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Subpixel text positioning (bevyengine#1196)
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* cleanup unnecessary changes from PR bevyengine#1171

* add feature to correctly render glyphs with sub-pixel positioning
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blunted2night authored and rparrett committed Jan 27, 2021
1 parent 69a13ff commit b54f18d
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Showing 7 changed files with 122 additions and 21 deletions.
3 changes: 3 additions & 0 deletions Cargo.toml
Original file line number Diff line number Diff line change
Expand Up @@ -72,6 +72,9 @@ serialize = ["bevy_internal/serialize"]
wayland = ["bevy_internal/wayland"]
x11 = ["bevy_internal/x11"]

# enable rendering of font glyphs using subpixel accuracy
subpixel_glyph_atlas = ["bevy_internal/subpixel_glyph_atlas"]

[dependencies]
bevy_dylib = {path = "crates/bevy_dylib", version = "0.4.0", default-features = false, optional = true}
bevy_internal = {path = "crates/bevy_internal", version = "0.4.0", default-features = false}
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3 changes: 3 additions & 0 deletions crates/bevy_internal/Cargo.toml
Original file line number Diff line number Diff line change
Expand Up @@ -38,6 +38,9 @@ serialize = ["bevy_input/serialize"]
wayland = ["bevy_winit/wayland"]
x11 = ["bevy_winit/x11"]

# enable rendering of font glyphs using subpixel accuracy
subpixel_glyph_atlas = ["bevy_text/subpixel_glyph_atlas"]

[dependencies]
# bevy
bevy_app = { path = "../bevy_app", version = "0.4.0" }
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3 changes: 3 additions & 0 deletions crates/bevy_text/Cargo.toml
Original file line number Diff line number Diff line change
Expand Up @@ -12,6 +12,9 @@ repository = "https://github.com/bevyengine/bevy"
license = "MIT"
keywords = ["bevy"]

[features]
subpixel_glyph_atlas = []

[dependencies]
# bevy
bevy_app = { path = "../bevy_app", version = "0.4.0" }
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54 changes: 47 additions & 7 deletions crates/bevy_text/src/font_atlas.rs
Original file line number Diff line number Diff line change
@@ -1,13 +1,44 @@
use ab_glyph::GlyphId;
use ab_glyph::{GlyphId, Point};
use bevy_asset::{Assets, Handle};
use bevy_math::Vec2;
use bevy_render::texture::{Extent3d, Texture, TextureDimension, TextureFormat};
use bevy_sprite::{DynamicTextureAtlasBuilder, TextureAtlas};
use bevy_utils::HashMap;

#[cfg(feature = "subpixel_glyph_atlas")]
#[derive(Copy, Clone, Eq, PartialEq, Hash, Debug)]
pub struct SubpixelOffset {
x: u16,
y: u16,
}

#[cfg(feature = "subpixel_glyph_atlas")]
impl From<Point> for SubpixelOffset {
fn from(p: Point) -> Self {
fn f(v: f32) -> u16 {
((v % 1.) * (u16::MAX as f32)) as u16
}
Self {
x: f(p.x),
y: f(p.y),
}
}
}

#[cfg(not(feature = "subpixel_glyph_atlas"))]
#[derive(Copy, Clone, Eq, PartialEq, Hash, Debug)]
pub struct SubpixelOffset;

#[cfg(not(feature = "subpixel_glyph_atlas"))]
impl From<Point> for SubpixelOffset {
fn from(_: Point) -> Self {
Self
}
}

pub struct FontAtlas {
pub dynamic_texture_atlas_builder: DynamicTextureAtlasBuilder,
pub glyph_to_atlas_index: HashMap<GlyphId, u32>,
pub glyph_to_atlas_index: HashMap<(GlyphId, SubpixelOffset), u32>,
pub texture_atlas: Handle<TextureAtlas>,
}

Expand All @@ -31,27 +62,36 @@ impl FontAtlas {
}
}

pub fn get_glyph_index(&self, glyph_id: GlyphId) -> Option<u32> {
self.glyph_to_atlas_index.get(&glyph_id).copied()
pub fn get_glyph_index(
&self,
glyph_id: GlyphId,
subpixel_offset: SubpixelOffset,
) -> Option<u32> {
self.glyph_to_atlas_index
.get(&(glyph_id, subpixel_offset))
.copied()
}

pub fn has_glyph(&self, glyph_id: GlyphId) -> bool {
self.glyph_to_atlas_index.contains_key(&glyph_id)
pub fn has_glyph(&self, glyph_id: GlyphId, subpixel_offset: SubpixelOffset) -> bool {
self.glyph_to_atlas_index
.contains_key(&(glyph_id, subpixel_offset))
}

pub fn add_glyph(
&mut self,
textures: &mut Assets<Texture>,
texture_atlases: &mut Assets<TextureAtlas>,
glyph_id: GlyphId,
subpixel_offset: SubpixelOffset,
texture: &Texture,
) -> bool {
let texture_atlas = texture_atlases.get_mut(&self.texture_atlas).unwrap();
if let Some(index) =
self.dynamic_texture_atlas_builder
.add_texture(texture_atlas, textures, texture)
{
self.glyph_to_atlas_index.insert(glyph_id, index);
self.glyph_to_atlas_index
.insert((glyph_id, subpixel_offset), index);
true
} else {
false
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25 changes: 19 additions & 6 deletions crates/bevy_text/src/font_atlas_set.rs
Original file line number Diff line number Diff line change
@@ -1,5 +1,5 @@
use crate::{error::TextError, Font, FontAtlas};
use ab_glyph::{GlyphId, OutlinedGlyph};
use ab_glyph::{GlyphId, OutlinedGlyph, Point};
use bevy_asset::{Assets, Handle};
use bevy_core::FloatOrd;
use bevy_math::Vec2;
Expand Down Expand Up @@ -35,11 +35,13 @@ impl FontAtlasSet {
self.font_atlases.iter()
}

pub fn has_glyph(&self, glyph_id: GlyphId, font_size: f32) -> bool {
pub fn has_glyph(&self, glyph_id: GlyphId, glyph_position: Point, font_size: f32) -> bool {
self.font_atlases
.get(&FloatOrd(font_size))
.map_or(false, |font_atlas| {
font_atlas.iter().any(|atlas| atlas.has_glyph(glyph_id))
font_atlas
.iter()
.any(|atlas| atlas.has_glyph(glyph_id, glyph_position.into()))
})
}

Expand All @@ -51,6 +53,7 @@ impl FontAtlasSet {
) -> Result<GlyphAtlasInfo, TextError> {
let glyph = outlined_glyph.glyph();
let glyph_id = glyph.id;
let glyph_position = glyph.position;
let font_size = glyph.scale.y;
let font_atlases = self
.font_atlases
Expand All @@ -64,7 +67,13 @@ impl FontAtlasSet {
});
let glyph_texture = Font::get_outlined_glyph_texture(outlined_glyph);
let add_char_to_font_atlas = |atlas: &mut FontAtlas| -> bool {
atlas.add_glyph(textures, texture_atlases, glyph_id, &glyph_texture)
atlas.add_glyph(
textures,
texture_atlases,
glyph_id,
glyph_position.into(),
&glyph_texture,
)
};
if !font_atlases.iter_mut().any(add_char_to_font_atlas) {
font_atlases.push(FontAtlas::new(
Expand All @@ -76,19 +85,23 @@ impl FontAtlasSet {
textures,
texture_atlases,
glyph_id,
glyph_position.into(),
&glyph_texture,
) {
return Err(TextError::FailedToAddGlyph(glyph_id));
}
}

Ok(self.get_glyph_atlas_info(font_size, glyph_id).unwrap())
Ok(self
.get_glyph_atlas_info(font_size, glyph_id, glyph_position)
.unwrap())
}

pub fn get_glyph_atlas_info(
&self,
font_size: f32,
glyph_id: GlyphId,
position: Point,
) -> Option<GlyphAtlasInfo> {
self.font_atlases
.get(&FloatOrd(font_size))
Expand All @@ -97,7 +110,7 @@ impl FontAtlasSet {
.iter()
.find_map(|atlas| {
atlas
.get_glyph_index(glyph_id)
.get_glyph_index(glyph_id, position.into())
.map(|glyph_index| (glyph_index, atlas.texture_atlas.clone_weak()))
})
.map(|(glyph_index, texture_atlas)| GlyphAtlasInfo {
Expand Down
49 changes: 41 additions & 8 deletions crates/bevy_text/src/glyph_brush.rs
Original file line number Diff line number Diff line change
@@ -1,4 +1,4 @@
use ab_glyph::{Font as _, FontArc, ScaleFont as _};
use ab_glyph::{Font as _, FontArc, Glyph, ScaleFont as _};
use bevy_asset::{Assets, Handle};
use bevy_math::{Size, Vec2};
use bevy_render::prelude::Texture;
Expand Down Expand Up @@ -80,16 +80,16 @@ impl GlyphBrush {
font_id: _,
} = sg;
let glyph_id = glyph.id;
let base_x = glyph.position.x.floor();
glyph.position.x = 0.;
let glyph_position = glyph.position;
let adjust = GlyphPlacementAdjuster::new(&mut glyph);
if let Some(outlined_glyph) = font.font.outline_glyph(glyph) {
let bounds = outlined_glyph.px_bounds();
let handle_font_atlas: Handle<FontAtlasSet> = handle.as_weak();
let font_atlas_set = font_atlas_set_storage
.get_or_insert_with(handle_font_atlas, FontAtlasSet::default);

let atlas_info = font_atlas_set
.get_glyph_atlas_info(font_size, glyph_id)
.get_glyph_atlas_info(font_size, glyph_id, glyph_position)
.map(Ok)
.unwrap_or_else(|| {
font_atlas_set.add_glyph_to_atlas(texture_atlases, textures, outlined_glyph)
Expand All @@ -100,11 +100,9 @@ impl GlyphBrush {
let glyph_width = glyph_rect.width();
let glyph_height = glyph_rect.height();

let x = base_x + bounds.min.x + glyph_width / 2.0 - min_x;
// the 0.5 accounts for odd-numbered heights (bump up by 1 pixel)
// max_y = text block height, and up is negative (whereas for transform, up is positive)
let x = bounds.min.x + glyph_width / 2.0 - min_x;
let y = max_y - bounds.max.y + glyph_height / 2.0;
let position = Vec2::new(x, y);
let position = adjust.position(Vec2::new(x, y));

positioned_glyphs.push(PositionedGlyph {
position,
Expand All @@ -129,3 +127,38 @@ pub struct PositionedGlyph {
pub position: Vec2,
pub atlas_info: GlyphAtlasInfo,
}

#[cfg(feature = "subpixel_glyph_atlas")]
struct GlyphPlacementAdjuster;

#[cfg(feature = "subpixel_glyph_atlas")]
impl GlyphPlacementAdjuster {
#[inline(always)]
pub fn new(_: &mut Glyph) -> Self {
Self
}

#[inline(always)]
pub fn position(&self, p: Vec2) -> Vec2 {
p
}
}

#[cfg(not(feature = "subpixel_glyph_atlas"))]
struct GlyphPlacementAdjuster(f32);

#[cfg(not(feature = "subpixel_glyph_atlas"))]
impl GlyphPlacementAdjuster {
#[inline(always)]
pub fn new(glyph: &mut Glyph) -> Self {
let v = glyph.position.x.round();
glyph.position.x = 0.;
glyph.position.y = glyph.position.y.ceil();
Self(v)
}

#[inline(always)]
pub fn position(&self, v: Vec2) -> Vec2 {
Vec2::new(self.0, 0.) + v
}
}
6 changes: 6 additions & 0 deletions docs/cargo_features.md
Original file line number Diff line number Diff line change
Expand Up @@ -71,3 +71,9 @@ Vorbis audio format support.
### wayland

Enable this to use Wayland display server protocol other than X11.

### subpixel_glyph_atlas

Enable this to cache glyphs using subpixel accuracy. This increases texture
memory usage as each position requires a separate sprite in the glyph atlas, but
provide more accurate character spacing.

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