From 72c31255c382f55be68a115b9a2fa0086905a901 Mon Sep 17 00:00:00 2001
From: Loukas Agorgianitis <loukas@agorgianitis.com>
Date: Mon, 14 Apr 2025 11:38:47 +0200
Subject: [PATCH] util/box: introduce wlr_fbox_intersection

Signed-off-by: Loukas Agorgianitis <loukas@agorgianitis.com>
---
 include/wlr/util/box.h |  8 ++++++++
 util/box.c             | 28 ++++++++++++++++++++++++++++
 2 files changed, 36 insertions(+)

diff --git a/include/wlr/util/box.h b/include/wlr/util/box.h
index 64dcbc5cf..816bece7e 100644
--- a/include/wlr/util/box.h
+++ b/include/wlr/util/box.h
@@ -61,6 +61,14 @@ void wlr_box_closest_point(const struct wlr_box *box, double x, double y,
 bool wlr_box_intersection(struct wlr_box *dest, const struct wlr_box *box_a,
 	const struct wlr_box *box_b);
 
+/**
+ * Gives the intersecting box between two struct wlr_fbox.
+ *
+ * Returns an empty box if the provided boxes don't intersect.
+ */
+bool wlr_fbox_intersection(struct wlr_fbox *dest, const struct wlr_fbox *box_a,
+	const struct wlr_fbox *box_b);
+
 /**
  * Verifies if a point is contained within the bounds of a given struct wlr_box.
  *
diff --git a/util/box.c b/util/box.c
index aae09888f..087a33d19 100644
--- a/util/box.c
+++ b/util/box.c
@@ -74,6 +74,34 @@ bool wlr_box_intersection(struct wlr_box *dest, const struct wlr_box *box_a,
 	return true;
 }
 
+bool wlr_fbox_intersection(struct wlr_fbox *dest, const struct wlr_fbox *box_a,
+		const struct wlr_fbox *box_b) {
+	bool a_empty = wlr_fbox_empty(box_a);
+	bool b_empty = wlr_fbox_empty(box_b);
+
+	if (a_empty || b_empty) {
+		*dest = (struct wlr_fbox){0};
+		return false;
+	}
+
+	double x1 = fmax(box_a->x, box_b->x);
+	double y1 = fmax(box_a->y, box_b->y);
+	double x2 = fmin(box_a->x + box_a->width, box_b->x + box_b->width);
+	double y2 = fmin(box_a->y + box_a->height, box_b->y + box_b->height);
+
+	dest->x = x1;
+	dest->y = y1;
+	dest->width = x2 - x1;
+	dest->height = y2 - y1;
+
+	if (wlr_fbox_empty(dest)) {
+		*dest = (struct wlr_fbox){0};
+		return false;
+	}
+
+	return true;
+}
+
 bool wlr_box_contains_point(const struct wlr_box *box, double x, double y) {
 	if (wlr_box_empty(box)) {
 		return false;