TextRenderer with Graphics transform

3
votes

I've been working on a custom control and I've run into an issue with TextRenderer acting a bit surprisingly. In my OnPaint event I apply transform to the Graphics object to compensate for the scroll position like this:

e.Graphics.Transform = new System.Drawing.Drawing2D.Matrix(1, 0, 0, 1, this.AutoScrollPosition.X, this.AutoScrollPosition.Y);

Then I pass the graphic object to all sub elements of the control so that they paint themselves onto it. One of this elements should draw text string onto the graphics surface. And this is where I've got an issue. This line seems to work correctly when scrolling:

 e.Graphics.DrawString(this.Text, this.Font, brush, new PointF(this.Rectangle.X, this.Rectangle.Y));

But when I use TextRenderer I get a completely different result. Heres the text line that supposed to draw the text:

TextRenderer.DrawText(e.Graphics, this.Text, this.Font, this.Rectangle, this.TextColor, TextFormatFlags.PreserveGraphicsClipping | TextFormatFlags.PreserveGraphicsTranslateTransform);

I thought that these two lines should produce the same result. But for some reason the second one applies the graphics transform differently and as a result, when I scroll the control all the text lines move around with different speed than the rest of the elements on the drawing surface. Could someone explain me why this is happening?

1
c#gdi+
Have you tried using e.Graphics.TranslateTransform(this.AutoScrollPosition.X, this.AutoScrollPosition.Y) instead of your 2d matrix? It shouldn't really make any difference, but then again, TextRenderer should work properly too ... - takrl
@takrl Didn't help:( Still transforms differently for me. - L.E.O

1 Answers

11
votes

Here's my best guess at this: TextRenderer.DrawText is GDI-based and therefore resolution-dependant. Graphics.DrawString is GDI+ and therefore resolution-independant. See also this article.

Since you say that the texts "move around with different speed", probably what happens is that the GDI call uses a different "default" resolution than the one your Graphics object has. That'd mean that you'd have to adjust your AutoScrollCoordinates to respect the difference between your Graphics object resolution and the "default" GDI resolution.