Prevent Templates From Discarding DOM Elements

Question

I am attempting to integrate a D3.js visualization into a Meteor app. After the page has loaded, a D3 function injects DOM elements into a <div> in my template, based on available data.

Whenever there is a reactive update anywhere on the page, however, Meteor dumps the contents of the template that were injected by my D3.js function. I can re-insert the elements, but this leads to an undesirable flicker and decrease in performance.

Any idea on how to suppress this dropping of externally injected elements? I gather that since these elements were not part of the template originally, they are discarded as part of Meteor's 'cleanup' process.

Answer 1

With the introduction of the Spark templating engine in version 0.4.0, they've introduced the {{#constant}} block helpers to address this issue.

http://meteor.com/blog/2012/08/31/introducing-spark-a-new-live-page-update-engine

Your html template should look something like this....

<template name="samplePageTemplate">
    <div id="samplePage" class="page">
        {{#constant}}
        <div id="sampleGraph"></div>
        {{/constant}}
    </div>
</template>

And the javascript should look something like this...

Template.samplePageTemplate.destroyed = function () {
    this.handle && this.handle.stop();
};
Template.samplePageTemplate.rendered = function () {
    self.node = self.find("svg");
    if (!self.handle) {
        self.handle = Meteor.autorun(function(){

            $('#sampleGraph').html('');
            renderChart();

        });
    };
};

function renderChart(){

    // lots of d3 chart specific stuff 

    var vis = d3.select("#sampleGraph").append("svg:svg")
        .attr("width", window.innerWidth)
        .attr("height", window.innerHeight)
        .append("svg:g")
        .attr("transform", "translate(" + m[3] + "," + m[0] + ")");

    // more d3 chart specific stuff

    });
};

I've sometimes had to use self.node instead of self.handle, but otherwise it should be fairly straight forward.