On Tue, 2002-11-05 at 05:28, Henric Andersson wrote:
> This is getting stranger still... It seems that the FlipBuffer function in
> the savage driver isn't used. Instead, it falls back to the generic
> framebuffer thingy. Whats more, savagefb has primary and a secondary layer
> ?? And only the primary layer is used (it seems) and that would explain some
> of the strange behaviour. But not all... far from it. The secondary layer
> seems to "lock" the user into 640x480 display? Go figure....
> 
> Does someone know what all this means? The source isn't exactly filled with
> comments :(
> 
The primary Layer is the framebuffer.  Other layers are extras that are
not supported by fbdev, for instance Video Overlay.  

So all DirectFB drivers will have a Primary layer, and the default flip
command is fbdev's pan_display, if supported.

Other layers, because they are extras, need to have device-specific
hooks.  In this case the FlipBuffer() function that you see is probably
for the Secondary Layer.  Most of drivers that has a secondary layer
issues a dfb_surface_flip_buffers() before doing anything else.  This
does _not_ call pan_display, but just swap the front and backbuffer
pointers.  The actual flip will be done by the driver itself.

Tony




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