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Try harder to succeed at fall-backing to a Monospace font

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A combination of some ideas:

 * Try all Monospace fonts before giving up.
 * Relax exact weight restriction on font matching when trying Monospace
   fall-back. Try smaller weights if needed.
 * Make the fall-back try order weight-offset aware, AND script-aware.
 * And finally, add the option to adjust the font size of glyphs using
   fall-back Monospace fonts, so the width of them matches the default
   font width.

   For my use-case, the current fall-back attempt always fails with
   Arabic script. And none of the Arabic-supporting Monospace fonts in
   my system also support medium weight. So, if my default font is set
   to medium weight, script-aware fall-back alone will still not work.

Signed-off-by: Mohammad AlSaleh <CE.Mohammad.AlSaleh@gmail.com>
This commit is contained in:
Mohammad AlSaleh 2024-01-17 12:32:33 +03:00 • committed by Jeremy Soller
parent 054b7da828
commit 329941c4a6
8 changed files with 177 additions and 39 deletions
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25
src/shape.rs
View file

@ -144,6 +144,7 @@ fn shape_fallback(
y_offset,
ascent,
descent,
font_monospace_em_width: font.monospace_em_width(),
font_id: font.id(),
glyph_id: info.glyph_id.try_into().expect("failed to cast glyph ID"),
//TODO: color should not be related to shaping
@ -344,6 +345,7 @@ fn shape_skip(
let font = font_iter.next().expect("no default font found");
let font_id = font.id();
let font_monospace_em_width = font.monospace_em_width();
let font = font.as_swash();
let charmap = font.charmap();
@ -371,6 +373,7 @@ fn shape_skip(
y_offset: 0.0,
ascent,
descent,
font_monospace_em_width,
font_id,
glyph_id,
color_opt: attrs.color_opt,
@ -392,6 +395,7 @@ pub struct ShapeGlyph {
pub y_offset: f32,
pub ascent: f32,
pub descent: f32,
pub font_monospace_em_width: Option<f32>,
pub font_id: fontdb::ID,
pub glyph_id: u16,
pub color_opt: Option<Color>,
@ -875,6 +879,7 @@ impl ShapeLine {
line_width: f32,
wrap: Wrap,
align: Option<Align>,
match_mono_width: Option<f32>,
) -> Vec<LayoutLine> {
let mut lines = Vec::with_capacity(1);
self.layout_to_buffer(
@ -884,6 +889,7 @@ impl ShapeLine {
wrap,
align,
&mut lines,
match_mono_width,
);
lines
}
@ -896,6 +902,7 @@ impl ShapeLine {
wrap: Wrap,
align: Option<Align>,
layout_lines: &mut Vec<LayoutLine>,
match_mono_width: Option<f32>,
) {
// For each visual line a list of (span index, and range of words in that span)
// Note that a BiDi visual line could have multiple spans or parts of them
@ -1236,8 +1243,20 @@ impl ShapeLine {
(false, true) => &word.glyphs[..ending_glyph],
(true, true) => &word.glyphs[starting_glyph..ending_glyph],
};
let match_mono_em_width = match_mono_width.map(|w| w / font_size);
for glyph in included_glyphs {
let x_advance = font_size * glyph.x_advance
let glyph_font_size = match(match_mono_em_width, glyph.font_monospace_em_width) {
(Some(match_em_width), Some(glyph_em_width)) if glyph_em_width != match_em_width => {
let glyph_font_size = font_size * (match_em_width / glyph_em_width);
log::trace!("Adjusted glyph font size ({font_size} => {glyph_font_size})");
glyph_font_size
},
_ => font_size,
};
let x_advance = glyph_font_size * glyph.x_advance
+ if word.blank {
justification_expansion
} else {
@ -1246,8 +1265,8 @@ impl ShapeLine {
if self.rtl {
x -= x_advance;
}
let y_advance = font_size * glyph.y_advance;
glyphs.push(glyph.layout(font_size, x, y, x_advance, span.level));
let y_advance = glyph_font_size * glyph.y_advance;
glyphs.push(glyph.layout(glyph_font_size, x, y, x_advance, span.level));
if !self.rtl {
x += x_advance;
}