Merge pull request #939 from l0ng-ai/feat/720-font-smoothing

feat(fonts): make macOS stroke thickening configurable

Cargo.toml

@@ -222,7 +222,10 @@ objc2-app-kit = { version = "0.3", features = ["NSApplication", "NSResponder", "
 # `set_dock_icon_for_bare_binary` in main.rs.
 # NSUserNotification is the click-to-reveal notification path — see
 # `terminal::remote::macos_notify` for why it is driven directly.
-objc2-foundation = { version = "0.3", features = ["NSData", "NSString", "NSUserNotification"] }
+# NSUserDefaults (with NSDictionary / NSValue for the domain it takes) pins
+# `AppleFontSmoothing` for this process when `font_thicken` is off — see
+# `apply_font_thicken` in main.rs.
+objc2-foundation = { version = "0.3", features = ["NSData", "NSDictionary", "NSString", "NSUserDefaults", "NSUserNotification", "NSValue"] }
 
 # Dictionary-based Chinese word segmentation for double-click selection
 # (`terminal::smart_select`), as a *fallback* where the OS has no tokenizer of

crates/tty7-core/src/core/config.rs

@@ -135,6 +135,16 @@ pub struct Config {
     pub font_family_bold: Option<String>,
     pub font_family_italic: Option<String>,
     pub font_features: Option<FontFeatures>,
+    /// macOS only: let CoreGraphics font smoothing thicken glyph strokes — by
+    /// more the lighter the text, which is why light-on-dark looks bolder.
+    /// On by default, because it is what every macOS app draws with.
+    ///
+    /// Off pins `AppleFontSmoothing` to `0` for this process alone, so glyphs
+    /// are drawn at the face's own weight. gpui reads that preference once, the
+    /// first time it rasterizes text, so a change applies at the next launch.
+    /// Ignored elsewhere, where there is no such dilation to turn off.
+    #[serde(default = "default_true")]
+    pub font_thicken: bool,
     pub font_size: f32,
     pub line_height: f32,
     /// The interface's root font size, in pixels — everything outside the
@@ -629,6 +639,7 @@ impl Default for Config {
             font_family_bold: None,
             font_family_italic: None,
             font_features: None,
+            font_thicken: true,
             font_size: 15.0,
             line_height: 1.4,
             ui_font_size: default_ui_font_size(),
@@ -1497,6 +1508,18 @@ mod tests {
         assert!(default_cfg.font_features.is_none());
     }
 
+    #[test]
+    fn font_thicken_defaults_on_and_reads_an_explicit_off() {
+        // On is what tty7 drew before the key existed, so a config that never
+        // names it must keep rendering exactly as it did.
+        let cfg: Config = serde_json::from_str("{}").unwrap();
+        assert!(cfg.font_thicken);
+        assert!(Config::default().font_thicken);
+
+        let cfg: Config = serde_json::from_str(r#"{"font_thicken":false}"#).unwrap();
+        assert!(!cfg.font_thicken);
+    }
+
     #[test]
     fn font_features_round_trip_to_integer_valued_json() {
         let features: FontFeatures =

docs/customization/fonts.mdx

@@ -15,6 +15,7 @@ description: "The bundled default, fallback chains, ligatures, and why CJK needs
 | **Line height** | 1.4 | A multiple of the font size |
 | **Bold font** / **Italic font** | — | Distinct faces, when you want them |
 | **Font ligatures** | off | `calt`, `liga` and `clig` all stay off unless you ask |
+| **Thicken strokes** | on | macOS only — see [Stroke weight on macOS](#stroke-weight-on-macos) |
 
 ## Hack is bundled
 
@@ -71,6 +72,35 @@ on. Name them explicitly if you want both:
 }
 ```
 
+## Stroke weight on macOS
+
+macOS font smoothing thickens glyph strokes, and by how much depends on the
+text colour: the lighter the text, the bolder it draws. That is why light text
+on a dark theme can look heavier in tty7 than in a terminal that turns the
+effect off, and why a thinner weight of the same family does not fully make up
+for it.
+
+**Settings → Appearance → Terminal text → Thicken strokes** (`font_thicken`)
+turns it off, so glyphs draw at the face's own weight whatever their colour:
+
+```json
+{
+  "font_thicken": false
+}
+```
+
+<Note>
+  The change applies the next time tty7 starts: the preference is read once,
+  when text is first drawn. It covers tty7 alone — no other app, and not the
+  system-wide setting.
+</Note>
+
+Leaving it on changes nothing, so an existing
+`defaults write com.github.tty7 AppleFontSmoothing -int 0` keeps working. This
+is the same switch as Ghostty's `font-thicken` and iTerm2's thin strokes, with
+tty7 defaulting to the macOS look. Windows and Linux do not thicken strokes, so
+the key does nothing there.
+
 ## CJK and the two-column grid
 
 <Info>

docs/reference/configuration.mdx

@@ -35,6 +35,7 @@ failing the file.
 | `font_family_bold` | string | — | A distinct bold face. |
 | `font_family_italic` | string | — | A distinct italic face. |
 | `font_features` | object | — | OpenType tags, e.g. `{"calt": true, "liga": 1}`. Four alphanumeric characters per tag. |
+| `font_thicken` | bool | `true` | macOS: let font smoothing thicken strokes, light text most. `false` draws glyphs at their own weight. Applies after a restart. |
 | `font_size` | number | `15` | Terminal text size in px (4–256). |
 | `line_height` | number | `1.4` | Multiple of the font size (0.5–4). |
 | `ui_font_size` | number | `16` | The interface's root size in px (12–24). |

src/main.rs

@@ -441,6 +441,41 @@ fn set_dock_icon_for_bare_binary() {
     }
 }
 
+/// Turns CoreGraphics' stroke thickening off for this process when
+/// `font_thicken` is off; with it on there is nothing to do, and whatever the
+/// system (or a hand-written `defaults write`) says stands.
+///
+/// gpui decides whether to dilate a glyph from `AppleFontSmoothing`, read with
+/// `CFPreferencesCopyAppValue` the first time it rasterizes text and cached for
+/// the life of the process. So this has to land before the application exists,
+/// and a change waits for the next launch.
+///
+/// The value goes into the argument domain — the volatile one that
+/// `-AppleFontSmoothing 0` on the command line would fill. It outranks both this
+/// app's persisted defaults and the global domain, and it lives only in this
+/// process's memory: nothing reaches disk, so no other app sees it and a later
+/// launch with the key back on does not inherit it.
+#[cfg(target_os = "macos")]
+fn apply_font_thicken(thicken: bool) {
+    use objc2_foundation::{
+        NSArgumentDomain, NSMutableCopying, NSNumber, NSUserDefaults, ns_string,
+    };
+
+    if thicken {
+        return;
+    }
+    let defaults = NSUserDefaults::standardUserDefaults();
+    // SAFETY: a Foundation constant, initialized before `main` runs.
+    let domain = unsafe { NSArgumentDomain };
+    // Merged into, not replaced: the domain already holds any `-Key value`
+    // pairs the process was launched with.
+    let arguments = defaults.volatileDomainForName(domain).mutableCopy();
+    arguments.insert(ns_string!("AppleFontSmoothing"), &*NSNumber::new_i32(0));
+    // SAFETY: keys are `NSString` and values property-list objects, which is
+    // the shape a defaults domain requires.
+    unsafe { defaults.setVolatileDomain_forName(&arguments, domain) };
+}
+
 /// Delivers Finder document opens and LaunchServices URL opens after gpui has
 /// created the application. The native callback queues requests; UI state is
 /// then changed on gpui's application loop.
@@ -593,6 +628,8 @@ fn main() {
 
     let (config, config_outcome) = crate::core::config::Config::load_with_outcome();
     let gui_language = config.gui_language.clone();
+    #[cfg(target_os = "macos")]
+    apply_font_thicken(config.font_thicken);
 
     // After the PATH enrichment above, which is what makes the candidate scan
     // see the user's real PATH rather than the stub a Finder launch inherits —

src/ui/app.rs

@@ -3497,6 +3497,12 @@ impl Tty7App {
         self.update_config(cx, |cfg| cfg.show_tray_icon = on);
     }
 
+    /// Saved only: gpui reads the preference this drives once per process, so
+    /// it takes hold at the next launch (see `apply_font_thicken` in main.rs).
+    pub(crate) fn set_font_thicken(&mut self, on: bool, cx: &mut Context<Self>) {
+        self.update_config(cx, |cfg| cfg.font_thicken = on);
+    }
+
     pub(crate) fn set_macos_option_as_alt(&mut self, on: bool, cx: &mut Context<Self>) {
         self.update_config(cx, |cfg| cfg.macos_option_as_alt = on);
     }

src/ui/i18n/en.rs

@@ -133,6 +133,10 @@ pub fn translate_en(key: L10nKey) -> &'static str {
         L10nKey::SettingsFontLigaturesDesc => {
             "Enable common programming ligature features for terminal text."
         }
+        L10nKey::SettingsFontThicken => "Thicken strokes",
+        L10nKey::SettingsFontThickenDesc => {
+            "macOS font smoothing: draws text a little bolder, light text most. Takes effect after restarting tty7."
+        }
         L10nKey::SettingsCursor => "Cursor",
         L10nKey::SettingsCursorShape => "Cursor shape",
         L10nKey::SettingsCursorShapeDesc => "How the terminal cursor is drawn.",
@@ -842,6 +846,9 @@ pub fn translate_en(key: L10nKey) -> &'static str {
         L10nKey::SettingsSearchFocusFollowsMouseKeywords => "pane hover activate",
         L10nKey::SettingsSearchFontFamilyKeywords => "typeface monospace typography",
         L10nKey::SettingsSearchFontLigaturesKeywords => "typography glyph fira",
+        L10nKey::SettingsSearchFontThickenKeywords => {
+            "font smoothing thicken bold weight thin dilation antialiasing AppleFontSmoothing"
+        }
         L10nKey::SettingsSearchFontSizeKeywords => "typography text bigger smaller zoom",
         L10nKey::SettingsSearchForwardSshLoopbackLinksKeywords => {
             "ssh remote port tunnel localhost forward links ports autoforward detect"

src/ui/i18n/ja.rs

@@ -135,6 +135,10 @@ pub fn translate_ja(key: L10nKey) -> Option<&'static str> {
         L10nKey::SettingsFontLigaturesDesc => {
             "ターミナルテキストで一般的なプログラミング用リガチャー（合字）を有効にする"
         }
+        L10nKey::SettingsFontThicken => "ストロークを太くする",
+        L10nKey::SettingsFontThickenDesc => {
+            "macOS のフォントスムージング：文字をやや太く描画し、明るい文字ほど太くなる。tty7 の再起動後に反映"
+        }
         L10nKey::SettingsCursor => "カーソル",
         L10nKey::SettingsCursorShape => "カーソルの形状",
         L10nKey::SettingsCursorShapeDesc => "ターミナルカーソルの描画方法",
@@ -876,6 +880,9 @@ pub fn translate_ja(key: L10nKey) -> Option<&'static str> {
         L10nKey::SettingsSearchFontLigaturesKeywords => {
             "タイポグラフィ グリフ fira font ligatures typography glyph fira"
         }
+        L10nKey::SettingsSearchFontThickenKeywords => {
+            "フォントスムージング 太字 細字 ウェイト font smoothing thicken bold weight thin AppleFontSmoothing"
+        }
         L10nKey::SettingsSearchFontSizeKeywords => {
             "タイポグラフィ 文字 拡大 縮小 ズーム font size typography text bigger smaller zoom"
         }

src/ui/i18n/mod.rs

@@ -181,6 +181,8 @@ l10n_keys! {
     SettingsItalicFontDesc,
     SettingsFontLigatures,
     SettingsFontLigaturesDesc,
+    SettingsFontThicken,
+    SettingsFontThickenDesc,
     SettingsCursor,
     SettingsCursorShape,
     SettingsCursorShapeDesc,
@@ -644,6 +646,7 @@ l10n_keys! {
     SettingsSearchFocusFollowsMouseKeywords,
     SettingsSearchFontFamilyKeywords,
     SettingsSearchFontLigaturesKeywords,
+    SettingsSearchFontThickenKeywords,
     SettingsSearchFontSizeKeywords,
     SettingsSearchForwardSshLoopbackLinksKeywords,
     SettingsSearchGeminiKeywords,

src/ui/i18n/zh.rs

@@ -119,6 +119,10 @@ pub fn translate_zh(key: L10nKey) -> Option<&'static str> {
         L10nKey::SettingsItalicFontDesc => "斜体文字使用的字体；默认由主字体合成。",
         L10nKey::SettingsFontLigatures => "字体连字",
         L10nKey::SettingsFontLigaturesDesc => "为终端文字启用常见的编程连字特性。",
+        L10nKey::SettingsFontThicken => "笔画加粗",
+        L10nKey::SettingsFontThickenDesc => {
+            "macOS 字体平滑：文字画得稍粗，浅色文字最明显。重启 tty7 后生效。"
+        }
         L10nKey::SettingsCursor => "光标",
         L10nKey::SettingsCursorShape => "光标形状",
         L10nKey::SettingsCursorShapeDesc => "终端光标的绘制方式。",
@@ -771,6 +775,9 @@ pub fn translate_zh(key: L10nKey) -> Option<&'static str> {
         L10nKey::SettingsSearchFontLigaturesKeywords => {
             "字体连字 连字 字形 typography ligatures glyph fira"
         }
+        L10nKey::SettingsSearchFontThickenKeywords => {
+            "字体平滑 加粗 变细 字重 笔画 font smoothing thicken bold weight thin AppleFontSmoothing"
+        }
         L10nKey::SettingsSearchFontSizeKeywords => {
             "字号 字体大小 文字 放大 缩小 typography font size bigger smaller zoom"
         }

src/ui/settings.rs

@@ -549,6 +549,12 @@ fn settings_search_entries() -> &'static [SearchEntry] {
             title: SettingsFontLigatures,
             keywords: SettingsSearchFontLigaturesKeywords,
         },
+        #[cfg(target_os = "macos")]
+        SearchEntry {
+            section: Appearance,
+            title: SettingsFontThicken,
+            keywords: SettingsSearchFontThickenKeywords,
+        },
         SearchEntry {
             section: Appearance,
             title: SettingsCursorShape,
@@ -920,6 +926,7 @@ impl SearchEntry {
             L10nKey::SettingsItalicFont => "font_family_italic",
             L10nKey::SettingsUiFontFamily => "ui_font_family",
             L10nKey::SettingsFontLigatures => "font_features",
+            L10nKey::SettingsFontThicken => "font_thicken",
             L10nKey::SettingsOpacity => "window_opacity",
             L10nKey::SettingsBlur => "window_blur",
             L10nKey::SettingsBackdrop => "window_backdrop",
@@ -956,6 +963,7 @@ impl SearchEntry {
             L10nKey::SettingsBoldFont => t(L10nKey::SettingsBoldFontDesc),
             L10nKey::SettingsItalicFont => t(L10nKey::SettingsItalicFontDesc),
             L10nKey::SettingsFontLigatures => t(L10nKey::SettingsFontLigaturesDesc),
+            L10nKey::SettingsFontThicken => t(L10nKey::SettingsFontThickenDesc),
             L10nKey::SettingsCursorShape => t(L10nKey::SettingsCursorShapeDesc),
             L10nKey::SettingsCursorBlink => t(L10nKey::SettingsCursorBlinkDesc),
             L10nKey::SettingsBackgroundImage => t(L10nKey::SettingsBackgroundImageDesc),
@@ -1123,6 +1131,7 @@ impl SearchEntry {
                 cfg.working_directory.path != defaults.working_directory.path
             }
             L10nKey::SettingsFontLigatures => cfg.font_features != defaults.font_features,
+            L10nKey::SettingsFontThicken => cfg.font_thicken != defaults.font_thicken,
             _ => false,
         }
     }
@@ -3488,6 +3497,7 @@ impl Tty7App {
         let cfg = cx.global::<Config>();
         let cursor_style = cfg.cursor_style;
         let cursor_blink = cfg.cursor_blink;
+        let font_thicken = cfg.font_thicken;
         let font_ligatures = cfg.font_features.as_ref().is_some_and(|features| {
             features.is_calt_enabled() == Some(true)
                 || features
@@ -3591,6 +3601,19 @@ impl Tty7App {
             .checked(font_ligatures)
             .on_click(cx.listener(|this, on: &bool, _w, cx| this.set_font_ligatures(*on, cx)))
             .into_any_element();
+        // macOS alone dilates glyph strokes, so elsewhere there is no row.
+        let thicken_row = cfg!(target_os = "macos").then(|| {
+            let thicken_switch = crate::ui::theme::switch("font-thicken", cx)
+                .checked(font_thicken)
+                .on_click(cx.listener(|this, on: &bool, _w, cx| this.set_font_thicken(*on, cx)))
+                .into_any_element();
+            self.settings_row(
+                t(L10nKey::SettingsFontThicken),
+                t(L10nKey::SettingsFontThickenDesc),
+                thicken_switch,
+                cx,
+            )
+        });
 
         let cursor_idx = match cursor_style {
             CursorStyle::Block => 0,
@@ -3682,6 +3705,7 @@ impl Tty7App {
                 ligature_switch,
                 cx,
             ))
+            .when_some(thicken_row, |v, row| v.child(row))
             .child(self.section_rule(cx))
             .child(self.section_header(t(L10nKey::SettingsCursor), cx))
             .child(self.settings_row(