Fix broken ligature glyphs in monospaced font #12
Conversation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
[why] For some reason reading a font into fontforge looses data on glyphs. As a workaround their `font-patcher` script has the switch `--mono` to ascertain an equal width of all glyphs. We want to (and need to) use that mode of the script to get a new font that is detected as monospaced by Windows. Sometimes that workaround fails. For example it breaks ligature glyphs in some circumstances; they seem to be moved sideways. [how] The workaround is done in two steps: First each glyph is checked for negative bearings. If these are found they are set to fixed zero. Afterwards the glyph width is set to the font global width. The ligature glyphs have already the correct width, they just have negative bearings that they indeed need. There is no reason to change the (correct) bearings to get a monospaced font. In strict monospaced fonts that would be impossible, but the ligatures are only used in applications that could work with negative bearings and so they should be there. Strict monospaced usage does ignore the bearings anyhow. So what is needed is a change in the font-patcher script. This can be done in two ways: - patch the font-patcher script - do not use font-patcher's `--mono` and instead implement it as part of our rename script or additional script Of course the best solution would be to fix upstream font-patcher. But that might take some time. Meanwhile we can patch the font-patcher as it is rather stable (no recent commits) and our patch will most likely not fail in the near future. Forking font-patcher is not desirable I think. [note] There is some work in progress regarding Cascadia Code in Nerd Font's repository, but that seems slow ;) Project too big. Fixes: 3 Signed-off-by: Fini Jastrow <ulf.fini.jastrow@desy.de>
|
Hmm, this introduces a regression of Bug #5, albeit not as severe. Working... |
[why] Some glyphs are just used as overlays for 'real' glyphs. These are for example U+0300 .. U+036F (the 'COMBINING ...' diactritics) like U+0300, gravecomb, COMBINING GRAVE ACCENT U+0301, acutecomb, COMBINING ACUTE ACCENT U+0308, uni0308, COMBINING DIAERESIS They are never used on their own, at least they are overlayed over a blanc (U+0020, space). For the font rendering engine they need to have the correct negative bearings, so they are shifted to take no space by themselves. The font-patcher script does not allow negative bearings in monospaced fonts. This makes sense if every glyph is in itself a 'letter' that should not reach beyond it's allotted (monospaced) space. But well, this is not how Cascadia Code is assembled. [how] In the font-patcher script we do not touch the bearings of such overlay glyphs. They can be identified by their width of zero. For Windows to detect this font as 'monospaced' we need to change the width to the standard width, though. Signed-off-by: Fini Jastrow <ulf.fini.jastrow@desy.de>
|
Thanks for diving into this @Finii! Can you please post an issue/PR to font-patcher with your fixes as well? They may not take it for a while but it could help others with a similar issue. |
5 tasks
|
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
[why]
For some reason reading a font into fontforge looses data on glyphs. As
a workaround their
font-patcherscript has the switch--monotoascertain an equal width of all glyphs. We want to (and need to) use
that mode of the script to get a new font that is detected as monospaced
by Windows.
Sometimes that workaround fails. For example it breaks ligature glyphs
in some circumstances; they seem to be moved sideways.
[how]
The workaround is done in two steps: First each glyph is checked for
negative bearings. If these are found they are set to fixed zero.
Afterwards the glyph width is set to the font global width.
The ligature glyphs have already the correct width, they just have
negative bearings that they indeed need. There is no reason to change
the (correct) bearings to get a monospaced font. In strict monospaced
fonts that would be impossible, but the ligatures are only used in
applications that could work with negative bearings and so they should
be there. Strict monospaced usage does ignore the bearings anyhow.
So what is needed is a change in the font-patcher script. This can be
done in two ways:
--monoand instead implement it aspart of our rename script or additional script
Of course the best solution would be to fix upstream font-patcher. But
that might take some time. Meanwhile we can patch the font-patcher as it
is rather stable (no recent commits) and our patch will most likely not
fail in the near future.
Forking font-patcher is not desirable I think.
[note]
There is some work in progress regarding Cascadia Code in Nerd Font's
repository, but that seems slow ;) Project too big.
Fixes: #3
Signed-off-by: Fini Jastrow ulf.fini.jastrow@desy.de