Misc Uncaught TypeError when trying to inspect elements in the New 3DS browser’s developer mode

[Nightcat]

The New 3DS browser contains a hidden mode that allows you to remotely debug webpages from your computer by holding X+Y while launching the browser. However, the element tree is busted. Trying to inspect anything throws an error:

treeoutline.js:1120 Uncaught TypeError: window.getComputedStyle(...).getPropertyCSSValue is not a function
    at WebInspector.ElementsTreeElement.TreeElement.isEventWithinDisclosureTriangle (treeoutline.js:1120)
    at HTMLLIElement.TreeElement.treeElementMouseDown (treeoutline.js:806)

I’ve tried the latest Chrome and Firefox as well as Chrome 49 and 69 all with no success.

Digging into treeoutline.js shows a comment explaining that this code is not okay:

TreeElement.prototype.isEventWithinDisclosureTriangle = function(event)
{
    // FIXME: We should not use getComputedStyle(). For that we need to get rid of using ::before for disclosure triangle.
    var computedLeftPadding = window.getComputedStyle(this._listItemNode).getPropertyCSSValue("padding-left").getFloatValue(CSSPrimitiveValue.CSS_PX);
    var left = this._listItemNode.totalOffsetLeft() + computedLeftPadding;
    return event.pageX >= left && event.pageX <= left + this.arrowToggleWidth && this.hasChildren;
}

This issue was marked as RESOLVED WONTFIX on WebKit Bugzilla in June 2016. I can’t fix this myself and Nintendo definitely won’t, so where do I go from here?

 

[jeffyTheHomebrewer]

I'm no developer, (and honestly the tools for me feel more of a "fuck around and find out" thing rather than anything I'd actually use for development, mostly) but it seems to work for me? I can edit text and attributes just fine..

 

[Nightcat]

Ran into a need to try this again and I kinda assumed this months ago given how many connectivity issues I was having in my basement, but it works on an iMac running Safari closer to my router so I’m assuming it was just my poor/dropped connection.