Unable to fetch background colors on unstyled elements in Firefox

[jdan]

Related to #32. This may not be specific to FF.

Tracing through GoogleChrome/accessibility-developer-tools on FF, the following parseColor method:

/**
 * @param {string} colorString The color string from CSS.
 * @return {?axs.color.Color}
 */
axs.color.parseColor = function(colorString) {
    var rgbRegex = /^rgb\((\d+), (\d+), (\d+)\)$/;
    var match = colorString.match(rgbRegex);

    if (match) {
        var r = parseInt(match[1], 10);
        var g = parseInt(match[2], 10);
        var b = parseInt(match[3], 10);
        var a = 1;
        return new axs.color.Color(r, g, b, a);
    }

    var rgbaRegex = /^rgba\((\d+), (\d+), (\d+), (\d*(\.\d+)?)\)/;
    match = colorString.match(rgbaRegex);
    if (match) {
        var r = parseInt(match[1], 10);
        var g = parseInt(match[2], 10);
        var b = parseInt(match[3], 10);
        var a = parseFloat(match[4]);
        return new axs.color.Color(r, g, b, a);
    }

    return null;
};

When this method returns null, the getBgColor method that's used to compute the contrast ratio will also return null - which is causing the error.

This method expects to find rgb(...) and rgba(...) values for the CSSStyleDeclaration's backgroundColor property. In Firefox, unstyled elements have a backgroundColor of "transparent", while on Chrome the value is "rgba(0, 0, 0, 0)".

This might be worth reporting upstream, but in the meantime I can see if this is an isolated edge case and put up a quick patch.

[jdan]

I've filed a bug upstream: GoogleChrome/accessibility-developer-tools#180