fix(emulator): add fallback to `x11` when `wayland` fails
What the developer wrote
Authored by M1nd3r
fix(emulator): add fallback to `x11` when `wayland` fails
- Wayland may fail on ubuntu 26.
[no changelog]
What changed, and why it matters
This change is a compatibility fix for the Trezor emulator's display on Linux. It makes the emulator try the older X11 graphics protocol if the newer Wayland protocol fails to create a display window. There is no security issue here; it simply improves reliability when running the emulator on certain Linux distributions.
No security action required. Treat as a normal emulator compatibility fix.
Security signals we found
No strong security signals were identified.
Evidence from the diff
The patch modifies display initialization in the Unix emulator driver. It wraps SDL_CreateWindow/SDL_CreateRenderer in a retry loop. On the first attempt, if the current SDL video driver is Wayland and renderer creation fails, it tears down the video subsystem, forces the ‘x11’ driver via SDL_HINT_VIDEO_DRIVER with SDL_HINT_OVERRIDE, reinitializes SDL video, and retries. This is a fallback mechanism for environments where SDL3’s Wayland backend fails (noted for Ubuntu 26).
Changed components
core/embed/io/display/unix/display_driver.cInspect captured patch +45 / −5
diff --git a/core/embed/io/display/unix/display_driver.c b/core/embed/io/display/unix/display_driver.c
index e599282d..0eb641ba 100644
--- a/core/embed/io/display/unix/display_driver.c
+++ b/core/embed/io/display/unix/display_driver.c
@@ -123,24 +123,64 @@ bool display_init(display_content_mode_t mode) {
window_title_alloc = NULL;
}
- drv->window = SDL_CreateWindow(window_title, WINDOW_WIDTH, WINDOW_HEIGHT,
+ Uint32 window_flags =
#ifdef TREZOR_EMULATOR_RASPI
- SDL_WINDOW_FULLSCREEN
+ SDL_WINDOW_FULLSCREEN;
#else
- 0 // windows are visible by default in SDL3
+ 0; // windows are visible by default in SDL3
#endif
- );
+
+ // SDL3 renderer creation can fail on Wayland.
+ // On failure falls back to X11 via XWayland.
+ for (int attempt = 1; attempt <= 2; attempt++) {
+ if (attempt == 2) {
+ // Second attempt: tear down Wayland, reinit with X11
+ LOG_WARN("Renderer failed on Wayland (%s), retrying with X11",
+ SDL_GetError());
+ SDL_DestroyWindow(drv->window);
+ drv->window = NULL;
+ SDL_QuitSubSystem(SDL_INIT_VIDEO);
+
+ SDL_SetHintWithPriority(SDL_HINT_VIDEO_DRIVER, "x11", SDL_HINT_OVERRIDE);
+ if (!SDL_InitSubSystem(SDL_INIT_VIDEO)) {
+ free(window_title_alloc);
+ LOG_ERR("X11 fallback: %s", SDL_GetError());
+ error_shutdown("SDL_Init error");
+ }
+ }
+
+ drv->window = SDL_CreateWindow(window_title, WINDOW_WIDTH, WINDOW_HEIGHT,
+ window_flags);
+ if (!drv->window) {
+ break;
+ }
+
+ drv->renderer = SDL_CreateRenderer(drv->window, NULL);
+ if (drv->renderer) {
+ break; // success
+ }
+
+ // Retry if we're on Wayland and this is the first attempt
+ const char *video_driver = SDL_GetCurrentVideoDriver();
+ if (attempt == 1 && video_driver && strcmp(video_driver, "wayland") == 0) {
+ continue; // try fallback with x11
+ }
+ break; // no fallback possible
+ }
+
free(window_title_alloc);
+
if (!drv->window) {
LOG_ERR("%s", SDL_GetError());
error_shutdown("SDL_CreateWindow error");
}
- drv->renderer = SDL_CreateRenderer(drv->window, NULL);
+
if (!drv->renderer) {
LOG_ERR("%s", SDL_GetError());
SDL_DestroyWindow(drv->window);
error_shutdown("SDL_CreateRenderer error");
}
+
SDL_SetRenderDrawColor(drv->renderer, 0, 0, 0, 255);
SDL_RenderClear(drv->renderer);
Why this scored 15/100
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