Wayland Backend Not Working on Raspberry Pi

[jefftranter]

I am trying to get LVGL to work on a Raspberry Pi 3 using Wayland.
It is running the most recent version of Raspberry Pi OS which uses Wayland by default.
I am using the latest code from https://github.com/lvgl/lv_port_linux
In lv_conf.h I have set:

#define LV_USE_LINUX_FBDEV 0
#define LV_USE_LINUX_DRM 0
#define LV_USE_SDL 0
#define LV_USE_WAYLAND 1

The demo builds without without errors, but when run it get no display and I see these errors:

[Warn] (0.000, +0) lv_init: Memory integrity checks are enabled via LV_USE_ASSERT_MEM_INTEGRITY which makes LVGL much slower lv_init.c:262
[Warn] (0.000, +0) lv_init: Object sanity checks are enabled via LV_USE_ASSERT_OBJ which makes LVGL much slower lv_init.c:266
[Warn] (0.000, +0) lv_init: Style sanity checks are enabled that uses more RAM lv_init.c:270
wl_registry#2: error 0: invalid version for global xdg_wm_base (18): have 2, wanted 4
[Error] (0.000, +0) wayland_init: Asserted at expression: (application.shm_format != SHM_FORMAT_UNKNOWN) (WL_SHM_FORMAT not available) lv_wayland.c:2399
pi@raspberrypi

I tried changing LV_COLOR_DEPTH from 32 to 16 and to 24 but I get the same results.

On the same machine I am able to run the demo using SDL2.

I've attached the output of wayland-info.

wayland-info.txt

[csujq]

Have you solved your issue？

[jefftranter]

No, I am still seeing the issue with the latest LVGL code under the last Raspberry Pi OS.

[csujq]

No, I am still seeing the issue with the latest LVGL code under the last Raspberry Pi OS.

you can try this commandexport WAYLAND_DISPLAY=wayland-1 or export WAYLAND_DISPLAY=wayland-0

[jefftranter]

That didn't help. The OS was already setting WAYLAND_DISPLAY=wayland-0.
When set to wayland-1 it cannot connect to the Wayland server.

[csujq]

That didn't help. The OS was already setting WAYLAND_DISPLAY=wayland-0. When set to wayland-1 it cannot connect to the Wayland server.

I had this problem before, but I solved it by typing this command.

[etag4048]

@jefftranter Hello, this is because the wayland driver uses version 4 of the xdg-shell protocol. More specifically it sets up a listener for theconfigure_bounds event which requires version 4 - but it's not even used... Apparently, the wayland compositor on the RaspberryPI OS still uses version 2 of the xdg-shell. So you will have to patch out some lines and this seems to work on my machine

diff --git a/src/drivers/wayland/lv_wayland.c b/src/drivers/wayland/lv_wayland.c
index 8b85ae5a0..08bdf8799 100644
--- a/src/drivers/wayland/lv_wayland.c
+++ b/src/drivers/wayland/lv_wayland.c
@@ -1227,24 +1227,9 @@ static void xdg_toplevel_handle_close(void * data, struct xdg_toplevel * xdg_top
     LV_UNUSED(xdg_toplevel);
 }
 
-static void xdg_toplevel_handle_configure_bounds(void * data, struct xdg_toplevel * xdg_toplevel,
-                                                 int32_t width, int32_t height)
-{
-
-    LV_UNUSED(width);
-    LV_UNUSED(height);
-    LV_UNUSED(data);
-    LV_UNUSED(xdg_toplevel);
-
-    /* Optional: Could set window width/height upper bounds, however, currently
-     *           we'll honor the set width/height.
-     */
-}
-
 static const struct xdg_toplevel_listener xdg_toplevel_listener = {
     .configure = xdg_toplevel_handle_configure,
     .close = xdg_toplevel_handle_close,
-    .configure_bounds = xdg_toplevel_handle_configure_bounds
 };
 
 static void xdg_wm_base_ping(void * data, struct xdg_wm_base * xdg_wm_base, uint32_t serial)
@@ -1292,8 +1277,8 @@ static void handle_global(void * data, struct wl_registry * registry,
 #endif
 #if LV_WAYLAND_XDG_SHELL
     else if(strcmp(interface, xdg_wm_base_interface.name) == 0) {
-        /* Explicitly support version 4 of the xdg protocol */
-        app->xdg_wm = wl_registry_bind(app->registry, name, &xdg_wm_base_interface, 4);
+        /* The compositor on Raspberry Pi OS still uses version 2 */
+        app->xdg_wm = wl_registry_bind(app->registry, name, &xdg_wm_base_interface, 2);
         xdg_wm_base_add_listener(app->xdg_wm, &xdg_wm_base_listener, app);
     }
 #endif

Can you confirm ?

[jefftranter]

I can confirm that it works with this patch!
It would be good to document this somewhere or handle it with #ifdefs in the code or similar.
Many thanks.