src/dygraph-interaction-model.js
function(event, g, context) {
    if (context.cancelNextDblclick) {
      context.cancelNextDblclick = false;
      return;
    }

    // Give plugins a chance to grab this event.
    var e = {
      canvasx: context.dragEndX,
      canvasy: context.dragEndY,
      cancelable: true,
    };
    if (g.cascadeEvents_('dblclick', e)) {
      return;
    }

    if (event.altKey || event.shiftKey) {
      return;
    }
    g.resetZoom();
  }
function(event, g, context) {
    if (context.cancelNextDblclick) {
      context.cancelNextDblclick = false;
      return;
    }

    // Give plugins a chance to grab this event.
    var e = {
      canvasx: context.dragEndX,
      canvasy: context.dragEndY,
      cancelable: true,
    };
    if (g.cascadeEvents_('dblclick', e)) {
      return;
    }

    if (event.altKey || event.shiftKey) {
      return;
    }
    g.resetZoom();
  }
Disable zooming out if panning.