util/box: stabilize interface

include/wlr/util/box.h

@@ -1,40 +1,79 @@
 /*
- * This an unstable interface of wlroots. No guarantees are made regarding the
- * future consistency of this API.
+* This is a stable interface of wlroots. Future changes will be limited to:
+ *
+ * - New functions
+ * - New struct members
+ * - New enum members
+ *
+ * Note that wlroots does not make an ABI compatibility promise - in the future,
+ * the layout and size of structs used by wlroots may change, requiring code
+ * depending on this header to be recompiled (but not edited).
+ *
+ * Breaking changes are announced in the release notes and follow a 1-year
+ * deprecation schedule.
  */
-#ifndef WLR_USE_UNSTABLE
-#error "Add -DWLR_USE_UNSTABLE to enable unstable wlroots features"
-#endif
-
-#ifndef WLR_TYPES_WLR_BOX_H
-#define WLR_TYPES_WLR_BOX_H
+#ifndef WLR_UTIL_BOX_H
+#define WLR_UTIL_BOX_H
 
-#include <pixman.h>
 #include <stdbool.h>
 #include <wayland-server-protocol.h>
 
+/**
+ * A box representing a rectangle region in a 2D space.
+ *
+ * The x and y coordinates are inclusive, and the width and height lengths are
+ * exclusive. In other words, the box starts from the coordinates (x, y), and
+ * goes up to but not including (x + width, y + height)
+ */
 struct wlr_box {
 	int x, y;
 	int width, height;
 };
 
+/**
+ * A floating-point box representing a rectangle region in a 2D space.
+ *
+ * wlr_fbox has the same semantics as wlr_box
+ */
 struct wlr_fbox {
 	double x, y;
 	double width, height;
 };
 
+/**
+ * Finds the closest point within the box bounds
+ * 
+ * Returns NAN if the box is empty
+ */
 void wlr_box_closest_point(const struct wlr_box *box, double x, double y,
 	double *dest_x, double *dest_y);
 
+/**
+ * Gives the intersecting box betweem two wlr_box.
+ *
+ * Returns an empty wlr_box if the provided wlr_box don't intersect.
+ */
 bool wlr_box_intersection(struct wlr_box *dest, const struct wlr_box *box_a,
 	const struct wlr_box *box_b);
 
+/**
+ * Verifies if a point is contained within the bounds of a given wlr_box.
+ *
+ * For example: 
+ *   - A point at (100, 50) is not contained in the box (0, 0, 100, 50).
+ *   - A point at (10, 10) is contained in the box (10, 0, 50, 50).
+ */
 bool wlr_box_contains_point(const struct wlr_box *box, double x, double y);
 
+/**
+ * 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_box_empty(const struct wlr_box *box);
 
 /**
- * Transforms a box inside a `width` x `height` box.
+ * Transforms a box inside a (0, 0, width, height) box.
  */
 void wlr_box_transform(struct wlr_box *dest, const struct wlr_box *box,
 	enum wl_output_transform transform, int width, int height);