Related: tdf#100925 background not getting set under X sometimes

not sure why this is the case, but it is reminiscent of rhbz#1283420 which
results in missing glyphs in some circumstances
X11CairoTextRender::getCairoContext has a hack in it for that problem, whic
forces a read from the underlying X Drawable before writing to it which seems
to have the effect of syncing it up.

So, just before drawing the bg, draw a glyph on it to get it synced, and then
overwrite it.

Change-Id: I2ffff7e8e989b91821869d8b75a59728ac513d1b
Reviewed-on: https://gerrit.libreoffice.org/52810Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>

sc/source/ui/view/gridwin4.cxx

@@ -1021,7 +1021,12 @@ void ScGridWindow::DrawContent(OutputDevice &rDevice, const ScTableInfo& rTableI
         }
 
         // paint the background
-        rDevice.DrawRect(rDevice.PixelToLogic(aBackground));
+        tools::Rectangle aLogicRect(rDevice.PixelToLogic(aBackground));
+        //tdf#100925, rhbz#1283420, Draw some text here, to get
+        //X11CairoTextRender::getCairoContext called, so that the forced read
+        //from the underlying X Drawable gets it to sync.
+        rDevice.DrawText(aLogicRect.BottomLeft(), " ");
+        rDevice.DrawRect(aLogicRect);
 
         // paint the editeng text
         tools::Rectangle aEditRect(Point(nScrX, nScrY), Size(aOutputData.GetScrW(), aOutputData.GetScrH()));