fdm: add hook priorities

There are now three hook priorities: low, normal, high.

High priority hooks are executed *first*. Normal next, and last the
low priority hooks.

The renderer's terminal refresh hook now runs as a normal priority
hook.

fdm.c

@@ -26,12 +26,16 @@ struct hook {
     void *callback_data;
 };
 
+typedef tll(struct hook) hooks_t;
+
 struct fdm {
     int epoll_fd;
     bool is_polling;
     tll(struct handler *) fds;
     tll(struct handler *) deferred_delete;
-    tll(struct hook) hooks;
+    hooks_t hooks_low;
+    hooks_t hooks_normal;
+    hooks_t hooks_high;
 };
 
 struct fdm *
@@ -49,7 +53,9 @@ fdm_init(void)
         .is_polling = false,
         .fds = tll_init(),
         .deferred_delete = tll_init(),
-        .hooks = tll_init(),
+        .hooks_low = tll_init(),
+        .hooks_normal = tll_init(),
+        .hooks_high = tll_init(),
     };
     return fdm;
 }
@@ -63,16 +69,24 @@ fdm_destroy(struct fdm *fdm)
     if (tll_length(fdm->fds) > 0)
         LOG_WARN("FD list not empty");
 
-    if (tll_length(fdm->hooks) > 0)
+    if (tll_length(fdm->hooks_low) > 0 ||
+        tll_length(fdm->hooks_normal) > 0 ||
+        tll_length(fdm->hooks_high) > 0)
+    {
         LOG_WARN("hook list not empty");
+    }
 
     assert(tll_length(fdm->fds) == 0);
     assert(tll_length(fdm->deferred_delete) == 0);
-    assert(tll_length(fdm->hooks) == 0);
+    assert(tll_length(fdm->hooks_low) == 0);
+    assert(tll_length(fdm->hooks_normal) == 0);
+    assert(tll_length(fdm->hooks_high) == 0);
 
     tll_free(fdm->fds);
     tll_free(fdm->deferred_delete);
-    tll_free(fdm->hooks);
+    tll_free(fdm->hooks_low);
+    tll_free(fdm->hooks_normal);
+    tll_free(fdm->hooks_high);
     close(fdm->epoll_fd);
     free(fdm);
 }
@@ -207,11 +221,27 @@ fdm_event_del(struct fdm *fdm, int fd, int events)
     return false;
 }
 
-bool
-fdm_hook_add(struct fdm *fdm, fdm_hook_t hook, void *data)
+static hooks_t *
+hook_priority_to_list(struct fdm *fdm, enum fdm_hook_priority priority)
 {
+    switch (priority) {
+    case FDM_HOOK_PRIORITY_LOW:    return &fdm->hooks_low;
+    case FDM_HOOK_PRIORITY_NORMAL: return &fdm->hooks_normal;
+    case FDM_HOOK_PRIORITY_HIGH:   return &fdm->hooks_high;
+    }
+
+    assert(false);
+    return NULL;
+}
+
+bool
+fdm_hook_add(struct fdm *fdm, fdm_hook_t hook, void *data,
+             enum fdm_hook_priority priority)
+{
+    hooks_t *hooks = hook_priority_to_list(fdm, priority);
+
 #if defined(_DEBUG)
-    tll_foreach(fdm->hooks, it) {
+    tll_foreach(*hooks, it) {
         if (it->item.callback == hook) {
             LOG_ERR("hook=%p already registered", hook);
             return false;
@@ -219,18 +249,20 @@ fdm_hook_add(struct fdm *fdm, fdm_hook_t hook, void *data)
     }
 #endif
 
-    tll_push_back(fdm->hooks, ((struct hook){hook, data}));
+    tll_push_back(*hooks, ((struct hook){hook, data}));
     return true;
 }
 
 bool
-fdm_hook_del(struct fdm *fdm, fdm_hook_t hook)
+fdm_hook_del(struct fdm *fdm, fdm_hook_t hook, enum fdm_hook_priority priority)
 {
-    tll_foreach(fdm->hooks, it) {
+    hooks_t *hooks = hook_priority_to_list(fdm, priority);
+
+    tll_foreach(*hooks, it) {
         if (it->item.callback != hook)
             continue;
 
-        tll_remove(fdm->hooks, it);
+        tll_remove(*hooks, it);
         return true;
     }
 
@@ -247,8 +279,18 @@ fdm_poll(struct fdm *fdm)
         return false;
     }
 
-    tll_foreach(fdm->hooks, it) {
-        LOG_DBG("executing hook %p(fdm=%p, data=%p)",
+    tll_foreach(fdm->hooks_high, it) {
+        LOG_DBG("executing high priority hook %p(fdm=%p, data=%p)",
+                it->item.callback, fdm, it->item.callback_data);
+        it->item.callback(fdm, it->item.callback_data);
+    }
+    tll_foreach(fdm->hooks_normal, it) {
+        LOG_DBG("executing normal priority hook %p(fdm=%p, data=%p)",
+                it->item.callback, fdm, it->item.callback_data);
+        it->item.callback(fdm, it->item.callback_data);
+    }
+    tll_foreach(fdm->hooks_low, it) {
+        LOG_DBG("executing low priority hook %p(fdm=%p, data=%p)",
                 it->item.callback, fdm, it->item.callback_data);
         it->item.callback(fdm, it->item.callback_data);
     }

fdm.h

@@ -7,6 +7,12 @@ struct fdm;
 typedef bool (*fdm_handler_t)(struct fdm *fdm, int fd, int events, void *data);
 typedef void (*fdm_hook_t)(struct fdm *fdm, void *data);
 
+enum fdm_hook_priority {
+    FDM_HOOK_PRIORITY_LOW,
+    FDM_HOOK_PRIORITY_NORMAL,
+    FDM_HOOK_PRIORITY_HIGH
+};
+
 struct fdm *fdm_init(void);
 void fdm_destroy(struct fdm *fdm);
 
@@ -17,7 +23,8 @@ bool fdm_del_no_close(struct fdm *fdm, int fd);
 bool fdm_event_add(struct fdm *fdm, int fd, int events);
 bool fdm_event_del(struct fdm *fdm, int fd, int events);
 
-bool fdm_hook_add(struct fdm *fdm, fdm_hook_t hook, void *data);
-bool fdm_hook_del(struct fdm *fdm, fdm_hook_t hook);
+bool fdm_hook_add(struct fdm *fdm, fdm_hook_t hook, void *data,
+                  enum fdm_hook_priority priority);
+bool fdm_hook_del(struct fdm *fdm, fdm_hook_t hook, enum fdm_hook_priority priority);
 
 bool fdm_poll(struct fdm *fdm);

render.c

@@ -45,7 +45,9 @@ render_init(struct fdm *fdm, struct wayland *wayl)
         .wayl = wayl,
     };
 
-    if (!fdm_hook_add(fdm, &fdm_hook_refresh_pending_terminals, renderer)) {
+    if (!fdm_hook_add(fdm, &fdm_hook_refresh_pending_terminals, renderer,
+                      FDM_HOOK_PRIORITY_NORMAL))
+    {
         LOG_ERR("failed to register FDM hook");
         free(renderer);
         return NULL;
@@ -60,7 +62,8 @@ render_destroy(struct renderer *renderer)
     if (renderer == NULL)
         return;
 
-    fdm_hook_del(renderer->fdm, &fdm_hook_refresh_pending_terminals);
+    fdm_hook_del(renderer->fdm, &fdm_hook_refresh_pending_terminals,
+                 FDM_HOOK_PRIORITY_NORMAL);
 }
 
 static void __attribute__((destructor))