correctly handle cursor motion when button is held (for layer surfaces)

client.h

@@ -307,3 +307,18 @@ toplevel_from_popup(struct wlr_xdg_popup *popup)
 		}
 	}
 }
+
+static inline void *
+toplevel_from_wlr_layer_surface(struct wlr_surface *s)
+{
+	Client *c;
+	struct wlr_layer_surface_v1 *wlr_layer_surface;
+
+	if ((c = client_from_wlr_surface(s)))
+		return c;
+	else if (s && wlr_surface_is_layer_surface(s)
+			&& (wlr_layer_surface = wlr_layer_surface_v1_from_wlr_surface(s)))
+		return wlr_layer_surface->data;
+
+	return NULL;
+}

dwl.c

@@ -1504,6 +1504,7 @@ motionnotify(uint32_t time)
 {
 	double sx = 0, sy = 0;
 	Client *c = NULL;
+	LayerSurface *l;
 	struct wlr_surface *surface = NULL;
 	struct wlr_drag_icon *icon;
 
@@ -1536,10 +1537,12 @@ motionnotify(uint32_t time)
 	xytonode(cursor->x, cursor->y, &surface, &c, NULL, &sx, &sy);
 
 	if (cursor_mode == CurPressed && !seat->drag) {
-		surface = seat->pointer_state.focused_surface;
-		c = client_from_wlr_surface(surface);
-		sx = c ? cursor->x - c->geom.x : 0;
-		sy = c ? cursor->y - c->geom.y : 0;
+		if ((l = toplevel_from_wlr_layer_surface(
+				 seat->pointer_state.focused_surface))) {
+			surface = seat->pointer_state.focused_surface;
+			sx = cursor->x - l->geom.x;
+			sy = cursor->y - l->geom.y;
+		}
 	}
 
 	/* If there's no client surface under the cursor, set the cursor image to a