Add xkb_state_key_get_one_sym

The trivial wrapper around xkb_state_key_get_syms that every user to
date has implemented.

Signed-off-by: Daniel Stone <daniel@fooishbar.org>

src/state.c

@@ -765,6 +765,22 @@ err:
     return 0;
 }
 
+/**
+ * Provides either exactly one symbol, or XKB_KEY_NoSymbol.
+ */
+XKB_EXPORT xkb_keysym_t
+xkb_state_key_get_one_sym(struct xkb_state *state, xkb_keycode_t kc)
+{
+    xkb_keysym_t *syms;
+    int num_syms;
+
+    num_syms = xkb_state_key_get_syms(state, kc, &syms);
+    if (num_syms != 1)
+        return XKB_KEY_NoSymbol;
+
+    return syms[0];
+}
+
 /**
  * Serialises the requested modifier state into an xkb_mod_mask_t, with all
  * the same disclaimers as in xkb_state_update_mask.

test/state.c

@@ -96,6 +96,7 @@ test_update_key(struct xkb_keymap *keymap)
 {
     struct xkb_state *state = xkb_state_new(keymap);
     const xkb_keysym_t *syms;
+    xkb_keysym_t one_sym;
     int num_syms;
 
     assert(state);
@@ -174,6 +175,20 @@ test_update_key(struct xkb_keymap *keymap)
     num_syms = xkb_state_key_get_syms(state, KEY_Q + EVDEV_OFFSET, &syms);
     assert(num_syms == 1 && syms[0] == XKB_KEY_q);
 
+    /* Multiple symbols */
+    num_syms = xkb_state_key_get_syms(state, KEY_6 + EVDEV_OFFSET, &syms);
+    assert(num_syms == 5 &&
+           syms[0] == XKB_KEY_H && syms[1] == XKB_KEY_E &&
+           syms[2] == XKB_KEY_L && syms[3] == XKB_KEY_L &&
+           syms[4] == XKB_KEY_O);
+    one_sym = xkb_state_key_get_one_sym(state, KEY_6 + EVDEV_OFFSET);
+    assert(one_sym == XKB_KEY_NoSymbol);
+    xkb_state_update_key(state, KEY_6 + EVDEV_OFFSET, XKB_KEY_DOWN);
+    xkb_state_update_key(state, KEY_6 + EVDEV_OFFSET, XKB_KEY_UP);
+
+    one_sym = xkb_state_key_get_one_sym(state, KEY_5 + EVDEV_OFFSET);
+    assert(one_sym == XKB_KEY_5);
+
     xkb_state_unref(state);
 }
 

xkbcommon/xkbcommon.h

@@ -724,6 +724,13 @@ int
 xkb_state_key_get_syms(struct xkb_state *state, xkb_keycode_t key,
                        const xkb_keysym_t **syms_out);
 
+/**
+ * As with xkb_state_key_get_syms, but either returns exactly keysym, or
+ * XKB_KEY_NoSymbol if there are either zero or more than one symbols.
+ */
+xkb_keysym_t
+xkb_state_key_get_one_sym(struct xkb_state *state, xkb_keycode_t key);
+
 /**
  * Returns the layout number that would be active for a particular key with
  * the given state.