update use dedicated row identifiers

src/mango.c

@@ -374,6 +374,7 @@ struct Client {
 	double old_master_mfact_per, old_master_inner_per, old_stack_innder_per;
 	double old_scroller_pproportion;
 	bool ismaster;
+	int dual_scroller_row; // 0 = top row, 1 = bottom row, -1 = not set
 	bool cursor_in_upper_half, cursor_in_left_half;
 	bool isleftstack;
 	int tearing_hint;
@@ -2785,6 +2786,7 @@ createnotify(struct wl_listener *listener, void *data) {
 	c = toplevel->base->data = ecalloc(1, sizeof(*c));
 	c->surface.xdg = toplevel->base;
 	c->bw = borderpx;
+	c->dual_scroller_row = -1; // Not assigned to a row yet
 
 	LISTEN(&toplevel->base->surface->events.commit, &c->commit, commitnotify);
 	LISTEN(&toplevel->base->surface->events.map, &c->map, mapnotify);
@@ -3744,6 +3746,11 @@ mapnotify(struct wl_listener *listener, void *data) {
 		}
 
 		if (at_client) {
+			// For row-based layouts, assign new client to same row as focused client
+			if (is_row_layout(selmon) && at_client->dual_scroller_row >= 0) {
+				c->dual_scroller_row = at_client->dual_scroller_row;
+			}
+
 			at_client->link.next->prev = &c->link;
 			c->link.prev = &at_client->link;
 			c->link.next = at_client->link.next;
@@ -5803,6 +5810,7 @@ void createnotifyx11(struct wl_listener *listener, void *data) {
 	c = xsurface->data = ecalloc(1, sizeof(*c));
 	c->surface.xwayland = xsurface;
 	c->type = X11;
+	c->dual_scroller_row = -1; // Not assigned to a row yet
 	/* Listen to the various events it can emit */
 	LISTEN(&xsurface->events.associate, &c->associate, associatex11);
 	LISTEN(&xsurface->events.destroy, &c->destroy, destroynotify);