Bug 100132 – negative scale values in -webkit-image-set are handled incorrectly

• Status: NEW
• Component: CSS

[Rick Byers]

I noticed none of the existing image-set-parsing tests checked negative scale values, eg:
background-image: url(a.png) -2x, url(b.png) -1x

I tried this in chromium and it appears like it's simply ignorning the leading negative sign.  I.e., the '-2x' image is used when the device scale factor is 2.  The cssText property also shows the absolute value without the sign.

I'm assuming such rules should be invalid.  I glanced at the code for this, and it looks like CSSParser::parseImageSet is supposed to fail on negative values:
        if (imageScaleFactor <= 0)
            return 0;

So parseDouble is presumably ignorning a leading '-'.  I haven't dug in further.

[Ahmad Saleem]

@Tim & @Antti - is it still an issue, since with Interop 2023 - `image-set` support is improved significantly - https://wpt.fyi/results/css/css-images/image-set?label=master&label=experimental&aligned&view=interop&q=label%3Ainterop-2023-webcompat