Add rulers option (#2060)

* Add color_column option

* Rename to ruler

Co-authored-by: DeviousStoat <devious@stoat.com>

4 files changed, 33 insertions, 0 deletions

diff --git a/book/src/configuration.md b/book/src/configuration.md
index 3ec2bedb..153ebb80 100644
--- a/book/src/configuration.md
+++ b/book/src/configuration.md
@@ -43,6 +43,7 @@ hidden = false
 | `completion-trigger-len` | The min-length of word under cursor to trigger autocompletion | `2` |
 | `auto-info` | Whether to display infoboxes | `true` |
 | `true-color` | Set to `true` to override automatic detection of terminal truecolor support in the event of a false negative. | `false` |
+| `rulers` | List of column positions at which to display the rulers. Can be overidden by language specific `rulers` in `languages.toml` file. | `[]` |
 
 ### `[editor.lsp]` Section
 
diff --git a/helix-core/src/syntax.rs b/helix-core/src/syntax.rs
index 905b3347..2fd4ed9b 100644
--- a/helix-core/src/syntax.rs
+++ b/helix-core/src/syntax.rs
@@ -104,6 +104,8 @@ pub struct LanguageConfiguration {
     /// global setting.
     #[serde(default, skip_serializing, deserialize_with = "deserialize_auto_pairs")]
     pub auto_pairs: Option<AutoPairs>,
+
+    pub rulers: Option<Vec<u16>>, // if set, override editor's rulers
 }
 
 #[derive(Debug, Serialize, Deserialize)]
diff --git a/helix-term/src/ui/editor.rs b/helix-term/src/ui/editor.rs
index 459a8c87..fc8b6470 100644
--- a/helix-term/src/ui/editor.rs
+++ b/helix-term/src/ui/editor.rs
@@ -126,6 +126,7 @@ impl EditorView {
 
         Self::render_text_highlights(doc, view.offset, inner, surface, theme, highlights);
         Self::render_gutter(editor, doc, view, view.area, surface, theme, is_focused);
+        Self::render_rulers(editor, doc, view, inner, surface, theme);
 
         if is_focused {
             Self::render_focused_view_elements(view, doc, inner, theme, surface);
@@ -152,6 +153,32 @@ impl EditorView {
         self.render_statusline(doc, view, statusline_area, surface, theme, is_focused);
     }
 
+    pub fn render_rulers(
+        editor: &Editor,
+        doc: &Document,
+        view: &View,
+        viewport: Rect,
+        surface: &mut Surface,
+        theme: &Theme,
+    ) {
+        let editor_rulers = &editor.config().rulers;
+        let ruler_theme = theme.get("ui.virtual.ruler");
+
+        let rulers = doc
+            .language_config()
+            .and_then(|config| config.rulers.as_ref())
+            .unwrap_or(editor_rulers);
+
+        rulers
+            .iter()
+            // View might be horizontally scrolled, convert from absolute distance
+            // from the 1st column to relative distance from left of viewport
+            .filter_map(|ruler| ruler.checked_sub(1 + view.offset.col as u16))
+            .filter(|ruler| ruler < &viewport.width)
+            .map(|ruler| viewport.clip_left(ruler).with_width(1))
+            .for_each(|area| surface.set_style(area, ruler_theme))
+    }
+
     /// Get syntax highlights for a document in a view represented by the first line
     /// and column (`offset`) and the last line. This is done instead of using a view
     /// directly to enable rendering syntax highlighted docs anywhere (eg. picker preview)
diff --git a/helix-view/src/editor.rs b/helix-view/src/editor.rs
index dd805c00..0c2fad2b 100644
--- a/helix-view/src/editor.rs
+++ b/helix-view/src/editor.rs
@@ -146,6 +146,8 @@ pub struct Config {
     #[serde(default)]
     pub search: SearchConfig,
     pub lsp: LspConfig,
+    /// Column numbers at which to draw the rulers. Default to `[]`, meaning no rulers.
+    pub rulers: Vec<u16>,
 }
 
 #[derive(Debug, Default, Clone, PartialEq, Serialize, Deserialize)]
@@ -285,6 +287,7 @@ impl Default for Config {
             true_color: false,
             search: SearchConfig::default(),
             lsp: LspConfig::default(),
+            rulers: Vec::new(),
         }
     }
 }