557584 - when combining :link/:visited colors, don't use the color components of 'transparent'

Status: RESOLVED FIXED

(Core :: CSS Parsing and Computation, defect, P2)

Description

[David Baron :dbaron: (⌚️UTC-4, no longer working on Mozilla)]

With the patch to bug 147777, I noticed an issue on the WBS forms used by the W3C for voting (no public example, I think).  The issue is essentially that some links are styled with what boils down to:
  :link { background: white }
  :visited { background: transparent }

The current rule for combining colors is to use the R, G, and B components of the appropriate color and the A component of the color-if-unvisited.  In this case, it produces bad results, because 'transparent' has R, G, and B components that are black, so we end up with visited links having a black background.

This is relatively straightforward to fix, though... I think it would improve things if, when the :visited color is rgba(0, 0, 0, 0), we don't bother switching to its r, g, b components when the relevant link is visited.

I have a patch to do this.

Comment 1

[David Baron :dbaron: (⌚️UTC-4, no longer working on Mozilla)]

Attachment: patch

Comment 2

[Boris Zbarsky [:bzbarsky]]

Comment on attachment 437390 [details] [diff] [review]
patch

r=bzbarsky

Comment 3

[David Baron :dbaron: (⌚️UTC-4, no longer working on Mozilla)]

http://hg.mozilla.org/mozilla-central/rev/1adc864a08ce