facf7224cd748f19e845b
Reviewed-by: Axel Spoerl <axel.spoerl@qt.io>

1 files changed, 3 insertions, 5 deletions

diff --git a/src/widgets/kernel/qwidgetrepaintmanager.cpp b/src/widgets/kernel/qwidgetrepaintmanager.cpp
index c63f745446..e6b57d9872 100644
--- a/src/widgets/kernel/qwidgetrepaintmanager.cpp
+++ b/src/widgets/kernel/qwidgetrepaintmanager.cpp
@@ -706,7 +706,9 @@ void QWidgetRepaintManager::paintAndFlush()
 
     const QRect tlwRect = tlw->data->crect;
     if (!updatesDisabled && store->size() != tlwRect.size()) {
-        if (hasStaticContents() && !store->size().isEmpty() ) {
+        QPlatformIntegration *integration = QGuiApplicationPrivate::platformIntegration();
+        if (hasStaticContents() && !store->size().isEmpty()
+            && integration->hasCapability(QPlatformIntegration::BackingStoreStaticContents)) {
             // Repaint existing dirty area and newly visible area.
             const QRect clipRect(QPoint(0, 0), store->size());
             const QRegion staticRegion(staticContents(nullptr, clipRect));
@@ -1140,11 +1142,7 @@ void QWidgetRepaintManager::removeStaticWidget(QWidget *widget)
 
 bool QWidgetRepaintManager::hasStaticContents() const
 {
-#if defined(Q_OS_WIN)
     return !staticWidgets.isEmpty();
-#else
-    return !staticWidgets.isEmpty() && false;
-#endif
 }
 
 /*!