x11: cache X11 atoms

On every keymap notify event, the keymap should be refreshed, which
fetches the required X11 atoms. A big keymap might have a few hundred of
atoms.

A profile by a user has shown this *might* be slow when some intensive
amount of keymap activity is occurring. It might also be slow on a
remote X server.

While I'm not really sure this is the actual bottleneck, caching the
atoms is easy enough and only needs a couple kb of memory, so do that.

On the added bench-x11:

Before: retrieved 2500 keymaps from X in 11.233237s
After : retrieved 2500 keymaps from X in 1.592339s

Signed-off-by: Ran Benita <ran@unusedvar.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/src/context.h b/src/context.h
index ead2508..44367cc 100644
--- a/src/context.h
+++ b/src/context.h
@@ -45,6 +45,9 @@ struct xkb_context {
 
     struct atom_table *atom_table;
 
+    /* Used and allocated by xkbcommon-x11, free()d with the context. */
+    void *x11_atom_cache;
+
     /* Buffer for the *Text() functions. */
     char text_buffer[2048];
     size_t text_next;