input: test if tablet device is a libinput device

Otherwise we might end with a failed assertion if the
tablet or pad isn't a libinput device.

Fixes https://github.com/labwc/labwc/issues/1916

diff --git a/src/input/tablet-pad.c b/src/input/tablet-pad.c
index 1729e356aeadefecccfc0af3b8b06fe76745c814..37f597ff4fc2bcbe55464647cf89de4425e2a502 100644 (file)
--- a/src/input/tablet-pad.c
+++ b/src/input/tablet-pad.c
@@ -25,12 +25,25 @@ tablet_pad_attach_tablet(struct seat *seat)
        /* loop over all tablets and all pads and link by device group */
        struct drawing_tablet *tablet;
        wl_list_for_each(tablet, &seat->tablets, link) {
+               if (!wlr_input_device_is_libinput(tablet->wlr_input_device)) {
+                       /*
+                        * Prevent iterating over non-libinput devices. This might
+                        * be the case when a tablet is exposed by the Wayland
+                        * protocol backend when running labwc as a nested compositor.
+                        */
+                       continue;
+               }
+
                struct libinput_device *tablet_device =
                        wlr_libinput_get_device_handle(tablet->wlr_input_device);
                struct libinput_device_group *tablet_group =
                        libinput_device_get_device_group(tablet_device);
 
                wl_list_for_each(pad, &seat->tablet_pads, link) {
+                       if (!wlr_input_device_is_libinput(pad->wlr_input_device)) {
+                               continue;
+                       }
+
                        struct libinput_device *pad_device =
                                wlr_libinput_get_device_handle(pad->wlr_input_device);
                        struct libinput_device_group *pad_group =