This is my final set of fixes to the font patcher/icon scaling code. It
builds on #8563 and there's not much reason to pay attention here until
that one has been reviewed (the unique changes in this PR only touch the
two `nerd_font_*` files; the other 8 files in the diff are just #8563).
However, I wanted to make sure the full set of changes/fixes I propose
are out in the open, such that any substantial edits by maintainers
(like in #7953) can take into account the full context.
I think this and the related patches should be considered fixes, not
features, so I hope they can be considered for a 1.2.x release.
This PR fixes some bugs in the extraction of scale and alignment rules
from the `font_patcher` script. Roughly in order of importance:
* Nerd fonts apply an offset to some codepoint ranges when extracting
glyphs from their original font (e.g., Font Awesome) and placing them in
a Nerd Font. Rules are specified in terms of the former codepoints, but
must be applied to the latter. This offset was previously not taken into
account, so rules were applied to the wrong glyphs, and some glyphs that
should have rules didn't get any.
* Previously, the rules from every single patch set was included, but
the embedded Symbols Only font doesn't contain all of them. Most
importantly, there's a legacy patch set that only exists for historical
reasons and is never used anymore, which was overwriting some other
rules because of overlapping codepoint ranges. Also, the Symbols Only
font contains no box drawing characters, so those rules should not be
included. With this PR, irrelevant patch sets are filtered out.
* Some patch sets specify overlapping codepoint ranges, though in
reality the original fonts don't actually cover the full ranges and the
overlaps just imply that they're filling each other's gaps. During font
patching, the presence/absence of a glyph at each codepoint in the
original font takes care of the ambiguity. Since we don't have that
information, we need to hardcode which patch set "wins" for each case
(it's not always the latest set in the list). Luckily, there are only
two cases.
* Many glyphs belong to scale groups that should be scaled and aligned
as a unit. However, in `font_patcher`, the scale group is _not_ used for
_horizontal_ alignment, _unless_ the entire scale group has a single
advance width (remember, the original symbol fonts are not monospace).
This PR implements this rule by only setting `relative_width` and
`relative_x` if the group is monospace.
There are some additional tweaks to ensure that each codepoint actually
gets the rule it's supposed to when it belongs to multiple scale groups
or patch sets, and to avoid setting rules for codepoints that don't
exist in the embedded font.
I changed my mind, this is a pretty small change and relevant to the
intent of the PR. This brings the appearance of the embedded symbols
much closer to patched fonts.
With this, the sizes of most symbols are nearly identical to a patched
font, the only big difference is positioning (and TBH I think we do a
better job positioning than the patcher does, since we have knowledge
about the cell size).
We do this by characterizing the shared bounding boxes in a static copy
of the symbols only nerd font when we're doing the codegen. This allows
us to get results of our scaling that are just as good as in a patched
font, since related glyphs can now be sized and positioned relative to
each other.
Icons were often WAY too big before because they were filling the whole
cell in height, which isn't great lol. This commit adds an `icon_height`
metric which is used to constrain glyphs that shouldn't be the size of
the entire cell.
The nerd font patcher uses `ypadding` as a single subtraction from the
cell height, which means that half of it should go to the top padding
and the other half to the bottom, this was making the heavy brackets way
too small lol (0.4 of the cell height instead of 0.7)
This mostly applies to powerline glyphs, but is also relevant for heavy
bracket characters, which need to always be 1 wide otherwise they look
silly because they misalign depending on if there's a space after them
or not.
Previously `ypadding` was effectively ignored, since it's mutually
exclusive with `overlap`. This had a noticeable effect on the heavy
bracket characters U+276C...U+2771, which were much taller than they
should have been.
I also fixed the vertical overlap limit, since negative `overlap` values
are used in the nerd font attributes to create padding on all sides of
the cell, so we don't want to limit the magnitude of the overlap for
vertical padding, we only want to limit it if the value is positive.
That change fixed the vertical padding for a handful of ranges, which
should give more consistent results.
This reverts commit 2fca0477bc.
The idea of using stdin and stdout was the integrate it in to the build
script, but since we don't want to do that because it contains an eval,
it just makes it more annoying to use.
