620278 - disabling ligatures (e.g. in SVG text with rotated glyphs, or HTML text with letterspacing) doesn't work for Helvetica on OS X 10.6

Status: RESOLVED WORKSFORME

(Core :: Layout: Text and Fonts, defect)

Description

[Cameron McCormack (:heycam)]

Attachment: Reduced test

If an SVG <text> element has a rotate="" attribute, and the text includes characters that will be rendered as a ligature, then the ligature will not be rendered.

With the attached test on my Mac, whatever font sans-serif is mapping to must have an "fi" ligature, as that is not rendered.

Comment 1

[Robert Longson [:longsonr]]

We attempt to disable ligatures for rotated text in nsSVGGlyphFrame::GetTextRunFlags. I thought that was working on Mac. Does dynamic-text-04-ref.svg not work for you?

Comment 2

[Cameron McCormack (:heycam)]

That test works for me unless I add a font-family="sans-serif" on the root.  It must be that the font "serif" maps to (at least on my machine) doesn't have an "fi" ligature.

Comment 3

[Robert Longson [:longsonr]]

It's down to the font backend to honour the disable ligatures flag. My understanding was that the Mac backend did so. Roc or Jonathan Kew would know more.

Comment 4

[Jonathan Kew [:jfkthame]]

OK, so this is not an SVG bug; the same problem occurs with HTML text if letter-spacing is applied (which is supposed to disable ligatures). It seems to be specific to the Helvetica font; thus,

data:text/html,<p style="font-family:helvetica; letter-spacing: 1em">specified

shows the problem, while

data:text/html,<p style="font-family:arial; letter-spacing: 1em">specified

does not. Even the Light face of Helvetica is OK, as shown by:

data:text/html,<p style="font-family:helvetica; font-weight: 100; letter-spacing: 1em">specified

Checking the Typography palette in TextEdit.app, it doesn't show any features for Helvetica (although it does for Helvetica Light). I haven't tried exploring the actual font tables yet, but I suspect this may indicate a missing or broken 'feat' table, meaning that we don't get proper control of the AAT features.

Moving this to Layout:Text for now, but I suspect it's really an Apple font bug.

Comment 5

[Jonathan Kew [:jfkthame]]

ftxdumperfuser (from the Apple font tool suite) shows that the Helvetica fonts have a 'morx' table but no 'feat' table.

Filed rdar://8787569 to report this to Apple.

Comment 6

[Robert Longson [:longsonr]]

OK on my Mac and Firefox no longer supports 10.6