util: introduce rectangle packing helper

include/wlr/util/rectpack.h

@@ -0,0 +1,48 @@
+/*
+ * This an unstable interface of wlroots. No guarantees are made regarding the
+ * future consistency of this API.
+ */
+#ifndef WLR_USE_UNSTABLE
+#error "Add -DWLR_USE_UNSTABLE to enable unstable wlroots features"
+#endif
+
+#ifndef WLR_UTIL_RECTPACK_H
+#define WLR_UTIL_RECTPACK_H
+
+#include <pixman.h>
+#include <wayland-server-protocol.h>
+
+#include <wlr/util/box.h>
+#include <wlr/util/edges.h>
+
+struct wlr_layer_surface_v1;
+
+struct wlr_rectpack_rules {
+	// If true, the corresponding side will be stretched to take all available area
+	bool grow_width, grow_height;
+};
+
+/**
+ * Place a rectangle within bounds so that it doesn't intersect with the
+ * exclusive region.
+ *
+ * exclusive may be NULL.
+ *
+ * Returns false if there's not enough space or on memory allocation error.
+ */
+bool wlr_rectpack_place(const struct wlr_box *bounds, pixman_region32_t *exclusive,
+		const struct wlr_box *box, struct wlr_rectpack_rules *rules, struct wlr_box *out);
+
+/**
+ * Place a struct wlr_layer_surface_v1 within bounds so that it doesn't
+ * intersect with the exclusive region. If the layer surface has exclusive zone,
+ * the corresponding area will be added to the exclusive region.
+ *
+ * Returns false if there's not enough space or on memory allocation error, in
+ * which case the exclusive region is left intact.
+ */
+bool wlr_rectpack_place_wlr_layer_surface_v1(const struct wlr_box *bounds,
+		pixman_region32_t *exclusive, struct wlr_layer_surface_v1 *surface, struct wlr_box *out);
+
+
+#endif