Linux: Experiment with CosmicText based Text System (#7539)

h3mosphere , gabydd , and Mikayla Maki created

This is a rebase of @gabydds text_system updates. with some small
cleanups.

Currently cannot test this as build is not working in linux. Im just
putting it up here before I forget about it.

---------

Co-authored-by: gabydd <gabydinnerdavid@gmail.com>
Co-authored-by: Mikayla Maki <mikayla@zed.dev>

Change summary

Cargo.lock                                    | 174 ++++++++
crates/gpui/Cargo.toml                        |   1 
crates/gpui/src/platform/linux/text_system.rs | 394 ++++++++++++++++++--
crates/gpui/src/style.rs                      |   8 
crates/gpui/src/text_system.rs                |   1 
5 files changed, 531 insertions(+), 47 deletions(-)

Detailed changes

Cargo.lock 🔗

@@ -1917,6 +1917,27 @@ dependencies = [
  "bindgen 0.64.0",
 ]
 
+[[package]]
+name = "cosmic-text"
+version = "0.10.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "75acbfb314aeb4f5210d379af45ed1ec2c98c7f1790bf57b8a4c562ac0c51b71"
+dependencies = [
+ "fontdb 0.15.0",
+ "libm",
+ "log",
+ "rangemap",
+ "rustc-hash",
+ "rustybuzz 0.11.0",
+ "self_cell",
+ "swash",
+ "sys-locale",
+ "unicode-bidi",
+ "unicode-linebreak",
+ "unicode-script",
+ "unicode-segmentation",
+]
+
 [[package]]
 name = "cpal"
 version = "0.15.2"
@@ -2875,6 +2896,21 @@ dependencies = [
  "yeslogic-fontconfig-sys",
 ]
 
+[[package]]
+name = "font-types"
+version = "0.4.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0bd7f3ea17572640b606b35df42cfb6ecdf003704b062580e59918692190b73d"
+
+[[package]]
+name = "fontconfig-parser"
+version = "0.5.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6a595cb550439a117696039dfc69830492058211b771a2a165379f2a1a53d84d"
+dependencies = [
+ "roxmltree 0.19.0",
+]
+
 [[package]]
 name = "fontdb"
 version = "0.5.4"
@@ -2882,10 +2918,24 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "e58903f4f8d5b58c7d300908e4ebe5289c1bfdf5587964330f12023b8ff17fd1"
 dependencies = [
  "log",
- "memmap2",
+ "memmap2 0.2.3",
  "ttf-parser 0.12.3",
 ]
 
+[[package]]
+name = "fontdb"
+version = "0.15.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "020e203f177c0fb250fb19455a252e838d2bbbce1f80f25ecc42402aafa8cd38"
+dependencies = [
+ "fontconfig-parser",
+ "log",
+ "memmap2 0.8.0",
+ "slotmap",
+ "tinyvec",
+ "ttf-parser 0.19.2",
+]
+
 [[package]]
 name = "foreign-types"
 version = "0.3.2"
@@ -3385,6 +3435,7 @@ dependencies = [
  "core-foundation",
  "core-graphics 0.22.3",
  "core-text",
+ "cosmic-text",
  "ctor",
  "derive_more",
  "dhat",
@@ -4278,9 +4329,9 @@ dependencies = [
 
 [[package]]
 name = "libm"
-version = "0.2.7"
+version = "0.2.8"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f7012b1bbb0719e1097c47611d3898568c546d597c2e74d66f6087edd5233ff4"
+checksum = "4ec2a862134d2a7d32d7983ddcdd1c4923530833c9f2ea1a44fc5fa473989058"
 
 [[package]]
 name = "libmimalloc-sys"
@@ -4614,6 +4665,15 @@ dependencies = [
  "libc",
 ]
 
+[[package]]
+name = "memmap2"
+version = "0.8.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "43a5a03cefb0d953ec0be133036f14e109412fa594edc2f77227249db66cc3ed"
+dependencies = [
+ "libc",
+]
+
 [[package]]
 name = "memoffset"
 version = "0.6.5"
@@ -6397,6 +6457,12 @@ dependencies = [
  "rand_core 0.5.1",
 ]
 
+[[package]]
+name = "rangemap"
+version = "1.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "977b1e897f9d764566891689e642653e5ed90c6895106acd005eb4c1d0203991"
+
 [[package]]
 name = "raw-window-handle"
 version = "0.5.2"
@@ -6453,6 +6519,15 @@ version = "0.3.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "be9e29cb19c8fe84169fcb07f8f11e66bc9e6e0280efd4715c54818296f8a4a8"
 
+[[package]]
+name = "read-fonts"
+version = "0.15.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a1362980db95801b70031dd592dc052a44b1810ca9da8fbcf7b25983f3174ed0"
+dependencies = [
+ "font-types",
+]
+
 [[package]]
 name = "recent_projects"
 version = "0.1.0"
@@ -6791,6 +6866,12 @@ dependencies = [
  "xmlparser",
 ]
 
+[[package]]
+name = "roxmltree"
+version = "0.19.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "3cd14fd5e3b777a7422cca79358c57a8f6e3a703d9ac187448d0daf220c2407f"
+
 [[package]]
 name = "rpc"
 version = "0.1.0"
@@ -7041,6 +7122,23 @@ dependencies = [
  "unicode-script",
 ]
 
+[[package]]
+name = "rustybuzz"
+version = "0.11.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2ee8fe2a8461a0854a37101fe7a1b13998d0cfa987e43248e81d2a5f4570f6fa"
+dependencies = [
+ "bitflags 1.3.2",
+ "bytemuck",
+ "libm",
+ "smallvec",
+ "ttf-parser 0.20.0",
+ "unicode-bidi-mirroring",
+ "unicode-ccc",
+ "unicode-properties",
+ "unicode-script",
+]
+
 [[package]]
 name = "ryu"
 version = "1.0.15"
@@ -7297,6 +7395,12 @@ dependencies = [
  "libc",
 ]
 
+[[package]]
+name = "self_cell"
+version = "1.0.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "58bf37232d3bb9a2c4e641ca2a11d83b5062066f88df7fed36c28772046d65ba"
+
 [[package]]
 name = "semantic_index"
 version = "0.1.0"
@@ -8248,6 +8352,17 @@ dependencies = [
  "siphasher 0.2.3",
 ]
 
+[[package]]
+name = "swash"
+version = "0.1.12"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d06ff4664af8923625604261c645f5c4cc610cc83c84bec74b50d76237089de7"
+dependencies = [
+ "read-fonts",
+ "yazi",
+ "zeno",
+]
+
 [[package]]
 name = "syn"
 version = "1.0.109"
@@ -8286,6 +8401,15 @@ dependencies = [
  "libc",
 ]
 
+[[package]]
+name = "sys-locale"
+version = "0.3.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e801cf239ecd6ccd71f03d270d67dd53d13e90aab208bf4b8fe4ad957ea949b0"
+dependencies = [
+ "libc",
+]
+
 [[package]]
 name = "sysinfo"
 version = "0.29.10"
@@ -9393,6 +9517,18 @@ version = "0.12.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "7ae2f58a822f08abdaf668897e96a5656fe72f5a9ce66422423e8849384872e6"
 
+[[package]]
+name = "ttf-parser"
+version = "0.19.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "49d64318d8311fc2668e48b63969f4343e0a85c4a109aa8460d6672e364b8bd1"
+
+[[package]]
+name = "ttf-parser"
+version = "0.20.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "17f77d76d837a7830fe1d4f12b7b4ba4192c1888001c7164257e4bc6d21d96b4"
+
 [[package]]
 name = "tungstenite"
 version = "0.16.0"
@@ -9495,6 +9631,12 @@ version = "1.0.12"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "3354b9ac3fae1ff6755cb6db53683adb661634f67557942dea4facebec0fee4b"
 
+[[package]]
+name = "unicode-linebreak"
+version = "0.1.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "3b09c83c3c29d37506a3e260c08c03743a6bb66a9cd432c6934ab501a190571f"
+
 [[package]]
 name = "unicode-normalization"
 version = "0.1.22"
@@ -9504,6 +9646,12 @@ dependencies = [
  "tinyvec",
 ]
 
+[[package]]
+name = "unicode-properties"
+version = "0.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e4259d9d4425d9f0661581b804cb85fe66a4c631cadd8f490d1c13a35d5d9291"
+
 [[package]]
 name = "unicode-script"
 version = "0.5.5"
@@ -9579,14 +9727,14 @@ dependencies = [
  "base64 0.13.1",
  "data-url",
  "flate2",
- "fontdb",
+ "fontdb 0.5.4",
  "kurbo",
  "log",
- "memmap2",
+ "memmap2 0.2.3",
  "pico-args",
  "rctree",
- "roxmltree",
- "rustybuzz",
+ "roxmltree 0.14.1",
+ "rustybuzz 0.3.0",
  "simplecss",
  "siphasher 0.2.3",
  "svgtypes",
@@ -10564,6 +10712,12 @@ version = "0.5.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "09041cd90cf85f7f8b2df60c646f853b7f535ce68f85244eb6731cf89fa498ec"
 
+[[package]]
+name = "yazi"
+version = "0.1.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c94451ac9513335b5e23d7a8a2b61a7102398b8cca5160829d313e84c9d98be1"
+
 [[package]]
 name = "yeslogic-fontconfig-sys"
 version = "3.2.0"
@@ -10733,6 +10887,12 @@ dependencies = [
  "serde",
 ]
 
+[[package]]
+name = "zeno"
+version = "0.2.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "dd15f8e0dbb966fd9245e7498c7e9e5055d9e5c8b676b95bd67091cd11a1e697"
+
 [[package]]
 name = "zeroize"
 version = "1.6.0"

crates/gpui/Cargo.toml 🔗

@@ -102,3 +102,4 @@ as-raw-xcb-connection = "1"
 blade-graphics = { git = "https://github.com/kvark/blade", rev = "26bc5e8b9ef67b4f2970eb95888db733eace98f3" }
 blade-macros = { git = "https://github.com/kvark/blade", rev = "26bc5e8b9ef67b4f2970eb95888db733eace98f3" }
 bytemuck = "1"
+cosmic-text = "0.10.0"

crates/gpui/src/platform/linux/text_system.rs 🔗

@@ -1,40 +1,49 @@
 //todo!(linux) remove
 #[allow(unused)]
+use crate::{point, size, FontStyle, FontWeight, Point, ShapedGlyph};
 use crate::{
-    Bounds, DevicePixels, Font, FontId, FontMetrics, FontRun, GlyphId, LineLayout, Pixels,
-    PlatformTextSystem, RenderGlyphParams, SharedString, Size,
+    Bounds, DevicePixels, Font, FontFeatures, FontId, FontMetrics, FontRun, GlyphId, LineLayout,
+    Pixels, PlatformTextSystem, RenderGlyphParams, SharedString, Size,
 };
+use anyhow::Ok;
 use anyhow::Result;
+use anyhow::{anyhow, Context};
 use collections::HashMap;
-use font_kit::{font::Font as FontKitFont, source::SystemSource, sources::mem::MemSource};
-use parking_lot::RwLock;
+use cosmic_text::fontdb::Query;
+use cosmic_text::{
+    Attrs, AttrsList, BufferLine, CacheKey, Family, Font as CosmicTextFont, FontSystem, SwashCache,
+};
+use parking_lot::{RwLock, RwLockUpgradableReadGuard};
+use pathfinder_geometry::rect::RectF;
+use pathfinder_geometry::rect::RectI;
+use pathfinder_geometry::vector::{Vector2F, Vector2I};
 use smallvec::SmallVec;
-use std::borrow::Cow;
+use std::{borrow::Cow, sync::Arc};
 
 pub(crate) struct LinuxTextSystem(RwLock<LinuxTextSystemState>);
 
 struct LinuxTextSystemState {
-    memory_source: MemSource,
-    system_source: SystemSource,
-    fonts: Vec<FontKitFont>,
+    swash_cache: SwashCache,
+    font_system: FontSystem,
+    fonts: Vec<Arc<CosmicTextFont>>,
     font_selections: HashMap<Font, FontId>,
-    font_ids_by_postscript_name: HashMap<String, FontId>,
     font_ids_by_family_name: HashMap<SharedString, SmallVec<[FontId; 4]>>,
     postscript_names_by_font_id: HashMap<FontId, String>,
 }
 
-// todo!(linux): Double check this
-unsafe impl Send for LinuxTextSystemState {}
-unsafe impl Sync for LinuxTextSystemState {}
-
 impl LinuxTextSystem {
     pub(crate) fn new() -> Self {
+        let mut font_system = FontSystem::new();
+
+        // todo!(linux) make font loading non-blocking
+        font_system.db_mut().load_system_fonts();
+
         Self(RwLock::new(LinuxTextSystemState {
-            memory_source: MemSource::empty(),
-            system_source: SystemSource::new(),
+            font_system,
+            swash_cache: SwashCache::new(),
             fonts: Vec::new(),
             font_selections: HashMap::default(),
-            font_ids_by_postscript_name: HashMap::default(),
+            // font_ids_by_postscript_name: HashMap::default(),
             font_ids_by_family_name: HashMap::default(),
             postscript_names_by_font_id: HashMap::default(),
         }))
@@ -49,14 +58,20 @@ impl Default for LinuxTextSystem {
 
 #[allow(unused)]
 impl PlatformTextSystem for LinuxTextSystem {
-    // todo!(linux)
     fn add_fonts(&self, fonts: Vec<Cow<'static, [u8]>>) -> Result<()> {
-        Ok(())
+        self.0.write().add_fonts(fonts)
     }
 
-    // todo!(linux)
+    // todo!(linux) ensure that this integrates with platform font loading
+    // do we need to do more than call load_system_fonts()?
     fn all_font_names(&self) -> Vec<String> {
-        Vec::new()
+        self.0
+            .read()
+            .font_system
+            .db()
+            .faces()
+            .map(|face| face.post_script_name.clone())
+            .collect()
     }
 
     // todo!(linux)
@@ -64,51 +79,112 @@ impl PlatformTextSystem for LinuxTextSystem {
         Vec::new()
     }
 
-    // todo!(linux)
-    fn font_id(&self, descriptor: &Font) -> Result<FontId> {
-        Ok(FontId(0))
+    fn font_id(&self, font: &Font) -> Result<FontId> {
+        // todo!(linux): Do we need to use CosmicText's Font APIs? Can we consolidate this to use font_kit?
+        let lock = self.0.upgradable_read();
+        if let Some(font_id) = lock.font_selections.get(font) {
+            Ok(*font_id)
+        } else {
+            let mut lock = RwLockUpgradableReadGuard::upgrade(lock);
+            let candidates = if let Some(font_ids) = lock.font_ids_by_family_name.get(&font.family)
+            {
+                font_ids.as_slice()
+            } else {
+                let font_ids = lock.load_family(&font.family, font.features)?;
+                lock.font_ids_by_family_name
+                    .insert(font.family.clone(), font_ids);
+                lock.font_ids_by_family_name[&font.family].as_ref()
+            };
+
+            let id = lock
+                .font_system
+                .db()
+                .query(&Query {
+                    families: &[Family::Name(&font.family)],
+                    weight: font.weight.into(),
+                    style: font.style.into(),
+                    stretch: Default::default(),
+                })
+                .context("no font")?;
+
+            let font_id = if let Some(font_id) = lock.fonts.iter().position(|font| font.id() == id)
+            {
+                FontId(font_id)
+            } else {
+                // Font isn't in fonts so add it there, this is because we query all the fonts in the db
+                // and maybe we haven't loaded it yet
+                let font_id = FontId(lock.fonts.len());
+                let font = lock.font_system.get_font(id).unwrap();
+                lock.fonts.push(font);
+                font_id
+            };
+
+            lock.font_selections.insert(font.clone(), font_id);
+            Ok(font_id)
+        }
     }
 
-    // todo!(linux)
     fn font_metrics(&self, font_id: FontId) -> FontMetrics {
-        unimplemented!()
+        let metrics = self.0.read().fonts[font_id.0].as_swash().metrics(&[]);
+
+        FontMetrics {
+            units_per_em: metrics.units_per_em as u32,
+            ascent: metrics.ascent,
+            descent: -metrics.descent, // todo!(linux) confirm this is correct
+            line_gap: metrics.leading,
+            underline_position: metrics.underline_offset,
+            underline_thickness: metrics.stroke_size,
+            cap_height: metrics.cap_height,
+            x_height: metrics.x_height,
+            // todo!(linux): Compute this correctly
+            bounding_box: Bounds {
+                origin: point(0.0, 0.0),
+                size: size(metrics.max_width, metrics.ascent + metrics.descent),
+            },
+        }
     }
 
-    // todo!(linux)
     fn typographic_bounds(&self, font_id: FontId, glyph_id: GlyphId) -> Result<Bounds<f32>> {
-        unimplemented!()
+        let lock = self.0.read();
+        let metrics = lock.fonts[font_id.0].as_swash().metrics(&[]);
+        let glyph_metrics = lock.fonts[font_id.0].as_swash().glyph_metrics(&[]);
+        let glyph_id = glyph_id.0 as u16;
+        // todo!(linux): Compute this correctly
+        // see https://github.com/servo/font-kit/blob/master/src/loaders/freetype.rs#L614-L620
+        Ok(Bounds {
+            origin: point(0.0, 0.0),
+            size: size(
+                glyph_metrics.advance_width(glyph_id),
+                glyph_metrics.advance_height(glyph_id),
+            ),
+        })
     }
 
-    // todo!(linux)
     fn advance(&self, font_id: FontId, glyph_id: GlyphId) -> Result<Size<f32>> {
-        unimplemented!()
+        self.0.read().advance(font_id, glyph_id)
     }
 
-    // todo!(linux)
     fn glyph_for_char(&self, font_id: FontId, ch: char) -> Option<GlyphId> {
-        None
+        self.0.read().glyph_for_char(font_id, ch)
     }
 
-    // todo!(linux)
     fn glyph_raster_bounds(&self, params: &RenderGlyphParams) -> Result<Bounds<DevicePixels>> {
-        unimplemented!()
+        self.0.write().raster_bounds(params)
     }
 
-    // todo!(linux)
     fn rasterize_glyph(
         &self,
         params: &RenderGlyphParams,
         raster_bounds: Bounds<DevicePixels>,
     ) -> Result<(Size<DevicePixels>, Vec<u8>)> {
-        unimplemented!()
+        self.0.write().rasterize_glyph(params, raster_bounds)
     }
 
-    // todo!(linux)
     fn layout_line(&self, text: &str, font_size: Pixels, runs: &[FontRun]) -> LineLayout {
-        LineLayout::default() //TODO
+        self.0.write().layout_line(text, font_size, runs)
     }
 
-    // todo!(linux)
+    // todo!(linux) Confirm that this has been superseded by the LineWrapper
     fn wrap_line(
         &self,
         text: &str,
@@ -119,3 +195,245 @@ impl PlatformTextSystem for LinuxTextSystem {
         unimplemented!()
     }
 }
+
+impl LinuxTextSystemState {
+    fn add_fonts(&mut self, fonts: Vec<Cow<'static, [u8]>>) -> Result<()> {
+        let db = self.font_system.db_mut();
+        for bytes in fonts {
+            match bytes {
+                Cow::Borrowed(embedded_font) => {
+                    db.load_font_data(embedded_font.to_vec());
+                }
+                Cow::Owned(bytes) => {
+                    db.load_font_data(bytes);
+                }
+            }
+        }
+        Ok(())
+    }
+
+    fn load_family(
+        &mut self,
+        name: &SharedString,
+        _features: FontFeatures,
+    ) -> Result<SmallVec<[FontId; 4]>> {
+        let mut font_ids = SmallVec::new();
+        let family = self
+            .font_system
+            .get_font_matches(Attrs::new().family(cosmic_text::Family::Name(name)));
+        for font in family.as_ref() {
+            let font = self.font_system.get_font(*font).unwrap();
+            if font.as_swash().charmap().map('m') == 0 {
+                self.font_system.db_mut().remove_face(font.id());
+                continue;
+            };
+
+            let font_id = FontId(self.fonts.len());
+            font_ids.push(font_id);
+            self.fonts.push(font);
+        }
+        Ok(font_ids)
+    }
+
+    fn advance(&self, font_id: FontId, glyph_id: GlyphId) -> Result<Size<f32>> {
+        let width = self.fonts[font_id.0]
+            .as_swash()
+            .glyph_metrics(&[])
+            .advance_width(glyph_id.0 as u16);
+        let height = self.fonts[font_id.0]
+            .as_swash()
+            .glyph_metrics(&[])
+            .advance_height(glyph_id.0 as u16);
+        Ok(Size { width, height })
+    }
+
+    fn glyph_for_char(&self, font_id: FontId, ch: char) -> Option<GlyphId> {
+        let glyph_id = self.fonts[font_id.0].as_swash().charmap().map(ch);
+        if glyph_id == 0 {
+            None
+        } else {
+            Some(GlyphId(glyph_id.into()))
+        }
+    }
+
+    fn is_emoji(&self, font_id: FontId) -> bool {
+        // todo!(linux): implement this correctly
+        self.postscript_names_by_font_id
+            .get(&font_id)
+            .map_or(false, |postscript_name| {
+                postscript_name == "AppleColorEmoji"
+            })
+    }
+
+    // todo!(linux) both raster functions have problems because I am not sure this is the correct mapping from cosmic text to gpui system
+    fn raster_bounds(&mut self, params: &RenderGlyphParams) -> Result<Bounds<DevicePixels>> {
+        let font = &self.fonts[params.font_id.0];
+        let font_system = &mut self.font_system;
+        let image = self
+            .swash_cache
+            .get_image(
+                font_system,
+                CacheKey::new(
+                    font.id(),
+                    params.glyph_id.0 as u16,
+                    params.font_size.into(),
+                    (0.0, 0.0),
+                )
+                .0,
+            )
+            .clone()
+            .unwrap();
+        Ok(Bounds {
+            origin: point(image.placement.left.into(), (-image.placement.top).into()),
+            size: size(image.placement.width.into(), image.placement.height.into()),
+        })
+    }
+
+    fn rasterize_glyph(
+        &mut self,
+        params: &RenderGlyphParams,
+        glyph_bounds: Bounds<DevicePixels>,
+    ) -> Result<(Size<DevicePixels>, Vec<u8>)> {
+        if glyph_bounds.size.width.0 == 0 || glyph_bounds.size.height.0 == 0 {
+            Err(anyhow!("glyph bounds are empty"))
+        } else {
+            // todo!(linux) handle subpixel variants
+            let bitmap_size = glyph_bounds.size;
+            let font = &self.fonts[params.font_id.0];
+            let font_system = &mut self.font_system;
+            let image = self
+                .swash_cache
+                .get_image(
+                    font_system,
+                    CacheKey::new(
+                        font.id(),
+                        params.glyph_id.0 as u16,
+                        params.font_size.into(),
+                        (0.0, 0.0),
+                    )
+                    .0,
+                )
+                .clone()
+                .unwrap();
+
+            Ok((bitmap_size, image.data))
+        }
+    }
+
+    // todo!(linux) This is all a quick first pass, maybe we should be using cosmic_text::Buffer
+    fn layout_line(&mut self, text: &str, font_size: Pixels, font_runs: &[FontRun]) -> LineLayout {
+        let mut attrs_list = AttrsList::new(Attrs::new());
+        let mut offs = 0;
+        for run in font_runs {
+            // todo!(linux) We need to check we are doing utf properly
+            let font = &self.fonts[run.font_id.0];
+            let font = self.font_system.db().face(font.id()).unwrap();
+            attrs_list.add_span(
+                offs..run.len,
+                Attrs::new()
+                    .family(Family::Name(&font.families.first().unwrap().0))
+                    .stretch(font.stretch)
+                    .style(font.style)
+                    .weight(font.weight),
+            );
+            offs += run.len;
+        }
+        let mut line = BufferLine::new(text, attrs_list, cosmic_text::Shaping::Advanced);
+        let layout = line.layout(
+            &mut self.font_system,
+            font_size.0,
+            f32::MAX, // todo!(linux) we don't have a width cause this should technically not be wrapped I believe
+            cosmic_text::Wrap::None,
+        );
+        let mut runs = Vec::new();
+        // todo!(linux) what I think can happen is layout returns possibly multiple lines which means we should be probably working with it higher up in the text rendering
+        let layout = layout.first().unwrap();
+        for glyph in &layout.glyphs {
+            let font_id = glyph.font_id;
+            let font_id = FontId(
+                self.fonts
+                    .iter()
+                    .position(|font| font.id() == font_id)
+                    .unwrap(),
+            );
+            let mut glyphs = SmallVec::new();
+            // todo!(linux) this is definitely wrong, each glyph in glyphs from cosmic-text is a cluster with one glyph, ShapedRun takes a run of glyphs with the same font and direction
+            glyphs.push(ShapedGlyph {
+                id: GlyphId(glyph.glyph_id as u32),
+                position: point((glyph.x).into(), glyph.y.into()),
+                index: glyph.start,
+                is_emoji: self.is_emoji(font_id),
+            });
+            runs.push(crate::ShapedRun { font_id, glyphs });
+        }
+        LineLayout {
+            font_size,
+            width: layout.w.into(),
+            ascent: layout.max_ascent.into(),
+            descent: layout.max_descent.into(),
+            runs,
+            len: text.len(),
+        }
+    }
+}
+
+impl From<RectF> for Bounds<f32> {
+    fn from(rect: RectF) -> Self {
+        Bounds {
+            origin: point(rect.origin_x(), rect.origin_y()),
+            size: size(rect.width(), rect.height()),
+        }
+    }
+}
+
+impl From<RectI> for Bounds<DevicePixels> {
+    fn from(rect: RectI) -> Self {
+        Bounds {
+            origin: point(DevicePixels(rect.origin_x()), DevicePixels(rect.origin_y())),
+            size: size(DevicePixels(rect.width()), DevicePixels(rect.height())),
+        }
+    }
+}
+
+impl From<Vector2I> for Size<DevicePixels> {
+    fn from(value: Vector2I) -> Self {
+        size(value.x().into(), value.y().into())
+    }
+}
+
+impl From<RectI> for Bounds<i32> {
+    fn from(rect: RectI) -> Self {
+        Bounds {
+            origin: point(rect.origin_x(), rect.origin_y()),
+            size: size(rect.width(), rect.height()),
+        }
+    }
+}
+
+impl From<Point<u32>> for Vector2I {
+    fn from(size: Point<u32>) -> Self {
+        Vector2I::new(size.x as i32, size.y as i32)
+    }
+}
+
+impl From<Vector2F> for Size<f32> {
+    fn from(vec: Vector2F) -> Self {
+        size(vec.x(), vec.y())
+    }
+}
+
+impl From<FontWeight> for cosmic_text::Weight {
+    fn from(value: FontWeight) -> Self {
+        cosmic_text::Weight(value.0 as u16)
+    }
+}
+
+impl From<FontStyle> for cosmic_text::Style {
+    fn from(style: FontStyle) -> Self {
+        match style {
+            FontStyle::Normal => cosmic_text::Style::Normal,
+            FontStyle::Italic => cosmic_text::Style::Italic,
+            FontStyle::Oblique => cosmic_text::Style::Oblique,
+        }
+    }
+}

crates/gpui/src/style.rs 🔗

@@ -208,8 +208,12 @@ impl Default for TextStyle {
     fn default() -> Self {
         TextStyle {
             color: black(),
-            // Helvetica is a web safe font, so it should be available
-            font_family: "Helvetica".into(),
+            // todo!(linux) make this configurable or choose better default
+            font_family: if cfg!(target_os = "linux") {
+                "FreeMono".into()
+            } else {
+                "Helvetica".into()
+            },
             font_features: FontFeatures::default(),
             font_size: rems(1.).into(),
             line_height: phi(),

crates/gpui/src/text_system.rs 🔗

@@ -725,6 +725,7 @@ pub struct FontMetrics {
     pub(crate) x_height: f32,
 
     /// The outer limits of the area that the font covers.
+    /// Corresponds to the xMin / xMax / yMin / yMax values in the OpenType `head` table
     pub(crate) bounding_box: Bounds<f32>,
 }