Resolves tdf#122118 - Toolbar dropdown button triangles are too large

Fix values for toolbar expander triangles with 7px resp. 4px
depend now on the actual toolbar height.

Change-Id: I0241e3cfa9472bfbd2533afa84bcbfd9ef92c920
Reviewed-on: https://gerrit.libreoffice.org/66166
Tested-by: Jenkins
Reviewed-by: Heiko Tietze <tietze.heiko@gmail.com>

vcl/source/window/toolbox.cxx

@@ -2492,9 +2492,12 @@ static void ImplDrawDropdownArrow(vcl::RenderContext& rRenderContext, const tool
     float fScaleFactor = rRenderContext.GetDPIScaleFactor();
 
     tools::Polygon aPoly(4);
+    int iTBHeight = rRenderContext.GetOutputSize().Height(); //scale triangle depending on theme/toolbar height
 
-    long width = 7 * fScaleFactor;
-    long height = 4 * fScaleFactor;
+    long width = round(iTBHeight/5.5) * fScaleFactor; // 7 for gtk, 5 for gen
+    long height = round(iTBHeight/9.5) * fScaleFactor; // 4 for gtk, 3 for gen
+    if (width < 4) width = 4;
+    if (height < 3) height = 3;
 
     long x = rDropDownRect.Left() + (rDropDownRect.getWidth() - width)/2;
     long y = rDropDownRect.Top() + (rDropDownRect.getHeight() - height)/2;