Fix logic used for mouse_warping output

Turns out we don't need to store the previous focus, and it should be
based on which output the cursor was in.

include/sway/input/seat.h

@@ -52,7 +52,6 @@ struct sway_seat {
 	bool has_focus;
 	struct wl_list focus_stack; // list of containers in focus order
 	struct sway_workspace *workspace;
-	struct sway_node *prev_focus;
 
 	// If the focused layer is set, views cannot receive keyboard focus
 	struct wlr_layer_surface_v1 *focused_layer;

sway/input/seat.c

@@ -646,7 +646,6 @@ void seat_set_focus(struct sway_seat *seat, struct sway_node *node) {
 	}
 
 	struct sway_node *last_focus = seat_get_focus(seat);
-	seat->prev_focus = last_focus;
 	if (last_focus == node) {
 		return;
 	}
@@ -1190,13 +1189,18 @@ void seat_pointer_notify_button(struct sway_seat *seat, uint32_t time_msec,
 
 void seat_consider_warp_to_focus(struct sway_seat *seat) {
 	struct sway_node *focus = seat_get_focus(seat);
-	if (config->mouse_warping == WARP_NO || !focus || !seat->prev_focus) {
+	if (config->mouse_warping == WARP_NO || !focus) {
 		return;
 	}
-	if (config->mouse_warping == WARP_OUTPUT &&
-			node_get_output(focus) == node_get_output(seat->prev_focus)) {
+	if (config->mouse_warping == WARP_OUTPUT) {
+		struct sway_output *output = node_get_output(focus);
+		struct wlr_box box;
+		output_get_box(output, &box);
+		if (wlr_box_contains_point(&box,
+					seat->cursor->cursor->x, seat->cursor->cursor->y)) {
 			return;
 		}
+	}
 
 	if (focus->type == N_CONTAINER) {
 		cursor_warp_to_container(seat->cursor, focus->sway_container);