Render To a div, and then export as jpeg - rally

Question

In Rally App SDK 2.0, I would like to show a dropdown and button in line, and a chart below. The button would export (save as) the chart as a jpeg.
1) how do I specify the div to render objects to? The below code ignores the renderTo
2) is there sample code for exporting a jpeg image? using Canvas generates error
this.add({
xtype: 'rallycombobox',
fieldLabel: 'Select an Enterprise Release',
width: '500px',
renderTo: Ext.get("dropdownDiv"),
storeConfig: {
autoLoad: true,
model: 'Program',
fetch: 'Name,Releases,ReleaseStartDate,ReleaseDate',
sorters: [
{
property: 'Name',
direction: 'ASC'
}
]
},
listeners: {
select: this._onSelect,
scope: this
}
});
this.add({
xtype: 'rallybutton',
text: 'Export',
renderTo: Ext.get("buttonDiv"),
handler: function() {
var canvas = document.getElementById("chartDiv");
var img = canvas.toDataURL("image/jpeg");
// .toDataURL generates error, TypeError: canvas.toDataURL is not a function
document.write('<img src="'+img+'"/>');
}
});
this.add({
id: 'chartCmp',
xtype: 'rallychart',
renderTo: Ext.get("chartDiv"),
flex: 1,
chartConfig: chartConfig
});
// here is the body statement, removed <> so it will show
body
table
tr
td
div id="dropdownDiv" style="height:50px; width:500px;"/div
/td
td
div id="buttonDiv" style="height:50px; width:50px;"/div
/td
/tr
/table
div id="chartDiv"/div
/body

Answer 1

In Ext there are two ways to get a component rendered. The first is by adding a config object with an xtype to a container. That would be the this.add(); lines in your app. The second is by instantiating the component using Ext.create and specifying a renderTo in its config.
this.add({xtype: 'component', html: 'hello world'});
Ext.create('Ext.Component', { html: 'hello world', renderTo: 'aDiv' });
The preferred way is the first since then your component participates in the layout of the app. Also the preferred way for creating dom elements in an app (especially for initial layout) is through the items config rather than static html in the app body.
So:
Ext.define('My.App', {
extend: 'Rally.app.App',
items: [
{ xtype: 'container' itemId: 'dropdownDiv' },
{ xtype: 'container', itemId: 'chartDiv' }
]
});
And then you can add content in the launch method like so:
this.down('#chartDiv').add(chartConfig);
As far as your canvas question goes I'm not sure. You may want to post that as a separate question with more details on the specific error.