Closed Bug 443853 Opened 16 years ago Closed 13 years ago

ligatures enabled even when letter-spacing is non-zero


(Core :: Graphics, defect)

Windows XP
Not set





(Reporter: mr.chen.k12, Unassigned)



(2 files)

User-Agent:       Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9) Gecko/2008052906 Firefox/3.0
Build Identifier: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9) Gecko/2008052906 Firefox/3.0


	<style rel="stylesheet" type="text/css">




Reproducible: Always

Steps to Reproduce:
1.You type the code above and save it as a .html file.
2.Open it by Firefox.
3.The result is            I n t r o d u c ti o n
Actual Results:  
The actual result displayed by firefox:        I n t r o d u c ti o n

The t and i characters got sticked together.

Expected Results:  
The expected result should be there is a .5em space between each character. In other words  I n t r o d u c t i o n

The t and i characters got sticked together.

I tried using an external stylesheet file, the same bug is being produced.

I tried opening it using I.E., the proper display was shown.
Thank you for looking into it! :)
Component: Error Console → GFX: Thebes
Product: Firefox → Core
QA Contact: error.console → thebes
Attached file html test page
Assignee: nobody → jmathies
Ever confirmed: true
confirmed - still happening in the latest nightlies.
Assignee: jmathies → nobody
Component: Graphics → Layout: Text
QA Contact: thebes → layout.fonts-and-text
Sounds like we're using a ligature; we shouldn't be doing that if letter-spacing is not "normal", right?
Yes, we have code that's supposed to prevent that; we pass the TEXT_DISABLE_OPTIONAL_LIGATURES when creating the textrun.
Yes, it looks like we're not enforcing the breaking of ligatures when letter-spacing is non-zero.  Chrome shows the same problem when text-rendering: optimizeLegibility is set.
Note: with harfbuzz enabled the testcase renders properly.
Summary: letter-spacing for Calibri font is not displaying properly → ligatures enabled even when letter-spacing is non-zero
Looks like only the CoreText and Harfbuzz code pays attention to the TEXT_DISABLE_OPTIONAL_LIGATURES flag.  Probably because Uniscribe doesn't provide an easy way of disabling only optional ligatures that I can find.  The Vista-and-beyond Uniscribe API's do but that's way too much work for code that harfbuzz will replace.

One option would be to force GDI shaping based on the TEXT_DISABLE_OPTIONAL_LIGATURES flag.  That's the reason this bug only shows up in text sized 20px and above in 3.6, up until 3.6 all text below 20px was rendered via the GDI shaping codepath.
Component: Layout: Text → Graphics
QA Contact: layout.fonts-and-text → thebes
Version: unspecified → Trunk
I think we should just WONTFIX this bug as it pertains to Uniscribe and other non-Harfbuzz shapers and concentrate on getting Harfbuzz enabled as broadly as possible.
Resolving this as FIXED because we're now using harfbuzz by default, which fixes the issue reported here.
Closed: 13 years ago
Resolution: --- → FIXED
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