hooks: Double-registration protection

In most cases, one only wants a single copy of a hook. On the other hand,
plugins that depend on other plugins, may want to make it easier for the
end-user to use the plugin, and call the setup function of the dependent plugins
too. In case the end-user calls the same setup function, we'd end up with hooks
registered multiple times.

To avoid this, protection against double-registration has been introduced. The
new `event_handler_hook_use` and `loop_hook_use` functions will only allow one
copy of the hook. The `event_handler_hook_append` and `loop_hook_append`
functions will, on the other hand, just append the hooks, and not care about
protection.

The `event_handler_hook_add` and `loop_hook_add` functions are gone, but for the
time being, they are aliases to the `_use` functions, until all plugins have
been updated, and the aliases can be removed.

Signed-off-by: Gergely Nagy <algernon@madhouse-project.org>

src/KeyboardioFirmware.cpp

@@ -14,8 +14,8 @@ Keyboardio_::setup(const byte keymap_count) {
     KeyboardHardware.setup();
     LEDControl.setup();
 
-    event_handler_hook_add (NULL);
+    event_handler_hook_use (NULL);
-    loop_hook_add (NULL);
+    loop_hook_use (NULL);
 
     Layer.defaultLayer (Storage.load_primary_keymap (keymap_count));
 }

src/hooks.cpp

@@ -11,10 +11,19 @@ event_handler_hook_replace (custom_handler_t oldHook, custom_handler_t newHook)
 }
 
 void
-event_handler_hook_add (custom_handler_t hook) {
+event_handler_hook_append (custom_handler_t hook) {
     event_handler_hook_replace ((custom_handler_t)NULL, hook);
 }
 
+void
+event_handler_hook_use (custom_handler_t hook) {
+    for (byte i = 0; i < HOOK_MAX; i++) {
+        if (eventHandlers[i] == hook)
+            return;
+    }
+    event_handler_hook_append (hook);
+}
+
 void
 loop_hook_replace (custom_loop_t oldHook, custom_loop_t newHook) {
     for (byte i = 0; i < HOOK_MAX; i++) {
@@ -26,6 +35,15 @@ loop_hook_replace (custom_loop_t oldHook, custom_loop_t newHook) {
 }
 
 void
-loop_hook_add (custom_loop_t hook) {
+loop_hook_append (custom_loop_t hook) {
     loop_hook_replace ((custom_loop_t)NULL, hook);
 }
+
+void
+loop_hook_use (custom_loop_t hook) {
+    for (byte i = 0; i < HOOK_MAX; i++) {
+        if (loopHooks[i] == hook)
+            return;
+    }
+    loop_hook_append (hook);
+}

src/hooks.h

@@ -8,11 +8,15 @@
 typedef Key (*custom_handler_t)(Key mappedKey, byte row, byte col, uint8_t keyState);
 extern custom_handler_t eventHandlers[HOOK_MAX];
 
-void event_handler_hook_add (custom_handler_t hook);
+void event_handler_hook_use (custom_handler_t hook);
+void event_handler_hook_append (custom_handler_t hook);
 void event_handler_hook_replace (custom_handler_t oldHook, custom_handler_t newHook);
+#define event_handler_hook_add event_handler_hook_use
 
 typedef void (*custom_loop_t)(bool postClear);
 extern custom_loop_t loopHooks[HOOK_MAX];
 
-void loop_hook_add (custom_loop_t hook);
+void loop_hook_use (custom_loop_t hook);
+void loop_hook_append (custom_loop_t hook);
 void loop_hook_replace (custom_loop_t oldHook, custom_loop_t newHook);
+#define loop_hook_add loop_hook_use