Wayland window transparency

Pekka Paalanen ppaalanen at gmail.com
Wed Mar 12 07:25:35 PDT 2014

On Wed, 12 Mar 2014 11:21:46 +0100
Daniel Stone <daniel at fooishbar.org> wrote:

> Hi,
> On 11 March 2014 14:30, Pekka Paalanen <ppaalanen at gmail.com> wrote:
> > On X11 you are probably used to getting an opaque window, no matter
> > what values you write to the alpha channel. On Wayland, the alpha
> > channel is actually used by the server to blend your window to the rest
> > of the desktop, always.
> ... always? You can request XRGB buffers in wl_shm, or an EGL config
> without an alpha channel.  This will give you storage you can use for
> alpha, but the compositor will discard it and render fully opaque.

True for wl_shm, but if you ask EGL to use a config without any alpha
bits, I suppose you cannot store any non-1.0 alpha values in the
framebuffer, not reliably at least. The story does not tell, if Neal
actually needs any alpha storage on the framebuffer. :-)

Anyway, if an alpha channel exists, it is always used on Wayland,
unlike with X11. I don't count an X-channel as an alpha-channel. ;-)

Neal, slightly relevant:


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