From f8061a97ebd88fd43dd00b90630df25f7c25739d Mon Sep 17 00:00:00 2001
From: Trevor Parscal <trevorparscal@gmail.com>
Date: Tue, 11 Dec 2012 11:10:22 -0800
Subject: [PATCH] Improve truncate and truncateRange to allow negative values

Positive values will move the end, negative values will move the start

Change-Id: I566653664bf2a8a74781f1059a51873ab72560f9
---
 modules/ve/dm/ve.dm.SurfaceFragment.js |  2 +-
 modules/ve/ve.Range.js                 | 14 ++++++++++----
 2 files changed, 11 insertions(+), 5 deletions(-)

diff --git a/modules/ve/dm/ve.dm.SurfaceFragment.js b/modules/ve/dm/ve.dm.SurfaceFragment.js
index 9a1026f724..44b53c9ee9 100644
--- a/modules/ve/dm/ve.dm.SurfaceFragment.js
+++ b/modules/ve/dm/ve.dm.SurfaceFragment.js
@@ -126,7 +126,7 @@ ve.dm.SurfaceFragment.prototype.adjustRange = function ( start, end ) {
  * Gets a new fragment with a truncated length.
  *
  * @method
- * @param {Number} limit Maximum length of range
+ * @param {Number} limit Maximum length of range (negative for left-side truncation)
  * @returns {ve.dm.SurfaceFragment} Truncated fragment
  */
 ve.dm.SurfaceFragment.prototype.truncateRange = function ( limit ) {
diff --git a/modules/ve/ve.Range.js b/modules/ve/ve.Range.js
index 1b987d0e38..67eb00ac5d 100644
--- a/modules/ve/ve.Range.js
+++ b/modules/ve/ve.Range.js
@@ -141,14 +141,20 @@ ve.Range.prototype.equals = function ( other ) {
  * Creates a new ve.Range object.
  *
  * @method
- * @param {Number} Length of the new range.
+ * @param {Number} Length of the new range (negative for left-side truncation)
  * @returns {ve.Range} A new range.
  */
 ve.Range.prototype.truncate = function ( length ) {
 	this.normalize();
-	return new ve.Range(
-		this.start, Math.max( this.start, Math.min( this.start + length, this.end ) )
-	);
+	if ( length >= 0 ) {
+		return new ve.Range(
+			this.start, Math.min( this.start + length, this.end )
+		);
+	} else {
+		return new ve.Range(
+			Math.max( this.end + length, this.start ), this.end
+		);
+	}
 };
 
 /**