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Code Issues Releases Activity

Illustrate more font problems

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* etc/PROBLEMS (Runtime problems specific to Android): Mention
problems with three other fonts users have inquired into.
This commit is contained in:
Po Lu 2023-08-22 21:42:06 +08:00
parent 6ab90effbe
commit 5ac8c19826
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@ -3453,6 +3453,47 @@ Then, reassemble the font from the modified XML:
which should produce a modified font by the name of
Anonymous_Pro#1.ttf.
** The "IBM Plex Mono" font displays incorrectly.
This problem is precipitated by an attempt to exploit the undocumented
feature of the MS font scaler explicated within the previous heading.
Its remedy is also unsurprisingly alike the fix described there: both
patching the preprogram to reset the point movement vectors and
replacing the instruction code with code generated by "ttfautohint"
will adequately resolve the problem.
** Glyphs are missing within the "Arial" font or it does not load.
On account of its origins at Microsoft, instruction code included
within this font is awash with references to behavior specific to the
MS scaler. It is incorrigibly broken, to a degree that even
"ttfautohint" cannot repair; your only recourse is to select some
other font.
This issue may extend beyond Arial to encompass a larger selection of
fonts designed by Microsoft.
** Some TrueType test fonts don't work.
It is unlikely that any of these fonts will really prove useful for
text editing tasks, since they are designed for the express purpose of
testing a TrueType font scaler. The following explanation is present
only to satisfy a cat-like curiosity.
Most TrueType test fonts "hide" points by moving them to a
preposterous location outside the confines of the glyph bounding box.
The Microsoft scaler and FreeType promptly disregard such points.
Nothing in the TrueType specifications implies that points "hidden" in
this fashion should be afforded any special treatment, and thus Emacs
eschews doing so. Consequentially, black streaks are displayed as
Emacs interpolates glyph edges between points within the glyph and
points the test font attempts to hide.
Since this behavior does not influence the display of real fonts, no
action will be taken to address this problem.
** CJK text does not display in Emacs, but does in other programs.
When inserting CJK text into a buffer or visiting a file containing