Custom windows form border, TransparencyKey Flicker

[Guest]

Hello,
I've got a question regarding a small amount of flicker I am seeing when
a form is first drawn that has a transparent background.

I have a custom panel that I'm drawing myself which takes up all of the
client area of a form (rounded corners, gradients etc).

I have set the background color and the transparencykey of the container
form to the same values.

Everything draws and looks great however right before the form is displayed
I see a black flicker or flash right before the form is rendered. It's a
really really quick flash.

Is there anyway to get around this? I've tried just a blank form and
setting the transparency key and the backcolor to the same values with the
same result.

thanks,
bp

 

[Bob Powell [MVP]]

The transparency key of the form will have no bearing on the problem.

Are you trying to double-buffer the control? This might be a bad idea. See
Windows Forms Tips and Tricks for transparent control info.

--
Bob Powell [MVP]
Visual C#, System.Drawing

Ramuseco Limited .NET consulting
http://www.ramuseco.com

Find great Windows Forms articles in Windows Forms Tips and Tricks
http://www.bobpowell.net/tipstricks.htm

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[Guest]

Thanks for getting back with me Bob,
Said control is double buffered. However, the problem is not with the
control it's with the form. Test case:
Create a default windows form,
Change the size of the form to something really large (800x600)
Set backcolor and transparency key of the form to the same color (gainesburo).
Add a panel with a label and some text (change the backcolor of the panel to
yellow or something) and make it take up 50% of the form
Set formborder style to none
Show the form.

I get a flash right before it's rendered.

thanks,
-bp

Show the form.

This will cause a small flash to occur right before the form is rendered.
Any ideas?

-bp

 

[Bob Powell [MVP]]

I'm not surprised. The form is trying to be transparent when the control has
no notion of how to draw itself transparently clears the screen area with
it's OnPaintBackground implementation.

I think that the only way you'll get any sense out of what I think you want
to do is to implement the layered window API on your main window and custom
paint the content.

--
Bob Powell [MVP]
Visual C#, System.Drawing

Ramuseco Limited .NET consulting
http://www.ramuseco.com

Find great Windows Forms articles in Windows Forms Tips and Tricks
http://www.bobpowell.net/tipstricks.htm

Answer those GDI+ questions with the GDI+ FAQ
http://www.bobpowell.net/faqmain.htm

All new articles provide code in C# and VB.NET.
Subscribe to the RSS feeds provided and never miss a new article.

 

[Guest]

Thanks Bob,
At least you pointed me in the right direction. I was able to minimize the
flicker by doing the following:

I manually implemented the layered window API as you suggested within the
load event of the chromeless form. I wrapped the win32 layered API calls
within a FreezePainting (Google) API call as well. This appears to really
minimize the flash I was seeing. It's there to the trained eye but I'm sure
most people will not even notice.


thanks again,
-brett