terminal: Make CursorShape configurable (#18530)

This builds on top of @Yevgen's #15840 and combines it with the settings
names introduced in #17572.

Closes #4731.

Release Notes:

- Added a setting for the terminal's default cursor shape. The setting
is `{"terminal": {"cursor_shape": "block"}}``. Possible values: `block`,
`bar`, `hollow`, `underline`.

Demo:


https://github.com/user-attachments/assets/96ed28c2-c222-436b-80cb-7cd63eeb47dd

crates/terminal/src/terminal.rs

@@ -18,7 +18,9 @@ use alacritty_terminal::{
         Config, RenderableCursor, TermMode,
     },
     tty::{self},
-    vte::ansi::{ClearMode, Handler, NamedPrivateMode, PrivateMode},
+    vte::ansi::{
+        ClearMode, CursorStyle as AlacCursorStyle, Handler, NamedPrivateMode, PrivateMode,
+    },
     Term,
 };
 use anyhow::{bail, Result};
@@ -40,7 +42,7 @@ use serde::{Deserialize, Serialize};
 use settings::Settings;
 use smol::channel::{Receiver, Sender};
 use task::{HideStrategy, Shell, TaskId};
-use terminal_settings::{AlternateScroll, TerminalBlink, TerminalSettings};
+use terminal_settings::{AlternateScroll, CursorShape, TerminalBlink, TerminalSettings};
 use theme::{ActiveTheme, Theme};
 use util::truncate_and_trailoff;
 
@@ -314,6 +316,7 @@ impl TerminalBuilder {
         shell: Shell,
         mut env: HashMap<String, String>,
         blink_settings: Option<TerminalBlink>,
+        cursor_shape: CursorShape,
         alternate_scroll: AlternateScroll,
         max_scroll_history_lines: Option<usize>,
         window: AnyWindowHandle,
@@ -353,6 +356,7 @@ impl TerminalBuilder {
         // Setup Alacritty's env, which modifies the current process's environment
         alacritty_terminal::tty::setup_env();
 
+        let default_cursor_style = AlacCursorStyle::from(cursor_shape);
         let scrolling_history = if task.is_some() {
             // Tasks like `cargo build --all` may produce a lot of output, ergo allow maximum scrolling.
             // After the task finishes, we do not allow appending to that terminal, so small tasks output should not
@@ -365,6 +369,7 @@ impl TerminalBuilder {
         };
         let config = Config {
             scrolling_history,
+            default_cursor_style,
             ..Config::default()
         };
 
@@ -951,6 +956,10 @@ impl Terminal {
         &self.last_content
     }
 
+    pub fn set_cursor_shape(&mut self, cursor_shape: CursorShape) {
+        self.term.lock().set_cursor_style(Some(cursor_shape.into()));
+    }
+
     pub fn total_lines(&self) -> usize {
         let term = self.term.clone();
         let terminal = term.lock_unfair();

crates/terminal/src/terminal_settings.rs

@@ -1,3 +1,6 @@
+use alacritty_terminal::vte::ansi::{
+    CursorShape as AlacCursorShape, CursorStyle as AlacCursorStyle,
+};
 use collections::HashMap;
 use gpui::{
     px, AbsoluteLength, AppContext, FontFallbacks, FontFeatures, FontWeight, Pixels, SharedString,
@@ -32,6 +35,7 @@ pub struct TerminalSettings {
     pub font_weight: Option<FontWeight>,
     pub line_height: TerminalLineHeight,
     pub env: HashMap<String, String>,
+    pub cursor_shape: Option<CursorShape>,
     pub blinking: TerminalBlink,
     pub alternate_scroll: AlternateScroll,
     pub option_as_meta: bool,
@@ -129,6 +133,11 @@ pub struct TerminalSettingsContent {
     ///
     /// Default: {}
     pub env: Option<HashMap<String, String>>,
+    /// Default cursor shape for the terminal.
+    /// Can be "bar", "block", "underscore", or "hollow".
+    ///
+    /// Default: None
+    pub cursor_shape: Option<CursorShape>,
     /// Sets the cursor blinking behavior in the terminal.
     ///
     /// Default: terminal_controlled
@@ -282,3 +291,37 @@ pub struct ToolbarContent {
     /// Default: true
     pub title: Option<bool>,
 }
+
+#[derive(Clone, Copy, Debug, Default, Serialize, Deserialize, PartialEq, Eq, JsonSchema)]
+#[serde(rename_all = "snake_case")]
+pub enum CursorShape {
+    /// Cursor is a block like `█`.
+    #[default]
+    Block,
+    /// Cursor is an underscore like `_`.
+    Underline,
+    /// Cursor is a vertical bar like `⎸`.
+    Bar,
+    /// Cursor is a hollow box like `▯`.
+    Hollow,
+}
+
+impl From<CursorShape> for AlacCursorShape {
+    fn from(value: CursorShape) -> Self {
+        match value {
+            CursorShape::Block => AlacCursorShape::Block,
+            CursorShape::Underline => AlacCursorShape::Underline,
+            CursorShape::Bar => AlacCursorShape::Beam,
+            CursorShape::Hollow => AlacCursorShape::HollowBlock,
+        }
+    }
+}
+
+impl From<CursorShape> for AlacCursorStyle {
+    fn from(value: CursorShape) -> Self {
+        AlacCursorStyle {
+            shape: value.into(),
+            blinking: false,
+        }
+    }
+}