From 89c468924e9c94cb80f2fe09b3581b12b6697588 Mon Sep 17 00:00:00 2001
From: Zachary Yedidia <zyedidia@gmail.com>
Date: Fri, 11 Nov 2016 20:12:21 -0500
Subject: [PATCH] Fix rare out of bounds error with selections

Fixes #446
---
 cmd/micro/cursor.go | 9 ++++++---
 cmd/micro/loc.go    | 9 +++++++++
 2 files changed, 15 insertions(+), 3 deletions(-)

diff --git a/cmd/micro/cursor.go b/cmd/micro/cursor.go
index c6eb92ae..a40aa9cf 100644
--- a/cmd/micro/cursor.go
+++ b/cmd/micro/cursor.go
@@ -73,10 +73,13 @@ func (c *Cursor) DeleteSelection() {
 
 // GetSelection returns the cursor's selection
 func (c *Cursor) GetSelection() string {
-	if c.CurSelection[0].GreaterThan(c.CurSelection[1]) {
-		return c.buf.Substr(c.CurSelection[1], c.CurSelection[0])
+	if InBounds(c.CurSelection[0], c.buf) && InBounds(c.CurSelection[1], c.buf) {
+		if c.CurSelection[0].GreaterThan(c.CurSelection[1]) {
+			return c.buf.Substr(c.CurSelection[1], c.CurSelection[0])
+		}
+		return c.buf.Substr(c.CurSelection[0], c.CurSelection[1])
 	}
-	return c.buf.Substr(c.CurSelection[0], c.CurSelection[1])
+	return ""
 }
 
 // SelectLine selects the current line
diff --git a/cmd/micro/loc.go b/cmd/micro/loc.go
index ce0806a1..263e0fb3 100644
--- a/cmd/micro/loc.go
+++ b/cmd/micro/loc.go
@@ -28,6 +28,15 @@ func ToCharPos(start Loc, buf *Buffer) int {
 	return loc
 }
 
+// InBounds returns whether the given location is a valid character position in the given buffer
+func InBounds(pos Loc, buf *Buffer) bool {
+	if pos.Y < 0 || pos.Y >= buf.NumLines || pos.X < 0 || pos.X > Count(buf.Line(pos.Y)) {
+		return false
+	}
+
+	return true
+}
+
 // ByteOffset is just like ToCharPos except it counts bytes instead of runes
 func ByteOffset(pos Loc, buf *Buffer) int {
 	x, y := pos.X, pos.Y