Re: [Qemu-devel] [PATCH] ui/egl-helpers: fix egl 1.5 display init

["Marc-André Lureau" <marcandre.lureau@gmail.com>]

On Fri, Mar 17, 2017 at 12:12 PM Gerd Hoffmann <kraxel@redhat.com> wrote:

> Unfortunaly switching to getPlatformDisplayEXT isn't as easy as
> implemented by 0ea1523fb6703aa0dcd65e66b59e96fec028e60a.  See the
> longish comment for the complete story.
>
> Cc: Frediano Ziglio <fziglio@redhat.com>
> Suggested-by: Hans de Goede <hdegoede@redhat.com>
> Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
> ---
>  ui/egl-helpers.c | 53
> +++++++++++++++++++++++++++++++++++++++++++++++------
>  1 file changed, 47 insertions(+), 6 deletions(-)
>
> diff --git a/ui/egl-helpers.c b/ui/egl-helpers.c
> index 584dd1b..48686cf 100644
> --- a/ui/egl-helpers.c
> +++ b/ui/egl-helpers.c
> @@ -192,6 +192,51 @@ EGLSurface qemu_egl_init_surface_x11(EGLContext ectx,
> Window win)
>
>  /* ----------------------------------------------------------------------
> */
>
> +/*
> + * Taken from glamor_egl.h from the Xorg xserver, which is MIT licensed
> + *
> + * Create an EGLDisplay from a native display type. This is a little
> quirky
> + * for a few reasons.
> + *
> + * 1: GetPlatformDisplayEXT and GetPlatformDisplay are the API you want to
> + * use, but have different function signatures in the third argument; this
> + * happens not to matter for us, at the moment, but it means epoxy won't
> alias
> + * them together.
> + *
> + * 2: epoxy 1.3 and earlier don't understand EGL client extensions, which
> + * means you can't call "eglGetPlatformDisplayEXT" directly, as the
> resolver
> + * will crash.
> + *
> + * 3: You can't tell whether you have EGL 1.5 at this point, because
> + * eglQueryString(EGL_VERSION) is a property of the display, which we
> don't
> + * have yet. So you have to query for extensions no matter what.
> Fortunately
> + * epoxy_has_egl_extension _does_ let you query for client extensions, so
> + * we don't have to write our own extension string parsing.
> + *
> + * 4. There is no EGL_KHR_platform_base to complement the EXT one, thus
> one
> + * needs to know EGL 1.5 is supported in order to use the
> eglGetPlatformDisplay
> + * function pointer.
> + * We can workaround this (circular dependency) by probing for the EGL 1.5
> + * platform extensions (EGL_KHR_platform_gbm and friends) yet it doesn't
> seem
> + * like mesa will be able to adverise these (even though it can do EGL
> 1.5).
>

 adverise -> advertise

+ */
> +static EGLDisplay qemu_egl_get_display(void *native)
> +{
> +#ifdef EGL_PLATFORM_GBM_MESA
> +    /* In practise any EGL 1.5 implementation would support the EXT
> extension */
> +    if (epoxy_has_egl_extension(NULL, "EGL_EXT_platform_base")) {
> +        PFNEGLGETPLATFORMDISPLAYEXTPROC getPlatformDisplayEXT =
> +            (void *) eglGetProcAddress("eglGetPlatformDisplayEXT");
> +        if (getPlatformDisplayEXT) {
> +            return getPlatformDisplayEXT(EGL_PLATFORM_GBM_MESA, native,
> NULL);
> +        }
> +    }
> +#endif
> +
> +    /* fallback */
> +    return eglGetDisplay(native);
> +}
> +
>  int qemu_egl_init_dpy(EGLNativeDisplayType dpy, bool gles, bool debug)
>  {
>      static const EGLint conf_att_gl[] = {
> @@ -222,12 +267,8 @@ int qemu_egl_init_dpy(EGLNativeDisplayType dpy, bool
> gles, bool debug)
>          setenv("LIBGL_DEBUG", "verbose", true);
>      }
>
> -    egl_dbg("eglGetDisplay (dpy %p) ...\n", dpy);
> -#ifdef EGL_MESA_platform_gbm
> -    qemu_egl_display = eglGetPlatformDisplayEXT(EGL_PLATFORM_GBM_MESA,
> dpy, NULL);
> -#else
> -    qemu_egl_display = eglGetDisplay(dpy);
> -#endif
> +    egl_dbg("qemu_egl_get_display (dpy %p) ...\n", dpy);
> +    qemu_egl_display = qemu_egl_get_display(dpy);
>      if (qemu_egl_display == EGL_NO_DISPLAY) {
>          error_report("egl: eglGetDisplay failed");
>          return -1;
> --
> 1.8.3.1
>
>
> --
Marc-André Lureau