migrations/egui
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improve fallback fonts alignment (#2724)

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* use font metrics in layout

* properly center scaled fonts

* adjust docs

* fix raised text

* fix easymark viewer small text alignment
caused by variable row heights
This commit is contained in:
lictex_
2023-03-29 20:36:09 +08:00
committed by GitHub
parent 089c7b46f3
commit 94f8b02286
5 changed files with 173 additions and 110 deletions
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176
crates/epaint/src/text/font.rs
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@@ -1,5 +1,6 @@
use crate::{
mutex::{Mutex, RwLock},
text::FontTweak,
TextureAtlas,
};
use emath::{vec2, Vec2};
@@ -42,6 +43,17 @@ pub struct GlyphInfo {
/// Unit: points.
pub advance_width: f32,
/// `ascent` value from the font metrics.
/// this is the distance from the top to the baseline.
///
/// Unit: points.
pub ascent: f32,
/// row height computed from the font metrics.
///
/// Unit: points.
pub row_height: f32,
/// Texture coordinates.
pub uv_rect: UvRect,
}
@@ -52,6 +64,8 @@ impl Default for GlyphInfo {
Self {
id: ab_glyph::GlyphId(0),
advance_width: 0.0,
ascent: 0.0,
row_height: 0.0,
uv_rect: Default::default(),
}
}
@@ -69,6 +83,7 @@ pub struct FontImpl {
height_in_points: f32,
// move each character by this much (hack)
y_offset: f32,
ascent: f32,
pixels_per_point: f32,
glyph_info_cache: RwLock<ahash::HashMap<char, GlyphInfo>>, // TODO(emilk): standard Mutex
atlas: Arc<Mutex<TextureAtlas>>,
@@ -80,20 +95,37 @@ impl FontImpl {
pixels_per_point: f32,
name: String,
ab_glyph_font: ab_glyph::FontArc,
scale_in_pixels: u32,
y_offset_points: f32,
scale_in_pixels: f32,
tweak: FontTweak,
) -> FontImpl {
assert!(scale_in_pixels > 0);
assert!(scale_in_pixels > 0.0);
assert!(pixels_per_point > 0.0);
let height_in_points = scale_in_pixels as f32 / pixels_per_point;
use ab_glyph::*;
let scaled = ab_glyph_font.as_scaled(scale_in_pixels);
let ascent = scaled.ascent() / pixels_per_point;
let descent = scaled.descent() / pixels_per_point;
let line_gap = scaled.line_gap() / pixels_per_point;
// TODO(emilk): use these font metrics?
// use ab_glyph::ScaleFont as _;
// let scaled = ab_glyph_font.as_scaled(scale_in_pixels as f32);
// dbg!(scaled.ascent());
// dbg!(scaled.descent());
// dbg!(scaled.line_gap());
// Tweak the scale as the user desired
let scale_in_pixels = scale_in_pixels * tweak.scale;
let baseline_offset = {
let scale_in_points = scale_in_pixels / pixels_per_point;
scale_in_points * tweak.baseline_offset_factor
};
let y_offset_points = {
let scale_in_points = scale_in_pixels / pixels_per_point;
scale_in_points * tweak.y_offset_factor
} + tweak.y_offset;
// center scaled glyphs properly
let y_offset_points = y_offset_points + (tweak.scale - 1.0) * 0.5 * (ascent + descent);
// Round to an even number of physical pixels to get even kerning.
// See https://github.com/emilk/egui/issues/382
let scale_in_pixels = scale_in_pixels.round() as u32;
// Round to closest pixel:
let y_offset = (y_offset_points * pixels_per_point).round() / pixels_per_point;
@@ -102,8 +134,9 @@ impl FontImpl {
name,
ab_glyph_font,
scale_in_pixels,
height_in_points,
height_in_points: ascent - descent + line_gap,
y_offset,
ascent: ascent + baseline_offset,
pixels_per_point,
glyph_info_cache: Default::default(),
atlas,
@@ -194,15 +227,7 @@ impl FontImpl {
if glyph_id.0 == 0 {
None // unsupported character
} else {
let glyph_info = allocate_glyph(
&mut self.atlas.lock(),
&self.ab_glyph_font,
glyph_id,
self.scale_in_pixels as f32,
self.y_offset,
self.pixels_per_point,
);
let glyph_info = self.allocate_glyph(glyph_id);
self.glyph_info_cache.write().insert(c, glyph_info);
Some(glyph_info)
}
@@ -231,6 +256,62 @@ impl FontImpl {
pub fn pixels_per_point(&self) -> f32 {
self.pixels_per_point
}
fn allocate_glyph(&self, glyph_id: ab_glyph::GlyphId) -> GlyphInfo {
assert!(glyph_id.0 != 0);
use ab_glyph::{Font as _, ScaleFont};
let glyph = glyph_id.with_scale_and_position(
self.scale_in_pixels as f32,
ab_glyph::Point { x: 0.0, y: 0.0 },
);
let uv_rect = self.ab_glyph_font.outline_glyph(glyph).map(|glyph| {
let bb = glyph.px_bounds();
let glyph_width = bb.width() as usize;
let glyph_height = bb.height() as usize;
if glyph_width == 0 || glyph_height == 0 {
UvRect::default()
} else {
let atlas = &mut self.atlas.lock();
let (glyph_pos, image) = atlas.allocate((glyph_width, glyph_height));
glyph.draw(|x, y, v| {
if v > 0.0 {
let px = glyph_pos.0 + x as usize;
let py = glyph_pos.1 + y as usize;
image[(px, py)] = v;
}
});
let offset_in_pixels = vec2(bb.min.x, bb.min.y);
let offset = offset_in_pixels / self.pixels_per_point + self.y_offset * Vec2::Y;
UvRect {
offset,
size: vec2(glyph_width as f32, glyph_height as f32) / self.pixels_per_point,
min: [glyph_pos.0 as u16, glyph_pos.1 as u16],
max: [
(glyph_pos.0 + glyph_width) as u16,
(glyph_pos.1 + glyph_height) as u16,
],
}
}
});
let uv_rect = uv_rect.unwrap_or_default();
let advance_width_in_points = self
.ab_glyph_font
.as_scaled(self.scale_in_pixels as f32)
.h_advance(glyph_id)
/ self.pixels_per_point;
GlyphInfo {
id: glyph_id,
advance_width: advance_width_in_points,
ascent: self.ascent,
row_height: self.row_height(),
uv_rect,
}
}
}
type FontIndex = usize;
@@ -429,58 +510,3 @@ fn invisible_char(c: char) -> bool {
| '\u{FEFF}' // ZERO WIDTH NO-BREAK SPACE
)
}
fn allocate_glyph(
atlas: &mut TextureAtlas,
font: &ab_glyph::FontArc,
glyph_id: ab_glyph::GlyphId,
scale_in_pixels: f32,
y_offset: f32,
pixels_per_point: f32,
) -> GlyphInfo {
assert!(glyph_id.0 != 0);
use ab_glyph::{Font as _, ScaleFont};
let glyph =
glyph_id.with_scale_and_position(scale_in_pixels, ab_glyph::Point { x: 0.0, y: 0.0 });
let uv_rect = font.outline_glyph(glyph).map(|glyph| {
let bb = glyph.px_bounds();
let glyph_width = bb.width() as usize;
let glyph_height = bb.height() as usize;
if glyph_width == 0 || glyph_height == 0 {
UvRect::default()
} else {
let (glyph_pos, image) = atlas.allocate((glyph_width, glyph_height));
glyph.draw(|x, y, v| {
if v > 0.0 {
let px = glyph_pos.0 + x as usize;
let py = glyph_pos.1 + y as usize;
image[(px, py)] = v;
}
});
let offset_in_pixels = vec2(bb.min.x, scale_in_pixels + bb.min.y);
let offset = offset_in_pixels / pixels_per_point + y_offset * Vec2::Y;
UvRect {
offset,
size: vec2(glyph_width as f32, glyph_height as f32) / pixels_per_point,
min: [glyph_pos.0 as u16, glyph_pos.1 as u16],
max: [
(glyph_pos.0 + glyph_width) as u16,
(glyph_pos.1 + glyph_height) as u16,
],
}
}
});
let uv_rect = uv_rect.unwrap_or_default();
let advance_width_in_points =
font.as_scaled(scale_in_pixels).h_advance(glyph_id) / pixels_per_point;
GlyphInfo {
id: glyph_id,
advance_width: advance_width_in_points,
uv_rect,
}
}