How to customize Interaction Model

Question

I'm using Dygraphs to implement some graphs and am having trouble customizing the zoom options using the interactiveModel option. Following the website's suggestion on how to use it, it doesn't seem to specify what downV3, moveV3, etc are and my program does not recognize them. I copied and pasted an example of Dygraphs using the option in jsFiddle. Does someone know how to efficiently use this and/or what the correct syntax is? Thanks!

var g3 = new Dygraph(document.getElementById("div_g3"),
           NoisyData, { errorBars : true, interactionModel : {
            'mousedown' : downV3,
            'mousemove' : moveV3,
            'mouseup' : upV3,
            'click' : clickV3,
            'dblclick' : dblClickV3,
            'mousewheel' : scrollV3
      }});

Answer 1

Just had the same problem with the interaction and the documentation about the interactionModel property doesn't exists... In hope this answer will help futur users...

If you want to modify only one or more of theses function you can use the defaultInteractionModel:

interactionModel: {
    'dblclick': function (event, g, context) { Dygraph.defaultInteractionModel.dblclick(event, g, context); },
    'mousedown': function (event, g, context) { Dygraph.defaultInteractionModel.mousedown(event, g, context); },
    'touchend': function (event, g, context) { Dygraph.defaultInteractionModel.touchend(event, g, context); },
    'touchmove': function (event, g, context) { Dygraph.defaultInteractionModel.touchmove(event, g, context); },
    'touchstart': function (event, g, context) { Dygraph.defaultInteractionModel.touchstart(event, g, context); },
    willDestroyContextMyself: true
}

Here is the base code for the 6 functions from the Dygraphs interaction example that you can modify to suit your needs:

// Code for a variety of interaction models. Used in interaction.html, but split out from
// that file so they can be tested in isolation.
//
function downV3(event, g, context) {
  context.initializeMouseDown(event, g, context);
  if (event.altKey || event.shiftKey) {
    Dygraph.startZoom(event, g, context);
  } else {
    Dygraph.startPan(event, g, context);
  }
}

function moveV3(event, g, context) {
  if (context.isPanning) {
    Dygraph.movePan(event, g, context);
  } else if (context.isZooming) {
    Dygraph.moveZoom(event, g, context);
  }
}

function upV3(event, g, context) {
  if (context.isPanning) {
    Dygraph.endPan(event, g, context);
  } else if (context.isZooming) {
    Dygraph.endZoom(event, g, context);
  }
}

// Take the offset of a mouse event on the dygraph canvas and
// convert it to a pair of percentages from the bottom left. 
// (Not top left, bottom is where the lower value is.)
function offsetToPercentage(g, offsetX, offsetY) {
  // This is calculating the pixel offset of the leftmost date.
  var xOffset = g.toDomCoords(g.xAxisRange()[0], null)[0];
  var yar0 = g.yAxisRange(0);

  // This is calculating the pixel of the higest value. (Top pixel)
  var yOffset = g.toDomCoords(null, yar0[1])[1];

  // x y w and h are relative to the corner of the drawing area,
  // so that the upper corner of the drawing area is (0, 0).
  var x = offsetX - xOffset;
  var y = offsetY - yOffset;

  // This is computing the rightmost pixel, effectively defining the
  // width.
  var w = g.toDomCoords(g.xAxisRange()[1], null)[0] - xOffset;

  // This is computing the lowest pixel, effectively defining the height.
  var h = g.toDomCoords(null, yar0[0])[1] - yOffset;

  // Percentage from the left.
  var xPct = w == 0 ? 0 : (x / w);
  // Percentage from the top.
  var yPct = h == 0 ? 0 : (y / h);

  // The (1-) part below changes it from "% distance down from the top"
  // to "% distance up from the bottom".
  return [xPct, (1-yPct)];
}

function dblClickV3(event, g, context) {
  // Reducing by 20% makes it 80% the original size, which means
  // to restore to original size it must grow by 25%

  if (!(event.offsetX && event.offsetY)){
    event.offsetX = event.layerX - event.target.offsetLeft;
    event.offsetY = event.layerY - event.target.offsetTop;
  }

  var percentages = offsetToPercentage(g, event.offsetX, event.offsetY);
  var xPct = percentages[0];
  var yPct = percentages[1];

  if (event.ctrlKey) {
    zoom(g, -.25, xPct, yPct);
  } else {
    zoom(g, +.2, xPct, yPct);
  }
}

var lastClickedGraph = null;

function clickV3(event, g, context) {
  lastClickedGraph = g;
  event.preventDefault();
  event.stopPropagation();
}

function scrollV3(event, g, context) {
  if (lastClickedGraph != g) {
    return;
  }
  var normal = event.detail ? event.detail * -1 : event.wheelDelta / 40;
  // For me the normalized value shows 0.075 for one click. If I took
  // that verbatim, it would be a 7.5%.
  var percentage = normal / 50;

  if (!(event.offsetX && event.offsetY)){
    event.offsetX = event.layerX - event.target.offsetLeft;
    event.offsetY = event.layerY - event.target.offsetTop;
  }

  var percentages = offsetToPercentage(g, event.offsetX, event.offsetY);
  var xPct = percentages[0];
  var yPct = percentages[1];

  zoom(g, percentage, xPct, yPct);
  event.preventDefault();
  event.stopPropagation();
}

// Adjusts [x, y] toward each other by zoomInPercentage%
// Split it so the left/bottom axis gets xBias/yBias of that change and
// tight/top gets (1-xBias)/(1-yBias) of that change.
//
// If a bias is missing it splits it down the middle.
function zoom(g, zoomInPercentage, xBias, yBias) {
  xBias = xBias || 0.5;
  yBias = yBias || 0.5;
  function adjustAxis(axis, zoomInPercentage, bias) {
    var delta = axis[1] - axis[0];
    var increment = delta * zoomInPercentage;
    var foo = [increment * bias, increment * (1-bias)];
    return [ axis[0] + foo[0], axis[1] - foo[1] ];
  }
  var yAxes = g.yAxisRanges();
  var newYAxes = [];
  for (var i = 0; i < yAxes.length; i++) {
    newYAxes[i] = adjustAxis(yAxes[i], zoomInPercentage, yBias);
  }

  g.updateOptions({
    dateWindow: adjustAxis(g.xAxisRange(), zoomInPercentage, xBias),
    valueRange: newYAxes[0]
    });
}

The source file can be found here