tdf#92982 vcl rendercontext: fix missing background repaint of Edit

Change-Id: Ic45f65d10835eb39b6709e7adeed1392905ea631
(cherry picked from commit f4a2c604)
Reviewed-on: https://gerrit.libreoffice.org/17564Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>

vcl/source/control/edit.cxx

@@ -1023,6 +1023,27 @@ void Edit::ImplClearBackground(vcl::RenderContext& rRenderContext, long nXStart,
 
     if( !(ImplUseNativeBorder(rRenderContext, GetStyle()) || IsPaintTransparent()))
         rRenderContext.Erase(aRect);
+    else if (SupportsDoubleBuffering() && mbIsSubEdit)
+    {
+        // ImplPaintBorder() is a NOP, we have a native border, and this is a sub-edit of a control.
+        // That means we have to draw the parent native widget to paint the edit area to clear our background.
+        long nLeft = mnXOffset + ImplGetExtraXOffset();
+        long nTop = ImplGetTextYPosition();
+        long nRight = GetOutputWidthPixel();
+        long nHeight = GetTextHeight();
+        Rectangle aEditArea(nLeft, nTop, nRight, nTop + nHeight);
+
+        ControlType aCtrlType = ImplGetNativeControlType();
+        ControlPart aCtrlPart = PART_ENTIRE_CONTROL;
+        Rectangle aCtrlRegion(0, 0, GetParent()->GetOutputWidthPixel(), GetParent()->GetOutputHeightPixel());
+        ControlState nState = ControlState::ENABLED;
+        ImplControlValue aControlValue;
+
+        rRenderContext.Push(PushFlags::CLIPREGION);
+        rRenderContext.SetClipRegion(vcl::Region(aEditArea));
+        rRenderContext.DrawNativeControl(aCtrlType, aCtrlPart, aCtrlRegion, nState, aControlValue, OUString());
+        rRenderContext.Pop();
+    }
 }
 
 void Edit::ImplPaintBorder(vcl::RenderContext& rRenderContext, long nXStart, long nXEnd)

vcl/source/window/paint.cxx

@@ -190,18 +190,6 @@ void PaintHelper::StartBufferedPaint()
     ImplFrameData* pFrameData = m_pWindow->mpWindowImpl->mpFrameData;
     assert(!pFrameData->mbInBufferedPaint);
 
-    // Instead of creating a new VirtualDevice, just erase the area we'll be
-    // painting over, as VirtualDevice::ImplInitVirDev() would do.
-    // The painted area is m_aPaintRect, or in case it's empty, then the whole window.
-    pFrameData->mpBuffer->SetBackground(Wallpaper(Color(COL_WHITE)));
-    {
-        PaintBufferGuard g(pFrameData, m_pWindow);
-        if (m_aPaintRect.IsEmpty())
-            pFrameData->mpBuffer->Erase(Rectangle(Point(0, 0), m_pWindow->GetOutputSize()));
-        else
-            pFrameData->mpBuffer->Erase(m_aPaintRect);
-    }
-
     pFrameData->mbInBufferedPaint = true;
     m_bStartedBufferedPaint = true;
 }