1 files changed, 23 insertions, 0 deletions

diff --git a/js/tools/PanTool.js b/js/tools/PanTool.js
index 71301d46..0537a27b 100755
--- a/js/tools/PanTool.js
+++ b/js/tools/PanTool.js
@@ -81,6 +81,14 @@ exports.PanTool = Montage.create(toolBase,
                         {
                 this._altKeyDown = true;
             }
+                        else if (event.shiftKey)
+                        {
+                                if (!this._shiftKeyDown)
+                                {
+                                                this._shiftKeyDown = true;
+                                                this._shiftPt = this._lastGPt.slice();
+                                }
+                        }
         }
     },
 
@@ -90,6 +98,10 @@ exports.PanTool = Montage.create(toolBase,
                         {
                 this._altKeyDown = false;
             }
+                        else if (event.keyCode === Keyboard.SHIFT)
+                        {
+                                this._shiftKeyDown = false;
+                        }
         }
     },
 
@@ -221,6 +233,7 @@ exports.PanTool = Montage.create(toolBase,
                                         var tmpLocal   = MathUtils.transformAndDivideHomogeneousPoint( this._globalPt, globalToLocalMat );
 
                                         this._lastGPt = this._globalPt.slice();
+                                        this._shiftPt = this._lastGPt.slice();
                                         this._lastY = this._lastGPt[1];
 
                                         // set up the matrices we will be needing
@@ -285,6 +298,16 @@ exports.PanTool = Montage.create(toolBase,
                                         this._globalPt[2] += dy;
                                         gPt = [this._lastGPt[0], this._lastGPt[1], this._globalPt[2]];
                                 }
+                                else if (this._shiftKeyDown)
+                                {
+                                        var dx = Math.abs( this._shiftPt[0] - gPt[0] ),
+                                                dy = Math.abs( this._shiftPt[1] - gPt[1] );
+
+                                        if (dx >= dy)
+                                                gPt[1] = this._shiftPt[1];
+                                        else
+                                                gPt[0] = this._shiftPt[0];
+                                }
 
                                 // update the scrollbars
                                 var deltaGPt = VecUtils.vecSubtract(2, gPt, this._lastGPt);