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fonts: detect colr glyphs better

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Freetype's support for colr is relatively rudimentary, which is fine,
but we want more control, so we probe a bit harder to figure out
whether a glyph has colr information before allowing freetype
to rasterize it, so that we have the opportunity to reroute
that rendering to our own logic.
This commit is contained in:
Wez Furlong 2023-08-22 07:35:55 -07:00
parent 7af61159a8
commit 67f4450d8f
No known key found for this signature in database
GPG Key ID: 7A7F66A31EC9B387
2 changed files with 40 additions and 11 deletions
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43
wezterm-font/src/ftwrap.rs
View File

@ -135,6 +135,10 @@ pub struct SelectedFontSize {
#[error("Glyph is SVG")] #[error("Glyph is SVG")]
pub struct IsSvg; pub struct IsSvg;
#[derive(Debug, thiserror::Error)]
#[error("Glyph is COLR1 or later")]
pub struct IsColr1OrLater;
impl Face { impl Face {
pub fn family_name(&self) -> String { pub fn family_name(&self) -> String {
unsafe { unsafe {
@ -926,14 +930,16 @@ impl Face {
synthesize_bold: bool, synthesize_bold: bool,
) -> anyhow::Result<&FT_GlyphSlotRec_> { ) -> anyhow::Result<&FT_GlyphSlotRec_> {
unsafe { unsafe {
ft_result(FT_Load_Glyph(self.face, glyph_index, load_flags), ()).with_context( ft_result(
|| { FT_Load_Glyph(self.face, glyph_index, load_flags | FT_LOAD_NO_SVG as i32),
format!( (),
"load_and_render_glyph: FT_Load_Glyph glyph_index:{}", )
glyph_index .with_context(|| {
) format!(
}, "load_and_render_glyph: FT_Load_Glyph glyph_index:{}",
)?; glyph_index
)
})?;
let slot = &mut *(*self.face).glyph; let slot = &mut *(*self.face).glyph;
if slot.format == FT_Glyph_Format_::FT_GLYPH_FORMAT_SVG { if slot.format == FT_Glyph_Format_::FT_GLYPH_FORMAT_SVG {
@ -944,8 +950,29 @@ impl Face {
FT_GlyphSlot_Embolden(slot as *mut _); FT_GlyphSlot_Embolden(slot as *mut _);
} }
// Current versions of freetype overload the operation of FT_LOAD_COLOR
// and the resulting glyph format such that we cannot determine solely
// from the flags whether we got a regular set of outlines,
// or its COLR v0 synthesized glyphs, or whether it's COLR v1 or later
// and it can't render the result.
// So, we probe here to look for color layer information: if we find it,
// we don't call freetype's renderer and instead bubble up an error
// that the embedding application can trap and decide what to do.
if slot.format == FT_Glyph_Format_::FT_GLYPH_FORMAT_OUTLINE {
if self
.get_color_glyph_paint(
glyph_index,
FT_Color_Root_Transform::FT_COLOR_NO_ROOT_TRANSFORM,
)
.is_ok()
{
return Err(IsColr1OrLater.into());
}
}
ft_result(FT_Render_Glyph(slot, render_mode), ()) ft_result(FT_Render_Glyph(slot, render_mode), ())
.context("load_and_render_glyph: FT_Render_Glyph")?; .context("load_and_render_glyph: FT_Render_Glyph")?;
Ok(slot) Ok(slot)
} }
} }

8
wezterm-font/src/rasterizer/freetype.rs
View File

@ -1,7 +1,7 @@
use crate::ftwrap::{ use crate::ftwrap::{
composite_mode_to_operator, vector_x_y, FT_Affine23, FT_ColorIndex, FT_ColorLine, FT_ColorStop, composite_mode_to_operator, vector_x_y, FT_Affine23, FT_ColorIndex, FT_ColorLine, FT_ColorStop,
FT_Fixed, FT_Get_Colorline_Stops, FT_Int32, FT_PaintExtend, IsSvg, SelectedFontSize, FT_Fixed, FT_Get_Colorline_Stops, FT_Int32, FT_PaintExtend, IsColr1OrLater, IsSvg,
FT_LOAD_NO_HINTING, SelectedFontSize, FT_LOAD_NO_HINTING,
}; };
use crate::parser::ParsedFont; use crate::parser::ParsedFont;
use crate::rasterizer::colr::{ use crate::rasterizer::colr::{
@ -64,7 +64,9 @@ impl FontRasterizer for FreeTypeRasterizer {
) { ) {
Ok(g) => g, Ok(g) => g,
Err(err) => { Err(err) => {
if err.root_cause().downcast_ref::<IsSvg>().is_some() { if err.root_cause().downcast_ref::<IsSvg>().is_some()
|| err.root_cause().downcast_ref::<IsColr1OrLater>().is_some()
{
drop(face); drop(face);
let config = config::configuration(); let config = config::configuration();