[haiku-development] Re: Video Problem

Gerald Zajac wrote:
> When switching from a color depth of 32 bits/pixel (bpp) to 8, 15, or 16 
> bpp either the drawing will be extremely slow such that the Screen 
> Preferences dialog will take a couple seconds to redraw, or drawing will 
> be fine at the lower color depth but when trying to switch back to 32 bpp 
> the following error is displayed:  "The screen mode could not be set:  
> General system error".
> 
> The result depends upon the amount of video memory.  If using a 
> resolution of 1280x1024, and the video memory is >= 16 MB, the slow 
> drawing occurs;  however, if there is only 8 MB of video memory, drawing 
> is fine but you can't switch back to 32 bpp color depth as described 
> above.  This second case might depend upon whether the video driver uses 
> the virtual screen size to compute the required video memory.  When 
> switching back to 32 bpp, the virtual screen height in the display_mode 
> struct passed to the video driver is double the actual screen height; 
> thus, with a resolution of 1280x1024, the amount of memory required is 
> 1280 x 2048 x 4 = 10 MB which is greater that 8 MB.
> 
> Actually, when switching back to 32 bpp, the virtual screen height is 
> always double the actual screen height, but the error message does not 
> occur if there is enough video memory to cover it.
> 
> These problems seemed to have initially appeared between r28289 and 
> r28303.  That is, these problems did not occur under r28289, but did 
> occur under r28303.

It was definitely the plan to fall back to using single buffered mode if 
the memory does not suffice. Perhaps I can make myself a good test case for 
this.

As for the slow drawing, that is really weird and I wonder if it has 
something to do with the other problem. But if you say it occured at around 
the same time... hm.

Best regards,
-Stephan

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