Bug 47157 – CSS 2.1 failure: background-position-001, background-position-002

• Component: Layout and Rendering
• Status: RESOLVED FIXED

[Simon Fraser (smfr)]

Created attachment 69752 [details]
background-position-001.htm

These tests fail:

html4/background-position-001	fail
html4/background-position-002	fail

[Simon Fraser (smfr)]

These tests rely on 'ex' units.

[Simon Fraser (smfr)]

We're getting an xHeight of 20 for the Ahem font at 20px, but it seems that the xHeight should be 80% of this <http://hixie.ch/resources/fonts/>

CTFontGetBoundingRectsForGlyphs() returns a rect of 0,-4, 20x20, which
 boundingBox.setY(-boundingBox.bottom());
converts to  0,-16, 20x20
which seems wrong.

Right, on Mac OS X, WebKit prefers the height of the lowercase x glyph over the x-height encoded in the font.

[Simon Fraser (smfr)]

Ah, the culprit is:

        // Use the maximum of either width or height because "x" is nearly square
        // and web pages that foolishly use this metric for width will be laid out
        // poorly if we return an accurate height. Classic case is Times 13 point,
        // which has an "x" that is 7x6 pixels.
        m_xHeight = static_cast<float>(max(CGRectGetMaxX(xBox), -CGRectGetMinY(xBox)));

Maybe we should make an exception for the Ahem font?

[Simon Fraser (smfr)]

The tests covered by bug 47158 also rely on ex units.

[Simon Fraser (smfr)]

Fixed by http://trac.webkit.org/changeset/80662 ?

[Dave Hyatt]

*** Bug 47158 has been marked as a duplicate of this bug. ***

[Dave Hyatt]

No, not fixed by r80662.  Actual patch coming shortly.

[Dave Hyatt]

Created attachment 85379 [details]
Patch

[Simon Fraser (smfr)]

Comment on attachment 85379 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=85379&action=review

> Source/WebCore/ChangeLog:5
> +        https://bugs.webkit.org/show_bug.cgi?id=47157, CSS2.1 test failures because the ex unit is broken

We normally put the bug URL on its own line.

> LayoutTests/accessibility/image-map-title-causes-crash-expected.txt:-10
> - 1
> -Requesting the title of an AccessibilityImageMapLink can cause a crash when the map's area element has been removed.
> -
> -On success, you will see a series of "PASS" messages, followed by "TEST COMPLETE".
> -
> -
> -PASS successfullyParsed is true
> -
> -TEST COMPLETE
> -

Why did this result go away?

[Dave Hyatt]

Fixed in r80755.