Retrieve the clipping region before setting the drawable and reset the

windows/dce.c

@@ -645,7 +645,7 @@ HDC16 WINAPI GetDCEx16( HWND16 hwnd, HRGN16 hrgnClip, DWORD flags )
  */
 HDC WINAPI GetDCEx( HWND hwnd, HRGN hrgnClip, DWORD flags )
 {
-    HRGN 	hrgnVisible = 0;
+    HRGN 	hCopyClipRgn=0,hrgnVisible = 0;
     HDC 	hdc = 0;
     DCE * 	dce;
     DC * 	dc;
@@ -792,9 +792,32 @@ HDC WINAPI GetDCEx( HWND hwnd, HRGN hrgnClip, DWORD flags )
     }
     bUpdateVisRgn = bUpdateVisRgn || (dc->w.flags & DC_DIRTY);
 
-    /* recompute visible region */
+    /*
+     * The pSetDrawable function might change the coordinate system (DCOrgX,DCOrgY) 
+     * values. When it moves the origin, other data like the current clipping 
+     * region will not be moved to that new origin. In the case of DCs that are class
+     * or window DCs that clipping region might be a valid value from a previous use
+     * of the DC and changing the origin of the DC without moving the clip region 
+     * results in a clip region that is not placed properly in the DC.
+     * This code will retrieve the current clipping region, let the pSetDrawable
+     * modify the origin and reset the clipping. When the clipping is set, it is moved
+     * according to the new DC origin.
+     */
+    if ( (wndPtr->class->style & (CS_OWNDC | CS_CLASSDC)) && (dc->w.hClipRgn > 0)) 
+    {
+        hCopyClipRgn=CreateRectRgn( 0, 0, 0, 0 );
+        GetClipRgn(hdc,hCopyClipRgn);
+    }
 
+    /* recompute visible region */
     wndPtr->pDriver->pSetDrawable( wndPtr, dc, flags, bUpdateClipOrigin );
+
+    if (hCopyClipRgn)
+    {    
+        SelectClipRgn(hdc,hCopyClipRgn);
+        DeleteObject(hCopyClipRgn);
+    }
+
     if( bUpdateVisRgn )
     {
 	TRACE("updating visrgn for %08x dce, hwnd [%04x]\n", (unsigned)dce, hwnd);