bugFree UCS Outline Fonts - Bugs: bug #22994, combining marks (0-width...

 
 

bug #22994: combining marks (0-width characters) in Mono

Submitter:  Steve White <Stevan_White>
Submitted:  Sun 20 Apr 2008 11:28:07 AM UTC
   
 
Category:  character range Severity:  3 - Normal
Item Group:  letter positioning poor Status:  Fixed
Privacy:  Public Assigned to:  Stevan_White
Open/Closed:  Closed Release:  * 2006-01-26
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Fri 12 Sep 2008 08:21:50 AM UTC, comment #2: 

In release 20080912

Steve White <Stevan_White>
Group administrator
Sun 07 Sep 2008 10:11:42 AM UTC, comment #1: 

Zero-width characters could be regarded as "non-advancing".  This concept that had meaning on mechanical character printers, and is used in the Unicode FAQ on the topic. 

Putting in a few zero-width characters in a monospace font can be made to work, with complications: see below.

The FreeMono currently in CVS contains 0-width characters for "combining diacritics".

  • diacritics don't seem to work with xterm
  • diacritics work with many other unix apps
  • in Windows, TrueType version not recognized as monospace: use the OpenType version


Experiments
===========
Linux
-----
Both gedit and kedit are both happy with monospace fonts that have 0-width characters, and play well with them. 
Xterm doesn't seem to notice (although I still haven't got Joe's stargate example to display the diacritics properly). 
Firefox also sees such fonts as being monospace.

Windows Vista
-------------
The situation is more complicated, depending on whether the font is installed as TrueType or OpenType.
PuTTy, gVim, Firefox: only see fonts with 0-width characters as monospace if loaded as OpenType.
The TrueType version can be loaded and used, but I have never seen it regarded as monospace.


Steve White <Stevan_White>
Group administrator
Sun 20 Apr 2008 11:28:07 AM UTC, original submission:  

How (or whether) to implement combining marks in a monospace font?

A couple of people have complained lately, so I'm opening this bug report to track it.

Many applications insist that the widths of the bounding boxes of all characters in a monospace font should be the same.  There are exceptions, but it is safest for them really all to be the same.

On the other hand, a primitive way to implement combining marks is an "overstrike", a character of zero width whose glyph is placed to one side, so it is drawn over a neighboring character.

It would seem to be a conflict.

So far I know:

1) Many Linux apps tolerate zero-width characters in a monospace font (but not other widths!)

2) In Windows, fonts loaded as TrueType are recognized as monospace only if all characters are of the same width.

3) In Windows, fonts loaded as OpenType may be recognized as monospace if they have some zero-width characters.

4) On my system (Ubuntu gutsy), xterms (and derivatives) clip these overstrike characters, rendering the point moot.

Joe Wells has reported that older xterms worked with older versions of FreeMono to effect an overstrike.  He wants this behaviour to continue.

At this point, I'm not sure what to do about this.  I'm not even sure it is to be regarded as a font problem.

Steve White <Stevan_White>
Group administrator

 

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Carbon-Copy List
  • -email is unavailable- added by Stevan_White (Submitted the item)
  • -email is unavailable- added by Stevan_White
  • -email is unavailable- added by Stevan_White
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    Follow 6 latest changes.

    Date Changed by Updated Field Previous Value => Replaced by
    2008-09-12 Stevan_White StatusFix posted Fixed
        Open/ClosedOpen Closed
    2008-09-07 Stevan_White StatusProceeding Fix posted
        Summarycombining marks in Mono combining marks (0-width characters) in Mono
    2008-04-20 Stevan_White Carbon-Copy- Added -email is unavailable-
        Carbon-Copy- Added joe wells <jbw@macs.hw.ac.uk>

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