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.NET Forum / Windows Forms / WinForm General / June 2007Fade Transition Trick
We are trying to use basic windows forms to do "fancy" transitions on our application. When switching between main form controls (docked to full), we want to make it look like one is fading out and the other fading in. Since the UserControls don't support 'Opacity' I built a transition panel that shows a modal form (with internal timer) that fades out, then back in when the next control is shown. The Transition form is shown over the area of the main form's child controls. It functions as expected, however when the transition form hits opacity 1.0 (goes from 0 to 1, to 0 again to simulate fading out then back in), I get a flash of black once before it starts to fade back to 0 opacity. The backcolor and forecolor are set to white. I have overriden OnPaintBackground, but it isn't being called. It definitely seems like the parent is refreshing (because I change the control states of the main control to visible at the mid fade point) and causing the modal dialog to repaint black. If it flashed white, I would be OK with that, but I would prefer it to always repaint the current screen. In MFC and C++ I recall that you could setup the default brush for erasing. Not sure if there is a .NET equivalent. I do have a picture box on the form. Is it possible that it's OnPaingBackground is causing the flash? Any thougths would be helpful. I am sure I am missing some vital step here.  SignatureBrian R. For almost any reasonably intellient paint scheme one should disable the OnPaintBackground. Signature-- 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. > We are trying to use basic windows forms to do "fancy" transitions on our > application. When switching between main form controls (docked to full), [quoted text clipped - 32 lines] > Any thougths would be helpful. I am sure I am missing some vital step > here. So how do I disable the OnPaintBackground? I tried overriding OnPaintBackground but it never gets called. I tried setting window styles to UserPaint and AllPaintingInWMPaint, but that didn't make either OnPaint or OnPaintBackground get called. Could this be related to layered windows? I read something about the .NET transition to a layered window has an error that causes flicker. The workaround was to set a transparent key color, which forces .NET to layer the window. This solved the flicker problem, BUT it made the window insanely slow to transition, esepcially when maximized. SignatureBrian R. > For almost any reasonably intellient paint scheme one should disable the > OnPaintBackground. [quoted text clipped - 35 lines] > > Any thougths would be helpful. I am sure I am missing some vital step > > here. Hi Brian, It would be better for me to look into this issue if you could send me a simple project that could just reproduce the problem. To get my actual email address, remove 'online' from my displayed email address. Thank you for your understanding and cooperation! Sincerely, Linda Liu Microsoft Online Community Support ================================================== Get notification to my posts through email? Please refer to http://msdn.microsoft.com/subscriptions/managednewsgroups/default.aspx#notif ications. Note: The MSDN Managed Newsgroup support offering is for non-urgent issues where an initial response from the community or a Microsoft Support Engineer within 1 business day is acceptable. Please note that each follow up response may take approximately 2 business days as the support professional working with you may need further investigation to reach the most efficient resolution. The offering is not appropriate for situations that require urgent, real-time or phone-based interactions or complex project analysis and dump analysis issues. Issues of this nature are best handled working with a dedicated Microsoft Support Engineer by contacting Microsoft Customer Support Services (CSS) at http://msdn.microsoft.com/subscriptions/support/default.aspx. ================================================== This posting is provided "AS IS" with no warranties, and confers no rights. Are you directly using the LayeredWindow API? Signature-- 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. > So how do I disable the OnPaintBackground? I tried overriding > OnPaintBackground but it never gets called. I tried setting window styles [quoted text clipped - 55 lines] >> > Any thougths would be helpful. I am sure I am missing some vital step >> > here. No. All I did was set the .NET Windows Form property: TransparencyKey. That got rid of the flicker but made the window fade SO Much slower. The article I read stated that this property, when set, forces System.Windows.Forms to layer the window. See the last section from this code project article that addresses opacity and layered windows. http://www.codeproject.com/csharp/notanotherformfader.asp SignatureBrian R. > Are you directly using the LayeredWindow API? > [quoted text clipped - 57 lines] > >> > Any thougths would be helpful. I am sure I am missing some vital step > >> > here. Hi Brian, Thank you for your sample project. I run it on my machine and see the TransitionForm flashes when it is closed. I have a try setting the TransparencyKey property of the TransitionForm to Lime, and see that the flicker is eliminated. But I don't see the transition becomes slower after I set the TransitionForm's TransparencyKey property. I think a simple workaround to this slow transition problem is to decrease the transition range of the Opacity, e.g. from 0.5 to 1 and then from 1 to 0.5. To do this, you can set the TransitionForm's Opacity property to 0.5 in the designer and modify one line of code in the FadeInTimerElapsed method as follows: // modify the original line of code if (Opacity <= 0.0) // to the code below if (Opacity <=0.5) Hope this helps. If you have any concern, please feel free to let me know. Sincerely, Linda Liu Microsoft Online Community Support Free MagazinesGet these publications absolutely FREE for up to 12 months. There are no hidden fees and no obligation. Simply choose a title, complete the application form and submit it. Read more ...
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