feat(sdl/egl): detect driver at runtime and explain x11 limitation (#9972)

docs/src/integration/pc/sdl.mdx

@@ -126,6 +126,17 @@ The SDL driver can leverage OpenGL for hardware-accelerated rendering. LVGL prov
 
 See the [Complete OpenGL overview](/integration/embedded_linux/opengl) for more information.
 
+<Callout type="info" title="Driver Support">
+OpenGL-based rendering is only supported on Linux when using `x11` as the SDL video driver.
+
+When the EGL/OpenGL path is enabled, LVGL currently forces SDL to use the `x11`
+video driver, overriding `SDL_VIDEODRIVER`. As a result, selecting drivers such as
+`wayland` or `kmsdrm` via `SDL_VIDEODRIVER` will not take effect in this mode.
+
+To use those SDL backends, do not enable the OpenGL/EGL rendering path; use the
+regular SDL renderer instead.
+</Callout>
+
 ## See Also
 
 - [SDL Draw Unit](/integration/embedded_linux/draw_sdl) - SDL texture-based rendering

src/drivers/sdl/lv_sdl_egl.c

@@ -79,7 +79,9 @@ static lv_result_t init_display(lv_display_t * display)
     }
     ddata->egl_ctx = lv_opengles_egl_context_create(&ifc);
     if(!ddata->egl_ctx) {
-        LV_LOG_ERROR("Failed to initialize EGL context");
+        LV_LOG_ERROR("Failed to initialize EGL context.");
+        LV_LOG_ERROR("This probably means you're trying to use an unsupported SDL_VIDEO_DRIVER.");
+        LV_LOG_ERROR("Try setting SDL_VIDEODRIVER=x11 via an environment variable");
         lv_free(ddata);
         return LV_RESULT_INVALID;
     }
@@ -161,19 +163,26 @@ static void * create_window_cb(void * driver_data, const lv_egl_native_window_pr
     lv_display_t * display = (lv_display_t *)driver_data;
     SDL_SysWMinfo wmInfo;
     SDL_VERSION(&wmInfo.version);
-    SDL_GetWindowWMInfo(lv_sdl_window_get_window(display), &wmInfo);
+    if(SDL_GetWindowWMInfo(lv_sdl_window_get_window(display), &wmInfo) != SDL_TRUE) {
+        LV_LOG_ERROR("SDL_GetWindowWMInfo failed: %s", SDL_GetError());
+        return NULL;
+    }
 
     EGLNativeWindowType native_window;
-#if defined(SDL_VIDEO_DRIVER_WINDOWS)
-    native_window = wmInfo.info.win.window;
-#elif defined(SDL_VIDEO_DRIVER_X11)
-    native_window = wmInfo.info.x11.window;
-#elif defined(SDL_VIDEO_DRIVER_WAYLAND)
-    native_window = wmInfo.info.wl.surface;
+    const char * driver = SDL_GetCurrentVideoDriver();
+
+    if(driver && strcmp(driver, "x11") == 0) {
+#if defined(SDL_VIDEO_DRIVER_X11)
+        native_window = (EGLNativeWindowType)wmInfo.info.x11.window;
 #else
-    LV_LOG_ERROR("Unsupported platform for EGL");
-    return NULL;
+        LV_LOG_ERROR("SDL built without X11 support");
+        return NULL;
 #endif
+    }
+    else {
+        LV_LOG_ERROR("Unsupported SDL video driver: (%s)", driver ? driver : "(null)");
+        return NULL;
+    }
     return (void *)native_window;
 }
 

src/drivers/sdl/lv_sdl_window.c

@@ -61,6 +61,7 @@ lv_display_t * lv_sdl_window_create(int32_t hor_res, int32_t ver_res)
 {
     if(!inited) {
 #if LV_SDL_USE_EGL && defined(SDL_VIDEO_DRIVER_X11)
+        /* We only support x11 with EGL for now*/
         SDL_SetHintWithPriority("SDL_VIDEODRIVER", "x11", SDL_HINT_OVERRIDE);
         SDL_SetHint(SDL_HINT_VIDEO_X11_FORCE_EGL, "1");
 #endif