[haiku-appserver] Transparent bitmap dragging

  • From: "Stephan Assmus" <superstippi@xxxxxx>
  • To: haiku-appserver@xxxxxxxxxxxxx
  • Date: Thu, 19 May 2005 17:48:34 +0200 CEST

Hi all,

I had an idea today how to implement this. As you all probably know, 
the rendering backend now runs in single buffered mode with HW 
acceleration. But the double buffering was a nice idea for composing a 
transparent bitmap on top of the backbuffer while transfering it into 
the front buffer (in graphics mem). Now I was thinking if it might be a 
cool idea to make the rendering backend temporarily switch into double 
buffered mode just for the time a transparent bitmap is being dragged. 
Potentially, this could elliminate any flickering when the system has 
to redraw underneath the bitmap. Problems:

1.) The current frame buffer has to be read at least in parts to get an 
up2date backbuffer when switching.
2.) No HW acceleration is available during the dragging, but is 
unlikely to be needed. (That's unless you implement auto-scrolling in 
your applications drop target.)

Anything else I have missed?

Of course, if it would be an option to extend the Accelerant interface, 
other solutions become possible. :-) 

Best regards,

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