Some QWindowSurface implementations might implement flush as a buffer

flip. Such window surfaces therefore destroy the contents during flush.
In order to render correctly on these surfaces, any update, no matter
how small, needs to trigger the entire window to be redrawn.

Auto test included.

Task-number: Relates to QTBUG-9978
Reviewed-by: tom

4 files changed, 80 insertions, 24 deletions

diff --git a/src/gui/painting/qbackingstore.cpp b/src/gui/painting/qbackingstore.cpp
index 8de9eaa..f9cd59b 100644
--- a/src/gui/painting/qbackingstore.cpp
+++ b/src/gui/painting/qbackingstore.cpp
@@ -263,7 +263,7 @@ bool QWidgetBackingStore::bltRect(const QRect &rect, int dx, int dy, QWidget *wi
 {
     const QPoint pos(tlwOffset + widget->mapTo(tlw, rect.topLeft()));
     const QRect tlwRect(QRect(pos, rect.size()));
-    if (dirty.intersects(tlwRect))
+    if (fullUpdatePending || dirty.intersects(tlwRect))
         return false; // We don't want to scroll junk.
     return windowSurface->scroll(tlwRect, dx, dy);
 }
@@ -402,7 +402,7 @@ QRegion QWidgetBackingStore::dirtyRegion(QWidget *widget) const
     const bool widgetDirty = widget && widget != tlw;
     const QRect tlwRect(topLevelRect());
     const QRect surfaceGeometry(windowSurface->geometry());
-    if (surfaceGeometry != tlwRect && surfaceGeometry.size() != tlwRect.size()) {
+    if (fullUpdatePending || (surfaceGeometry != tlwRect && surfaceGeometry.size() != tlwRect.size())) {
         if (widgetDirty) {
             const QRect dirtyTlwRect = QRect(QPoint(), tlwRect.size());
             const QPoint offset(widget->mapTo(tlw, QPoint()));
@@ -555,6 +555,18 @@ void QWidgetBackingStore::markDirty(const QRegion &rgn, QWidget *widget, bool up
         return;
     }
 
+    if (fullUpdatePending) {
+        if (updateImmediately)
+            sendUpdateRequest(tlw, updateImmediately);
+        return;
+    }
+
+    if (!windowSurface->hasPartialUpdateSupport()) {
+        fullUpdatePending = true;
+        sendUpdateRequest(tlw, updateImmediately);
+        return;
+    }
+
     const QPoint offset = widget->mapTo(tlw, QPoint());
     const QRect widgetRect = widget->d_func()->effectiveRectFor(widget->rect());
     if (qt_region_strictContains(dirty, widgetRect.translated(offset))) {
@@ -638,6 +650,18 @@ void QWidgetBackingStore::markDirty(const QRect &rect, QWidget *widget, bool upd
         return;
     }
 
+    if (fullUpdatePending) {
+        if (updateImmediately)
+            sendUpdateRequest(tlw, updateImmediately);
+        return;
+    }
+
+    if (!windowSurface->hasPartialUpdateSupport()) {
+        fullUpdatePending = true;
+        sendUpdateRequest(tlw, updateImmediately);
+        return;
+    }
+
     const QRect widgetRect = widget->d_func()->effectiveRectFor(rect);
     const QRect translatedRect(widgetRect.translated(widget->mapTo(tlw, QPoint())));
     if (qt_region_strictContains(dirty, translatedRect)) {
@@ -833,6 +857,7 @@ void QWidgetBackingStore::updateLists(QWidget *cur)
 
 QWidgetBackingStore::QWidgetBackingStore(QWidget *topLevel)
     : tlw(topLevel), dirtyOnScreenWidgets(0), hasDirtyFromPreviousSync(false)
+    , fullUpdatePending(0)
 {
     windowSurface = tlw->windowSurface();
     if (!windowSurface)
@@ -1122,6 +1147,7 @@ void QWidgetBackingStore::sync()
             for (int i = 0; i < dirtyWidgets.size(); ++i)
                 resetWidget(dirtyWidgets.at(i));
             dirtyWidgets.clear();
+            fullUpdatePending = false;
         }
         return;
     }
@@ -1132,28 +1158,28 @@ void QWidgetBackingStore::sync()
     const QRect surfaceGeometry(windowSurface->geometry());
     bool repaintAllWidgets = false;
 
-    if (inTopLevelResize || surfaceGeometry != tlwRect) {
-        if ((inTopLevelResize || surfaceGeometry.size() != tlwRect.size()) && !updatesDisabled) {
-            if (hasStaticContents()) {
-                // Repaint existing dirty area and newly visible area.
-                const QRect clipRect(0, 0, surfaceGeometry.width(), surfaceGeometry.height());
-                const QRegion staticRegion(staticContents(0, clipRect));
-                QRegion newVisible(0, 0, tlwRect.width(), tlwRect.height());
-                newVisible -= staticRegion;
-                dirty += newVisible;
-                windowSurface->setStaticContents(staticRegion);
-            } else {
-                // Repaint everything.
-                dirty = QRegion(0, 0, tlwRect.width(), tlwRect.height());
-                for (int i = 0; i < dirtyWidgets.size(); ++i)
-                    resetWidget(dirtyWidgets.at(i));
-                dirtyWidgets.clear();
-                repaintAllWidgets = true;
-            }
+    if ((fullUpdatePending || inTopLevelResize || surfaceGeometry.size() != tlwRect.size()) && !updatesDisabled) {
+        if (hasStaticContents()) {
+            // Repaint existing dirty area and newly visible area.
+            const QRect clipRect(0, 0, surfaceGeometry.width(), surfaceGeometry.height());
+            const QRegion staticRegion(staticContents(0, clipRect));
+            QRegion newVisible(0, 0, tlwRect.width(), tlwRect.height());
+            newVisible -= staticRegion;
+            dirty += newVisible;
+            windowSurface->setStaticContents(staticRegion);
+        } else {
+            // Repaint everything.
+            dirty = QRegion(0, 0, tlwRect.width(), tlwRect.height());
+            for (int i = 0; i < dirtyWidgets.size(); ++i)
+                resetWidget(dirtyWidgets.at(i));
+            dirtyWidgets.clear();
+            repaintAllWidgets = true;
         }
-        windowSurface->setGeometry(tlwRect);
     }
 
+    if (inTopLevelResize || surfaceGeometry != tlwRect)
+        windowSurface->setGeometry(tlwRect);
+
     if (updatesDisabled)
         return;
 
@@ -1212,6 +1238,8 @@ void QWidgetBackingStore::sync()
     }
     dirtyWidgets.clear();
 
+    fullUpdatePending = false;
+
     if (toClean.isEmpty()) {
         // Nothing to repaint. However, we might have newly exposed areas on the
         // screen if this function was called from sync(QWidget *, QRegion)), so
diff --git a/src/gui/painting/qbackingstore_p.h b/src/gui/painting/qbackingstore_p.h
index 02c0f7c..6510b57 100644
--- a/src/gui/painting/qbackingstore_p.h
+++ b/src/gui/painting/qbackingstore_p.h
@@ -91,6 +91,7 @@ public:
     inline bool isDirty() const
     {
         return !(dirtyWidgets.isEmpty() && dirty.isEmpty() && !hasDirtyFromPreviousSync
+                 && !fullUpdatePending
 #if defined(Q_WS_QWS) && !defined(QT_NO_QWS_MANAGER)
                  && !hasDirtyWindowDecoration()
 #endif
@@ -115,7 +116,8 @@ private:
 #ifdef Q_BACKINGSTORE_SUBSURFACES
     QList<QWindowSurface*> subSurfaces;
 #endif
-    bool hasDirtyFromPreviousSync;
+    uint hasDirtyFromPreviousSync : 1;
+    uint fullUpdatePending : 1;
 
     QPoint tlwOffset;
 
diff --git a/src/gui/painting/qwindowsurface.cpp b/src/gui/painting/qwindowsurface.cpp
index 8bd6344..e18ea3f 100644
--- a/src/gui/painting/qwindowsurface.cpp
+++ b/src/gui/painting/qwindowsurface.cpp
@@ -49,13 +49,19 @@ QT_BEGIN_NAMESPACE
 class QWindowSurfacePrivate
 {
 public:
-    QWindowSurfacePrivate(QWidget *w) : window(w), staticContentsSupport(false) {}
+    QWindowSurfacePrivate(QWidget *w)
+        : window(w)
+        , staticContentsSupport(0)
+        , partialUpdateSupport(1)
+    {
+    }
 
     QWidget *window;
     QRect geometry;
     QRegion staticContents;
     QList<QImage*> bufferImages;
-    bool staticContentsSupport;
+    uint staticContentsSupport : 1;
+    uint partialUpdateSupport : 1;
 };
 
 /*!
@@ -284,6 +290,10 @@ bool QWindowSurface::hasStaticContentsSupport() const
 
 void QWindowSurface::setStaticContentsSupport(bool enable)
 {
+    if (enable && !d_ptr->partialUpdateSupport) {
+        qWarning("QWindowSurface::setStaticContentsSupport: static contents support requires partial update support");
+        return;
+    }
     d_ptr->staticContentsSupport = enable;
 }
 
@@ -302,6 +312,20 @@ bool QWindowSurface::hasStaticContents() const
     return d_ptr->staticContentsSupport && !d_ptr->staticContents.isEmpty();
 }
 
+bool QWindowSurface::hasPartialUpdateSupport() const
+{
+    return d_ptr->partialUpdateSupport;
+}
+
+void QWindowSurface::setPartialUpdateSupport(bool enable)
+{
+    if (!enable && d_ptr->staticContentsSupport) {
+        qWarning("QWindowSurface::setPartialUpdateSupport: static contents support requires partial update support");
+        return;
+    }
+    d_ptr->partialUpdateSupport = enable;
+}
+
 void qt_scrollRectInImage(QImage &img, const QRect &rect, const QPoint &offset)
 {
     // make sure we don't detach
diff --git a/src/gui/painting/qwindowsurface_p.h b/src/gui/painting/qwindowsurface_p.h
index 0a453af..e6ee5f6 100644
--- a/src/gui/painting/qwindowsurface_p.h
+++ b/src/gui/painting/qwindowsurface_p.h
@@ -90,6 +90,7 @@ public:
     inline QRect rect(const QWidget *widget) const;
 
     bool hasStaticContentsSupport() const;
+    bool hasPartialUpdateSupport() const;
 
     void setStaticContents(const QRegion &region);
     QRegion staticContents() const;
@@ -97,6 +98,7 @@ public:
 protected:
     bool hasStaticContents() const;
     void setStaticContentsSupport(bool enable);
+    void setPartialUpdateSupport(bool enable);
 
 private:
     QWindowSurfacePrivate *d_ptr;