ui/sdl2: Explicitly specify EGL platform

[PATCH] ui/sdl2: Explicitly specify EGL platform

Posted by Akihiko Odaki 1 month, 2 weeks ago

Mesa's eglGetDisplay() chooses the native EGL platform from
EGL_PLATFORM, limited autodetection, or the build-time default. If that
selects Wayland while SDL is using the X11 video backend, Mesa can treat
the X11 Display pointer as a wl_display and crash during eglInitialize().

Probe EGL with the X11 platform explicitly before enabling
SDL_HINT_VIDEO_X11_FORCE_EGL.

Resolves: https://gitlab.com/qemu-project/qemu/-/work_items/3540
Signed-off-by: Akihiko Odaki <odaki@rsg.ci.i.u-tokyo.ac.jp>
---
Resolving the issue described in the GitLab work item also requires:
https://github.com/libsdl-org/SDL/pull/15806
---
 include/ui/egl-helpers.h | 5 +++++
 ui/egl-helpers.c         | 4 ++--
 ui/sdl2.c                | 3 ++-
 3 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/include/ui/egl-helpers.h b/include/ui/egl-helpers.h
index acf993fcf52f..c97a0d5c248f 100644
--- a/include/ui/egl-helpers.h
+++ b/include/ui/egl-helpers.h
@@ -61,6 +61,11 @@ void egl_dmabuf_create_fence(QemuDmaBuf *dmabuf);
 
 EGLSurface qemu_egl_init_surface_x11(EGLContext ectx, EGLNativeWindowType win);
 
+#if defined(CONFIG_X11) || defined(CONFIG_GBM) || defined(WIN32)
+EGLDisplay qemu_egl_get_display(EGLNativeDisplayType native,
+                                EGLenum platform);
+#endif
+
 #if defined(CONFIG_X11) || defined(CONFIG_GBM)
 
 int qemu_egl_init_dpy_x11(EGLNativeDisplayType dpy, DisplayGLMode mode);
diff --git a/ui/egl-helpers.c b/ui/egl-helpers.c
index e3f2872cc14b..069a52495541 100644
--- a/ui/egl-helpers.c
+++ b/ui/egl-helpers.c
@@ -520,8 +520,8 @@ EGLSurface qemu_egl_init_surface_x11(EGLContext ectx, EGLNativeWindowType win)
  * platform extensions (EGL_KHR_platform_gbm and friends) yet it doesn't seem
  * like mesa will be able to advertise these (even though it can do EGL 1.5).
  */
-static EGLDisplay qemu_egl_get_display(EGLNativeDisplayType native,
-                                       EGLenum platform)
+EGLDisplay qemu_egl_get_display(EGLNativeDisplayType native,
+                                EGLenum platform)
 {
     EGLDisplay dpy = EGL_NO_DISPLAY;
 
diff --git a/ui/sdl2.c b/ui/sdl2.c
index 4fcdbd79d3c0..ce14bd1f4e15 100644
--- a/ui/sdl2.c
+++ b/ui/sdl2.c
@@ -862,7 +862,8 @@ static void sdl2_set_hint_x11_force_egl(void)
     }
 
     /* Prefer EGL over GLX to get dma-buf support. */
-    egl_display = eglGetDisplay((EGLNativeDisplayType)x_disp);
+    egl_display = qemu_egl_get_display((EGLNativeDisplayType)x_disp,
+                                       EGL_PLATFORM_X11_KHR);
 
     if (egl_display != EGL_NO_DISPLAY) {
         /*

---
base-commit: 2db91528542672cf0db78b3f2cc0e22b36302b38
change-id: 20260611-sdl-a148cd469727

Best regards,
--  
Akihiko Odaki <odaki@rsg.ci.i.u-tokyo.ac.jp>

Re: [PATCH] ui/sdl2: Explicitly specify EGL platform

Posted by Michael Tokarev 1 month, 1 week ago

On 11.06.2026 14:58, Akihiko Odaki wrote:
> Mesa's eglGetDisplay() chooses the native EGL platform from
> EGL_PLATFORM, limited autodetection, or the build-time default. If that
> selects Wayland while SDL is using the X11 video backend, Mesa can treat
> the X11 Display pointer as a wl_display and crash during eglInitialize().
> 
> Probe EGL with the X11 platform explicitly before enabling
> SDL_HINT_VIDEO_X11_FORCE_EGL.
> 
> Resolves: https://gitlab.com/qemu-project/qemu/-/work_items/3540
> Signed-off-by: Akihiko Odaki <odaki@rsg.ci.i.u-tokyo.ac.jp>
> ---
> Resolving the issue described in the GitLab work item also requires:
> https://github.com/libsdl-org/SDL/pull/15806

This looks like a qemu-stable material (11.0.x only?).
I'm picking this up for qemu 11.0.x series.
Please let me know if I shouldn't.

>   include/ui/egl-helpers.h | 5 +++++
>   ui/egl-helpers.c         | 4 ++--
>   ui/sdl2.c                | 3 ++-
>   3 files changed, 9 insertions(+), 3 deletions(-)

Thanks,

/mjt

Re: [PATCH] ui/sdl2: Explicitly specify EGL platform

Posted by Alexander Kanavin 1 month, 2 weeks ago

On Thu, 11 Jun 2026 at 13:58, Akihiko Odaki
<odaki@rsg.ci.i.u-tokyo.ac.jp> wrote:
> Resolving the issue described in the GitLab work item also requires:
> https://github.com/libsdl-org/SDL/pull/15806

Thanks! The pull request is only towards SDL2. I believe SDL3 (via
sdl2 compat layer) isn't affected (it sets the platform correctly in
my testing). Is that right?

Alex

Re: [PATCH] ui/sdl2: Explicitly specify EGL platform

Posted by Akihiko Odaki 1 month, 2 weeks ago

On 2026/06/11 23:44, Alexander Kanavin wrote:
> On Thu, 11 Jun 2026 at 13:58, Akihiko Odaki
> <odaki@rsg.ci.i.u-tokyo.ac.jp> wrote:
>> Resolving the issue described in the GitLab work item also requires:
>> https://github.com/libsdl-org/SDL/pull/15806
> 
> Thanks! The pull request is only towards SDL2. I believe SDL3 (via
> sdl2 compat layer) isn't affected (it sets the platform correctly in
> my testing). Is that right?

Upstream developers are working on a fix:
https://github.com/libsdl-org/SDL/pull/15809

Regards,
Akihiko Odaki

Re: [PATCH] ui/sdl2: Explicitly specify EGL platform

Posted by Marc-André Lureau 1 month, 2 weeks ago

On Thu, Jun 11, 2026 at 4:00 PM Akihiko Odaki
<odaki@rsg.ci.i.u-tokyo.ac.jp> wrote:
>
> Mesa's eglGetDisplay() chooses the native EGL platform from
> EGL_PLATFORM, limited autodetection, or the build-time default. If that
> selects Wayland while SDL is using the X11 video backend, Mesa can treat
> the X11 Display pointer as a wl_display and crash during eglInitialize().
>
> Probe EGL with the X11 platform explicitly before enabling
> SDL_HINT_VIDEO_X11_FORCE_EGL.
>
> Resolves: https://gitlab.com/qemu-project/qemu/-/work_items/3540
> Signed-off-by: Akihiko Odaki <odaki@rsg.ci.i.u-tokyo.ac.jp>

Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>

> ---
> Resolving the issue described in the GitLab work item also requires:
> https://github.com/libsdl-org/SDL/pull/15806
> ---
>  include/ui/egl-helpers.h | 5 +++++
>  ui/egl-helpers.c         | 4 ++--
>  ui/sdl2.c                | 3 ++-
>  3 files changed, 9 insertions(+), 3 deletions(-)
>
> diff --git a/include/ui/egl-helpers.h b/include/ui/egl-helpers.h
> index acf993fcf52f..c97a0d5c248f 100644
> --- a/include/ui/egl-helpers.h
> +++ b/include/ui/egl-helpers.h
> @@ -61,6 +61,11 @@ void egl_dmabuf_create_fence(QemuDmaBuf *dmabuf);
>
>  EGLSurface qemu_egl_init_surface_x11(EGLContext ectx, EGLNativeWindowType win);
>
> +#if defined(CONFIG_X11) || defined(CONFIG_GBM) || defined(WIN32)
> +EGLDisplay qemu_egl_get_display(EGLNativeDisplayType native,
> +                                EGLenum platform);
> +#endif
> +
>  #if defined(CONFIG_X11) || defined(CONFIG_GBM)
>
>  int qemu_egl_init_dpy_x11(EGLNativeDisplayType dpy, DisplayGLMode mode);
> diff --git a/ui/egl-helpers.c b/ui/egl-helpers.c
> index e3f2872cc14b..069a52495541 100644
> --- a/ui/egl-helpers.c
> +++ b/ui/egl-helpers.c
> @@ -520,8 +520,8 @@ EGLSurface qemu_egl_init_surface_x11(EGLContext ectx, EGLNativeWindowType win)
>   * platform extensions (EGL_KHR_platform_gbm and friends) yet it doesn't seem
>   * like mesa will be able to advertise these (even though it can do EGL 1.5).
>   */
> -static EGLDisplay qemu_egl_get_display(EGLNativeDisplayType native,
> -                                       EGLenum platform)
> +EGLDisplay qemu_egl_get_display(EGLNativeDisplayType native,
> +                                EGLenum platform)
>  {
>      EGLDisplay dpy = EGL_NO_DISPLAY;
>
> diff --git a/ui/sdl2.c b/ui/sdl2.c
> index 4fcdbd79d3c0..ce14bd1f4e15 100644
> --- a/ui/sdl2.c
> +++ b/ui/sdl2.c
> @@ -862,7 +862,8 @@ static void sdl2_set_hint_x11_force_egl(void)
>      }
>
>      /* Prefer EGL over GLX to get dma-buf support. */
> -    egl_display = eglGetDisplay((EGLNativeDisplayType)x_disp);
> +    egl_display = qemu_egl_get_display((EGLNativeDisplayType)x_disp,
> +                                       EGL_PLATFORM_X11_KHR);
>
>      if (egl_display != EGL_NO_DISPLAY) {
>          /*
>
> ---
> base-commit: 2db91528542672cf0db78b3f2cc0e22b36302b38
> change-id: 20260611-sdl-a148cd469727
>
> Best regards,
> --
> Akihiko Odaki <odaki@rsg.ci.i.u-tokyo.ac.jp>
>
>