gistfile1.txt

_clippingFrameChanged: function() {
        // False positives here are very common, so check to make sure before
        // we take the slow path.
        var previousClippingFrame = this._previousClippingFrame;
        var clippingFrame = this.get('clippingFrame');
        if (previousClippingFrame === null ||
                !SC.rectsEqual(clippingFrame, previousClippingFrame)) {
            // Move the content of the editor around.
            if (previousClippingFrame !== null && this._bespin_canvas_canvasDom !== null) {
                var shiftY = previousClippingFrame.y - clippingFrame.y;
                this.moveRegion(0, 0, 
                    previousClippingFrame.width, previousClippingFrame.height,
                    0, shiftY);
                    
                var repaintRect = {};
                if (shiftY < 0) {
                    repaintRect = {
                        x: 0,
                        y: clippingFrame.y + clippingFrame.height + shiftY,
                        width: clippingFrame.width,
                        height: -shiftY + 10
                    };
                } else {
                    repaintRect = {
                        x: 0,
                        y: clippingFrame.y,
                        width: clippingFrame.width,
                        height: shiftY + 10
                    };
                }
                // console.log(clippingFrame, this.get('layerFrame'));
                //this._backgroundInvalid = true;
                    this._invalidRange = this.get('layoutManager').
                        characterRangeForBoundingRect(repaintRect);
                
            } else {
                this._invalidate();
            }
            this._previousClippingFrame = clippingFrame;
        }
    }.observes('clippingFrame'),