wayland: implement a proper repaint cycle

lib/renderers/wayland/wayland.c

@@ -25,6 +25,13 @@ render(const struct bm_menu *menu)
         return;
     }
 
+    struct window *window;
+    wl_list_for_each(window, &wayland->windows, link) {
+        if (window->render_pending)
+            bm_wl_window_render(window, wayland->display, menu);
+    }
+    wl_display_flush(wayland->display);
+
     struct epoll_event ep[16];
     uint32_t num = epoll_wait(efd, ep, 16, -1);
     for (uint32_t i = 0; i < num; ++i) {
@@ -38,10 +45,10 @@ render(const struct bm_menu *menu)
     }
 
     if (wayland->input.code != wayland->input.last_code) {
-        struct window *window;
+        wl_list_for_each(window, &wayland->windows, link) {
-            wl_list_for_each(window, &wayland->windows, link) {
+            bm_wl_window_schedule_render(window);
-            bm_wl_window_render(window, wayland->display, menu);
         }
+
         wayland->input.last_code = wayland->input.code;
     }
 }
@@ -263,6 +270,7 @@ constructor(struct bm_menu *menu)
             goto fail;
         window->notify.render = bm_cairo_paint;
         window->max_height = output->height;
+        window->render_pending = true;
         wl_list_insert(&wayland->windows, &window->link);
     }
 

lib/renderers/wayland/wayland.h

@@ -84,6 +84,7 @@ struct window {
     uint32_t displayed;
     struct wl_list link;
     bool bottom;
+    bool render_pending;
 
     struct {
         void (*render)(struct cairo *cairo, uint32_t width, uint32_t height, uint32_t max_height, const struct bm_menu *menu, struct cairo_paint_result *result);
@@ -117,6 +118,7 @@ struct wayland {
 void bm_wl_repeat(struct wayland *wayland);
 bool bm_wl_registry_register(struct wayland *wayland);
 void bm_wl_registry_destroy(struct wayland *wayland);
+void bm_wl_window_schedule_render(struct window *window);
 void bm_wl_window_render(struct window *window, struct wl_display *display, const struct bm_menu *menu);
 void bm_wl_window_set_bottom(struct window *window, struct wl_display *display, bool bottom);
 void bm_wl_window_grab_keyboard(struct window *window, struct wl_display *display, bool grab);

lib/renderers/wayland/window.c

@@ -197,17 +197,29 @@ frame_callback(void *data, struct wl_callback *callback, uint32_t time)
     struct window *window = data;
     wl_callback_destroy(callback);
     window->frame_cb = NULL;
+    window->render_pending = true;
 }
 
 static const struct wl_callback_listener listener = {
     frame_callback
 };
 
+void
+bm_wl_window_schedule_render(struct window *window)
+{
+    assert(window);
+    if (window->frame_cb)
+        return;
+
+    window->frame_cb = wl_surface_frame(window->surface);
+    wl_callback_add_listener(window->frame_cb, &listener, window);
+    wl_surface_commit(window->surface);
+}
+
 void
 bm_wl_window_render(struct window *window, struct wl_display *display, const struct bm_menu *menu)
 {
     assert(window && menu);
-
     struct buffer *buffer;
     for (int tries = 0; tries < 2; ++tries) {
         if (!(buffer = next_buffer(window))) {
@@ -232,13 +244,11 @@ bm_wl_window_render(struct window *window, struct wl_display *display, const str
         destroy_buffer(buffer);
     }
 
-    window->frame_cb = wl_surface_frame(window->surface);
-    wl_callback_add_listener(window->frame_cb, &listener, window);
-
     wl_surface_damage(window->surface, 0, 0, buffer->width, buffer->height);
     wl_surface_attach(window->surface, buffer->buffer, 0, 0);
     wl_surface_commit(window->surface);
     buffer->busy = true;
+    window->render_pending = false;
 }
 
 void