Add rectangle utility functions

Change-Id: Iebcddfc36733aab5131d2fcb9fd8c8a32eff84b8

1 files changed, 75 insertions, 0 deletions

diff --git a/firmware/export/rectangle.h b/firmware/export/rectangle.h
new file mode 100644
index 0000000000..0962611791
--- /dev/null
+++ b/firmware/export/rectangle.h
@@ -0,0 +1,75 @@
+/***************************************************************************
+ *             __________               __   ___.
+ *   Open      \______   \ ____   ____ |  | _\_ |__   _______  ___
+ *   Source     |       _//  _ \_/ ___\|  |/ /| __ \ /  _ \  \/  /
+ *   Jukebox    |    |   (  <_> )  \___|    < | \_\ (  <_> > <  <
+ *   Firmware   |____|_  /\____/ \___  >__|_ \|___  /\____/__/\_ \
+ *                     \/            \/     \/    \/            \/
+ * $Id$
+ *
+ * Copyright (C) 2022 Aidan MacDonald
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
+ * KIND, either express or implied.
+ *
+ ****************************************************************************/
+#ifndef _RECTANGLE_H_
+#define _RECTANGLE_H_
+
+#include <stdbool.h>
+
+struct rectangle
+{
+    int x, y, w, h;
+};
+
+/** Returns true if the rectangle is non-degenerate (positive width/height). */
+static inline bool rect_valid(const struct rectangle *r)
+{
+    return r->w > 0 && r->h > 0;
+}
+
+/** Returns true if ra contains rb. */
+bool rect_contains(const struct rectangle *ra, const struct rectangle *rb);
+
+/** Returns true if ra and rb overlap. */
+bool rect_overlap(const struct rectangle *ra, const struct rectangle *rb);
+
+/**
+ * Computes the biggest rectangle contained in ra and rb.
+ * Returns true if the intersection exists, and writes it to r_out.
+ *
+ * Returns false if there is no intersection, or either input
+ * rectangle is degenerate. In this case r_out may be uninitialized.
+ */
+bool rect_intersect(const struct rectangle *ra, const struct rectangle *rb,
+                    struct rectangle *r_out);
+
+/**
+ * Computes the smallest rectangle containing both ra and rb.
+ *
+ * If one input is degenerate, and the other is not, the output is a
+ * copy of the non-degenerate input. If both inputs are degenerate,
+ * then the output is degenerate but is otherwise unspecified.
+ */
+void rect_union(const struct rectangle *ra, const struct rectangle *rb,
+                struct rectangle *r_out);
+
+/**
+ * Computes the result of subtracting 'rsub' from 'rect'. Up to four
+ * non-overlapping output rectangles will written to 'rects_out'; the
+ * return value is the number of rectangles written.
+ *
+ * If 'rsub' does not overlap 'rect', or if either of the inputs are
+ * degenerate, the output is a single rectangle: a copy of 'rect'.
+ */
+int rect_difference(const struct rectangle *rect,
+                    const struct rectangle *rsub,
+                    struct rectangle rects_out[4]);
+
+#endif /* _RECTANGLE_H_ */