util/box: introduce wlr_fbox_empty

Same as wlr_box_empty, but for wlr_fbox.

include/wlr/util/box.h

@@ -78,9 +78,17 @@ bool wlr_box_empty(const struct wlr_box *box);
 void wlr_box_transform(struct wlr_box *dest, const struct wlr_box *box,
 	enum wl_output_transform transform, int width, int height);
 
+/**
+ * Checks whether a box is empty or not.
+ *
+ * A wlr_box is considered empty if its width and/or height is zero or negative.
+ */
+bool wlr_fbox_empty(const struct wlr_fbox *box);
+
 /**
  * Transforms a floating-point box inside a (0, 0, width, height) box.
  */
 void wlr_fbox_transform(struct wlr_fbox *dest, const struct wlr_fbox *box,
 	enum wl_output_transform transform, double width, double height);
+
 #endif

util/box.c

@@ -120,6 +120,10 @@ void wlr_box_transform(struct wlr_box *dest, const struct wlr_box *box,
 	}
 }
 
+bool wlr_fbox_empty(const struct wlr_fbox *box) {
+	return box == NULL || box->width <= 0 || box->height <= 0;
+}
+
 void wlr_fbox_transform(struct wlr_fbox *dest, const struct wlr_fbox *box,
 		enum wl_output_transform transform, double width, double height) {
 	struct wlr_fbox src = *box;