[PATCH weston 2/2] compositor-drm: pass ARGB fallback to gl create functions for XRGB formats

[Bryce Harrington]

On Mon, May 11, 2015 at 02:19:03PM -0500, Derek Foreman wrote:
> If the GL implementation doesn't provide an XRGB visual we may still be
> able to proceed with an ARGB one. Since we're not changing the scanout
> buffer format, and our current rendering loop always results in saturated
> alpha in the frame buffer, it should be Just Fine(tm) - and probably better
> than just exiting.
> 
> Signed-off-by: Derek Foreman <derekf at osg.samsung.com>

Reviewed-by: Bryce Harrington <bryce at osg.samsung.com>

> ---
>  src/compositor-drm.c | 54 ++++++++++++++++++++++++++++++++++++++++++----------
>  src/gl-renderer.c    |  8 ++++++++
>  2 files changed, 52 insertions(+), 10 deletions(-)
> 
> diff --git a/src/compositor-drm.c b/src/compositor-drm.c
> index 69bdcfd..48dfa29 100644
> --- a/src/compositor-drm.c
> +++ b/src/compositor-drm.c
> @@ -1391,14 +1391,43 @@ create_gbm_device(int fd)
>  	return gbm;
>  }
>  
> +/* When initializing EGL, if the preferred buffer format isn't availble
> + * we may be able to susbstitute an ARGB format for an XRGB one.
> + *
> + * This returns 0 if substitution isn't possible, but 0 might be a
> + * legitimate format for other EGL platforms, so the caller is
> + * responsible for checking for 0 before calling gl_renderer->create().
> + */
>  static int
> -drm_compositor_create_gl_renderer(struct drm_compositor *ec)
> +fallback_format_for(uint32_t format)
>  {
> -	EGLint format;
> +	switch (format) {
> +	case GBM_FORMAT_XRGB8888:
> +		return GBM_FORMAT_ARGB8888;
> +	case GBM_FORMAT_XRGB2101010:
> +		return GBM_FORMAT_ARGB2101010;
> +	default:
> +		return 0;
> +	}
> +}
>  
> -	format = ec->format;
> -	if (gl_renderer->create(&ec->base, EGL_PLATFORM_GBM_KHR, (void *) ec->gbm,
> -			       gl_renderer->opaque_attribs, &format, 1) < 0) {
> +static int
> +drm_compositor_create_gl_renderer(struct drm_compositor *ec)
> +{
> +	EGLint format[2] = {
> +		ec->format,
> +		fallback_format_for(ec->format),
> +	};
> +	int n_formats = 1;
> +
> +	if (format[1])
> +		n_formats = 2;
> +	if (gl_renderer->create(&ec->base,
> +				EGL_PLATFORM_GBM_KHR,
> +				(void *) ec->gbm,
> +				gl_renderer->opaque_attribs,
> +				format,
> +				n_formats) < 0) {
>  		return -1;
>  	}
>  
> @@ -1602,13 +1631,16 @@ find_crtc_for_connector(struct drm_compositor *ec,
>  static int
>  drm_output_init_egl(struct drm_output *output, struct drm_compositor *ec)
>  {
> -	EGLint format = output->format;
> -	int i, flags;
> +	EGLint format[2] = {
> +		output->format,
> +		fallback_format_for(output->format),
> +	};
> +	int i, flags, n_formats = 1;
>  
>  	output->surface = gbm_surface_create(ec->gbm,
>  					     output->base.current_mode->width,
>  					     output->base.current_mode->height,
> -					     format,
> +					     format[0],
>  					     GBM_BO_USE_SCANOUT |
>  					     GBM_BO_USE_RENDERING);
>  	if (!output->surface) {
> @@ -1616,12 +1648,14 @@ drm_output_init_egl(struct drm_output *output, struct drm_compositor *ec)
>  		return -1;
>  	}
>  
> +	if (format[1])
> +		n_formats = 2;
>  	if (gl_renderer->output_create(&output->base,
>  				       (EGLNativeDisplayType)output->surface,
>  				       output->surface,
>  				       gl_renderer->opaque_attribs,
> -				       &format,
> -				       1) < 0) {
> +				       format,
> +				       n_formats) < 0) {
>  		weston_log("failed to create gl renderer output state\n");
>  		gbm_surface_destroy(output->surface);
>  		return -1;
> diff --git a/src/gl-renderer.c b/src/gl-renderer.c
> index 6746a9b..87e8334 100644
> --- a/src/gl-renderer.c
> +++ b/src/gl-renderer.c
> @@ -934,6 +934,14 @@ output_rotate_damage(struct weston_output *output,
>  	go->border_damage[go->buffer_damage_index] = border_status;
>  }
>  
> +/* NOTE: We now allow falling back to ARGB gl visuals when XRGB is
> + * unavailable, so we're assuming the background has no transparency
> + * and that everything with a blend, like drop shadows, will have something
> + * opaque (like the background) drawn underneath it.
> + *
> + * Depending on the underlying hardware, violating that assumption could
> + * result in seeing through to another display plane.
> + */
>  static void
>  gl_renderer_repaint_output(struct weston_output *output,
>  			      pixman_region32_t *output_damage)
> -- 
> 2.1.4
> 
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