1 files changed, 47 insertions, 9 deletions
diff --git a/src/event.h b/src/event.h
index e439201..86a443e 100644
--- a/src/event.h
+++ b/src/event.h
@@ -20,15 +20,53 @@
 #define _EVENT_CAT4_(a, b, c, d) a##b##c##d
 #define _EVENT_CAT4(a, b, c, d) _EVENT_CAT4_(a, b, c, d)
 
-#define DECL_EVENT(evname) void _evemit_##evname(void);
-#define DEF_EVENT(evname) \
-	DECL_EVENT(evname) \
-	static inline void _evown_##evname(void) { _evemit_##evname(); }
-#define EMIT_EVENT(evname) _evown_##evname()
-
-#define HANDLE_EVENT(evname) \
-	void _EVENT_CAT4(_evhandler_, MODULE_NAME, _, evname)(void) \
-	/* function body here */
+/*
+ * Declares an event defined somewhere in the codebase, allowing a handler to be
+ * defined with HANDLE_EVENT() below. Takes an optional list of types for
+ * parameters. The handler will be called every time the event is emitted by the
+ * declaring module.
+ */
+#define DECL_EVENT(evname, ...) typedef void _must_declare_event_##evname;
+
+/*
+ * Declares a predicate - a special type of even returning bool. Predicates are
+ * used to determine whether some other action should be performed, and
+ * generally should not have side effects, since they get short-circuited and
+ * thus won't always fire when a check is being performed.
+ */
+#define DECL_PREDICATE(evname, ...) typedef bool _must_declare_event_##evname;
+
+/*
+ * Defines an event belonging to this module. Doing so allows EMIT_<event>() to
+ * be called to fire handlers in all modules. Two modules (i.e. source files)
+ * cannot define an event (or predicate) with the same name.
+ */
+#define DEF_EVENT(event, ...) void EMIT_##event(__VA_ARGS__);
+
+/*
+ * Defines a predicate belonging to this module. Doing so allows CHECK_<pred>()
+ * to be called to determine whether to perform some action. Predicates share a
+ * namespace with events and two modules cannot define two things with the same
+ * name.
+ */
+#define DEF_PREDICATE(pred, ...) bool CHECK_##pred(__VA_ARGS__);
+
+/*
+ * Begins an event handler function that gets hooked up to an event by the code
+ * generation system. This is type-generic: if the event is a regular event,
+ * the function will return void; if it is a predicate it will return bool.
+ * Takes a function argument list which must match the type lists given to the
+ * above DEF/DECL macros.
+ *
+ * Note again that predicates are not guaranteed to fire at all due to
+ * short-circuiting and thus generally should not have side effects.
+ *
+ * In the current event implementation, each source file may handle only one of
+ * each event type, as any more wouldn't be too useful anyway.
+ */
+#define HANDLE_EVENT(evname, ...) \
+	_must_declare_event_##evname _EVENT_CAT4(_evhandler_, MODULE_NAME, _, \
+			evname)(__VA_ARGS__) /* function body here */
 
 #endif