User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:81.0) Gecko/20100101 Firefox/81.0

Steps to reproduce:

https://www.amazon.com/stores/Bose/page/9E24AFD5-B420-4859-BD2F-A993BA579B20

See related Bug 1666059 - Plex overlays a transparent button on top of text, causing invisible text in high contrast mode

Actual results:

See screen shots.

FIle name Schema - FF = Firefox, IE = Internet Explorer, HC = Hight Contrast Mode

1. Firefox with High Contrast Mode
2. Firefox without High Contrast Mode
3. IE with High Contrast Mode

Expected results:

I should be able to view ALL images on the page.

So this is because they effectively have a semi-transparent, absolutely-positioned link overlaid on top of the image, and we make it fully opaque.

So it seems clear we need to deal with transparency in HCM somehow, not just resetting all backgrounds to the default one as we've done historically.

https://drafts.csswg.org/css-color-adjust-1/#forced-colors-properties seems to suggest we should just respect the alpha value and set the other components to the default background. Does that seem sensible? I suspect we should really set them to the "reverted" background in some cases, to make stuff like bug 1625036 work with backplating...

Thoughts?

(In reply to Emilio Cobos Álvarez (:emilio) from comment #5)

So it seems clear we need to deal with transparency in HCM somehow, not just resetting all backgrounds to the default one as we've done historically.

https://drafts.csswg.org/css-color-adjust-1/#forced-colors-properties seems to suggest we should just respect the alpha value and set the other components to the default background. Does that seem sensible? I suspect we should really set them to the "reverted" background in some cases, to make stuff like bug 1625036 work with backplating...

Thoughts?

Yeah, I agree with you. I saw the plex bug and was thinking the same thing.

But discard it when backplating behind text, so that text is readable.

This should be uncontroversial... Dealing with widgets is a bit harder
so TBD.

Backed out for perma failures.

Push with failure: https://treeherder.mozilla.org/#/jobs?repo=autoland&selectedTaskRun=K5fMJ7fnRLuSWq3RdOl_4w.0&resultStatus=pending%2Crunning%2Csuccess%2Ctestfailed%2Cbusted%2Cexception&searchStr=windows%2C10%2Cx64%2Cdebug%2Creftests%2Ctest-windows10-64%2Fdebug-reftest-e10s%2Cr3&revision=f1130dfcdbc4288385aa97c3c388be90d26d1c8e

Log: https://treeherder.mozilla.org/logviewer.html#/jobs?job_id=317078867&repo=autoland&lineNumber=8168

Backout: https://hg.mozilla.org/integration/autoland/rev/6c41ddbfb5874ed68fb542662208b89791edfaa1

Leaving this in (both of) your very capable hands. :) Thanks.

https://hg.mozilla.org/mozilla-central/rev/eaa908b5583c

Thank you all for the quick research and resolution. It will make a huge difference for me and other who use high contrast.