Add rainbow indentation guides

ref: https://github.com/helix-editor/helix/issues/4010
ref: https://github.com/helix-editor/helix/pull/4493

4 files changed, 48 insertions, 10 deletions

diff --git a/book/src/configuration.md b/book/src/configuration.md
index 22531868..6cb2ea0b 100644
--- a/book/src/configuration.md
+++ b/book/src/configuration.md
@@ -291,6 +291,7 @@ Options for rendering vertical indent guides.
 | `render`      | Whether to render indent guides                         | `false` |
 | `character`   | Literal character to use for rendering the indent guide | `│`     |
 | `skip-levels` | Number of indent levels to skip                         | `0`     |
+| `rainbow-option` | Enum to set rainbow indentations. Options: `normal`, `dim` and `none`. | `none` |
 
 Example:
 
@@ -299,6 +300,7 @@ Example:
 render = true
 character = "╎" # Some characters that work well: "▏", "┆", "┊", "⸽"
 skip-levels = 1
+rainbow-option = "normal"
 ```
 
 ### `[editor.gutters]` Section
diff --git a/helix-term/src/ui/document.rs b/helix-term/src/ui/document.rs
index b571b83c..d7e12584 100644
--- a/helix-term/src/ui/document.rs
+++ b/helix-term/src/ui/document.rs
@@ -7,9 +7,9 @@ use helix_core::syntax::Highlight;
 use helix_core::syntax::HighlightEvent;
 use helix_core::text_annotations::TextAnnotations;
 use helix_core::{visual_offset_from_block, Position, RopeSlice};
-use helix_view::editor::{WhitespaceConfig, WhitespaceRenderValue};
+use helix_view::editor::{RainbowIndentOptions, WhitespaceConfig, WhitespaceRenderValue};
 use helix_view::graphics::Rect;
-use helix_view::theme::Style;
+use helix_view::theme::{Modifier, Style};
 use helix_view::view::ViewPosition;
 use helix_view::Document;
 use helix_view::Theme;
@@ -339,6 +339,8 @@ pub struct TextRenderer<'a> {
     pub whitespace_style: Style,
     pub indent_guide_char: String,
     pub indent_guide_style: Style,
+    pub indent_guide_rainbow: RainbowIndentOptions,
+    pub theme: &'a Theme,
     pub newline: String,
     pub nbsp: String,
     pub nnbsp: String,
@@ -361,7 +363,7 @@ impl<'a> TextRenderer<'a> {
     pub fn new(
         surface: &'a mut Surface,
         doc: &Document,
-        theme: &Theme,
+        theme: &'a Theme,
         col_offset: usize,
         viewport: Rect,
     ) -> TextRenderer<'a> {
@@ -403,12 +405,19 @@ impl<'a> TextRenderer<'a> {
         };
 
         let text_style = theme.get("ui.text");
+        let basic_style = text_style.patch(
+            theme
+                .try_get("ui.virtual.indent-guide")
+                .unwrap_or_else(|| theme.get("ui.virtual.whitespace")),
+        );
 
         let indent_width = doc.indent_style.indent_width(tab_width) as u16;
 
         TextRenderer {
             surface,
             indent_guide_char: editor_config.indent_guides.character.into(),
+            indent_guide_rainbow: editor_config.indent_guides.rainbow_option.clone(),
+            theme,
             newline,
             nbsp,
             nnbsp,
@@ -420,11 +429,7 @@ impl<'a> TextRenderer<'a> {
             starting_indent: col_offset / indent_width as usize
                 + (col_offset % indent_width as usize != 0) as usize
                 + editor_config.indent_guides.skip_levels as usize,
-            indent_guide_style: text_style.patch(
-                theme
-                    .try_get("ui.virtual.indent-guide")
-                    .unwrap_or_else(|| theme.get("ui.virtual.whitespace")),
-            ),
+            indent_guide_style: basic_style,
             text_style,
             draw_indent_guides: editor_config.indent_guides.render,
             viewport,
@@ -522,8 +527,25 @@ impl<'a> TextRenderer<'a> {
                 as u16;
             let y = self.viewport.y + row;
             debug_assert!(self.surface.in_bounds(x, y));
-            self.surface
-                .set_string(x, y, &self.indent_guide_char, self.indent_guide_style);
+            match self.indent_guide_rainbow {
+                RainbowIndentOptions::None => {
+                    self.surface
+                        .set_string(x, y, &self.indent_guide_char, self.indent_guide_style)
+                }
+                RainbowIndentOptions::Dim => {
+                    let new_style = self
+                        .indent_guide_style
+                        .patch(self.theme.get_rainbow(i))
+                        .add_modifier(Modifier::DIM);
+                    self.surface
+                        .set_string(x, y, &self.indent_guide_char, new_style);
+                }
+                RainbowIndentOptions::Normal => {
+                    let new_style = self.indent_guide_style.patch(self.theme.get_rainbow(i));
+                    self.surface
+                        .set_string(x, y, &self.indent_guide_char, new_style);
+                }
+            };
         }
     }
 }
diff --git a/helix-view/src/editor.rs b/helix-view/src/editor.rs
index 4987c073..bd9ac0ab 100644
--- a/helix-view/src/editor.rs
+++ b/helix-view/src/editor.rs
@@ -818,11 +818,20 @@ impl Default for WhitespaceCharacters {
 }
 
 #[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
+#[serde(rename_all = "kebab-case")]
+pub enum RainbowIndentOptions {
+    None,
+    Dim,
+    Normal,
+}
+
+#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
 #[serde(default, rename_all = "kebab-case")]
 pub struct IndentGuidesConfig {
     pub render: bool,
     pub character: char,
     pub skip_levels: u8,
+    pub rainbow_option: RainbowIndentOptions,
 }
 
 impl Default for IndentGuidesConfig {
@@ -831,6 +840,7 @@ impl Default for IndentGuidesConfig {
             skip_levels: 0,
             render: false,
             character: '│',
+            rainbow_option: RainbowIndentOptions::None,
         }
     }
 }
diff --git a/helix-view/src/theme.rs b/helix-view/src/theme.rs
index 16da247f..8236d370 100644
--- a/helix-view/src/theme.rs
+++ b/helix-view/src/theme.rs
@@ -383,6 +383,10 @@ impl Theme {
     pub fn rainbow_length(&self) -> usize {
         self.rainbow_length
     }
+
+    pub fn get_rainbow(&self, index: usize) -> Style {
+        self.highlights[index % self.rainbow_length]
+    }
 }
 
 fn default_rainbow() -> Vec<Style> {