[Spice-devel] [common PATCH 9/9 v4] ppc: Fix alpha state checking on BE machines

[Lukas Venhoda]

Hi

On Fri, Dec 11, 2015 at 2:13 PM, Christophe Fergeau <cfergeau at redhat.com>
wrote:

> canvas_get_target_format() then has this code:
>
>     if (source_has_alpha) {
>         if (format == PIXMAN_x8r8g8b8) {
>             format = PIXMAN_a8r8g8b8;
>         }
>     }
>
> spice_surface_format_to_pixman(canvas::format) is not going to return
> PIXMAN_b8g8r8x8 on big-endian, is the canvas in a8r8g8b8 format on BE too?
> If yes, then this patch should be correct, if not, more work will be
> needed I'm afraid..
>

spice_surface_format_to_pixman(canvas->format) will always return LE order
colors (ARGB, XRGB).
With that, this function will also always return LE order colors, and that
is correct behavior.

What the patch does is that it ensures, that source_has_alpha is set
correctly,
because surface_format can be both BE, or LE.

If it is BE we will always convert to LE (surface_format != wanted_format
will always fail),
but we can also convert from alpha to non-alpha or vice versa.

If it is LE we will only convert, if the alpha needs to be converted
(surface_format != wanted_format will fail only when alpha is different)

Hope that answers your question.

-- 
Lukas Venhoda
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