Fix focusing topmost floating windows

Re-focus on the container on which the cursor hovers over.  A
special case is, if there are menus or other subsurfaces open
in the focused container.  It will prefer the focused container
as long as there are subsurfaces.

This commit starts caching the previous node as well as the
previous x/y cursor position.  Re-calculating the previous
focused node by looking at the current state of the cursor
position does not work, if the environment changes.

include/sway/input/cursor.h

@@ -10,6 +10,7 @@ struct sway_cursor {
 	struct wlr_cursor *cursor;
 	struct {
 		double x, y;
+		struct sway_node *node;
 	} previous;
 	struct wlr_xcursor_manager *xcursor_manager;
 

sway/input/cursor.c

@@ -567,15 +567,15 @@ void cursor_send_pointer_motion(struct sway_cursor *cursor, uint32_t time_msec,
 	struct wlr_surface *surface = NULL;
 	double sx, sy;
 
-	// Find the node beneath the pointer's previous position
-	struct sway_node *prev_node = node_at_coords(seat,
-			cursor->previous.x, cursor->previous.y, &surface, &sx, &sy);
+	struct sway_node *prev_node = cursor->previous.node;
+	struct sway_node *node = node_at_coords(seat,
+			cursor->cursor->x, cursor->cursor->y, &surface, &sx, &sy);
+
 	// Update the stored previous position
 	cursor->previous.x = cursor->cursor->x;
 	cursor->previous.y = cursor->cursor->y;
+	cursor->previous.node = node;
 
-	struct sway_node *node = node_at_coords(seat,
-			cursor->cursor->x, cursor->cursor->y, &surface, &sx, &sy);
 	if (node && config->focus_follows_mouse && allow_refocusing) {
 		struct sway_node *focus = seat_get_focus(seat);
 		if (focus && node->type == N_WORKSPACE) {

sway/tree/container.c

@@ -369,6 +369,13 @@ struct sway_container *container_at(struct sway_workspace *workspace,
 	}
 	// If focused is floating, focused view's non-popups
 	if (focus && focus->view && is_floating) {
+		// only switch to unfocused container if focused container has no menus open
+		bool has_subsurfaces = wl_list_length(&focus->view->surface->subsurfaces) > 0;
+		c = floating_container_at(lx, ly, surface, sx, sy);
+		if (!has_subsurfaces && c && c->view && *surface && c != focus) {
+			return c;
+		}
+
 		surface_at_view(focus, lx, ly, surface, sx, sy);
 		if (*surface) {
 			return focus;