code: function(ev) {
              ev.preventDefault();
  
              this.realMouseX = ev.pageX;
              this.realMouseY = ev.pageY;
  
              if (this.settings.axis !== Garnish.Y_AXIS) {
                  this.mouseX = ev.pageX;
              }
  
              if (this.settings.axis !== Garnish.X_AXIS) {
                  this.mouseY = ev.pageY;
              }
  
              this.mouseDistX = this.mouseX - this.mousedownX;
              this.mouseDistY = this.mouseY - this.mousedownY;
  
              if (!this.dragging) {
                  // Has the mouse moved far enough to initiate dragging yet?
                  this._handleMouseMove._mouseDist = Garnish.getDist(this.mousedownX, this.mousedownY, this.realMouseX, this.realMouseY);
  
                  if (this._handleMouseMove._mouseDist >= Garnish.BaseDrag.minMouseDist) {
                      this.startDragging();
                  }
              }
  
              if (this.dragging) {
                  this.drag(true);
              }
          }
docs: Handle Mouse Move