User Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:15.0) Gecko/15.0 Firefox/15.0a1 Build ID: 20120510030517 Steps to reproduce: Go to https://developer.mozilla.org/en/CSS/text-shadow, scroll to the examples. Actual results: In the second example, shadow artifacts appear at the descenders.

Another STR: 1. Set gfx.content.azure.enabled to True. 2. Add the following CSS in Stylish (blank style), or both userChrome.css and userContent.css: * { text-shadow: 0px 0px 1px #909090 !important; } 3. Go to https://en.wikipedia.org/wiki/Descender NB1: The artifact is present only if the blur-radius is exactly 1px. NB2: The artifact is present at default zoom level only. ----------- The above text-shadow also creates artifacts on tabs with some page titles only.

I suspect this is an artifact from not having EXTEND_NONE. Anyone who by any chance knows how these shadows are drawn back onto the final surface?

nsTextFrame::PaintOneShadow calls nsContextBoxBlur::DoPaint calls gfxAlphaBoxBlur::Paint calls gfxContext::Mask. Mask is called with a solid-color source and the blurred alpha as the mask surface.

Since mask is unbound my theory about EXTEND_NONE is probably correct, I'll look into adding a rectangular clip. That should fix this usecase without much of a performance cost.

You mean add a 1px border to the mask surface and clip to the original mask extents when drawing into the mask?

This patch should fix the issue.

(In reply to Robert O'Callahan (:roc) (Mozilla Corporation) from comment #6) > You mean add a 1px border to the mask surface and clip to the original mask > extents when drawing into the mask? This solution seems easier. But I could do that if you'd have a strong preference.