Add config option to set cursor thickness

Fixes #3526.

8 files changed, 93 insertions, 36 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 19e827e2..5e39a660 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -15,6 +15,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Default Command+N keybinding for SpawnNewInstance on macOS
 - Vi mode for copying text and opening links
 - `CopySelection` action which copies into selection buffer on Linux/BSD
+- Option `cursor.thickness` to set terminal cursor thickness
 
 ### Changed
 
diff --git a/alacritty.yml b/alacritty.yml
index f0e12747..17aaa280 100644
--- a/alacritty.yml
+++ b/alacritty.yml
@@ -318,6 +318,10 @@
   # window is not focused.
   #unfocused_hollow: true
 
+  # Thickness of the cursor relative to the cell width as floating point number
+  # from `0.0` to `1.0`.
+  #thickness: 0.15
+
 # Live config reload (changes require restart)
 #live_config_reload: true
 
diff --git a/alacritty/src/cursor.rs b/alacritty/src/cursor.rs
index e18816ed..253fdaa7 100644
--- a/alacritty/src/cursor.rs
+++ b/alacritty/src/cursor.rs
@@ -20,20 +20,19 @@ use alacritty_terminal::ansi::CursorStyle;
 
 use font::{BitmapBuffer, Metrics, RasterizedGlyph};
 
-/// Width/Height of the cursor relative to the font width
-pub const CURSOR_WIDTH_PERCENTAGE: f64 = 0.15;
-
 pub fn get_cursor_glyph(
     cursor: CursorStyle,
     metrics: Metrics,
     offset_x: i8,
     offset_y: i8,
     is_wide: bool,
+    cursor_thickness: f64,
 ) -> RasterizedGlyph {
     // Calculate the cell metrics
     let height = metrics.line_height as i32 + i32::from(offset_y);
     let mut width = metrics.average_advance as i32 + i32::from(offset_x);
-    let line_width = cmp::max((f64::from(width) * CURSOR_WIDTH_PERCENTAGE).round() as i32, 1);
+
+    let line_width = cmp::max((cursor_thickness * f64::from(width)).round() as i32, 1);
 
     // Double the cursor width if it's above a double-width glyph
     if is_wide {
diff --git a/alacritty/src/display.rs b/alacritty/src/display.rs
index c456fda8..eafab8c2 100644
--- a/alacritty/src/display.rs
+++ b/alacritty/src/display.rs
@@ -286,7 +286,15 @@ impl Display {
         size_info.cell_height = cell_height;
     }
 
-    /// Process update events
+    /// Clear glyph cache.
+    fn clear_glyph_cache(&mut self) {
+        let cache = &mut self.glyph_cache;
+        self.renderer.with_loader(|mut api| {
+            cache.clear_glyph_cache(&mut api);
+        });
+    }
+
+    /// Process update events.
     pub fn handle_update<T>(
         &mut self,
         terminal: &mut Term<T>,
@@ -298,6 +306,8 @@ impl Display {
         // Update font size and cell dimensions
         if let Some(font) = update_pending.font {
             self.update_glyph_cache(config, font);
+        } else if update_pending.cursor {
+            self.clear_glyph_cache();
         }
 
         let cell_width = self.size_info.cell_width;
diff --git a/alacritty/src/event.rs b/alacritty/src/event.rs
index e532ac12..3f2e3f77 100644
--- a/alacritty/src/event.rs
+++ b/alacritty/src/event.rs
@@ -49,13 +49,14 @@ use crate::window::Window;
 #[derive(Default, Clone, Debug, PartialEq)]
 pub struct DisplayUpdate {
     pub dimensions: Option<PhysicalSize<u32>>,
-    pub message_buffer: Option<()>,
+    pub message_buffer: bool,
     pub font: Option<Font>,
+    pub cursor: bool,
 }
 
 impl DisplayUpdate {
     fn is_empty(&self) -> bool {
-        self.dimensions.is_none() && self.font.is_none() && self.message_buffer.is_none()
+        self.dimensions.is_none() && self.font.is_none() && !self.message_buffer && !self.cursor
     }
 }
 
@@ -255,7 +256,7 @@ impl<'a, N: Notify + 'a, T: EventListener> input::ActionContext<T> for ActionCon
     }
 
     fn pop_message(&mut self) {
-        self.display_update_pending.message_buffer = Some(());
+        self.display_update_pending.message_buffer = true;
         self.message_buffer.pop();
     }
 
@@ -526,7 +527,7 @@ impl<N: Notify + OnResize> Processor<N> {
                 Event::ConfigReload(path) => Self::reload_config(&path, processor),
                 Event::Message(message) => {
                     processor.ctx.message_buffer.push(message);
-                    processor.ctx.display_update_pending.message_buffer = Some(());
+                    processor.ctx.display_update_pending.message_buffer = true;
                     processor.ctx.terminal.dirty = true;
                 },
                 Event::MouseCursorDirty => processor.reset_mouse_cursor(),
@@ -659,7 +660,7 @@ impl<N: Notify + OnResize> Processor<N> {
         T: EventListener,
     {
         processor.ctx.message_buffer.remove_target(LOG_TARGET_CONFIG);
-        processor.ctx.display_update_pending.message_buffer = Some(());
+        processor.ctx.display_update_pending.message_buffer = true;
 
         let config = match config::reload_from(&path) {
             Ok(config) => config,
@@ -671,6 +672,13 @@ impl<N: Notify + OnResize> Processor<N> {
 
         processor.ctx.terminal.update_config(&config);
 
+        // Reload cursor if we've changed its thickness
+        if (processor.ctx.config.cursor.thickness() - config.cursor.thickness()).abs()
+            > std::f64::EPSILON
+        {
+            processor.ctx.display_update_pending.cursor = true;
+        }
+
         if processor.ctx.config.font != config.font {
             // Do not update font size if it has been changed at runtime
             if *processor.ctx.font_size == processor.ctx.config.font.size {
diff --git a/alacritty/src/renderer/mod.rs b/alacritty/src/renderer/mod.rs
index 4526020a..caa2443f 100644
--- a/alacritty/src/renderer/mod.rs
+++ b/alacritty/src/renderer/mod.rs
@@ -213,10 +213,7 @@ impl GlyphCache {
             metrics,
         };
 
-        cache.load_glyphs_for_font(regular, loader);
-        cache.load_glyphs_for_font(bold, loader);
-        cache.load_glyphs_for_font(italic, loader);
-        cache.load_glyphs_for_font(bold_italic, loader);
+        cache.load_common_glyphs(loader);
 
         Ok(cache)
     }
@@ -302,17 +299,21 @@ impl GlyphCache {
         })
     }
 
+    /// Clear currently cached data in both GL and the registry.
+    pub fn clear_glyph_cache<L: LoadGlyph>(&mut self, loader: &mut L) {
+        loader.clear();
+        self.cache = HashMap::default();
+        self.cursor_cache = HashMap::default();
+
+        self.load_common_glyphs(loader);
+    }
+
     pub fn update_font_size<L: LoadGlyph>(
         &mut self,
         font: config::Font,
         dpr: f64,
         loader: &mut L,
     ) -> Result<(), font::Error> {
-        // Clear currently cached data in both GL and the registry
-        loader.clear();
-        self.cache = HashMap::default();
-        self.cursor_cache = HashMap::default();
-
         // Update dpi scaling
         self.rasterizer.update_dpr(dpr as f32);
 
@@ -332,10 +333,7 @@ impl GlyphCache {
         self.bold_italic_key = bold_italic;
         self.metrics = metrics;
 
-        self.load_glyphs_for_font(regular, loader);
-        self.load_glyphs_for_font(bold, loader);
-        self.load_glyphs_for_font(italic, loader);
-        self.load_glyphs_for_font(bold_italic, loader);
+        self.clear_glyph_cache(loader);
 
         Ok(())
     }
@@ -344,6 +342,14 @@ impl GlyphCache {
         self.metrics
     }
 
+    /// Prefetch glyphs that are almost guaranteed to be loaded anyways.
+    fn load_common_glyphs<L: LoadGlyph>(&mut self, loader: &mut L) {
+        self.load_glyphs_for_font(self.font_key, loader);
+        self.load_glyphs_for_font(self.bold_italic_key, loader);
+        self.load_glyphs_for_font(self.italic_key, loader);
+        self.load_glyphs_for_font(self.bold_italic_key, loader);
+    }
+
     // Calculate font metrics without access to a glyph cache
     pub fn static_metrics(font: Font, dpr: f64) -> Result<font::Metrics, font::Error> {
         let mut rasterizer = font::Rasterizer::new(dpr as f32, font.use_thin_strokes())?;
@@ -1019,6 +1025,7 @@ impl<'a, C> RenderApi<'a, C> {
                         self.config.font.offset.x,
                         self.config.font.offset.y,
                         cursor_key.is_wide,
+                        self.config.cursor.thickness(),
                     ))
                 });
                 self.add_render_item(cell, glyph);
diff --git a/alacritty_terminal/src/config/mod.rs b/alacritty_terminal/src/config/mod.rs
index df8d37bd..53aae91a 100644
--- a/alacritty_terminal/src/config/mod.rs
+++ b/alacritty_terminal/src/config/mod.rs
@@ -40,6 +40,7 @@ use crate::term::color::Rgb;
 
 pub const LOG_TARGET_CONFIG: &str = "alacritty_config";
 const MAX_SCROLLBACK_LINES: u32 = 100_000;
+const DEFAULT_CURSOR_THICKNESS: f32 = 0.15;
 
 pub type MockConfig = Config<HashMap<String, serde_yaml::Value>>;
 
@@ -67,7 +68,7 @@ pub struct Config<T> {
 
     /// Background opacity from 0.0 to 1.0
     #[serde(default, deserialize_with = "failure_default")]
-    background_opacity: Alpha,
+    background_opacity: Percentage,
 
     /// Window configuration
     #[serde(default, deserialize_with = "failure_default")]
@@ -213,7 +214,7 @@ impl<T> Config<T> {
 
     #[inline]
     pub fn background_opacity(&self) -> f32 {
-        self.background_opacity.0
+        self.background_opacity.0 as f32
     }
 }
 
@@ -242,20 +243,47 @@ impl Default for EscapeChars {
 }
 
 #[serde(default)]
-#[derive(Deserialize, Copy, Clone, Debug, Default, PartialEq, Eq)]
+#[derive(Deserialize, Copy, Clone, Debug, PartialEq)]
 pub struct Cursor {
     #[serde(deserialize_with = "failure_default")]
     pub style: CursorStyle,
     #[serde(deserialize_with = "option_explicit_none")]
     pub vi_mode_style: Option<CursorStyle>,
+    #[serde(deserialize_with = "deserialize_cursor_thickness")]
+    thickness: Percentage,
     #[serde(deserialize_with = "failure_default")]
     unfocused_hollow: DefaultTrueBool,
 }
 
 impl Cursor {
+    #[inline]
     pub fn unfocused_hollow(self) -> bool {
         self.unfocused_hollow.0
     }
+
+    #[inline]
+    pub fn thickness(self) -> f64 {
+        self.thickness.0 as f64
+    }
+}
+
+impl Default for Cursor {
+    fn default() -> Self {
+        Self {
+            style: Default::default(),
+            vi_mode_style: Default::default(),
+            thickness: Percentage::new(DEFAULT_CURSOR_THICKNESS),
+            unfocused_hollow: Default::default(),
+        }
+    }
+}
+
+pub fn deserialize_cursor_thickness<'a, D>(deserializer: D) -> Result<Percentage, D::Error>
+where
+    D: Deserializer<'a>,
+{
+    Ok(Percentage::deserialize(Value::deserialize(deserializer)?)
+        .unwrap_or_else(|_| Percentage::new(DEFAULT_CURSOR_THICKNESS)))
 }
 
 #[derive(Clone, Debug, Deserialize, PartialEq, Eq)]
@@ -300,13 +328,13 @@ pub struct Delta<T: Default + PartialEq + Eq> {
     pub y: T,
 }
 
-/// Wrapper around f32 that represents an alpha value between 0.0 and 1.0
+/// Wrapper around f32 that represents a percentage value between 0.0 and 1.0.
 #[derive(Clone, Copy, Debug, PartialEq)]
-pub struct Alpha(f32);
+pub struct Percentage(f32);
 
-impl Alpha {
+impl Percentage {
     pub fn new(value: f32) -> Self {
-        Alpha(if value < 0.0 {
+        Percentage(if value < 0.0 {
             0.0
         } else if value > 1.0 {
             1.0
@@ -316,18 +344,18 @@ impl Alpha {
     }
 }
 
-impl Default for Alpha {
+impl Default for Percentage {
     fn default() -> Self {
-        Alpha(1.0)
+        Percentage(1.0)
     }
 }
 
-impl<'a> Deserialize<'a> for Alpha {
+impl<'a> Deserialize<'a> for Percentage {
     fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
     where
         D: Deserializer<'a>,
     {
-        Ok(Alpha::new(f32::deserialize(deserializer)?))
+        Ok(Percentage::new(f32::deserialize(deserializer)?))
     }
 }
 
diff --git a/alacritty_terminal/src/config/scrolling.rs b/alacritty_terminal/src/config/scrolling.rs
index 358abc3b..899ca1b3 100644
--- a/alacritty_terminal/src/config/scrolling.rs
+++ b/alacritty_terminal/src/config/scrolling.rs
@@ -45,7 +45,7 @@ struct ScrollingMultiplier(u8);
 
 impl Default for ScrollingMultiplier {
     fn default() -> Self {
-        ScrollingMultiplier(3)
+        Self(3)
     }
 }
 
@@ -54,7 +54,7 @@ struct ScrollingHistory(u32);
 
 impl Default for ScrollingHistory {
     fn default() -> Self {
-        ScrollingHistory(10_000)
+        Self(10_000)
     }
 }