Fix occasional rendering problem in TextBoxes

See https://bugzilla.xamarin.com/show_bug.cgi?id=26258 for details.

1 files changed, 13 insertions, 1 deletions

diff --git a/mcs/class/Managed.Windows.Forms/System.Windows.Forms/TextBoxTextRenderer.cs b/mcs/class/Managed.Windows.Forms/System.Windows.Forms/TextBoxTextRenderer.cs
index 9917a9ab902..04bb3a3d152 100644
--- a/mcs/class/Managed.Windows.Forms/System.Windows.Forms/TextBoxTextRenderer.cs
+++ b/mcs/class/Managed.Windows.Forms/System.Windows.Forms/TextBoxTextRenderer.cs
@@ -92,7 +92,19 @@ namespace System.Windows.Forms
 			// used tends to be small, this is a good performance gain for

 			// not too much memory.

 			if (text.Length == 1) {

-				string key = font.GetHashCode ().ToString () + "|" + text;

+				// If g.VisibleClipBounds is {X=0, Y=0, Width=1, Height=1}, then some characters

+				// (in some fonts for some point sizes) return a different width then when the

+				// VisibleClipBounds has a different (usually but not always more reasonable) value.

+				// This state of the Graphics object can occur during initialization of text boxes

+				// with preset Text values. See https://bugzilla.xamarin.com/show_bug.cgi?id=26258

+				// for more details.

+				string sep;

+				var bounds = g.VisibleClipBounds;

+				if (bounds.Width == 1 && bounds.Height == 1 && bounds.X == 0 && bounds.Y == 0)

+					sep = "-1x1|";

+				else

+					sep = "|";

+				string key = font.GetHashCode ().ToString () + sep + text;

 				

 				if (measure_cache.ContainsKey (key)) {

 					return (SizeF)measure_cache[key];