From 4d0dde1f23c5ebb0bfbfa2229b105e5a424c64df Mon Sep 17 00:00:00 2001
From: Daniel Bulant <danbulant@gmail.com>
Date: Wed, 19 Aug 2026 00:48:55 +0200
Subject: [PATCH] feat(input): support custom text highlights

---
 crates/ui/src/input/element.rs | 42 +++++++++++++++++++---------------
 crates/ui/src/input/state.rs   | 25 ++++++++++++++++----
 2 files changed, 45 insertions(+), 22 deletions(-)

diff --git a/crates/ui/src/input/element.rs b/crates/ui/src/input/element.rs
index 4e7941cc..3b491923 100644
--- a/crates/ui/src/input/element.rs
+++ b/crates/ui/src/input/element.rs
@@ -752,30 +752,36 @@ impl TextElement {
             } => (highlighter.borrow(), diagnostics),
             _ => return None,
         };
-        let highlighter = highlighter.as_ref()?;
-
-        let mut offset = visible_byte_range.start;
+        let highlighter = highlighter.as_ref();
         let mut styles = vec![];
 
-        for line in text
-            .iter_lines()
-            .skip(visible_range.start)
-            .take(visible_range.len())
-        {
-            let line_len = if is_multi_line {
-                // +1 for `\n`
-                line.len() + 1
-            } else {
-                line.len()
-            };
+        if let Some(highlighter) = highlighter {
+            let mut offset = visible_byte_range.start;
+            for line in text
+                .iter_lines()
+                .skip(visible_range.start)
+                .take(visible_range.len())
+            {
+                let line_len = if is_multi_line {
+                    // +1 for `\n`
+                    line.len() + 1
+                } else {
+                    line.len()
+                };
 
-            let range = offset..offset + line_len;
-            let line_styles = highlighter.styles(&range, &cx.theme().highlight_theme);
-            styles = gpui::combine_highlights(styles, line_styles).collect();
+                let range = offset..offset + line_len;
+                let line_styles = highlighter.styles(&range, &cx.theme().highlight_theme);
+                styles = gpui::combine_highlights(styles, line_styles).collect();
 
-            offset = range.end;
+                offset = range.end;
+            }
         }
 
+        let custom_styles = state.custom_highlights.iter().filter(|(range, _)| {
+            range.start < visible_byte_range.end && range.end > visible_byte_range.start
+        });
+        styles = gpui::combine_highlights(styles, custom_styles.cloned()).collect();
+
         let diagnostic_styles = diagnostics.styles_for_range(&visible_byte_range, cx);
 
         // hover definition style
diff --git a/crates/ui/src/input/state.rs b/crates/ui/src/input/state.rs
index 89b3ffa9..494f97da 100644
--- a/crates/ui/src/input/state.rs
+++ b/crates/ui/src/input/state.rs
@@ -5,10 +5,11 @@
 use anyhow::Result;
 use gpui::{
     Action, App, AppContext, Bounds, ClipboardItem, Context, Entity, EntityInputHandler,
-    EventEmitter, FocusHandle, Focusable, InteractiveElement as _, IntoElement, KeyBinding,
-    KeyDownEvent, MouseButton, MouseDownEvent, MouseMoveEvent, MouseUpEvent, ParentElement as _,
-    Pixels, Point, Render, ScrollHandle, ScrollWheelEvent, SharedString, Styled as _, Subscription,
-    Task, UTF16Selection, Window, actions, div, point, prelude::FluentBuilder as _, px,
+    EventEmitter, FocusHandle, Focusable, HighlightStyle, InteractiveElement as _, IntoElement,
+    KeyBinding, KeyDownEvent, MouseButton, MouseDownEvent, MouseMoveEvent, MouseUpEvent,
+    ParentElement as _, Pixels, Point, Render, ScrollHandle, ScrollWheelEvent, SharedString,
+    Styled as _, Subscription, Task, UTF16Selection, Window, actions, div, point,
+    prelude::FluentBuilder as _, px,
 };
 use ropey::{Rope, RopeSlice};
 use serde::Deserialize;
@@ -298,6 +299,8 @@ pub struct InputState {
     pub(crate) deferred_scroll_offset: Option<Point<Pixels>>,
     /// The size of the scrollable content.
     pub(crate) scroll_size: gpui::Size<Pixels>,
+    /// Additional presentation-only styles keyed by UTF-8 byte range.
+    pub(super) custom_highlights: Vec<(Range<usize>, HighlightStyle)>,
 
     /// The mask pattern for formatting the input text
     pub(crate) mask_pattern: MaskPattern,
@@ -395,6 +398,7 @@ impl InputState {
             scroll_handle: ScrollHandle::new(),
             scroll_size: gpui::size(px(0.), px(0.)),
             deferred_scroll_offset: None,
+            custom_highlights: Vec::new(),
             preferred_column: None,
             placeholder: SharedString::default(),
             mask_pattern: MaskPattern::default(),
@@ -529,6 +533,19 @@ impl InputState {
         cx.notify();
     }
 
+    /// Replace presentation-only text styles keyed by UTF-8 byte range.
+    ///
+    /// Custom highlights are combined with syntax and diagnostic highlights and do not alter
+    /// the editor text, selection, or history.
+    pub fn set_custom_highlights(
+        &mut self,
+        highlights: Vec<(Range<usize>, HighlightStyle)>,
+        cx: &mut Context<Self>,
+    ) {
+        self.custom_highlights = highlights;
+        cx.notify();
+    }
+
     fn reset_highlighter(&mut self, cx: &mut Context<Self>) {
         match &mut self.mode {
             InputMode::CodeEditor { highlighter, .. } => {