Some diacritics end up with some parts below the descender limit, thus being
cut-off on Windows. This is rather bad. Ring below turns into a half ring below,
square below turns into half square below, combing tack..., combining plus, etc.
All those should have their shape preserved when combined with base characters
* expand the descender limit, thus messing up the whole font metrics (bad)
* shift and shrink the diacritics when necessary (solves it but can be
unpleasant, might not look good)
Created attachment 7785 [details]
shrunk and shifted ring below
screenshot of what a shrunk and shifted ring below looks like
I personally think shifting and adjusting the diacritics to fit in the Windows
visible area is the best option.
Win Ascent 1901
Win Descent -483
default line-spacing 11.49 points on 10 point
Current Required Metrics
Win Ascent 2544
Win Descent -822
default line-spacing 16.43 points on 10 point
For most fonts one should aim for 12 points on 10 point line-spacing.
WinAscent - WinDescent = 2458
If you think that is really not enough for Vietnamese stacking diacritic support,
increase the default leading to no more than 13 points on 10, which allows
WinAscent - WinDescent = 2662.
Look at body text with 130% fixed leading to judge if it too loose. 10 point Deju
Serif looks fine to my eyes set at 13 point leading. That should allow adequate
space for stacking diacritics, but only if they are redesigned. Either make the
ring above smaller, or place the acute beside it.
The tallest ascender is on LATIN CAPITAL A WITH RING ABOVE AND ACUTE (506). This is
a problematic glyph. The design should be changed to position the accent beside the
ring. (See my Verajja Font).
Both the ring above and the ring below should be reduced to about 67%.
Created attachment 8053 [details]
Low-profile Stacking Diacritics
Diacritics that are cropped ruin the font. Excessive line-spacing also ruins
the font. Either make a font especially tailored for Vietnamese, where the
greater line-spacing is tolerable, or compromise by compressing stacking
diacritics to fit within WinAscent/WinDescent. Designing outside of these
limits seems like a fundamental mistake as most applications will crop any
glyphs that exceed these limits.
The attachment shows how I solve the problem on three of the most difficult
glyphs. The metrics are designed for 13 point leading on 10 point.
Do you still experience this issue with newer soft ?
Please check the status of your issue.