Bug 38463 - Fails on Canvas test case: http://philip.html5.org/tests/canvas/suite/tests/2d.text.draw.baseline.top.html
Summary: Fails on Canvas test case: http://philip.html5.org/tests/canvas/suite/tests/2...
Status: NEW
Alias: None
Product: WebKit
Classification: Unclassified
Component: Layout and Rendering (show other bugs)
Version: 528+ (Nightly build)
Hardware: PC OS X 10.5
: P2 Normal
Assignee: Nobody
URL:
Keywords:
Depends on:
Blocks: 20553
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Reported: 2010-05-03 07:38 PDT by Chang Shu
Modified: 2013-01-31 10:57 PST (History)
7 users (show)

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Description Chang Shu 2010-05-03 07:38:08 PDT
http://philip.html5.org/tests/canvas/suite/tests/2d.text.draw.baseline.top.html
Run above test case on Safari.
Actual result: failed
Expected result: pass

The same test case passes on Firefox4.6.
Comment 1 Matthew Delaney 2010-05-11 15:31:52 PDT
Also fails on both Opera 10.53 and Chrome 5.0.375.38 beta on Snow Leopard.
Comment 2 Robert Hogan 2013-01-29 11:10:53 PST
I'd love to know what's going on with our font metrics here. The reason we fail this and the other canvas baseline tests is down to the ascent and descent we calculate for the font before drawing it. I imagine this varies between platforms but I've tested it on Chromium Linux.

Tony - this must be FontMetrics 101, can you shed any light on why Firefox and Chromium Linux (for example) return different ascent/descent for the same font?

The person at http://mudcu.be/journal/2011/01/html5-typographic-metrics/#baselineCanvas looked into this a bit and concluded it was 'invisible space'. :)
Comment 3 Tony Chang 2013-01-29 12:21:43 PST
I actually know very little about font metrics and don't know where this extra 'invisible space' comes from.  Levi or Emil probably know more.
Comment 4 Levi Weintraub 2013-01-31 10:57:23 PST
(In reply to comment #3)
> I actually know very little about font metrics and don't know where this extra 'invisible space' comes from.  Levi or Emil probably know more.

I'm afraid this one is beyond my expertise as well :-/