[PATCH] fb: Correctly implement CopyArea when using a window with depth 32 and 24bpp.

[Robert Ancell]

This fixes gnome-terminal not showing in qemu [1] and can be triggered
by the attached test case.

I haven't combined this with the patch in [2] because this patch is
internally coherent with the fb logic; I still don't know if fb is
doing the right thing here by allowing depth=32 bpp=24. The RENDER
patch is not required for gnome-terminal (and I suspect any
application using depth 32 visual and cairo/GTK+ to render) but
follows the same logic.

--Robert

[1] http://lists.x.org/archives/xorg-devel/2014-June/042723.html
[2] http://lists.x.org/archives/xorg-devel/2014-June/042721.html

On Fri, Jun 6, 2014 at 11:52 PM, Robert Ancell
<robert.ancell at canonical.com> wrote:
> When using the fb backend at 24bpp it allows a visual with 32 bit depth.
> When using CopyArea from a 32bpp pixmap to a window with a 32 bit depth it would
> read the ARGB as RGB.
>
> Fix is to correctly ignore the alpha channel in the pixmap when copying.
> ---
>  fb/fbcopy.c | 10 +++++++++-
>  1 file changed, 9 insertions(+), 1 deletion(-)
>
> diff --git a/fb/fbcopy.c b/fb/fbcopy.c
> index 541ef71..5455947 100644
> --- a/fb/fbcopy.c
> +++ b/fb/fbcopy.c
> @@ -242,8 +242,16 @@ fbCopyArea(DrawablePtr pSrcDrawable,
>             int xIn, int yIn, int widthSrc, int heightSrc, int xOut, int yOut)
>  {
>      miCopyProc copy;
> +    int src_bpp, dst_bpp;
>
> -    if (pSrcDrawable->bitsPerPixel != pDstDrawable->bitsPerPixel)
> +    src_bpp = pSrcDrawable->bitsPerPixel;
> +    if (src_bpp < pSrcDrawable->depth)
> +        src_bpp = BitsPerPixel (pSrcDrawable->depth);
> +    dst_bpp = pDstDrawable->bitsPerPixel;
> +    if (dst_bpp < pDstDrawable->depth)
> +        dst_bpp = BitsPerPixel (pDstDrawable->depth);
> +
> +    if (src_bpp != dst_bpp)
>          copy = fb24_32CopyMtoN;
>      else
>          copy = fbCopyNtoN;
> --
> 2.0.0
>
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