Weston does not do transparent backgrounds

[arunkrish20 .]

Hi pq,

Thanks for your valuable input...

I have tried to change the "alpha_attribs" for creating the output surface.
But still no update to alpha.

As you said, i have to look into some gl_blend function calls(for enable
and disable) and gl_blendfunc function calls.

As per your comment there is no gl_clear in the code and double buffer is
used for rendering, so that i am getting previous rendered output merged
with the latest output in the display.

I will check and update you once i get some more clues.

Thanks,
Arunkumar R




On Fri, Aug 26, 2016 at 9:03 PM, Pekka Paalanen <ppaalanen at gmail.com> wrote:

> On Fri, 26 Aug 2016 16:02:19 +0530
> "arunkrish20 ." <arunkrish20 at gmail.com> wrote:
>
> > Hi All,
> >
> > http://wayland-devel.freedesktop.narkive.com/
> dXZUCogH/desktop-shell-how-to-enable-really-alpha-blending-
> of-weston-background
> >
> > Our question is related to above mentioned link question.
> >
> > Environment
> > OS : Linux kernel 3.14
> > Version : Weston 1.9.0
> >
> > Weston fbdev-backend.
> >
> > In compositor-fbdev.c
> > fbdev_output_create()
> >
> > *called *
> > gl_renderer->output_create(&output->base,
> >                            (EGLNativeWindowType)NULL, NULL,
> >                            gl_renderer->*opaque_attribs*,
> >                            NULL, 0) < 0) {
> >             weston_log("gl_renderer_output_create failed.\n");
> >
> > *can be changed to*
> > gl_renderer->output_create(&output->base,
> >                            (EGLNativeWindowType)NULL, NULL,
> >                            gl_renderer->*alpha_attribs*,
> >                            NULL, 0) < 0) {
> >             weston_log("gl_renderer_output_create failed.\n");
> >
> > Is that change will give some help? I havn't tried. But in that link if
> we
> > use fbdev-backend then there is no hope to expect the alpha.
> >
> > Any update or direction, Could you please suggest...
>
> Hi,
>
> I can't say if that will help, that kind of use case was never
> intended. What will happen depends on the kernel driver and the EGL
> implementation, we cannot know what they (being proprietary) do.
>
> After you get that working, you still need to get the framebuffer
> rendered such that you actually get alpha < 1.0 on some parts. You
> may have problems with Weston's rendering. A non-opaque surface is
> always rendered with blending and weston never uses glClear, so that
> might cause blending artifacts. OTOH, in some cases the
> renderer deliberately ignores the alpha channel because Xwayland
> surfaces used to have garbage there. I'm also not sure if the
> blending equation used accounts for destination alpha != 1.0.
> Therefore there may be a few things you have to fix before you see
> anything.
>
> I believe you'll find that the assumption of an opaque
> primary framebuffer is quite deeply rooted in Weston.
>
> Also note that GL support has been removed from the fbdev backend,
> too. See:
> https://cgit.freedesktop.org/wayland/weston/commit/src/
> compositor-fbdev.c?id=e77f8ad79bdf3613dc7e587ea0cf5b9d39e4f8e0
>
>
> Thanks,
> pq
>
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