Wayland: fallback to X11 output when initialization fails

src/draw.c

@@ -51,7 +51,6 @@ void draw_setup(void)
         const struct output *out = output_create(settings.force_xwayland);
         output = out;
 
-        out->init();
         win = out->win_create();
 
         pango_fdesc = pango_font_description_from_string(settings.font);

src/output.c

@@ -8,7 +8,7 @@
 #include "wayland/wl.h"
 #endif
 
-const bool is_running_wayland(void) {
+bool is_running_wayland(void) {
         char* wayland_display = getenv("WAYLAND_DISPLAY");
         return !(wayland_display == NULL);
 }
@@ -55,18 +55,40 @@ const struct output output_wl = {
 };
 #endif
 
+const struct output* get_x11_output() {
+        const struct output* output = &output_x11;
+        if (output->init()) {
+                return output;
+        } else {
+                LOG_E("Couldn't initialize X11 output. Aborting...");
+        }
+}
+
+#ifdef ENABLE_WAYLAND
+const struct output* get_wl_output() {
+        const struct output* output = &output_wl;
+        if (output->init()) {
+                return output;
+        } else {
+                LOG_W("Couldn't initialize wayland output. Falling back to X11 output.");
+                output->deinit();
+                return get_x11_output();
+        }
+}
+#endif
+
 const struct output* output_create(bool force_xwayland)
 {
 #ifdef ENABLE_WAYLAND
         if (!force_xwayland && is_running_wayland()) {
                 LOG_I("Using Wayland output");
-                return &output_wl;
+                return get_wl_output();
         } else {
                 LOG_I("Using X11 output");
-                return &output_x11;
+                return get_x11_output();
         }
 #else
-        return &output_x11;
+        return get_x11_output();
 #endif
 }
 /* vim: set ft=c tabstop=8 shiftwidth=8 expandtab textwidth=0: */

src/output.h

@@ -27,7 +27,7 @@ struct screen_info {
 };
 
 struct output {
-        void (*init)(void);
+        bool (*init)(void);
         void (*deinit)(void);
 
         window (*win_create)(void);
@@ -47,9 +47,14 @@ struct output {
         bool (*have_fullscreen_window)(void);
 };
 
+/**
+ * return an initialized output, selecting the correct output type from either
+ * wayland or X11 according to the settings and environment.
+ * When the wayland output fails to initilize, it falls back to X11 output.
+ */
 const struct output* output_create(bool force_xwayland);
 
-const bool is_running_wayland(void);
+bool is_running_wayland(void);
 
 #endif
 /* vim: set ft=c tabstop=8 shiftwidth=8 expandtab textwidth=0: */

src/wayland/wl.c

@@ -320,14 +320,14 @@ static const struct wl_registry_listener registry_listener = {
         .global_remove = handle_global_remove,
 };
 
-bool init_wayland() {
+bool wl_init() {
         wl_list_init(&ctx.outputs);
-        //wl_list_init(&ctx.seats);
+        //wl_list_init(&ctx.seats); // TODO multi-seat support
 
         ctx.display = wl_display_connect(NULL);
 
         if (ctx.display == NULL) {
-                LOG_E("failed to create display");
+                LOG_W("failed to create display");
                 return false;
         }
 
@@ -336,15 +336,15 @@ bool init_wayland() {
         wl_display_roundtrip(ctx.display);
 
         if (ctx.compositor == NULL) {
-                LOG_E("compositor doesn't support wl_compositor");
+                LOG_W("compositor doesn't support wl_compositor");
                 return false;
         }
         if (ctx.shm == NULL) {
-                LOG_E("compositor doesn't support wl_shm");
+                LOG_W("compositor doesn't support wl_shm");
                 return false;
         }
         if (ctx.layer_shell == NULL) {
-                LOG_E("compositor doesn't support zwlr_layer_shell_v1");
+                LOG_W("compositor doesn't support zwlr_layer_shell_v1");
                 return false;
         }
         if (ctx.seat == NULL) {
@@ -362,7 +362,10 @@ bool init_wayland() {
         return true;
 }
 
-void finish_wayland() {
+void wl_deinit() {
+        // We need to check if any of these are NULL, since the initialization
+        // could have been aborted half way through, or the compositor doesn't
+        // support some of these features.
         if (ctx.layer_surface != NULL) {
                 zwlr_layer_surface_v1_destroy(ctx.layer_surface);
         }
@@ -372,25 +375,40 @@ void finish_wayland() {
         finish_buffer(&ctx.buffers[0]);
         finish_buffer(&ctx.buffers[1]);
 
+        // The output list is initialized at the start of init, so no need to
+        // check for NULL
         struct dunst_output *output, *output_tmp;
         wl_list_for_each_safe(output, output_tmp, &ctx.outputs, link) {
                 destroy_output(output);
         }
 
         if (ctx.seat) {
-                wl_pointer_release(ctx.pointer.wl_pointer);
+                if (ctx.pointer.wl_pointer)
+                        wl_pointer_release(ctx.pointer.wl_pointer);
                 wl_seat_release(ctx.seat);
                 ctx.seat = NULL;
         }
 
-        zwlr_layer_shell_v1_destroy(ctx.layer_shell);
-        wl_compositor_destroy(ctx.compositor);
-        wl_shm_destroy(ctx.shm);
-        wl_registry_destroy(ctx.registry);
-        wl_display_disconnect(ctx.display);
+        if (ctx.idle_handler)
+                org_kde_kwin_idle_destroy(ctx.idle_handler);
 
-        org_kde_kwin_idle_destroy(ctx.idle_handler);
-        org_kde_kwin_idle_timeout_release(ctx.idle_timeout);
+        if (ctx.idle_timeout)
+                org_kde_kwin_idle_timeout_release(ctx.idle_timeout);
+
+        if (ctx.layer_shell)
+                zwlr_layer_shell_v1_destroy(ctx.layer_shell);
+
+        if (ctx.compositor)
+                wl_compositor_destroy(ctx.compositor);
+
+        if (ctx.shm)
+                wl_shm_destroy(ctx.shm);
+
+        if (ctx.registry)
+                wl_registry_destroy(ctx.registry);
+
+        if (ctx.display)
+                wl_display_disconnect(ctx.display);
 }
 
 static struct dunst_output *get_configured_output() {
@@ -582,13 +600,6 @@ void set_dirty() {
         schedule_frame_and_commit();
 }
 
-void wl_init(void) {
-        init_wayland();
-}
-
-void wl_deinit(void) {
-}
-
 window wl_win_create(void) {
         struct window_wl *win = g_malloc0(sizeof(struct window_wl));
 

src/wayland/wl.h

@@ -7,7 +7,7 @@
 
 #include "../output.h"
 
-void wl_init(void);
+bool wl_init(void);
 void wl_deinit(void);
 
 window wl_win_create(void);

src/x11/x.c

@@ -501,14 +501,16 @@ static void XRM_update_db(void)
 /*
  * Setup X11 stuff
  */
-void x_setup(void)
+bool x_setup(void)
 {
 
         /* initialize xctx.dc, font, keyboard, colors */
         if (!setlocale(LC_CTYPE, "") || !XSupportsLocale())
                 LOG_W("No locale support");
+
         if (!(xctx.dpy = XOpenDisplay(NULL))) {
-                DIE("Cannot open X11 display.");
+                LOG_W("Cannot open X11 display.");
+                return false;
         }
 
         x_shortcut_init(&settings.close_ks);
@@ -532,6 +534,7 @@ void x_setup(void)
 
         init_screens();
         x_shortcut_grab(&settings.history_ks);
+        return true;
 }
 
 struct geometry x_parse_geometry(const char *geom_str)

src/x11/x.h

@@ -47,7 +47,7 @@ cairo_t* x_win_get_context(window);
 
 /* X misc */
 bool x_is_idle(void);
-void x_setup(void);
+bool x_setup(void);
 void x_free(void);
 
 struct geometry x_parse_geometry(const char *geom_str);