ExCtrl: Add comment to explain previous commit.

git-svn-id: https://svn.code.sf.net/p/lazarus-ccr/svn@7986 8e941d3f-bd1b-0410-a28a-d453659cc2b4

components/exctrls/source/exbuttons.pas

@@ -528,6 +528,8 @@ begin
   txtPt.Y := (Height - txtSize.CY + 1) div 2;
   R := Rect(txtPt.X, txtPt.Y, txtPt.X + txtSize.CX, txtPt.Y + txtSize.CY);
 
+  // Do not draw the text with DrawText(...) because it requires SingleLine=true
+  // for vertical centering.
   ts := lCanvas.TextStyle;
   ts.Alignment := lAlignment;
   ts.Layout := tlCenter;