bugThe FreeType Project - Bugs: bug #52215, Autohinter support for box drawing...


bug #52215: Autohinter support for box drawing unicode range

Submitted by:  Alexei Podtelezhnikov <podtelez>
Submitted on:  Thu 12 Oct 2017 03:41:38 PM UTC  
Votes:  50  
Severity:  1 - Wish Item Group:  Wishlist
Status:  None Privacy:  Public
Assigned to:  Werner LEMBERG <wl> Open/Closed:  Open
Planned Release:  None

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Thu 12 Oct 2017 03:59:59 PM UTC, comment #1: 

Never mind my first suggestion. It is impossible to scale to both rounded ascender and rounded descender lines at the same time, as those are two different scaling factors. Only rounding the pixel positions would work. So, indeed, autohinter support is necessary.

The same idea should apply to the native hinting. The truetype fonts must provide their own rounding instructions as well. DejaVu fonts as of 2.37 do not instruct box drawing characters.

Alexei Podtelezhnikov <podtelez>
Project Member
Thu 12 Oct 2017 03:41:38 PM UTC, original submission:  

For the box drawing to work, the characters in this range (U+2500-U+257F) have to be monospaced and span the exact distance between the descender and ascender lines. This distance and the distance between the lines is always rounded to pixels. Therefore, arbitrary scaling does not work for these characters. We should either

1) use discrete scaling that corresponds to the rounded metrics, or
2) round the edge pixels to the ascender and descender lines in the autohinter.

Note that, it is probably incorrect to modify the ascender and descender lines and line spacing for these characters because they are routinely used with other normal glyphs to draw tables.

Alexei Podtelezhnikov <podtelez>
Project Member


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