desktop: add commentary clarifying focus rules

include/labwc.h

@@ -375,6 +375,18 @@ void foreign_toplevel_update_outputs(struct view *view);
  *              cannot assume this means that the window actually has keyboard
  *              or pointer focus, in this compositor are they called together.
  */
+
+/**
+ * desktop_focus_view() - do multiple things to make a view "active" and
+ * ready to use:
+ *  - unminimize
+ *  - switch to the workspace it's on
+ *  - give input (keyboard) focus
+ *  - optionally raise above other views
+ *
+ * It's okay to call this function even if the view isn't mapped or the
+ * session is locked/input is inhibited; it will simply do nothing.
+ */
 void desktop_focus_view(struct view *view, bool raise);
 void desktop_arrange_all_views(struct server *server);
 void desktop_focus_output(struct output *output);
@@ -393,6 +405,15 @@ enum lab_cycle_dir {
  */
 struct view *desktop_cycle_view(struct server *server, struct view *start_view,
 	enum lab_cycle_dir dir);
+
+/**
+ * desktop_focus_topmost_view() - focus the topmost view on the current
+ * workspace, skipping views that claim not to want focus (those can
+ * still be focused by explicit request, e.g. by clicking in them).
+ *
+ * This function is typically called when the focused view is hidden
+ * (closes, is minimized, etc.) to focus the "next" view underneath.
+ */
 void desktop_focus_topmost_view(struct server *server);
 
 void keyboard_cancel_keybind_repeat(struct keyboard *keyboard);

src/desktop.c

@@ -73,6 +73,13 @@ desktop_focus_view(struct view *view, bool raise)
 		workspaces_switch_to(view->workspace, /*update_focus*/ false);
 	}
 
+	/*
+	 * Give input focus, even if the view claims not to want it (see
+	 * view->impl->wants_focus). This is a workaround for so-called
+	 * "globally active" X11 views (MATLAB known to be one such)
+	 * that expect to be able to control focus themselves, but can't
+	 * under labwc since it's disallowed at the wlroots level.
+	 */
 	struct seat *seat = &server->seat;
 	if (view->surface != seat->seat->keyboard_state.focused_surface) {
 		seat_focus_surface(seat, view->surface);

src/xwayland.c

@@ -49,7 +49,8 @@ xwayland_view_wants_focus(struct view *view)
 	 * Clients that use XSetInputFocus() to explicitly set the input
 	 * focus should set the WM_TAKE_FOCUS atom in WM_PROTOCOLS.
 	 * Currently, labwc does not support this method of taking focus
-	 * and thus makes no use of WM_TAKE_FOCUS.
+	 * and thus ignores WM_TAKE_FOCUS. These views can still be
+	 * focused by explicit user action (e.g. clicking in them).
 	 */
 	return (bool)hints->input;
 }