tdf#97739 - ensure we have a valid rectangle for spin-button controls.

Otherwise OpenGL can't render, cache and diff these; so we loose them.

Change-Id: Iac4f3ee0fc68154f708a881d5e0255fc9f8df62d

vcl/source/control/spinfld.cxx

@@ -81,7 +81,8 @@ bool ImplDrawNativeSpinfield(vcl::RenderContext& rRenderContext, vcl::Window* pW
             rRenderContext.IsNativeControlSupported(CTRL_SPINBOX, rSpinbuttonValue.mnLowerPart))
         {
             // only paint the embedded spin buttons, all buttons are painted at once
-            bNativeOK = rRenderContext.DrawNativeControl(CTRL_SPINBOX, PART_ALL_BUTTONS, Rectangle(),
+            Rectangle aUpperAndLowerButtons( rSpinbuttonValue.maUpperRect.GetUnion( rSpinbuttonValue.maLowerRect ) );
+            bNativeOK = rRenderContext.DrawNativeControl(CTRL_SPINBOX, PART_ALL_BUTTONS, aUpperAndLowerButtons,
                                                          ControlState::ENABLED, rSpinbuttonValue, OUString());
         }
         else