Resolves: tdf#92982 vcl rendercontext: handle buffered paint of vcl::Cursor

Instead of painting on the vcl::Window directly, take a
PaintBufferGuard, and use the vcl::RenderContext of it, that may be
either the vcl::Window or the toplevel frame's buffer.

Trigger the paint of the buffer by informing the guard what area was
painted. In case of direct painting, both the ctor and the dtor of the
guard is a NOP.

This means that finally we can also assert Invert() calls on the output
device, so that direct paint can't happen when double-buffering.

Change-Id: I0322563369dc63b3c49061cbe7c4a911cb13a2e2

vcl/inc/window.h

@@ -398,6 +398,8 @@ public:
     ~PaintBufferGuard();
     /// If this is called, then the dtor will also copy rRectangle to the window from the buffer, before restoring the state.
     void SetPaintRect(const Rectangle& rRectangle);
+    /// Returns either the frame's buffer or the window, in case of no buffering.
+    vcl::RenderContext* GetRenderContext();
 };
 
 // helper methods

vcl/source/outdev/rect.cxx

@@ -131,6 +131,7 @@ void OutputDevice::DrawRect( const Rectangle& rRect,
 
 void OutputDevice::Invert( const Rectangle& rRect, InvertFlags nFlags )
 {
+    assert(!is_double_buffered_window());
     if ( !IsDeviceOutputNecessary() )
         return;
 
@@ -163,6 +164,7 @@ void OutputDevice::Invert( const Rectangle& rRect, InvertFlags nFlags )
 
 void OutputDevice::Invert( const Polygon& rPoly, InvertFlags nFlags )
 {
+    assert(!is_double_buffered_window());
     if ( !IsDeviceOutputNecessary() )
         return;
 

vcl/source/window/cursor.cxx

@@ -44,7 +44,9 @@ struct ImplCursorData
 static void ImplCursorInvert( ImplCursorData* pData )
 {
     vcl::Window* pWindow  = pData->mpWindow;
-    vcl::RenderContext* pRenderContext = pWindow->GetOutDev();
+    PaintBufferGuard aGuard(pWindow->ImplGetWindowImpl()->mpFrameData, pWindow);
+    vcl::RenderContext* pRenderContext = aGuard.GetRenderContext();
+    Rectangle aPaintRect;
     bool    bMapMode = pRenderContext->IsMapModeEnabled();
     pRenderContext->EnableMapMode( false );
     InvertFlags nInvertStyle;
@@ -109,11 +111,16 @@ static void ImplCursorInvert( ImplCursorData* pData )
             if ( pData->mnOrientation )
                 aPoly.Rotate( pData->maPixRotOff, pData->mnOrientation );
             pRenderContext->Invert( aPoly, nInvertStyle );
+            aPaintRect = aPoly.GetBoundRect();
         }
     }
     else
+    {
         pRenderContext->Invert( aRect, nInvertStyle );
+        aPaintRect = aRect;
+    }
     pRenderContext->EnableMapMode( bMapMode );
+    aGuard.SetPaintRect(pRenderContext->PixelToLogic(aPaintRect));
 }
 
 void vcl::Cursor::ImplDraw()

vcl/source/window/paint.cxx

@@ -151,6 +151,14 @@ void PaintBufferGuard::SetPaintRect(const Rectangle& rRectangle)
     m_aPaintRect = rRectangle;
 }
 
+vcl::RenderContext* PaintBufferGuard::GetRenderContext()
+{
+    if (mpFrameData->mpBuffer)
+        return mpFrameData->mpBuffer;
+    else
+        return m_pWindow;
+}
+
 class PaintHelper
 {
 private: