state: support querying whether virtual modifiers are active

Previously it was not possible to query the status of virtual modifiers
with the following functions:
- `xkb_state_mod_index_is_active`
- `xkb_state_mod_indices_are_active`
- `xkb_state_mod_name_is_active`
- `xkb_state_mod_names_are_active`

Note that it may *overmatch* if some modifier mappings overlap. For
example, the default “us” PC layout maps both “Alt” and “Meta” to the
real modifier “Mod1”; thus “Mod1”, “Alt” and “Meta” modifiers will
return the same result with these functions.

changes/api/+query-virtual-modifiers-state.bugfix.md

@@ -0,0 +1,9 @@
+The following functions now allow to query also *virtual* modifiers, so they work
+with *any* modifiers (real *and* virtual):
+- `xkb_state_mod_index_is_active`
+- `xkb_state_mod_indices_are_active`
+- `xkb_state_mod_name_is_active`
+- `xkb_state_mod_names_are_active`
+
+Warning: they may overmatch in case there are overlappings virtual-to-real
+modifiers mappings.

include/xkbcommon/xkbcommon.h

@@ -1706,10 +1706,18 @@ xkb_state_serialize_layout(struct xkb_state *state,
 /**
  * Test whether a modifier is active in a given keyboard state by name.
  *
+ * @warning For [virtual modifiers], this function may *overmatch* in case
+ * there are virtual modifiers with overlapping mappings to real modifiers.
+ *
  * @returns 1 if the modifier is active, 0 if it is not.  If the modifier
  * name does not exist in the keymap, returns -1.
  *
  * @memberof xkb_state
+ *
+ * @since 0.1.0: Works only with *real* modifiers
+ * @since 1.8.0: Works also with *virtual* modifiers
+ *
+ * [virtual modifiers]: @ref virtual-modifier-def
  */
 int
 xkb_state_mod_name_is_active(struct xkb_state *state, const char *name,
@@ -1719,6 +1727,9 @@ xkb_state_mod_name_is_active(struct xkb_state *state, const char *name,
  * Test whether a set of modifiers are active in a given keyboard state by
  * name.
  *
+ * @warning For [virtual modifiers], this function may *overmatch* in case
+ * there are virtual modifiers with overlapping mappings to real modifiers.
+ *
  * @param state The keyboard state.
  * @param type  The component of the state against which to match the
  * given modifiers.
@@ -1731,6 +1742,11 @@ xkb_state_mod_name_is_active(struct xkb_state *state, const char *name,
  * the modifier names do not exist in the keymap, returns -1.
  *
  * @memberof xkb_state
+ *
+ * @since 0.1.0: Works only with *real* modifiers
+ * @since 1.8.0: Works also with *virtual* modifiers
+ *
+ * [virtual modifiers]: @ref virtual-modifier-def
  */
 int
 xkb_state_mod_names_are_active(struct xkb_state *state,
@@ -1741,10 +1757,18 @@ xkb_state_mod_names_are_active(struct xkb_state *state,
 /**
  * Test whether a modifier is active in a given keyboard state by index.
  *
+ * @warning For [virtual modifiers], this function may *overmatch* in case
+ * there are virtual modifiers with overlapping mappings to real modifiers.
+ *
  * @returns 1 if the modifier is active, 0 if it is not.  If the modifier
  * index is invalid in the keymap, returns -1.
  *
  * @memberof xkb_state
+ *
+ * @since 0.1.0: Works only with *real* modifiers
+ * @since 1.8.0: Works also with *virtual* modifiers
+ *
+ * [virtual modifiers]: @ref virtual-modifier-def
  */
 int
 xkb_state_mod_index_is_active(struct xkb_state *state, xkb_mod_index_t idx,
@@ -1754,6 +1778,9 @@ xkb_state_mod_index_is_active(struct xkb_state *state, xkb_mod_index_t idx,
  * Test whether a set of modifiers are active in a given keyboard state by
  * index.
  *
+ * @warning For [virtual modifiers], this function may *overmatch* in case
+ * there are virtual modifiers with overlapping mappings to real modifiers.
+ *
  * @param state The keyboard state.
  * @param type  The component of the state against which to match the
  * given modifiers.
@@ -1766,6 +1793,11 @@ xkb_state_mod_index_is_active(struct xkb_state *state, xkb_mod_index_t idx,
  * the modifier indices are invalid in the keymap, returns -1.
  *
  * @memberof xkb_state
+ *
+ * @since 0.1.0: Works only with *real* modifiers
+ * @since 1.8.0: Works also with *virtual* modifiers
+ *
+ * [virtual modifiers]: @ref virtual-modifier-def
  */
 int
 xkb_state_mod_indices_are_active(struct xkb_state *state,

src/state.c

@@ -1265,6 +1265,27 @@ mod_mask_get_effective(struct xkb_keymap *keymap, xkb_mod_mask_t mods)
     return mask;
 }
 
+/* [WARNING] Caller must ensure that the modifier index is valid! */
+static inline bool
+is_real_mod(struct xkb_keymap *keymap, xkb_mod_index_t mod) {
+    return !!(keymap->mods.mods[mod].type & MOD_REAL);
+}
+
+/*
+ * Get the mapping of a modifier.
+ * We cannot use `mods.mods[idx].mapping` directly, because it is
+ * not set for real modifiers.
+ *
+ * [WARNING] Caller must ensure that the modifier index is valid!
+ */
+static inline xkb_mod_mask_t
+get_mod_mapping(struct xkb_keymap *keymap, xkb_mod_index_t idx)
+{
+    return is_real_mod(keymap, idx)
+        ? (1u << idx)
+        : keymap->mods.mods[idx].mapping;
+}
+
 /**
  * Returns 1 if the given modifier is active with the specified type(s), 0 if
  * not, or -1 if the modifier is invalid.
@@ -1277,7 +1298,12 @@ xkb_state_mod_index_is_active(struct xkb_state *state,
     if (idx >= xkb_keymap_num_mods(state->keymap))
         return -1;
 
-    return !!(xkb_state_serialize_mods(state, type) & (1u << idx));
+    xkb_mod_mask_t mapping = get_mod_mapping(state->keymap, idx);
+    if (!mapping)
+        /* Modifier not mapped */
+        return 0;
+    /* WARNING: this may overmatch for virtual modifiers */
+    return !!((xkb_state_serialize_mods(state, type) & mapping) == mapping);
 }
 
 /**
@@ -1325,13 +1351,17 @@ xkb_state_mod_indices_are_active(struct xkb_state *state,
             ret = -1;
             break;
         }
-        wanted |= (1u << idx);
+        wanted |= get_mod_mapping(state->keymap, idx);
     }
     va_end(ap);
 
     if (ret == -1)
         return ret;
 
+    if (!wanted)
+        /* Modifiers not mapped */
+        return 0;
+
     return match_mod_masks(state, type, match, wanted);
 }
 
@@ -1376,13 +1406,17 @@ xkb_state_mod_names_are_active(struct xkb_state *state,
             ret = -1;
             break;
         }
-        wanted |= (1u << idx);
+        wanted |= get_mod_mapping(state->keymap, idx);
     }
     va_end(ap);
 
     if (ret == -1)
         return ret;
 
+    if (!wanted)
+        /* Modifiers not mapped */
+        return 0;
+
     return match_mod_masks(state, type, match, wanted);
 }