feat: add selection, active line, and incremental highlighting to code

view

crates/editor/src/code_view.rs

@@ -4,15 +4,47 @@
 
 use gpui::prelude::FluentBuilder as _;
 use gpui::{
-    Context, ElementId, HighlightStyle, Hsla, InteractiveElement as _, IntoElement,
-    ParentElement as _, Pixels, Render, ScrollStrategy, SharedString,
-    StatefulInteractiveElement as _, Styled as _, TextStyle, UniformListScrollHandle, Window, div,
-    uniform_list,
+    App, Bounds, ClipboardItem, Context, ElementId, HighlightStyle, Hsla, InteractiveElement as _,
+    IntoElement, KeyBinding, MouseButton, MouseDownEvent, MouseMoveEvent, MouseUpEvent,
+    ParentElement as _, Pixels, Point, Render, ScrollStrategy, SharedString,
+    StatefulInteractiveElement as _, Styled as _, TextStyle, UniformListScrollHandle, Window,
+    actions, canvas, div, uniform_list,
 };
-use gpui_native_core::scrollbar::{Scrollbar, ScrollbarVisibility};
+use gpui_native_core::scrollbar::{Scrollbar, ScrollbarHandle, ScrollbarVisibility};
 use gpui_native_theme::{ActiveTheme as _, ColorTokens, Ramps};
 
-use crate::highlight::{HighlightedCode, Language, Role, highlight};
+use crate::highlight::{HighlightedCode, Language, Role, highlight_with_tree};
+
+actions!(code_view, [Copy]);
+
+/// The key context the code view declares while it holds focus.
+pub const CODE_VIEW_CONTEXT: &str = "CodeView";
+
+/// Binds the code view's copy chord: cmd-c on macOS, ctrl-c elsewhere.
+///
+/// Call once at startup. Without it, selection copy has no key.
+pub fn bind_code_view_keys(cx: &mut App) {
+    let context = Some(CODE_VIEW_CONTEXT);
+    #[cfg(target_os = "macos")]
+    let copy = "cmd-c";
+    #[cfg(not(target_os = "macos"))]
+    let copy = "ctrl-c";
+    cx.bind_keys([KeyBinding::new(copy, Copy, context)]);
+}
+
+/// A point in the source, in lines and characters (not bytes).
+#[derive(Clone, Copy, Debug, Default, PartialEq, Eq)]
+pub struct SelectionPoint {
+    pub row: usize,
+    pub col: usize,
+}
+
+impl SelectionPoint {
+    /// The earlier of two points, in document order.
+    fn earlier_than(&self, other: &Self) -> bool {
+        (self.row, self.col) <= (other.row, other.col)
+    }
+}
 
 /// Retained state for a code view.
 pub struct CodeViewState {
@@ -20,26 +52,40 @@ pub struct CodeViewState {
     source: SharedString,
     language: Language,
     code: HighlightedCode,
+    /// The parse tree of `source`, so updates reparse incrementally instead of from scratch.
+    tree: Option<tree_sitter::Tree>,
     handle: UniformListScrollHandle,
+    /// The hovered line, driving the active-line wash and number emphasis.
+    active_line: Option<usize>,
+    /// `(anchor, head)` in the order they were set.
+    selection: Option<(SelectionPoint, SelectionPoint)>,
+    /// Whether a drag that started on a row is still extending the selection.
+    selecting: bool,
+    focus_handle: gpui::FocusHandle,
     a11y_label: Option<SharedString>,
 }
 
 impl CodeViewState {
     /// Builds the state, highlighting `source` with `language`.
-    pub fn new<I, S>(id: I, source: S, language: Language) -> Self
+    pub fn new<I, S>(id: I, source: S, language: Language, cx: &mut App) -> Self
     where
         I: Into<ElementId>,
         S: Into<SharedString>,
     {
         let source = source.into();
-        let code = highlight(&source, language);
+        let (code, tree) = highlight_with_tree(&source, language, None);
 
         Self {
             id: id.into(),
             source,
             language,
             code,
+            tree,
             handle: UniformListScrollHandle::new(),
+            active_line: None,
+            selection: None,
+            selecting: false,
+            focus_handle: cx.focus_handle(),
             a11y_label: None,
         }
     }
@@ -49,10 +95,48 @@ impl CodeViewState {
     where
         S: Into<SharedString>,
     {
-        self.source = source.into();
+        let source = source.into();
+
+        // The old tree is only reusable when the grammar stays the same.
+        let old_tree = if language == self.language {
+            self.tree.as_ref()
+        } else {
+            None
+        };
+
+        let (code, tree) = highlight_with_tree(&source, language, old_tree);
+        self.source = source;
         self.language = language;
-        self.code = highlight(&self.source, self.language);
+        self.code = code;
+        self.tree = tree;
+        self.selection = None;
         self.handle.scroll_to_item(0, ScrollStrategy::Top);
+
+        cx.notify();
+    }
+
+    /// Replaces one line's text and re-highlights the file.
+    pub fn update_line<T>(&mut self, line_ix: usize, text: T, cx: &mut Context<Self>)
+    where
+        T: AsRef<str>,
+    {
+        let trailing_newline = self.source.ends_with('\n');
+        let mut lines: Vec<String> = self.source.lines().map(str::to_string).collect();
+        let line_ix = line_ix.min(lines.len().saturating_sub(1));
+
+        let replacement: Vec<String> = if text.as_ref().is_empty() {
+            vec![String::new()]
+        } else {
+            text.as_ref().lines().map(str::to_string).collect()
+        };
+
+        lines.splice(line_ix..line_ix + 1, replacement);
+        self.source = (lines.join("\n") + if trailing_newline { "\n" } else { "" }).into();
+
+        let (code, tree) = highlight_with_tree(&self.source, self.language, self.tree.as_ref());
+        self.code = code;
+        self.tree = tree;
+        self.selection = None;
         cx.notify();
     }
 
@@ -79,6 +163,71 @@ impl CodeViewState {
         );
     }
 
+    /// The line the pointer last hovered, if any.
+    pub fn active_line(&self) -> Option<usize> {
+        self.active_line
+    }
+
+    /// Selects a range, endpoints in lines and characters.
+    pub fn select_range(
+        &mut self,
+        start: SelectionPoint,
+        end: SelectionPoint,
+        cx: &mut Context<Self>,
+    ) {
+        self.selection = if start.earlier_than(&end) {
+            Some((start, end))
+        } else {
+            Some((end, start))
+        };
+        self.selecting = false;
+        cx.notify();
+    }
+
+    /// The selected range, endpoints in document order, when there is one.
+    pub fn selection(&self) -> Option<(SelectionPoint, SelectionPoint)> {
+        self.selection.map(|(anchor, head)| {
+            if anchor.earlier_than(&head) {
+                (anchor, head)
+            } else {
+                (head, anchor)
+            }
+        })
+    }
+
+    /// The selected text, or `None` when nothing is selected.
+    pub fn selected_text(&self) -> Option<String> {
+        let (start, end) = self.selection()?;
+
+        let lines: Vec<&str> = self.source.split('\n').collect();
+        let mut selected = Vec::new();
+
+        for row in start.row..=end.row.min(lines.len().saturating_sub(1)) {
+            let line_chars: Vec<char> = lines.get(row)?.chars().collect();
+            let start_col = if row == start.row {
+                start.col.min(line_chars.len())
+            } else {
+                0
+            };
+
+            let end_col = if row == end.row {
+                end.col.min(line_chars.len())
+            } else {
+                line_chars.len()
+            };
+
+            selected.push(line_chars[start_col..end_col].iter().collect::<String>());
+        }
+
+        (!selected.is_empty()).then(|| selected.join("\n"))
+    }
+
+    /// Drops the selection.
+    pub fn clear_selection(&mut self) {
+        self.selection = None;
+        self.selecting = false;
+    }
+
     /// Overrides the accessibility label of the view.
     pub fn accessibility_label<L>(mut self, label: L) -> Self
     where
@@ -87,6 +236,39 @@ impl CodeViewState {
         self.a11y_label = Some(label.into());
         self
     }
+
+    /// Maps a window position to a point in the source.
+    fn position_at(
+        &self,
+        bounds: Bounds<Pixels>,
+        position: Point<Pixels>,
+        scroll_y: Pixels,
+        line_height: Pixels,
+        char_width: Pixels,
+        text_x: Pixels,
+    ) -> SelectionPoint {
+        let row = (((position.y - bounds.origin.y - scroll_y) / line_height).floor() as isize)
+            .clamp(0, self.code.lines.len() as isize - 1)
+            .max(0) as usize;
+
+        let chars = self.code.lines[row]
+            .spans
+            .iter()
+            .map(|span| span.text.chars().count())
+            .sum::<usize>();
+
+        let col = (((position.x - text_x) / char_width).round() as isize)
+            .clamp(0, chars as isize)
+            .max(0) as usize;
+
+        SelectionPoint { row, col }
+    }
+}
+
+impl gpui::Focusable for CodeViewState {
+    fn focus_handle(&self, _: &App) -> gpui::FocusHandle {
+        self.focus_handle.clone()
+    }
 }
 
 impl Render for CodeViewState {
@@ -96,24 +278,36 @@ impl Render for CodeViewState {
         let mono_font = theme.mono_font;
         let text_size = theme.sizes.small.text_size;
         let line_height = text_size * 1.5;
+        let char_width = text_size * 0.62;
+        let root_font_size = theme.root_font_size;
 
         let id = self.id.clone();
         let state = cx.entity();
         let line_count = self.code.lines.len();
+        let selection = self.selection();
+
         let gutter_chars = line_count.max(1).to_string().len().max(2);
         let gutter_width = text_size * 0.62 * gutter_chars as f32 + text_size;
 
+        let bounds_cell: std::rc::Rc<std::cell::RefCell<Option<Bounds<Pixels>>>> =
+            std::rc::Rc::new(std::cell::RefCell::new(None));
+
         let rows = uniform_list((id.clone(), "rows"), line_count, {
             let id = id.clone();
+            let state = state.clone();
             move |range, _window, cx| {
                 let code = state.read(cx);
+                let active_line = code.active_line;
                 let theme = cx.theme();
+
                 range
                     .map(|line_ix| {
                         render_row(
                             code,
                             &id,
                             line_ix,
+                            active_line == Some(line_ix),
+                            selection,
                             theme.mono_font,
                             theme.colors,
                             theme.ramps,
@@ -136,16 +330,135 @@ impl Render for CodeViewState {
             .text_size(text_size)
             .font_family(mono_font)
             .text_color(colors.foreground)
-            .when_some(self.a11y_label.clone(), |view, label| {
-                view.aria_label(label)
+            .key_context(CODE_VIEW_CONTEXT)
+            .track_focus(&self.focus_handle)
+            .on_mouse_down(MouseButton::Left, {
+                let state = state.clone();
+                let bounds_cell = bounds_cell.clone();
+                move |event: &MouseDownEvent, window: &mut Window, cx: &mut App| {
+                    window.focus(&state.read(cx).focus_handle.clone(), cx);
+
+                    let bounds = bounds_cell.borrow();
+                    let Some(bounds) = bounds.as_ref() else {
+                        return;
+                    };
+
+                    let text_x = bounds.origin.x + gutter_width + root_font_size;
+                    let point = {
+                        let code = state.read(cx);
+                        code.position_at(
+                            *bounds,
+                            event.position,
+                            Pixels::ZERO,
+                            line_height,
+                            char_width,
+                            text_x,
+                        )
+                    };
+
+                    state.update(cx, |state, cx| {
+                        if event.modifiers.shift {
+                            if let Some((anchor, _)) = state.selection {
+                                state.selection = Some((anchor, point));
+                            } else {
+                                state.selection = Some((point, point));
+                            }
+                        } else {
+                            state.selection = Some((point, point));
+                        }
+                        state.selecting = true;
+                        cx.notify();
+                    });
+                }
             })
-            .when_some(self.a11y_label.clone(), |view, label| {
-                view.aria_label(label)
+            .on_mouse_move({
+                let state = state.clone();
+                let bounds_cell = bounds_cell.clone();
+                move |event: &MouseMoveEvent, _window: &mut Window, cx: &mut App| {
+                    let bounds = bounds_cell.borrow();
+                    let Some(bounds) = bounds.as_ref() else {
+                        return;
+                    };
+
+                    let text_x = bounds.origin.x + gutter_width + root_font_size;
+                    let point = {
+                        let code = state.read(cx);
+                        code.position_at(
+                            *bounds,
+                            event.position,
+                            ScrollbarHandle::offset(&code.handle).y,
+                            line_height,
+                            char_width,
+                            text_x,
+                        )
+                    };
+
+                    let selecting = state.read(cx).selecting;
+                    if selecting {
+                        let changed = state
+                            .read(cx)
+                            .selection
+                            .map(|(_, head)| head != point)
+                            .unwrap_or(true);
+                        if changed {
+                            state.update(cx, |state, cx| {
+                                if let Some((anchor, _)) = state.selection {
+                                    state.selection = Some((anchor, point));
+                                }
+                                cx.notify();
+                            });
+                        }
+                        return;
+                    }
+
+                    let changed = state.read(cx).active_line != Some(point.row);
+                    if changed {
+                        state.update(cx, |state, cx| {
+                            state.active_line = Some(point.row);
+                            cx.notify();
+                        });
+                    }
+                }
             })
+            .on_mouse_up(MouseButton::Left, {
+                let state = state.clone();
+                move |_: &MouseUpEvent, _window: &mut Window, cx: &mut App| {
+                    if state.read(cx).selecting {
+                        state.update(cx, |state, cx| {
+                            state.selecting = false;
+                            cx.notify();
+                        });
+                    }
+                }
+            })
+            .on_action({
+                let state = state.clone();
+                move |_: &Copy, _window, cx| {
+                    if let Some(text) = state.read(cx).selected_text() {
+                        cx.write_to_clipboard(ClipboardItem::new_string(text));
+                    }
+                }
+            })
+            .child(
+                canvas(
+                    {
+                        let bounds_cell = bounds_cell.clone();
+                        move |bounds, _window, _cx| {
+                            *bounds_cell.borrow_mut() = Some(bounds);
+                        }
+                    },
+                    |_, _, _, _| {},
+                )
+                .absolute()
+                .inset_0(),
+            )
             .child(rows)
             .child(
                 Scrollbar::vertical(self.handle.clone()).visibility(ScrollbarVisibility::Platform),
             )
+            .when_some(self.a11y_label.clone(), |view, label| {
+                view.aria_label(label)
+            })
     }
 }
 
@@ -154,6 +467,8 @@ fn render_row(
     code: &CodeViewState,
     id: &ElementId,
     line_ix: usize,
+    active: bool,
+    selection: Option<(SelectionPoint, SelectionPoint)>,
     mono_font: &'static str,
     colors: ColorTokens,
     ramps: Ramps,
@@ -162,22 +477,74 @@ fn render_row(
     gutter_width: Pixels,
 ) -> gpui::AnyElement {
     let line = code.code().lines.get(line_ix).cloned().unwrap_or_default();
-    // One text element per line, colored by byte-range highlights
+
     let mut text = String::new();
-    let mut highlights: Vec<(std::ops::Range<usize>, HighlightStyle)> = Vec::new();
+    for span in &line.spans {
+        text.push_str(&span.text);
+    }
+
+    let char_count = text.chars().count();
+    let mut roles = vec![Role::Text; char_count];
+    let mut offset = 0usize;
 
     for span in &line.spans {
-        let start = text.len();
-        text.push_str(&span.text);
-        if span.role != Role::Text {
+        let chars = span.text.chars().count();
+        for slot in &mut roles[offset..offset + chars] {
+            *slot = span.role;
+        }
+        offset += chars;
+    }
+
+    let mut selected = vec![false; char_count];
+
+    if let Some((start, end)) = selection
+        && line_ix >= start.row
+        && line_ix <= end.row
+    {
+        let start_col = if line_ix == start.row {
+            start.col.min(char_count)
+        } else {
+            0
+        };
+
+        let end_col = if line_ix == end.row {
+            end.col.min(char_count)
+        } else {
+            char_count
+        };
+
+        for slot in &mut selected[start_col..end_col] {
+            *slot = true;
+        }
+    }
+
+    let mut highlights: Vec<(std::ops::Range<usize>, HighlightStyle)> = Vec::new();
+    let mut run_start = 0usize;
+    let mut run_end = 0usize;
+    let mut run_role = Role::Text;
+    let mut run_selected = false;
+
+    for (char_ix, (byte_ix, character)) in text.char_indices().enumerate() {
+        let fresh = char_ix == 0 || roles[char_ix] != run_role || selected[char_ix] != run_selected;
+        if fresh {
+            if char_ix > 0 {
                 highlights.push((
-                start..text.len(),
-                HighlightStyle {
-                    color: Some(role_color(span.role, colors, ramps)),
-                    ..Default::default()
-                },
+                    run_start..run_end,
+                    run_style(run_role, run_selected, colors, ramps),
                 ));
             }
+            run_start = byte_ix;
+            run_role = roles[char_ix];
+            run_selected = selected[char_ix];
+        }
+        run_end = byte_ix + character.len_utf8();
+    }
+
+    if run_end > run_start || !text.is_empty() {
+        highlights.push((
+            run_start..run_end,
+            run_style(run_role, run_selected, colors, ramps),
+        ));
     }
 
     let style = TextStyle {
@@ -185,6 +552,7 @@ fn render_row(
         font_family: SharedString::from(mono_font),
         font_size: text_size.into(),
         line_height: line_height.into(),
+        white_space: gpui::WhiteSpace::Nowrap,
         ..Default::default()
     };
 
@@ -194,31 +562,80 @@ fn render_row(
             move || name
         })
         .id(("code-row", line_ix))
+        .w_full()
         .h(line_height)
         .flex()
         .items_center()
         .overflow_hidden()
+        .when(active, |row| {
+            row.bg(Hsla {
+                a: colors.muted.a * 0.45,
+                ..colors.muted
+            })
+        })
         .child(
-            div()
-                .w(gutter_width)
-                .flex_none()
+            gutter_cell(
+                gutter_width,
+                line_height,
+                mono_font,
+                text_size,
+                if active {
+                    colors.foreground
+                } else {
+                    colors.muted_foreground
+                },
+                format!("{}", line_ix + 1),
+            )
+            .justify_end()
             .pr_2()
-                .text_right()
-                .font_family(mono_font)
-                .text_size(text_size)
-                .text_color(colors.muted_foreground)
-                .child(format!("{}", line_ix + 1)),
+            .whitespace_nowrap(),
         )
         .child(
             div()
                 .flex_1()
                 .min_w_0()
+                .ml_4()
                 .overflow_hidden()
+                .whitespace_nowrap()
                 .child(gpui::StyledText::new(text).with_default_highlights(&style, highlights)),
         )
         .into_any_element()
 }
 
+fn run_style(role: Role, selected: bool, colors: ColorTokens, ramps: Ramps) -> HighlightStyle {
+    HighlightStyle {
+        color: Some(role_color(role, colors, ramps)),
+        background_color: selected.then_some(colors.selection),
+        ..Default::default()
+    }
+}
+
+/// A gutter cell sized to the whole row.
+fn gutter_cell<E>(
+    width: Pixels,
+    height: Pixels,
+    mono_font: &'static str,
+    text_size: Pixels,
+    color: Hsla,
+    content: E,
+) -> gpui::Div
+where
+    E: IntoElement,
+{
+    div()
+        .w(width)
+        .h(height)
+        .flex()
+        .items_center()
+        .justify_center()
+        .flex_none()
+        .font_family(mono_font)
+        .text_size(text_size)
+        .line_height(gpui::relative(1.0))
+        .text_color(color)
+        .child(content)
+}
+
 /// Maps a highlight role to the theme's semantic palette.
 fn role_color(role: Role, colors: ColorTokens, ramps: Ramps) -> Hsla {
     match role {

crates/editor/src/highlight.rs

@@ -54,10 +54,62 @@ use tree_sitter::StreamingIterator as _;
 
 /// Highlights `source` with `language`'s tree-sitter grammar.
 pub fn highlight(source: &str, language: Language) -> HighlightedCode {
+    highlight_with_tree(source, language, None).0
+}
+
+/// Highlights `source`, reusing `old_tree` so only the changed region is re-lexed.
+pub fn highlight_with_tree(
+    source: &str,
+    language: Language,
+    old_tree: Option<&tree_sitter::Tree>,
+) -> (HighlightedCode, Option<tree_sitter::Tree>) {
     let Some((grammar, query_source)) = grammar_for(language) else {
-        return build_lines(source, &[]);
+        return (plain(source), None);
     };
-    highlight_with(grammar, query_source, source).unwrap_or_else(|| build_lines(source, &[]))
+
+    let mut parser = tree_sitter::Parser::new();
+    if parser.set_language(&grammar).is_err() {
+        return (plain(source), None);
+    }
+
+    let Some(tree) = parser.parse(source, old_tree) else {
+        return (plain(source), None);
+    };
+
+    let Ok(query) = tree_sitter::Query::new(&grammar, query_source) else {
+        return (plain(source), None);
+    };
+
+    let roles: Vec<Option<Role>> = query
+        .capture_names()
+        .iter()
+        .map(|name| role_for_capture(name))
+        .collect();
+
+    // One role per byte; matches arrive in query order
+    let mut role_at = vec![None; source.len()];
+    let mut cursor = tree_sitter::QueryCursor::new();
+    let mut matches = cursor.matches(&query, tree.root_node(), source.as_bytes());
+
+    while let Some(matched) = matches.next() {
+        for capture in matched.captures {
+            let Some(role) = roles.get(capture.index as usize).copied().flatten() else {
+                continue;
+            };
+            for byte in capture.node.byte_range() {
+                if let Some(slot) = role_at.get_mut(byte) {
+                    *slot = Some(role);
+                }
+            }
+        }
+    }
+
+    (build_lines(source, &role_at), Some(tree))
+}
+
+/// Source rendered without any grammar: plain text roles.
+pub(crate) fn plain(source: &str) -> HighlightedCode {
+    build_lines(source, &[])
 }
 
 /// The grammar and its highlight query for a language, when compiled in.
@@ -90,43 +142,6 @@ fn grammar_for(language: Language) -> Option<(tree_sitter::Language, &'static st
     }
 }
 
-fn highlight_with(
-    grammar: tree_sitter::Language,
-    query_source: &str,
-    source: &str,
-) -> Option<HighlightedCode> {
-    let mut parser = tree_sitter::Parser::new();
-    parser.set_language(&grammar).ok()?;
-
-    let tree = parser.parse(source, None)?;
-    let query = tree_sitter::Query::new(&grammar, query_source).ok()?;
-
-    let roles: Vec<Option<Role>> = query
-        .capture_names()
-        .iter()
-        .map(|name| role_for_capture(name))
-        .collect();
-
-    let mut role_at = vec![None; source.len()];
-    let mut cursor = tree_sitter::QueryCursor::new();
-    let mut matches = cursor.matches(&query, tree.root_node(), source.as_bytes());
-
-    while let Some(matched) = matches.next() {
-        for capture in matched.captures {
-            let Some(role) = roles.get(capture.index as usize).copied().flatten() else {
-                continue;
-            };
-            for byte in capture.node.byte_range() {
-                if let Some(slot) = role_at.get_mut(byte) {
-                    *slot = Some(role);
-                }
-            }
-        }
-    }
-
-    Some(build_lines(source, &role_at))
-}
-
 /// Maps a query capture name to a role; unmapped captures render as text.
 fn role_for_capture(name: &str) -> Option<Role> {
     match name.split('.').next()? {

crates/editor/tests/code_view.rs

@@ -2,10 +2,10 @@ use std::cell::RefCell;
 use std::rc::Rc;
 
 use gpui::{
-    AppContext as _, Context, Entity, IntoElement, ParentElement as _, Render, Styled as _,
-    TestAppContext, VisualTestContext, Window, div,
+    AppContext as _, Context, Entity, Focusable as _, IntoElement, ParentElement as _, Render,
+    Styled as _, TestAppContext, VisualTestContext, Window, div,
 };
-use gpui_native_editor::code_view::CodeViewState;
+use gpui_native_editor::code_view::{CodeViewState, bind_code_view_keys};
 use gpui_native_editor::highlight::{HighlightedCode, Language, Role, highlight};
 
 fn spans_with_role(code: &HighlightedCode, role: Role) -> Vec<&str> {
@@ -66,7 +66,11 @@ fn a_capture_spanning_newlines_styles_both_lines() {
 #[test]
 fn set_source_rehighlights_with_the_new_language() {
     let mut cx = TestAppContext::single();
-    let state = cx.new(|_| CodeViewState::new("test-code", "fn main() {}\n", Language::Rust));
+    cx.update(|cx| {
+        gpui_native_theme::Theme::init(cx);
+        bind_code_view_keys(cx);
+    });
+    let state = cx.new(|cx| CodeViewState::new("test-code", "fn main() {}\n", Language::Rust, cx));
 
     cx.update(|cx| {
         state.update(cx, |state, cx| {
@@ -98,16 +102,19 @@ fn code_view_window(
     line_count: usize,
 ) -> (TestAppContext, VisualTestContext, Entity<CodeViewState>) {
     let mut cx = TestAppContext::single();
-    cx.update(gpui_native_theme::Theme::init);
+    cx.update(|cx| {
+        gpui_native_theme::Theme::init(cx);
+        bind_code_view_keys(cx);
+    });
     let source: String = (0..line_count)
         .map(|line| format!("fn line_{line}() {{}}\n"))
         .collect();
-    let state = CodeViewState::new("test-code", source, Language::Rust);
     let state_cell: Rc<RefCell<Option<Entity<CodeViewState>>>> = Rc::new(RefCell::new(None));
     let cell = state_cell.clone();
-    let window = cx.add_window(move |_, cx| {
-        let code = cx.new(|_| state);
+    let window = cx.add_window(move |window, cx| {
+        let code = cx.new(|cx| CodeViewState::new("test-code", source, Language::Rust, cx));
         cell.borrow_mut().replace(code.clone());
+        window.focus(&code.read(cx).focus_handle(cx), cx);
         Host { code }
     });
     let state = state_cell.borrow().clone().expect("state captured");
@@ -145,3 +152,99 @@ fn rows_render_virtualized_and_scroll() {
         "the first row scrolled out"
     );
 }
+
+#[test]
+fn hovering_a_line_activates_it() {
+    let (cx, mut visual, state) = code_view_window(80);
+
+    let row = visual
+        .debug_bounds("test-code-row-3")
+        .expect("row 3 renders in the viewport");
+    visual.simulate_event(gpui::MouseMoveEvent {
+        position: row.center(),
+        ..Default::default()
+    });
+
+    let active = cx.update(|cx| state.read(cx).active_line());
+    assert_eq!(active, Some(3), "the hovered line becomes the active line");
+}
+
+#[test]
+fn selecting_then_copying_writes_the_clipboard() {
+    let (cx, mut visual, state) = code_view_window(10);
+
+    cx.update(|cx| {
+        state.update(cx, |state, cx| {
+            state.select_range(
+                gpui_native_editor::code_view::SelectionPoint { row: 0, col: 0 },
+                gpui_native_editor::code_view::SelectionPoint { row: 0, col: 3 },
+                cx,
+            );
+        });
+    });
+
+    visual.simulate_keystrokes("cmd-c");
+
+    let clipboard = cx.update(|cx| {
+        cx.read_from_clipboard()
+            .and_then(|item| item.text().map(|text| text.to_string()))
+    });
+    assert_eq!(
+        clipboard.as_deref(),
+        Some("fn "),
+        "the copy chord copies the selection"
+    );
+}
+
+#[test]
+fn update_line_replaces_a_single_line_and_rehighlights() {
+    let mut cx = TestAppContext::single();
+    cx.update(|cx| {
+        gpui_native_theme::Theme::init(cx);
+    });
+    let state = cx.new(|cx| {
+        CodeViewState::new(
+            "test-code",
+            "fn a() {}\nfn b() {}\nfn c() {}\n",
+            Language::Rust,
+            cx,
+        )
+    });
+
+    cx.update(|cx| {
+        state.update(cx, |state, cx| state.update_line(1, "struct S;", cx));
+    });
+
+    let (source, line_count, keyword_on_line_1) = cx.update(|cx| {
+        let state = state.read(cx);
+        (
+            state.source().to_string(),
+            state.code().lines.len(),
+            state.code().lines[1]
+                .spans
+                .iter()
+                .any(|span| span.role == Role::Keyword),
+        )
+    });
+
+    assert_eq!(source, "fn a() {}\nstruct S;\nfn c() {}\n");
+    assert_eq!(line_count, 4, "the line count survives the replacement");
+    assert!(keyword_on_line_1, "struct highlights as a keyword");
+}
+
+#[test]
+fn update_line_splices_multiline_text() {
+    let mut cx = TestAppContext::single();
+    cx.update(|cx| {
+        gpui_native_theme::Theme::init(cx);
+    });
+    let state =
+        cx.new(|cx| CodeViewState::new("test-code", "fn a() {}\nfn b() {}\n", Language::Rust, cx));
+
+    cx.update(|cx| {
+        state.update(cx, |state, cx| state.update_line(1, "one\ntwo\nthree", cx));
+    });
+
+    let source = cx.update(|cx| state.read(cx).source().to_string());
+    assert_eq!(source, "fn a() {}\none\ntwo\nthree\n");
+}

crates/editor/tests/code_view_bench.rs

@@ -7,7 +7,7 @@ use gpui::{
     ScrollDelta, ScrollEvent, Styled as _, TestAppContext, VisualTestContext, Window, div, point,
     px,
 };
-use gpui_native_editor::code_view::CodeViewState;
+use gpui_native_editor::code_view::{CodeViewState, bind_code_view_keys};
 use gpui_native_editor::highlight::Language;
 
 /// Deterministic pseudo-Rust with mixed tokens, roughly `lines` lines long.
@@ -50,12 +50,17 @@ impl Render for Host {
 #[test]
 fn scrolling_a_large_file_is_not_pathologically_slow() {
     let mut cx = TestAppContext::single();
-    cx.update(gpui_native_theme::Theme::init);
+    cx.update(|cx| {
+        gpui_native_theme::Theme::init(cx);
+        bind_code_view_keys(cx);
+    });
 
     let source = large_source(5000);
     let started = Instant::now();
-    let state = CodeViewState::new("bench-code", source.clone(), Language::Rust);
-    let highlight_elapsed = started.elapsed();
+    let (state, highlight_elapsed) = cx.update(|cx| {
+        let state = CodeViewState::new("bench-code", source.clone(), Language::Rust, cx);
+        (state, started.elapsed())
+    });
 
     let state_cell: Rc<RefCell<Option<Entity<CodeViewState>>>> = Rc::new(RefCell::new(None));
     let cell = state_cell.clone();

docs/CHECKLIST.md

@@ -9,15 +9,21 @@ is the first downstream consumer; its screens drive the order.
 
 ## Next
 
-- [ ] **Diff view** (M15, `editor`).
-    - [ ] API sketch
-    - [ ] Implementation
-    - [ ] Tests
-    - [ ] Gallery panel
+- [ ] **Code view interactions** (M15, `editor`) — active line, text
+      selection with copy, incremental line re-highlight.
+    - [x] API sketch
+    - [x] Implementation
+    - [x] Tests
+    - [x] Gallery panel
     - [ ] Review
 
 ## Queue — to follow
 
+- [ ] **Diff view** (`editor`) — implemented, then reverted to
+      `stash@{0}` ("pre-revert: diff view + gutter tweaks"); restore with
+      `git stash pop` and re-land after the code view interactions settle.
+- [ ] **Editor follow-ups** — language detection by file path, meta line
+      overlay, per-view config overrides (line height, gutter visibility).
 - [ ] **Markdown view** (M16, `editor`) — only if a consumer confirms.
 - [ ] **Pickers** — Calendar / DatePicker, TimeField, ColorPicker (decide at
       unit time).

examples/gallery/src/main.rs

@@ -2845,7 +2845,8 @@ struct CodeViewDemo {
 
 impl CodeViewDemo {
     fn new(cx: &mut Context<Self>) -> Self {
-        let code = cx.new(|_| CodeViewState::new("code-view-demo", RUST_SAMPLE, Language::Rust));
+        let code =
+            cx.new(|cx| CodeViewState::new("code-view-demo", RUST_SAMPLE, Language::Rust, cx));
         // The panel is a cached view in the dock: it re-renders only when
         // the code state it renders is notified.
         let subscription = cx.observe(&code, |_, _, cx| cx.notify());
@@ -3214,6 +3215,7 @@ fn main() {
         .with_http_client(std::sync::Arc::new(reqwest_client::ReqwestClient::new()))
         .run(|cx: &mut App| {
             gpui_native_core::init(cx);
+            gpui_native_editor::code_view::bind_code_view_keys(cx);
             cx.bind_keys([
                 KeyBinding::new("cmd-k", OpenCommandPalette, None),
                 KeyBinding::new("ctrl-k", OpenCommandPalette, None),