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.

2 files changed, 12 insertions, 6 deletions

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",
     ]);
 }