On Thu, 6 Jun 2002, Kevin Geiss wrote:
> i'm playing with the shadow frame buffer a bit, and I have a question:
>
> In 24 bit mode, how are the pixels layed out?
"24 bit" is ambiguous. depth != bpp
> my output device is expecting each pixel to be contained in a 32 bit word,
That's 32bpp.
> with the most significant byte unused, the next most significant byte
> containing the blue, then a red byte, and finally the least significant byte
> containing the green.
>
> But it looks like the shadow frame buffer is different. does it operate on
> a byte basis? with no unused bytes? if so, what order are the red, green,
> and blue in?
>
> Thanks in advance!!
The X11 specification makes no requirements on what the internal
format of the framebuffer is and the driver can do whatever it
wants. The default masks for depth 24 have blue in the lsb followed
by green then red. This is regardless of whether it is the 24bpp
or 32bpp variety of depth 24. The driver can advertise something
different but on platforms where XRGB are the norm, clients may
get confused. Clients should not assume a particular ordering,
but many still do.
Mark.
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