Add onRelease option to <keybind>

...to make keybind actions fire on the release event rather then when the
key is first pressed. This is useful for binding actions to modifier keys
only. The most likely use-case for this is the binding of a Super key to a
menu, for example:

    <keybind key="Super_L" onRelease="yes">
      <action name="Execute" command="rofi -show drun"/>
    </keybind>

If another keybind is issued between the press and release, the on-release
keybind is cancelled.

Co-authored-by: @johanmalm

docs/labwc-config.5.scd

@@ -492,6 +492,23 @@ extending outward from the snapped edge.
 	If set to "no" (or is absent) the keybind will be layout agnostic.
 	Default is no.
 
+*<keyboard><keybind key="" onRelease="yes|no">*
+	*onRelease*, when yes, fires the keybind action when the key or key
+	combination is released, rather than first pressed. This is useful to
+	bind actions to only modifier keys, where the action should fire when
+	the modifier is used without another key. Default is no.
+
+	The example below will trigger the launch of rofi when the super key is
+	pressed & released, without interference from other multi-key
+	combinations that include the super key:
+
+
+	```
+	<keybind key="Super_L" onRelease="yes">
+	  <action name="Execute" command="rofi -show drun"/>
+	</keybind>
+	```
+
 *<keyboard><keybind key=""><action name="">*
 	Keybind action. See labwc-actions(5).
 

include/config/keybind.h

@@ -20,6 +20,7 @@ struct keybind {
 	int keycodes_layout;
 	struct wl_list actions;  /* struct action.link */
 	struct wl_list link;     /* struct rcxml.keybinds */
+	bool on_release;
 };
 
 /**

include/input/keyboard.h

@@ -9,6 +9,7 @@ struct seat;
 struct keyboard;
 struct wlr_keyboard;
 
+void keyboard_reset_current_keybind(void);
 void keyboard_configure(struct seat *seat, struct wlr_keyboard *kb,
 	bool is_virtual);
 

src/config/rcxml.c

@@ -403,6 +403,8 @@ fill_keybind(char *nodename, char *content)
 	} else if (!current_keybind) {
 		wlr_log(WLR_ERROR, "expect <keybind key=\"\"> element first. "
 			"nodename: '%s' content: '%s'", nodename, content);
+	} else if (!strcasecmp(nodename, "onRelease")) {
+		set_bool(content, &current_keybind->on_release);
 	} else if (!strcasecmp(nodename, "layoutDependent")) {
 		set_bool(content, &current_keybind->use_syms_only);
 	} else if (!strcmp(nodename, "name.action")) {

src/input/keyboard.c

@@ -38,6 +38,15 @@ struct keyinfo {
 
 static bool should_cancel_cycling_on_next_key_release;
 
+static struct keybind *cur_keybind;
+
+/* Called on --reconfigure to prevent segfault when handling release keybinds */
+void
+keyboard_reset_current_keybind(void)
+{
+	cur_keybind = NULL;
+}
+
 static void
 change_vt(struct server *server, unsigned int vt)
 {
@@ -407,7 +416,19 @@ handle_compositor_keybindings(struct keyboard *keyboard,
 		keyinfo.is_modifier);
 
 	if (event->state == WL_KEYBOARD_KEY_STATE_RELEASED) {
-		return handle_key_release(server, event->keycode);
+		if (cur_keybind && cur_keybind->on_release) {
+			key_state_bound_key_remove(event->keycode);
+			if (seat->server->session_lock_manager->locked
+					|| seat->active_client_while_inhibited) {
+				cur_keybind = NULL;
+				return true;
+			}
+			actions_run(NULL, server, &cur_keybind->actions, 0);
+			cur_keybind = NULL;
+			return true;
+		} else {
+			return handle_key_release(server, event->keycode);
+		}
 	}
 
 	/* Catch C-A-F1 to C-A-F12 to change tty */
@@ -443,16 +464,19 @@ handle_compositor_keybindings(struct keyboard *keyboard,
 	/*
 	 * Handle compositor keybinds
 	 */
-	struct keybind *keybind =
-		match_keybinding(server, &keyinfo, keyboard->is_virtual);
-	if (keybind) {
+	cur_keybind = match_keybinding(server, &keyinfo, keyboard->is_virtual);
+	if (cur_keybind) {
 		/*
 		 * Update key-state before action_run() because the action
 		 * might lead to seat_focus() in which case we pass the
 		 * 'pressed-sent' keys to the new surface.
 		 */
 		key_state_store_pressed_key_as_bound(event->keycode);
-		actions_run(NULL, server, &keybind->actions, 0);
+		if (!cur_keybind->on_release) {
+			actions_run(NULL, server, &cur_keybind->actions, 0);
+			/* This cancels any pending on-release keybinds */
+			cur_keybind = NULL;
+		}
 		return true;
 	}
 

src/seat.c

@@ -592,6 +592,7 @@ seat_reconfigure(struct server *server)
 	struct input *input;
 	cursor_reload(seat);
 	overlay_reconfigure(seat);
+	keyboard_reset_current_keybind();
 	wl_list_for_each(input, &seat->inputs, link) {
 		switch (input->wlr_input_device->type) {
 		case WLR_INPUT_DEVICE_KEYBOARD: