From 5d8f4ab878159e641e885b90cb10299ce8f92336 Mon Sep 17 00:00:00 2001
From: Andreas Kling <kling@serenityos.org>
Date: Thu, 7 Apr 2022 14:02:28 +0200
Subject: [PATCH] LibGfx: Add Gfx::Quad<T> to represent arbitrary
 quadrilaterals

This comes with a very barebones API for now. You can ask for the
bounding rect of the quad, and also check if a point is inside of it.
---
 Userland/Libraries/LibGfx/Forward.h |  5 +++
 Userland/Libraries/LibGfx/Quad.h    | 55 +++++++++++++++++++++++++++++
 2 files changed, 60 insertions(+)
 create mode 100644 Userland/Libraries/LibGfx/Quad.h

diff --git a/Userland/Libraries/LibGfx/Forward.h b/Userland/Libraries/LibGfx/Forward.h
index 72bea7f1cd..5477b5a6f1 100644
--- a/Userland/Libraries/LibGfx/Forward.h
+++ b/Userland/Libraries/LibGfx/Forward.h
@@ -41,6 +41,9 @@ class Size;
 template<typename T>
 class Rect;
 
+template<typename T>
+class Quad;
+
 using IntLine = Line<int>;
 using FloatLine = Line<float>;
 
@@ -53,6 +56,8 @@ using FloatPoint = Point<float>;
 using IntSize = Size<int>;
 using FloatSize = Size<float>;
 
+using FloatQuad = Quad<float>;
+
 enum class BitmapFormat;
 enum class ColorRole;
 enum class TextAlignment;
diff --git a/Userland/Libraries/LibGfx/Quad.h b/Userland/Libraries/LibGfx/Quad.h
new file mode 100644
index 0000000000..4b1d00c87f
--- /dev/null
+++ b/Userland/Libraries/LibGfx/Quad.h
@@ -0,0 +1,55 @@
+/*
+ * Copyright (c) 2022, Andreas Kling <kling@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <LibGfx/Point.h>
+#include <LibGfx/Triangle.h>
+
+namespace Gfx {
+
+template<typename T>
+class Quad {
+public:
+    Quad(Point<T> p1, Point<T> p2, Point<T> p3, Point<T> p4)
+        : m_p1(p1)
+        , m_p2(p2)
+        , m_p3(p3)
+        , m_p4(p4)
+    {
+    }
+
+    Point<T> const& p1() const { return m_p1; }
+    Point<T> const& p2() const { return m_p2; }
+    Point<T> const& p3() const { return m_p3; }
+    Point<T> const& p4() const { return m_p4; }
+
+    Rect<T> bounding_rect() const
+    {
+        auto top = min(min(m_p1.y(), m_p2.y()), min(m_p3.y(), m_p4.y()));
+        auto right = max(max(m_p1.x(), m_p2.x()), max(m_p3.x(), m_p4.x()));
+        auto bottom = max(max(m_p1.y(), m_p2.y()), max(m_p3.y(), m_p4.y()));
+        auto left = min(min(m_p1.x(), m_p2.x()), min(m_p3.x(), m_p4.x()));
+        return { left, top, right - left, bottom - top };
+    }
+
+    bool contains(Point<T> point) const
+    {
+        // FIXME: There's probably a smarter way to do this.
+        return Triangle(m_p1, m_p2, m_p3).contains(point)
+            || Triangle(m_p1, m_p3, m_p4).contains(point)
+            || Triangle(m_p2, m_p4, m_p1).contains(point)
+            || Triangle(m_p2, m_p4, m_p3).contains(point);
+    }
+
+private:
+    Point<T> m_p1;
+    Point<T> m_p2;
+    Point<T> m_p3;
+    Point<T> m_p4;
+};
+
+}