Fix thin strokes on macOS

Remove the `font.use_thin_strokes` config, which only did anything on
macOS and only prior to Big Sur. Instead, we will enable or disable
"font smoothing" on macOS based on the `AppleFontSmoothing` user
default.

These changes let users get the "thin strokes" behavior by setting
`AppleFontSmoothing` to 0 with:

```sh
$ defaults write -g AppleFontSmoothing -int 0
```

(Or replace `-g` with `org.alacritty` to apply this setting only to
Alacritty.app, rather than the whole system.)

Add a `removed` config attribute to show helpful warnings to users
who are using config options that don't do anything anymore, and apply
this attribute to `font.use_thin_strokes`.

Bump `crossfont` to 0.5.0 to pick up the new font smoothing behavior.
This release also includes a fix for a crash when trying to load a
disabled font.

Fixes #4616.
Fixes #6108.

10 files changed, 39 insertions, 27 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index b6b31e05..4b585df9 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -34,10 +34,11 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 - `SpawnNewInstance` no longer inherits initial `--command`
 - Blinking cursor will timeout after `5` seconds by default
 - Deprecated `colors.search.bar`, use `colors.footer_bar` instead
+- On macOS, Alacritty now reads `AppleFontSmoothing` from user defaults to control font smoothing
 
 ### Fixed
 
-- Creating the IPC socket failing if WAYLAND_DISPLAY contains an absolute path
+- Creating the IPC socket failing if `WAYLAND_DISPLAY` contains an absolute path
 - Crash when resetting the terminal while in vi mode
 - `font.glyph_offset` not live reloading
 - Failure when running on 10-bit color system
@@ -50,6 +51,13 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 - Window flickering on resize on Wayland
 - Unnecessary config reload when using `/dev/null` as a config file
 - Windows `Open Alacritty Here` on root of drive displaying error
+- On macOS, `font.use_thin_strokes` did not work since Big Sur
+- On macOS, trying to load a disabled font would crash
+
+### Removed
+
+- `font.use_thin_strokes` config field; to use thin strokes on macOS, set
+    `AppleFontSmoothing` to 0 with `$ defaults write -g AppleFontSmoothing -int 0`
 
 ## 0.10.1
 
diff --git a/Cargo.lock b/Cargo.lock
index 1f579348..a25d5129 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -383,9 +383,9 @@ dependencies = [
 
 [[package]]
 name = "crossfont"
-version = "0.3.2"
+version = "0.5.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "1299695a4c6417b7e4a6957bd963478406e148b7b0351e2f2ce31296b0518251"
+checksum = "f66b1c1979c4362323f03ab6bf7fb522902bfc418e0c37319ab347f9561d980f"
 dependencies = [
  "cocoa",
  "core-foundation 0.9.3",
@@ -397,6 +397,8 @@ dependencies = [
  "freetype-rs",
  "libc",
  "log",
+ "objc",
+ "once_cell",
  "pkg-config",
  "servo-fontconfig",
  "winapi 0.3.9",
diff --git a/alacritty.yml b/alacritty.yml
index fcd46dfb..d8f05d3f 100644
--- a/alacritty.yml
+++ b/alacritty.yml
@@ -172,12 +172,6 @@
   #  x: 0
   #  y: 0
 
-  # Thin stroke font rendering (macOS only)
-  #
-  # Thin strokes are suitable for retina displays, but for non-retina screens
-  # it is recommended to set `use_thin_strokes` to `false`.
-  #use_thin_strokes: true
-
   # Use built-in font for box drawing characters.
   #
   # If `true`, Alacritty will use a custom built-in font for box drawing
diff --git a/alacritty/Cargo.toml b/alacritty/Cargo.toml
index 85b23c0a..9b610d86 100644
--- a/alacritty/Cargo.toml
+++ b/alacritty/Cargo.toml
@@ -28,7 +28,7 @@ serde_json = "1"
 glutin = { version = "0.28.0", default-features = false, features = ["serde"] }
 notify = "4"
 parking_lot = "0.11.0"
-crossfont = { version = "0.3.1", features = ["force_system_fontconfig"] }
+crossfont = { version = "0.5.0", features = ["force_system_fontconfig"] }
 copypasta = { version = "0.8.0", default-features = false }
 libc = "0.2"
 unicode-width = "0.1"
diff --git a/alacritty/src/config/font.rs b/alacritty/src/config/font.rs
index cdd84ff9..d3431171 100644
--- a/alacritty/src/config/font.rs
+++ b/alacritty/src/config/font.rs
@@ -22,6 +22,7 @@ pub struct Font {
     /// Glyph offset within character cell.
     pub glyph_offset: Delta<i8>,
 
+    #[config(removed = "set the AppleFontSmoothing user default instead")]
     pub use_thin_strokes: bool,
 
     /// Normal font face.
@@ -79,8 +80,8 @@ impl Default for Font {
     fn default() -> Font {
         Self {
             builtin_box_drawing: true,
-            use_thin_strokes: Default::default(),
             glyph_offset: Default::default(),
+            use_thin_strokes: Default::default(),
             bold_italic: Default::default(),
             italic: Default::default(),
             offset: Default::default(),
diff --git a/alacritty/src/display/mod.rs b/alacritty/src/display/mod.rs
index f1f51ec7..79e57307 100644
--- a/alacritty/src/display/mod.rs
+++ b/alacritty/src/display/mod.rs
@@ -411,7 +411,7 @@ impl Display {
         // Guess the target window dimensions.
         debug!("Loading \"{}\" font", &config.font.normal().family);
         let font = &config.font;
-        let rasterizer = Rasterizer::new(estimated_scale_factor as f32, font.use_thin_strokes)?;
+        let rasterizer = Rasterizer::new(estimated_scale_factor as f32)?;
         let mut glyph_cache = GlyphCache::new(rasterizer, font)?;
         let metrics = glyph_cache.font_metrics();
         let (cell_width, cell_height) = compute_cell_size(config, &metrics);
@@ -488,10 +488,6 @@ impl Display {
         let background_color = config.colors.primary.background;
         renderer.clear(background_color, config.window_opacity());
 
-        // Set subpixel anti-aliasing.
-        #[cfg(target_os = "macos")]
-        crossfont::set_font_smoothing(config.font.use_thin_strokes);
-
         // Disable shadows for transparent windows on macOS.
         #[cfg(target_os = "macos")]
         window.set_has_shadow(config.window_opacity() >= 1.0);
diff --git a/alacritty/src/renderer/text/builtin_font.rs b/alacritty/src/renderer/text/builtin_font.rs
index 36d1ccdc..a4bf65e3 100644
--- a/alacritty/src/renderer/text/builtin_font.rs
+++ b/alacritty/src/renderer/text/builtin_font.rs
@@ -90,6 +90,7 @@ fn box_drawing(character: char, metrics: &Metrics, offset: &Delta<i8>) -> Raster
                 left: 0,
                 height: height as i32,
                 width: width as i32,
+                advance: (0, 0),
                 buffer,
             };
         },
@@ -479,7 +480,15 @@ fn box_drawing(character: char, metrics: &Metrics, offset: &Delta<i8>) -> Raster
 
     let top = height as i32 + metrics.descent as i32;
     let buffer = BitmapBuffer::Rgb(canvas.into_raw());
-    RasterizedGlyph { character, top, left: 0, height: height as i32, width: width as i32, buffer }
+    RasterizedGlyph {
+        character,
+        top,
+        left: 0,
+        height: height as i32,
+        width: width as i32,
+        advance: (0, 0),
+        buffer,
+    }
 }
 
 #[repr(packed)]
diff --git a/alacritty/src/window_context.rs b/alacritty/src/window_context.rs
index a45b9404..7fe33fd0 100644
--- a/alacritty/src/window_context.rs
+++ b/alacritty/src/window_context.rs
@@ -210,10 +210,6 @@ impl WindowContext {
             self.display.window.set_title(config.window.identity.title.clone());
         }
 
-        // Set subpixel anti-aliasing.
-        #[cfg(target_os = "macos")]
-        crossfont::set_font_smoothing(config.font.use_thin_strokes);
-
         // Disable shadows for transparent windows on macOS.
         #[cfg(target_os = "macos")]
         self.display.window.set_has_shadow(config.window_opacity() >= 1.0);
diff --git a/alacritty_config_derive/src/de_struct.rs b/alacritty_config_derive/src/de_struct.rs
index ceb32fd9..cf7ea141 100644
--- a/alacritty_config_derive/src/de_struct.rs
+++ b/alacritty_config_derive/src/de_struct.rs
@@ -135,14 +135,14 @@ fn field_deserializer(field_streams: &mut FieldStreams, field: &Field) -> Result
                     config.#ident = serde::Deserialize::deserialize(unused).unwrap_or_default();
                 });
             },
-            "deprecated" => {
-                // Construct deprecation message and append optional attribute override.
-                let mut message = format!("Config warning: {} is deprecated", literal);
+            "deprecated" | "removed" => {
+                // Construct deprecation/removal message with optional attribute override.
+                let mut message = format!("Config warning: {} has been {}", literal, parsed.ident);
                 if let Some(warning) = parsed.param {
                     message = format!("{}; {}", message, warning.value());
                 }
 
-                // Append stream to log deprecation warning.
+                // Append stream to log deprecation/removal warning.
                 match_assignment_stream.extend(quote! {
                     log::warn!(target: #LOG_TARGET, #message);
                 });
diff --git a/alacritty_config_derive/tests/config.rs b/alacritty_config_derive/tests/config.rs
index 58ad8bd4..2cdae613 100644
--- a/alacritty_config_derive/tests/config.rs
+++ b/alacritty_config_derive/tests/config.rs
@@ -35,6 +35,8 @@ struct Test {
     enom_big: TestEnum,
     #[config(deprecated)]
     enom_error: TestEnum,
+    #[config(removed = "it's gone")]
+    gone: bool,
 }
 
 impl Default for Test {
@@ -48,6 +50,7 @@ impl Default for Test {
             enom_small: TestEnum::default(),
             enom_big: TestEnum::default(),
             enom_error: TestEnum::default(),
+            gone: false,
         }
     }
 }
@@ -90,6 +93,7 @@ fn config_deserialize() {
         enom_small: "one"
         enom_big: "THREE"
         enom_error: "HugaBuga"
+        gone: false
     "#,
     )
     .unwrap();
@@ -101,6 +105,7 @@ fn config_deserialize() {
     assert_eq!(test.enom_small, TestEnum::One);
     assert_eq!(test.enom_big, TestEnum::Three);
     assert_eq!(test.enom_error, Test::default().enom_error);
+    assert_eq!(test.gone, false);
     assert_eq!(test.nesting.field1, Test::default().nesting.field1);
     assert_eq!(test.nesting.field2, None);
     assert_eq!(test.nesting.field3, Test::default().nesting.field3);
@@ -116,8 +121,9 @@ fn config_deserialize() {
     ]);
     let warn_logs = logger.warn_logs.lock().unwrap();
     assert_eq!(warn_logs.as_slice(), [
-        "Config warning: field1 is deprecated; use field2 instead",
-        "Config warning: enom_error is deprecated",
+        "Config warning: field1 has been deprecated; use field2 instead",
+        "Config warning: enom_error has been deprecated",
+        "Config warning: gone has been removed; it's gone",
     ]);
 }