B2G/gecko/toolkit/content/tests/fennec-tile-testapp/chrome/content/WidgetStack.js
// dragStart: start a drag, with the current coordinates being clientX,clientY
start a drag, with the current coordinates being clientX,clientY
start a drag with the current coordinates being clientX clientY
function dragStart(clientX, clientY) {
    log("(dragStart)", clientX, clientY);
    if (this._dragState) {
      reportError("dragStart with drag already in progress? what?");
      this._dragState = null;
    }
    this._dragState = { };
    let t = Date.now();
    this._dragState.barrierState = [];
    this._dragState.startTime = t;
    this._dragState.outerStartX = clientX;
    this._dragState.outerStartY = clientY;
    this._dragCoordsFromClient(clientX, clientY, t);
    this._dragState.outerLastUpdateDX = 0;
    this._dragState.outerLastUpdateDY = 0;
    if (this._viewport) {
      this._viewport.dragStartRect = this._viewport.rect.clone();
    }
    this._dragState.dragging = true;
  }
function dragStart ( clientX , clientY ) { log ( "(dragStart)" , clientX , clientY ) ; if ( this . _dragState ) { reportError ( "dragStart with drag already in progress? what?" ) ; this . _dragState = null ; } this . _dragState = { } ; let t = Date . now ( ) ; this . _dragState . barrierState = [ ] ; this . _dragState . startTime = t ; this . _dragState . outerStartX = clientX ; this . _dragState . outerStartY = clientY ; this . _dragCoordsFromClient ( clientX , clientY , t ) ; this . _dragState . outerLastUpdateDX = 0 ; this . _dragState . outerLastUpdateDY = 0 ; if ( this . _viewport ) { this . _viewport . dragStartRect = this . _viewport . rect . clone ( ) ; } this . _dragState . dragging = true ; }
dragStart: start a drag, with the current coordinates being clientX,clientY
dragStart : start a drag with the current coordinates being clientX clientY
// outer x, that is outer from the viewport coordinates.  In stack-relative coords. // create a copy of these so that we can compute // deltas correctly to update the viewport