Bug 42973 – (color:8) media query does not evaluate to true for 32bpp displays on Windows

• Component: CSS
• Status: RESOLVED FIXED

[Adam Roben (:aroben)]

Created attachment 62566 [details]
test case

To reproduce:

1. Load attached test case

The box in the test case should be green, but is red. On Mac it is green.

The problem is that the (color:8) media query is evaluating to false. Surprisingly, (color:10) evaluates to true on Windows.

[Adam Roben (:aroben)]

The screenDepthPerComponent function is what is used to evaluate this media query: <http://trac.webkit.org/browser/trunk/WebCore/platform/win/PlatformScreenWin.cpp?rev=52791#L74>

The problem (as in bug 42972) is that deviceInfo.bmBitsPerPel is returning 32, rather than 24. 32 / 3 == 10 (with integer truncation), which is why (color:10) is evaluating to true.

Once we fix bug 42972, we could change screenDepthPerComponent to call through to screenDepth, rather than calling deviceInfoForWidget directly.

[Adam Roben (:aroben)]

<rdar://problem/8234072>

[Adam Roben (:aroben)]

Created attachment 69262 [details]
LayoutTests-compatible test case

[Adam Roben (:aroben)]

Created attachment 69264 [details]
Fix color media queries on Windows

[Adam Roben (:aroben)]

Comment on attachment 69264 [details]
Fix color media queries on Windows

View in context: https://bugs.webkit.org/attachment.cgi?id=69264&action=review

> LayoutTests/fast/media/color-does-not-include-alpha.html:12
> +    @media (color:8) {
> +        #test {
> +            background-color: green;
> +        }
> +    }

This test requires that all testers have 24bpp displays. Is this OK?

[Adam Roben (:aroben)]

Committed r68809: <http://trac.webkit.org/changeset/68809>

[Csaba Osztrogonác]

(In reply to comment #6)
> Committed r68809: <http://trac.webkit.org/changeset/68809>

The new test fails on Qt, I filed a new bug to track it:
https://bugs.webkit.org/show_bug.cgi?id=46966

[Adam Roben (:aroben)]

(In reply to comment #7)
> (In reply to comment #6)
> > Committed r68809: <http://trac.webkit.org/changeset/68809>
> 
> The new test fails on Qt, I filed a new bug to track it:
> https://bugs.webkit.org/show_bug.cgi?id=46966

Sorry about that, and thanks!