action: remember initial direction of PreviousView

...when cycling windows. Also make the toggling of direction when shift
is pressed relative to the initial direction. For example if W-j is
bound to PreviousWindow, subsequent key presses will continue to
cycle backwards unless shift if pressed.

Add documentation for using shift/arrow keys in Next/Previous

docs/labwc-actions.5.scd

@@ -99,11 +99,14 @@ Actions are used in menus and keyboard/mouse bindings.
 	Resize and move active window according to the given region.
 	See labwc-config(5) for further information on how to define regions.
 
-*<action name="NextWindow" />*
+*<action name="NextWindow" />*++
-	Cycle focus to next window.
-
 *<action name="PreviousWindow" />*
-	Cycle focus to previous window.
+	Cycle focus to next/previous window respectively.++
+	Default keybind for NextWindow is Alt-Tab.
+
+	The shift key is used to reverse direction while cycling.
+
+	The arrow keys are used to move forwards/backwards while cycling.
 
 *<action name="Reconfigure" />*
 	Re-load configuration and theme files.

include/labwc.h

@@ -210,6 +210,12 @@ struct seat {
 struct lab_data_buffer;
 struct workspace;
 
+enum lab_cycle_dir {
+	LAB_CYCLE_DIR_NONE,
+	LAB_CYCLE_DIR_FORWARD,
+	LAB_CYCLE_DIR_BACKWARD,
+};
+
 struct server {
 	struct wl_display *wl_display;
 	struct wl_event_loop *wl_event_loop;  /* Can be used for timer events */
@@ -349,6 +355,8 @@ struct server {
 		struct wlr_scene_tree *preview_parent;
 		struct wlr_scene_node *preview_anchor;
 		struct multi_rect *preview_outline;
+		enum lab_cycle_dir initial_direction;
+		bool initial_keybind_contained_shift;
 	} osd_state;
 
 	struct theme *theme;
@@ -442,12 +450,6 @@ struct view *desktop_topmost_focusable_view(struct server *server);
  */
 void desktop_update_top_layer_visiblity(struct server *server);
 
-enum lab_cycle_dir {
-	LAB_CYCLE_DIR_NONE,
-	LAB_CYCLE_DIR_FORWARD,
-	LAB_CYCLE_DIR_BACKWARD,
-};
-
 /**
  * desktop_cycle_view - return view to 'cycle' to
  * @start_view: reference point for finding next view to cycle to

src/action.c

@@ -701,6 +701,26 @@ run_if_action(struct view *view, struct server *server, struct action *action)
 	return !strcmp(branch, "then");
 }
 
+static bool
+shift_is_pressed(struct server *server)
+{
+	uint32_t modifiers = wlr_keyboard_get_modifiers(
+			&server->seat.keyboard_group->keyboard);
+	return modifiers & WLR_MODIFIER_SHIFT;
+}
+
+static void
+start_window_cycling(struct server *server, enum lab_cycle_dir direction)
+{
+	/* Remember direction so it can be followed by subsequent key presses */
+	server->osd_state.initial_direction = direction;
+	server->osd_state.initial_keybind_contained_shift =
+		shift_is_pressed(server);
+	server->osd_state.cycle_view = desktop_cycle_view(server,
+		server->osd_state.cycle_view, direction);
+	osd_update(server);
+}
+
 void
 actions_run(struct view *activator, struct server *server,
 	struct wl_list *actions, uint32_t resize_edges)
@@ -791,14 +811,10 @@ actions_run(struct view *activator, struct server *server,
 			}
 			break;
 		case ACTION_TYPE_NEXT_WINDOW:
-			server->osd_state.cycle_view = desktop_cycle_view(server,
+			start_window_cycling(server, LAB_CYCLE_DIR_FORWARD);
-				server->osd_state.cycle_view, LAB_CYCLE_DIR_FORWARD);
-			osd_update(server);
 			break;
 		case ACTION_TYPE_PREVIOUS_WINDOW:
-			server->osd_state.cycle_view = desktop_cycle_view(server,
+			start_window_cycling(server, LAB_CYCLE_DIR_BACKWARD);
-				server->osd_state.cycle_view, LAB_CYCLE_DIR_BACKWARD);
-			osd_update(server);
 			break;
 		case ACTION_TYPE_RECONFIGURE:
 			kill(getpid(), SIGHUP);

src/input/keyboard.c

@@ -383,6 +383,16 @@ handle_menu_keys(struct server *server, struct keysyms *syms)
 	}
 }
 
+static void
+toggle_direction(enum lab_cycle_dir *direction)
+{
+	if (*direction == LAB_CYCLE_DIR_FORWARD) {
+		*direction = LAB_CYCLE_DIR_BACKWARD;
+	} else if (*direction == LAB_CYCLE_DIR_BACKWARD) {
+		*direction = LAB_CYCLE_DIR_FORWARD;
+	}
+}
+
 static void
 handle_cycle_view_key(struct server *server, struct keyinfo *keyinfo)
 {
@@ -397,21 +407,36 @@ handle_cycle_view_key(struct server *server, struct keyinfo *keyinfo)
 
 	/* cycle to next */
 	if (!keyinfo->is_modifier) {
-		bool back_key = false;
+		enum lab_cycle_dir direction = server->osd_state.initial_direction;
 		for (int i = 0; i < keyinfo->translated.nr_syms; i++) {
 			if (keyinfo->translated.syms[i] == XKB_KEY_Up
 					|| keyinfo->translated.syms[i] == XKB_KEY_Left) {
-				back_key = true;
+				direction = LAB_CYCLE_DIR_BACKWARD;
-				break;
+				goto miss_shift_toggle;
+			}
+			if (keyinfo->translated.syms[i] == XKB_KEY_Down
+					|| keyinfo->translated.syms[i] == XKB_KEY_Right) {
+				direction = LAB_CYCLE_DIR_FORWARD;
+				goto miss_shift_toggle;
 			}
 		}
-		bool backwards = (keyinfo->modifiers & WLR_MODIFIER_SHIFT) || back_key;
 
-		enum lab_cycle_dir dir = backwards
+		bool shift_is_pressed = keyinfo->modifiers & WLR_MODIFIER_SHIFT;
-			? LAB_CYCLE_DIR_BACKWARD
+		if (shift_is_pressed != server->osd_state.initial_keybind_contained_shift) {
-			: LAB_CYCLE_DIR_FORWARD;
+			/*
+			 * Shift reverses the direction - unless shift was part of the
+			 * original keybind in which case we do the opposite.
+			 * For example with S-A-Tab bound to PreviousWindow, shift with
+			 * subsequent key presses should carry on cycling backwards.
+			 */
+			toggle_direction(&direction);
+		}
+
+	/* Only one direction modifier is allowed, either arrow keys OR shift */
+miss_shift_toggle:
+
 		server->osd_state.cycle_view = desktop_cycle_view(server,
-			server->osd_state.cycle_view, dir);
+			server->osd_state.cycle_view, direction);
 		osd_update(server);
 	}
 }