Extend window border to the masked rounded corners in non compositing mode

CCBUG: 230013

clients/oxygen/oxygenclient.cpp

@@ -1432,22 +1432,40 @@ namespace Oxygen
     QRegion Client::region( KDecorationDefines::Region r )
     {
 
-        if(
-            (r == KDecorationDefines::ExtendedBorderRegion) &&
-            configuration().useExtendedWindowBorder() &&
-            configuration().frameBorder() <= Configuration::BorderNoSide )
+        // return empty region for anything but extended borders, when enabled
+        if( !( r == KDecorationDefines::ExtendedBorderRegion && configuration().useExtendedWindowBorder() ) )
+        { return QRegion(); }
+
+        // return empty region for maximized windows
+        if( isMaximized() ) return QRegion();
+
+        // return 3 pixels extended borders for sides that have no visible borders
+        // also add the invisible pixels at the masked rounded corners, in non compositing mode
+        if( configuration().frameBorder() <= Configuration::BorderNoSide || !compositingActive() )
         {
 
-            const QRect rect = widget()->rect().adjusted(
-                0, 0,
-                -layoutMetric( LM_OuterPaddingLeft ) - layoutMetric( LM_OuterPaddingRight ),
-                -layoutMetric( LM_OuterPaddingTop ) - layoutMetric( LM_OuterPaddingBottom ) );
+            QRect rect = widget()->rect().adjusted(
+                layoutMetric( LM_OuterPaddingLeft ),
+                layoutMetric( LM_OuterPaddingTop ),
+                - layoutMetric( LM_OuterPaddingRight ),
+                - layoutMetric( LM_OuterPaddingBottom ) );
+
+            rect.translate( -layoutMetric( LM_OuterPaddingLeft ), -layoutMetric( LM_OuterPaddingTop ) );
+
+            // mask
+            QRegion mask( calcMask() );
+            if( mask.isEmpty() ) mask = rect;
+            else mask.translate( -layoutMetric( LM_OuterPaddingLeft ), -layoutMetric( LM_OuterPaddingTop ) );
 
             // only return non-empty region on the sides for which there is no border
-            if( configuration().frameBorder() == Configuration::BorderNone ) return QRegion( rect.adjusted( -3, 0, 3, 3 ) ) - rect;
-            else return QRegion( rect.adjusted( -3, 0, 3, 0 ) ) - rect;
+            if( configuration().frameBorder() == Configuration::BorderNone ) return QRegion( rect.adjusted( -3, 0, 3, 3 ) ) - mask;
+            else if( configuration().frameBorder() == Configuration::BorderNoSide ) return QRegion( rect.adjusted( -3, 0, 3, 0 ) ) - mask;
+            else if( !compositingActive() ) return QRegion( rect ) - mask;
+
+        }
 
-        } else return QRegion();
+        // fall back
+        return QRegion();
 
     }