Add undercurl config option (helix-editor#6196)

If set to 'true' this option will force terminal undercurl support.

book/src/configuration.md

@@ -53,6 +53,7 @@ signal to the Helix process on Unix operating systems, such as by using the comm
 | `completion-replace` | Set to `true` to make completions always replace the entire word and not just the part before the cursor | `false` |
 | `auto-info` | Whether to display info boxes | `true` |
 | `true-color` | Set to `true` to override automatic detection of terminal truecolor support in the event of a false negative | `false` |
+| `undercurl` | Set to `true` to override automatic detection of terminal undercurl support in the event of a false negative | `false` |
 | `rulers` | List of column positions at which to display the rulers. Can be overridden by language specific `rulers` in `languages.toml` file | `[]` |
 | `bufferline` | Renders a line at the top of the editor displaying open buffers. Can be `always`, `never` or `multiple` (only shown if more than one buffer is in use) | `never` |
 | `color-modes` | Whether to color the mode indicator with different colors depending on the mode itself | `false` |

helix-term/src/application.rs

@@ -137,7 +137,7 @@ impl Application {
         let syn_loader = std::sync::Arc::new(syntax::Loader::new(syn_loader_conf));
 
         #[cfg(not(feature = "integration"))]
-        let backend = CrosstermBackend::new(stdout());
+        let backend = CrosstermBackend::new(stdout(), &config.editor);
 
         #[cfg(feature = "integration")]
         let backend = TestBackend::new(120, 150);

helix-tui/src/backend/crossterm.rs

@@ -14,7 +14,10 @@ use crossterm::{
     terminal::{self, Clear, ClearType},
     Command,
 };
-use helix_view::graphics::{Color, CursorKind, Modifier, Rect, UnderlineStyle};
+use helix_view::{
+    editor::Config as EditorConfig,
+    graphics::{Color, CursorKind, Modifier, Rect, UnderlineStyle},
+};
 use once_cell::sync::OnceCell;
 use std::{
     fmt,
@@ -39,14 +42,15 @@ impl Capabilities {
     /// Detect capabilities from the terminfo database located based
     /// on the $TERM environment variable. If detection fails, returns
     /// a default value where no capability is supported.
-    pub fn from_env_or_default() -> Self {
+    pub fn from_env_or_default(config: &EditorConfig) -> Self {
         match termini::TermInfo::from_env() {
             Err(_) => Capabilities::default(),
             Ok(t) => Capabilities {
                 // Smulx, VTE: https://unix.stackexchange.com/a/696253/246284
                 // Su (used by kitty): https://sw.kovidgoyal.net/kitty/underlines
                 // WezTerm supports underlines but a lot of distros don't properly install it's terminfo
-                has_extended_underlines: t.extended_cap("Smulx").is_some()
+                has_extended_underlines: config.undercurl
+                    || t.extended_cap("Smulx").is_some()
                     || t.extended_cap("Su").is_some()
                     || vte_version() >= Some(5102)
                     || matches!(term_program().as_deref(), Some("WezTerm")),
@@ -65,10 +69,10 @@ impl<W> CrosstermBackend<W>
 where
     W: Write,
 {
-    pub fn new(buffer: W) -> CrosstermBackend<W> {
+    pub fn new(buffer: W, config: &EditorConfig) -> CrosstermBackend<W> {
         CrosstermBackend {
             buffer,
-            capabilities: Capabilities::from_env_or_default(),
+            capabilities: Capabilities::from_env_or_default(config),
             supports_keyboard_enhancement_protocol: OnceCell::new(),
         }
     }

helix-view/src/editor.rs

@@ -263,6 +263,8 @@ pub struct Config {
     pub cursor_shape: CursorShapeConfig,
     /// Set to `true` to override automatic detection of terminal truecolor support in the event of a false negative. Defaults to `false`.
     pub true_color: bool,
+    /// Set to `true` to override automatic detection of terminal undercurl support in the event of a false negative. Defaults to `false`.
+    pub undercurl: bool,
     /// Search configuration.
     #[serde(default)]
     pub search: SearchConfig,
@@ -731,6 +733,7 @@ impl Default for Config {
             statusline: StatusLineConfig::default(),
             cursor_shape: CursorShapeConfig::default(),
             true_color: false,
+            undercurl: false,
             search: SearchConfig::default(),
             lsp: LspConfig::default(),
             terminal: get_terminal_provider(),