keyboard: absolve release event if press was bound

When key press events are handled by compositor keybindings, do not
forward the corresponding release events to clients.

src/key-state.c

@@ -0,0 +1,69 @@
+#include <stdbool.h>
+#include <stdint.h>
+#include <string.h>
+
+#define MAX_PRESSED_KEYS (16)
+
+struct key_array {
+	uint32_t keys[MAX_PRESSED_KEYS];
+	int nr_keys;
+};
+
+static struct key_array pressed, bound;
+
+static void
+remove_key(struct key_array *array, uint32_t keycode)
+{
+	bool shifting = false;
+
+	for (int i = 0; i < MAX_PRESSED_KEYS; ++i) {
+		if (array->keys[i] == keycode) {
+			--array->nr_keys;
+			shifting = true;
+		}
+		if (shifting) {
+			array->keys[i] = i < MAX_PRESSED_KEYS - 1
+				? array->keys[i + 1] : 0;
+		}
+	}
+}
+
+static void
+add_key(struct key_array *array, uint32_t keycode)
+{
+	array->keys[array->nr_keys++] = keycode;
+}
+
+void
+key_state_set_pressed(uint32_t keycode, bool ispressed)
+{
+	if (ispressed) {
+		add_key(&pressed, keycode);
+	} else {
+		remove_key(&pressed, keycode);
+	}
+}
+
+void
+key_state_store_pressed_keys_as_bound(void)
+{
+	memcpy(bound.keys, pressed.keys, MAX_PRESSED_KEYS * sizeof(uint32_t));
+	bound.nr_keys = pressed.nr_keys;
+}
+
+bool
+key_state_corresponding_press_event_was_bound(uint32_t keycode)
+{
+	for (int i = 0; i < bound.nr_keys; ++i) {
+		if (bound.keys[i] == keycode) {
+			return true;
+		}
+	}
+	return false;
+}
+
+void
+key_state_bound_key_remove(uint32_t keycode)
+{
+	remove_key(&bound, keycode);
+}