Bug 24658 – Space reserved by tab character broken if the text contains characters in Hangul Jamo block

• Component: Layout and Rendering
• Status: RESOLVED CONFIGURATION CHANGED

Build: WebKit nightly build r41759
   OS: Windows, not test on Mac

Other Browsers:
  Firefox3.0.7: OK
           IE8: OK
  Chrome trunk: Fail

Steps:
1. Launch Safari
2. Open the attached test file
   >>Tab_in_Pre_Tag_Contains_Hangul-Jamo.html
3. Observe the second line

Result:
The space reserved by tab is broken compared with first line.

Expected:
The space should not be broken, so the first column and
the second column could have same layout

Notes:
1. This issue happens when use tab in "pre" tag, if the text contains characters in Hangul Jamo (U+1100 – U+11FF) block, then the space reserved by tab will be broken. 
2. It is OK for characters in Hangul Compatibility Jamo block and Hangul Syllables block.

Created attachment 28710 [details]
Reduced test file.

This is also tracked in Chromium as crbug.com/8492

[Alexey Proskuryakov]

If I understood this correctly, it also happens on the Mac, and that's because ATSUI is used for one line, but not another. But on Windows, the mechanism has to be different, obviously.

On Mac, the bug reproduces on Tiger and Leopard because the ATSUI code path does not handle tabs correctly. It does not seem to happen in the newer, Core Text-based code path. I don't remember the details of tab handling in the Uniscribe-based code path on Windows.

[Jungshik Shin]

This should be P3. Hangul Jamos in U+1100 block is not so widely used. They're only used for archaic Korean representation.  

Don't you get the same problem with anything else that triggers the complex text code path?

Created attachment 28812 [details]
Screenshot

Created attachment 28813 [details]
Complex Script test file

Seems complex scripts have the same problem as Hangul Jamos.

Attaching a test file including Devanagari, Tamil, Telugu, Thai and compared with Chinese.

[Ahmad Saleem]

I am not able to reproduce this issue in Safari 16.2 and it does respect space and does not depict issue similar to reference image and matches with the "Internet Explorer" from the screenshot.

All other browsers (Chrome Canary 111 and Firefox Nightly 110) also matches with Safari.

Marking this as "RESOLVED CONFIGURATION CHANGED". Thanks!

Please reopen, if it is still an issue, I test both "Complex" and "Reduced" and it is same across all browsers.