atom: get_atom now requires explicit xcb_connection_t

This is to make the access to X server more explicit, and make managing
the lifetime of xcb_connection_t a bit easier.

Signed-off-by: Yuxuan Shui <yshuiv7@gmail.com>

src/atom.c

@@ -8,13 +8,11 @@
 #include "log.h"
 #include "utils.h"
 
-static inline int
-atom_getter(struct cache *cache, const char *atom_name, struct cache_handle **value) {
-	struct atom *atoms = container_of(cache, struct atom, c);
+static inline int atom_getter(struct cache *cache attr_unused, const char *atom_name,
+                              struct cache_handle **value, void *user_data) {
+	xcb_connection_t *c = user_data;
 	xcb_intern_atom_reply_t *reply = xcb_intern_atom_reply(
-	    atoms->conn,
-	    xcb_intern_atom(atoms->conn, 0, to_u16_checked(strlen(atom_name)), atom_name),
-	    NULL);
+	    c, xcb_intern_atom(c, 0, to_u16_checked(strlen(atom_name)), atom_name), NULL);
 
 	xcb_atom_t atom = XCB_NONE;
 	if (reply) {
@@ -38,14 +36,22 @@ atom_entry_free(struct cache *cache attr_unused, struct cache_handle *handle) {
 	free(entry);
 }
 
+xcb_atom_t get_atom(struct atom *a, const char *key, xcb_connection_t *c) {
+	struct cache_handle *entry = NULL;
+	if (cache_get_or_fetch(&a->c, key, &entry, c, atom_getter) < 0) {
+		log_error("Failed to get atom %s", key);
+		return XCB_NONE;
+	}
+	return cache_entry(entry, struct atom_entry, entry)->atom;
+}
+
 /**
  * Create a new atom structure and fetch all predefined atoms
  */
 struct atom *init_atoms(xcb_connection_t *c) {
 	auto atoms = ccalloc(1, struct atom);
-	atoms->conn = c;
-	cache_init(&atoms->c, atom_getter);
-#define ATOM_GET(x) atoms->a##x = get_atom(atoms, #x)
+	atoms->c = CACHE_INIT;
+#define ATOM_GET(x) atoms->a##x = get_atom(atoms, #x, c)
 	LIST_APPLY(ATOM_GET, SEP_COLON, ATOM_LIST1);
 	LIST_APPLY(ATOM_GET, SEP_COLON, ATOM_LIST2);
 #undef ATOM_GET

src/atom.h

@@ -55,7 +55,6 @@
 #define ATOM_DEF(x) xcb_atom_t a##x
 
 struct atom {
-	xcb_connection_t *conn;
 	struct cache c;
 	LIST_APPLY(ATOM_DEF, SEP_COLON, ATOM_LIST1);
 	LIST_APPLY(ATOM_DEF, SEP_COLON, ATOM_LIST2);
@@ -66,20 +65,11 @@ struct atom_entry {
 	xcb_atom_t atom;
 };
 
-/// Create a new atom object with a xcb connection, note that this atom object will hold a
-/// reference to the connection, so the caller must keep the connection alive until the
-/// atom object is destroyed.
-struct atom *init_atoms(xcb_connection_t *);
-
-static inline xcb_atom_t get_atom(struct atom *a, const char *key) {
-	struct cache_handle *entry = NULL;
-	if (cache_get_or_fetch(&a->c, key, &entry) < 0) {
-		log_error("Failed to get atom %s", key);
-		return XCB_NONE;
-	}
-	return cache_entry(entry, struct atom_entry, entry)->atom;
-}
+/// Create a new atom object with a xcb connection. `struct atom` does not hold
+/// a reference to the connection.
+struct atom *init_atoms(xcb_connection_t *c);
 
+xcb_atom_t get_atom(struct atom *a, const char *key, xcb_connection_t *c);
 static inline xcb_atom_t get_atom_cached(struct atom *a, const char *key) {
 	return cache_entry(cache_get(&a->c, key), struct atom_entry, entry)->atom;
 }

src/c2.c

@@ -1047,7 +1047,7 @@ static bool c2_l_postprocess(session_t *ps, c2_l_t *pleaf) {
 
 	// Get target atom if it's not a predefined one
 	if (pleaf->predef == C2_L_PUNDEFINED) {
-		pleaf->tgtatom = get_atom(ps->atoms, pleaf->tgt);
+		pleaf->tgtatom = get_atom(ps->atoms, pleaf->tgt, ps->c.c);
 		if (!pleaf->tgtatom) {
 			log_error("Failed to get atom for target \"%s\".", pleaf->tgt);
 			return false;

src/cache.c

@@ -8,13 +8,14 @@ struct cache_handle *cache_get(struct cache *c, const char *key) {
 	return e;
 }
 
-int cache_get_or_fetch(struct cache *c, const char *key, struct cache_handle **value) {
+int cache_get_or_fetch(struct cache *c, const char *key, struct cache_handle **value,
+                       void *user_data, cache_getter_t getter) {
 	*value = cache_get(c, key);
 	if (*value) {
 		return 0;
 	}
 
-	int err = c->getter(c, key, value);
+	int err = getter(c, key, value, user_data);
 	assert(err <= 0);
 	if (err < 0) {
 		return err;
@@ -49,8 +50,3 @@ void cache_invalidate_all(struct cache *c, cache_free_t free_fn) {
 		cache_invalidate_impl(c, e, free_fn);
 	}
 }
-
-void cache_init(struct cache *cache, cache_getter_t getter) {
-	cache->getter = getter;
-	cache->entries = NULL;
-}

src/cache.h

@@ -12,27 +12,27 @@ struct cache_handle;
 /// Should return 0 if the value is fetched successfully, and a negative number if the
 /// value cannot be fetched. Getter doesn't need to initialize fields of `struct
 /// cache_handle`.
-typedef int (*cache_getter_t)(struct cache *, const char *key, struct cache_handle **value);
+typedef int (*cache_getter_t)(struct cache *, const char *key,
+                              struct cache_handle **value, void *user_data);
 typedef void (*cache_free_t)(struct cache *, struct cache_handle *value);
 
 struct cache {
-	cache_getter_t getter;
 	struct cache_handle *entries;
 };
 
+static const struct cache CACHE_INIT = {NULL};
+
 struct cache_handle {
 	char *key;
 	UT_hash_handle hh;
 };
 
-/// Initialize a cache with `getter`
-void cache_init(struct cache *cache, cache_getter_t getter);
-
 /// Get a value from the cache. If the value doesn't present in the cache yet, the
 /// getter will be called, and the returned value will be stored into the cache.
 /// Returns 0 if the value is already present in the cache, 1 if the value is fetched
 /// successfully, and a negative number if the value cannot be fetched.
-int cache_get_or_fetch(struct cache *, const char *key, struct cache_handle **value);
+int cache_get_or_fetch(struct cache *, const char *key, struct cache_handle **value,
+                       void *user_data, cache_getter_t getter);
 
 /// Get a value from the cache. If the value doesn't present in the cache, NULL will be
 /// returned.

src/picom.c

@@ -1346,7 +1346,7 @@ static int register_cm(session_t *ps) {
 			log_fatal("Failed to allocate memory");
 			return -1;
 		}
-		atom = get_atom(ps->atoms, buf);
+		atom = get_atom(ps->atoms, buf, ps->c.c);
 		free(buf);
 
 		xcb_get_selection_owner_reply_t *reply = xcb_get_selection_owner_reply(