Possible bug with Graphics.DrawString and TextRenderingHint in .Net Winforms

Question

Here's the OnPaint method of a control that simply inherits from control and provides a property to get/set the textrenderinghint:

 Private _mode as TextRenderingHint = SystemDefault.
 Public Property Mode as TextRenderingHint
    Get & Set _mode
 ...

 Protected Overrides Sub OnPaint(ByVal e As System.Windows.Forms.PaintEventArgs)
    Dim g = e.Graphics
    Dim savMode = g.Save
    g.TextRenderingHint = Me._mode
    g.DrawString(Me.Text, Me.Font, Brushes.Black, 0, 0)
    g.Restore(savMode)
    MyBase.OnPaint(e)
 End Sub

Now, if you place two of these on a form, leave the first as default and change the second to AntiAlias, it looks fine at design-time but when you run the app, the first label's rendering mode has changed. Its as if the DrawString method has changed the systemdefault.

Here's some observations:

(1) If I explicity set the first control's mode to ClearTypeGridFit, which is the same as the default in my case, it fixes the problem.

(2) If you place a third control on the form and leave at the default mode, it fixes the problem.

(3) TextRenderer.DrawText doesn't replicate the problem.

(4) If I inherit label control and override the onpaint method to set the rendering mode, the problem is not replicated even though I set UseCompatibleTextRendering - which forces the label to render with DrawString instead of DrawText.

I'm on XP with cleartype enabled and using visual studio 2008 express edition.

ETA: I've tried it in C# and the same thing happens

Answer 1

This sounds like the issue we ran into before. In your app startup code, is there a call to Application.SetCompatibleTextRenderingDefault(true)? (Or it might be set to false, I forget).

If so, toggle the state of that bool to change the text rendering mode and it should work as expected.