How to check if an embedded SVG document is loaded in an html page?

I need to edit (using javascript) an SVG document embedded in an html page.

When the SVG is loaded, I can access the dom of the SVG and its elements. But I am not able to know if the SVG dom is ready or not, so I cant' perform default actions on the SVG when the html page is loaded.

To access the SVG dom, I use this code:

var svg = document.getElementById("chart").getSVGDocument();

where "chart" is the id of the embed element.

If I try to access the SVG when the html document is ready, in this way:

jQuery(document).ready( function() {
var svg = document.getElementById("chart").getSVGDocument();
...

svg is always null. I just need to know when it is not null, so I can start manipulate it. Do you know if there is a way to do it?

Answers:

Answer

You could try polling every so often.

function checkReady() {
    var svg = document.getElementById("chart").getSVGDocument();
    if (svg == null) {
        setTimeout("checkReady()", 300);
    } else {
        ...
    }
}
Answer

On your embedding element (e.g 'embed', 'object', 'iframe') in the main document add an onload attribute which calls your function, or add the event listener in script, e.g embeddingElm.addEventListener('load', callbackFunction, false). Another option might be to listen for DOMContentLoaded, depends on what you want it for.

You can also add a load listener on the main document. jQuery(document).ready doesn't mean that all resources are loaded, just that the document itself has a DOM that is ready for action. However note that if you listen for load on the entire document your callback function won't be called until all resources in that document are loaded, css, javascript etc.

If you use inline svg, then jQuery(document).ready will work just fine however.

On a further note you might want to consider using embeddingElm.contentDocument (if available) instead of embeddingElm.getSVGDocument().

Answer

Assuming your SVG is in an <embed> tag:

<embed id="embedded-image" src="image.svg" type="image/svg+xml" />

The SVG image is essentially in a sub-document that will have a separate load event to that of the main document. However, you can listen for this event and handle it:

var embed = document.getElementById("embedded-image");
embed.addEventListener('load', function()
{
    var svg = embed.getSVGDocument();
    // Operate upon the SVG DOM here
});

This is better than polling as any modification you make to the SVG will happen before it is first painted, reducing flicker and CPU effort spent painting.

Answer

The load event of the embedding element (e.g. object) would be my preference but, if that isn't a viable solution for some reason, the only generic and reliable test I've found for SVG DOM ready is the getCurrentTime method of the SVG root element:

var element = document.getElementById( 'elementId' );
var svgDoc = element.contentDocument;
var svgRoot = svgDoc ? svgDoc.rootElement : null;

if ( svgRoot
    && svgRoot.getCurrentTime
    && ( svgRoot.getCurrentTime() > 0 ))
{
    /* SVG DOM ready */
}

The W3C SVG recommendation states that getCurrentTime on an SVGSVGElement:

Returns the current time in seconds relative to the start time for the current SVG document fragment. If getCurrentTime is called before the document timeline has begun (for example, by script running in a ‘script’ element before the document's SVGLoad event is dispatched), then 0 is returned.

Answer

You can assign an onload event handler to an element within your SVG document and have it call a javascript function in the html page. onload maps to SVGLoad.

http://www.w3.org/TR/SVG11/interact.html#LoadEvent

The event is triggered at the point at which the user agent has fully parsed the element and its descendants and is ready to act appropriately upon that element

Answer

You could use an onload event for the check.

Suppose some.svg is embedded in object tag :

<body>    
<object id="svgholder" data="some.svg" type="image/svg+xml"></object>
</body>

Jquery

var svgholder = $('body').find("object#svgholder");

svgholder.load("image/svg+xml", function() {
    alert("some svg loaded");
});

javascript

var svgholder = document.getElementById("svgholder");

svgholder.onload = function() {
    alert("some svg loaded");
}
Answer

Using jQuery you can bind to the window load event Erik mentions with:

$(window).load(function(){
    var svg = document.getElementById("chart").getSVGDocument();
});
Answer

For future reference: an Angular(8)/Typescript solution looks like this:

  @ViewChild('startimage', {static:false})
  private startimage: ElementRef;
...
  this.startimage.nativeElement.addEventListener('load', () => {
    alert('loaded');
  });

You can get to the svg by const svg = this.startimage.nativeElement.getSVGDocument();

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