atom: cache result of get_atom

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

src/atom.c

@@ -0,0 +1,37 @@
+#include <xcb/xcb.h>
+
+#include "atom.h"
+#include "common.h"
+#include "utils.h"
+
+/**
+ * Wrapper of XInternAtom() for convenience.
+ */
+static inline void *atom_getter(void *ud, const char *atom_name, int *err) {
+	xcb_connection_t *c = ud;
+	xcb_intern_atom_reply_t *reply = xcb_intern_atom_reply(
+	    c, xcb_intern_atom(c, 0, to_u16_checked(strlen(atom_name)), atom_name), NULL);
+
+	xcb_atom_t atom = XCB_NONE;
+	if (reply) {
+		log_debug("Atom %s is %d", atom_name, reply->atom);
+		atom = reply->atom;
+		free(reply);
+	} else {
+		log_error("Failed to intern atoms");
+		*err = 1;
+	}
+	return (void *)(intptr_t)atom;
+}
+
+/**
+ * Fetch all required atoms and save them to a session.
+ */
+struct atom *init_atoms(xcb_connection_t *c) {
+	auto atoms = ccalloc(1, struct atom);
+	atoms->c = new_cache((void *)c, atom_getter, NULL);
+#define ATOM_GET(x) atoms->a##x = (xcb_atom_t)(intptr_t)cache_get(atoms->c, #x, NULL)
+	LIST_APPLY(ATOM_GET, SEP_COLON, ATOM_LIST);
+#undef ATOM_GET
+	return atoms;
+}