HTML5 Canvas проблема

Есть ли способ остановить пользователей при перетаскивании мыши, чтобы они могли только щелкнуть, а не щелкнуть и перетащить. Я хочу, чтобы htem был только для того, чтобы нарисовать точки на холсте или любой узор, который я определяю, похожий на инструмент штампа.

function Sketcher( canvasID, brushImage ) {
this.renderFunction = (brushImage == null || brushImage == undefined) ? this.updateCanvasByLine : this.updateCanvasByBrush;
this.brush = brushImage;
this.touchSupported = Modernizr.touch;
this.canvasID = canvasID;
this.canvas = $("#"+canvasID);
this.context = this.canvas.get(0).getContext("2d"); 
this.context.strokeStyle = "#000000";
this.context.lineWidth = 3;
this.lastMousePoint = {x:0, y:0};

if (this.touchSupported) {
    this.mouseDownEvent = "touchstart";
    this.mouseMoveEvent = "touchmove";
    this.mouseUpEvent = "touchend";
}
else {
    this.mouseDownEvent = "mousedown";
    this.mouseMoveEvent = "mousemove";
    this.mouseUpEvent = "mouseup";
}

this.canvas.bind( this.mouseDownEvent, this.onCanvasMouseDown() );
 }

 Sketcher.prototype.onCanvasMouseDown = function () {
var self = this;
return function(event) {
    self.mouseMoveHandler = self.onCanvasMouseMove()
    self.mouseUpHandler = self.onCanvasMouseUp()

    $(document).bind( self.mouseMoveEvent, self.mouseMoveHandler );
    $(document).bind( self.mouseUpEvent, self.mouseUpHandler );

    self.updateMousePosition( event );
    self.renderFunction( event );
}
 }

  Sketcher.prototype.onCanvasMouseMove = function () {
var self = this;
return function(event) {

    self.renderFunction( event );
    event.preventDefault();
    return false;
}
}

Sketcher.prototype.onCanvasMouseUp = function (event) {
var self = this;
return function(event) {

    $(document).unbind( self.mouseMoveEvent, self.mouseMoveHandler );
    $(document).unbind( self.mouseUpEvent, self.mouseUpHandler );

    self.mouseMoveHandler = null;
    self.mouseUpHandler = null;
}
}

Sketcher.prototype.updateMousePosition = function (event) {
var target;
if (this.touchSupported) {
    target = event.originalEvent.touches[0]
}
else {
    target = event;
}

var offset = this.canvas.offset();
this.lastMousePoint.x = target.pageX - offset.left;
this.lastMousePoint.y = target.pageY - offset.top;

}

Sketcher.prototype.updateCanvasByLine = function (event) {

this.context.beginPath();
this.context.moveTo( this.lastMousePoint.x, this.lastMousePoint.y );
this.updateMousePosition( event );
this.context.lineTo( this.lastMousePoint.x, this.lastMousePoint.y );
this.context.stroke();
}

 Sketcher.prototype.updateCanvasByBrush = function (event) {
var halfBrushW = this.brush.width/2;
var halfBrushH = this.brush.height/2;

var start = { x:this.lastMousePoint.x, y: this.lastMousePoint.y };
this.updateMousePosition( event );
var end = { x:this.lastMousePoint.x, y: this.lastMousePoint.y };

var distance = parseInt( Trig.distanceBetween2Points( start, end ) );
var angle = Trig.angleBetween2Points( start, end );

var x,y;

for ( var z=0; (z<=distance || z==0); z++ )
{
    x = start.x + (Math.sin(angle) * z) - halfBrushW;
    y = start.y + (Math.cos(angle) * z) - halfBrushH;
    //console.log( x, y, angle, z );
    this.context.drawImage(this.brush, x, y);
}
}

 Sketcher.prototype.toString = function () {

var dataString = this.canvas.get(0).toDataURL("image/png");
var index = dataString.indexOf( "," )+1;
dataString = dataString.substring( index );

return dataString;
}

Sketcher.prototype.toDataURL = function () {

var dataString = this.canvas.get(0).toDataURL("image/png");
return dataString;
}

 Sketcher.prototype.clear = function () {

var c = this.canvas[0];
this.context.clearRect( 0, 0, c.width, c.height );
}