Add XKB_KEYSYM_MIN and XKB_KEYSYM_MAX

Keysyms are 32-bit integers with the 3 most significant bits always set
to zero. See: Appendix A “KEYSYM Encoding” of the X Window System
Protocol at https://www.x.org/releases/current/doc/xproto/x11protocol.html#keysym_encoding.

Add a new constants XKB_KEYSYM_MIN and XKB_KEYSYM_MAX to make the
interval of valid keysyms more obvious in the code.

2 files changed, 9 insertions, 1 deletions

diff --git a/src/keysym.c b/src/keysym.c
index 989ae7c..788b7a2 100644
--- a/src/keysym.c
+++ b/src/keysym.c
@@ -64,7 +64,7 @@ get_name(const struct name_keysym *entry)
 XKB_EXPORT int
 xkb_keysym_get_name(xkb_keysym_t ks, char *buffer, size_t size)
 {
-    if ((ks & ((unsigned long) ~0x1fffffff)) != 0) {
+    if (ks > XKB_KEYSYM_MAX) {
         snprintf(buffer, size, "Invalid");
         return -1;
     }
diff --git a/src/keysym.h b/src/keysym.h
index 2633963..e636746 100644
--- a/src/keysym.h
+++ b/src/keysym.h
@@ -50,6 +50,14 @@
 #ifndef KEYSYM_H
 #define KEYSYM_H
 
+/*
+ * NOTE: this is not defined in xkbcommon.h, because if we did, it may add
+ * overhead for library user: when handling keysyms they would also need to
+ * check min keysym when previously there was no reason to.
+ */
+/** Minimum keysym value */
+#define XKB_KEYSYM_MIN      0x00000000
+
 bool
 xkb_keysym_is_lower(xkb_keysym_t keysym);