From 8ab1ac6834edd43d91cbe24272897a87ce7e835e Mon Sep 17 00:00:00 2001
From: Nigel Tao <nigeltao@golang.org>
Date: Mon, 24 Aug 2015 10:24:01 +1000
Subject: [PATCH] math/fixed: add rectangle types and the R function.

Change-Id: Ibb3785bcd57f13c7b6f1dc37526f65e44b4ac695
Reviewed-on: https://go-review.googlesource.com/13823
Reviewed-by: Rob Pike <r@golang.org>
---
 math/fixed/fixed.go | 53 +++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 51 insertions(+), 2 deletions(-)

diff --git a/math/fixed/fixed.go b/math/fixed/fixed.go
index 60f83c8..2f25d0e 100644
--- a/math/fixed/fixed.go
+++ b/math/fixed/fixed.go
@@ -13,7 +13,7 @@ import (
 
 // I returns the integer value i as an Int26_6.
 //
-// For example, the integer value 2 is the Int26_6 128.
+// For example, passing the integer value 2 yields Int26_6(128).
 func I(i int) Int26_6 {
 	return Int26_6(i << 6)
 }
@@ -67,12 +67,14 @@ func (x Int52_12) String() string {
 
 // P returns the integer values x and y as a Point26_6.
 //
-// For example, the integer value pair (2, -3) is the Point26_6 (128, -192).
+// For example, passing the integer values (2, -3) yields Point26_6{128, -192}.
 func P(x, y int) Point26_6 {
 	return Point26_6{Int26_6(x << 6), Int26_6(y << 6)}
 }
 
 // Point26_6 is a 26.6 fixed-point coordinate pair.
+//
+// It is analogous to the image.Point type in the standard library.
 type Point26_6 struct {
 	X, Y Int26_6
 }
@@ -98,6 +100,8 @@ func (p Point26_6) Div(k Int26_6) Point26_6 {
 }
 
 // Point52_12 is a 52.12 fixed-point coordinate pair.
+//
+// It is analogous to the image.Point type in the standard library.
 type Point52_12 struct {
 	X, Y Int52_12
 }
@@ -121,3 +125,48 @@ func (p Point52_12) Mul(k Int52_12) Point52_12 {
 func (p Point52_12) Div(k Int52_12) Point52_12 {
 	return Point52_12{p.X * 4096 / k, p.Y * 4096 / k}
 }
+
+// R returns the integer values minX, minY, maxX, maxY as a Rectangle26_6.
+//
+// For example, passing the integer values (0, 1, 2, 3) yields
+// Rectangle26_6{Point26_6{0, 64}, Point26_6{128, 192}}.
+//
+// Like the image.Rect function in the standard library, the returned rectangle
+// has minimum and maximum coordinates swapped if necessary so that it is
+// well-formed.
+func R(minX, minY, maxX, maxY int) Rectangle26_6 {
+	if minX > maxX {
+		minX, maxX = maxX, minX
+	}
+	if minY > maxY {
+		minY, maxY = maxY, minY
+	}
+	return Rectangle26_6{
+		Point26_6{
+			Int26_6(minX << 6),
+			Int26_6(minY << 6),
+		},
+		Point26_6{
+			Int26_6(maxX << 6),
+			Int26_6(maxY << 6),
+		},
+	}
+}
+
+// Rectangle26_6 is a 26.6 fixed-point coordinate rectangle. The Min bound is
+// inclusive and the Max bound is exclusive. It is well-formed if Min.X <=
+// Max.X and likewise for Y.
+//
+// It is analogous to the image.Rectangle type in the standard library.
+type Rectangle26_6 struct {
+	Min, Max Point26_6
+}
+
+// Rectangle52_12 is a 52.12 fixed-point coordinate rectangle. The Min bound is
+// inclusive and the Max bound is exclusive. It is well-formed if Min.X <=
+// Max.X and likewise for Y.
+//
+// It is analogous to the image.Rectangle type in the standard library.
+type Rectangle52_12 struct {
+	Min, Max Point52_12
+}