feat: support horizontal mouse scrolling in buffers

2026-10-11 14:10:20 +02:00
parent 0ca0d89b9e
commit 0d4601b612
6 changed files with 272 additions and 31 deletions
@@ -135,6 +135,8 @@ impl Drop for TerminalSession {
 struct DocumentViewport {
    geometry: Option<(usize, Rect)>,
    manual: Option<ManualViewport>,
+    text_width: usize,
+    horizontal_extent: Option<(usize, u64, usize)>,
 }

 struct ManualViewport {
@@ -184,13 +186,12 @@ impl BufferViewports {
        }
    }

+    // Shift-wheel is the fallback for terminals without native horizontal reports.
+    // Keep classification shared with popup routing.
    fn scroll(&mut self, session: &mut EditorSession, mouse: MouseEvent) -> bool {
-        if !matches!(
-            mouse.kind,
-            MouseEventKind::ScrollUp | MouseEventKind::ScrollDown
-        ) {
+        let Some(kind) = wheel_kind(&mouse) else {
            return false;
-        }
+        };
        if self.panels.scroll(session, mouse) {
            return true;
        }
@@ -208,17 +209,47 @@ impl BufferViewports {
        {
            return false;
        }
-        let (top, _) = self.offsets.entry(buffer_id).or_default();
-        let last_page = editor
-            .lines()
-            .len()
-            .saturating_sub(usize::from(viewport.height));
-        *top = match mouse.kind {
-            MouseEventKind::ScrollUp => top.saturating_sub(3),
-            MouseEventKind::ScrollDown => top.saturating_add(3),
-            _ => unreachable!(),
+        let (top, left) = self.offsets.entry(buffer_id).or_default();
+        if matches!(
+            kind,
+            MouseEventKind::ScrollLeft | MouseEventKind::ScrollRight
+        ) {
+            let key = (buffer_id, editor.text_revision());
+            let columns = match self.document.horizontal_extent {
+                Some((id, revision, columns)) if (id, revision) == key => columns,
+                _ => {
+                    let columns = editor
+                        .lines()
+                        .iter()
+                        .map(|line| display_column(line, usize::MAX))
+                        .max()
+                        .unwrap_or(0);
+                    self.document.horizontal_extent = Some((key.0, key.1, columns));
+                    columns
+                }
+            };
+            *left = if kind == MouseEventKind::ScrollRight {
+                left.saturating_add(3)
+            } else {
+                left.saturating_sub(3)
+            }
+            .min(
+                columns
+                    .saturating_add(1)
+                    .saturating_sub(self.document.text_width.max(1)),
+            );
+        } else {
+            let last_page = editor
+                .lines()
+                .len()
+                .saturating_sub(usize::from(viewport.height));
+            *top = if kind == MouseEventKind::ScrollDown {
+                top.saturating_add(3)
+            } else {
+                top.saturating_sub(3)
+            }
+            .min(last_page);
        }
-        .min(last_page);
        if self.document.manual.is_none() {
            self.document.manual = Some(ManualViewport {
                buffer_id,
@@ -255,6 +286,22 @@ impl BufferViewports {
    }
 }

+fn wheel_kind(mouse: &MouseEvent) -> Option<MouseEventKind> {
+    Some(match mouse.kind {
+        MouseEventKind::ScrollUp if mouse.modifiers.contains(KeyModifiers::SHIFT) => {
+            MouseEventKind::ScrollLeft
+        }
+        MouseEventKind::ScrollDown if mouse.modifiers.contains(KeyModifiers::SHIFT) => {
+            MouseEventKind::ScrollRight
+        }
+        kind @ (MouseEventKind::ScrollUp
+        | MouseEventKind::ScrollDown
+        | MouseEventKind::ScrollLeft
+        | MouseEventKind::ScrollRight) => kind,
+        _ => return None,
+    })
+}
+
 fn draw_frame<W: io::Write>(
    terminal: &mut Terminal<CrosstermBackend<Vec<u8>>>,
    output: &mut W,
@@ -474,6 +521,7 @@ fn draw(
    .areas(viewport);
    let height = usize::from(viewport.height);
    let width = usize::from(viewport.width);
+    document.text_width = width;
    let cursor = editor.cursor();
    let mut document_caret = None;
    let carets = editor.carets();
@@ -499,6 +547,13 @@ fn draw(
        ),
    ));
    *top = (*top).min(editor.lines().len().saturating_sub(height));
+    if document.manual.is_some()
+        && let Some((id, revision, columns)) = document.horizontal_extent
+        && id == editor.buffer_id()
+        && revision == editor.text_revision()
+    {
+        *left = (*left).min(columns.saturating_add(1).saturating_sub(width.max(1)));
+    }
    if height > 0 && width > 0 {
        if document.manual.is_none() {
            if cursor.row < *top {
@@ -724,6 +779,7 @@ fn draw(
 struct DiffGeometry {
    regions: [(Rect, Focus); 3],
    viewport: Option<(u64, usize, usize, usize, usize)>,
+    text_widths: [u16; 2],
 }

 fn diff_panel(frame: &mut Frame, area: Rect, title: &str, focused: bool) -> Rect {
@@ -1217,6 +1273,7 @@ fn draw_diff(
                (Rect::default(), Focus::After),
            ],
            viewport: None,
+            text_widths: [0; 2],
        });
        if let Some(editor) = editor {
            draw_diff_popups(frame, editor, area, None, panels);
@@ -1358,6 +1415,16 @@ fn draw_diff(
            comparison.map(|comparison| comparison.files.as_slice()),
        );
    }
+    let mut text_widths = [0; 2];
+    let previous_text_widths = panels
+        .previous_diff
+        .as_ref()
+        .filter(|geometry| {
+            geometry.viewport.is_some_and(|(id, file, _, _, _)| {
+                Some(id) == diff.comparison_id && file == diff.file
+            })
+        })
+        .map(|geometry| geometry.text_widths);
    if let Some(file) = selected
        && let Some(syntax) = &panels.diff_syntax
    {
@@ -1372,8 +1439,13 @@ fn draw_diff(
                    before_area,
                    true,
                    &syntax.before,
-                    (top, before_left),
+                    (
+                        top,
+                        &mut before_left,
+                        previous_text_widths.map(|widths| widths[0]),
+                    ),
                );
+                text_widths[0] = text_area.width;
                if let Some(editor) =
                    editor.filter(|editor| editor.diff_buffer_focus() == Some(Focus::Before))
                {
@@ -1396,8 +1468,13 @@ fn draw_diff(
                    after_area,
                    false,
                    &syntax.after,
-                    (top, after_left),
+                    (
+                        top,
+                        &mut after_left,
+                        previous_text_widths.map(|widths| widths[1]),
+                    ),
                );
+                text_widths[1] = text_area.width;
                if let Some(editor) =
                    editor.filter(|editor| editor.diff_buffer_focus() == Some(Focus::After))
                {
@@ -1439,6 +1516,7 @@ fn draw_diff(
        viewport: diff
            .comparison_id
            .map(|id| (id, diff.file, top, before_left, after_left)),
+        text_widths,
    });
    if let Some(picker) = &diff.files
        && diff.files_visible
@@ -1476,7 +1554,7 @@ fn draw_diff_pane(
    area: Rect,
    before: bool,
    syntax: &SyntaxCache,
-    viewport: (usize, usize),
+    viewport: (usize, &mut usize, Option<u16>),
 ) -> Rect {
    if area.width == 0 || area.height == 0 {
        return area;
@@ -1509,7 +1587,7 @@ fn draw_diff_pane(
        return content;
    }
    let source = if before { &file.before } else { &file.after };
-    let (top, left) = viewport;
+    let (top, left, previous_width) = viewport;
    let digits = source.len().max(1).ilog10() as usize + 1;
    let gutter = if usize::from(content.width) > digits + 2 {
        digits + 2
@@ -1517,6 +1595,10 @@ fn draw_diff_pane(
        0
    };
    let width = usize::from(content.width).saturating_sub(gutter);
+    if previous_width.is_some_and(|previous| usize::from(previous) != width) {
+        *left = diff.bound_horizontal(focus, *left, width);
+    }
+    let left = *left;
    for (display_row, row) in diff
        .display_rows
        .iter()
@@ -1738,6 +1820,7 @@ struct WheelPanels {
    manual_files: Option<FileWheelOffset>,
    diff: Option<DiffGeometry>,
    diff_syntax: Option<DiffSyntaxCache>,
+    previous_diff: Option<DiffGeometry>,
 }

 struct FileWheelOffset {
@@ -1772,7 +1855,7 @@ impl WheelPanels {
        self.hover = None;
        self.completion = None;
        self.files = None;
-        self.diff = None;
+        self.previous_diff = self.diff.take();
    }

    // Keyboard/paste may change the catalog without changing its length.
@@ -1801,12 +1884,31 @@ impl WheelPanels {
        top
    }

+    // A horizontal report over a popup must not pan the underlying buffer.
    fn scroll(&mut self, session: &mut EditorSession, mouse: MouseEvent) -> bool {
-        let down = match mouse.kind {
-            MouseEventKind::ScrollDown => true,
-            MouseEventKind::ScrollUp => false,
-            _ => return false,
+        let Some(kind) = wheel_kind(&mouse) else {
+            return false;
        };
+        let horizontal = matches!(
+            kind,
+            MouseEventKind::ScrollLeft | MouseEventKind::ScrollRight
+        );
+        let down = matches!(
+            kind,
+            MouseEventKind::ScrollDown | MouseEventKind::ScrollRight
+        );
+        let position = Position::new(mouse.column, mouse.row);
+        if horizontal
+            && (session.editor().palette().is_some()
+                || session.editor().startup_diagnostic().is_some()
+                || self.completion.is_some_and(|area| area.contains(position))
+                || self.hover.is_some_and(|(area, _)| area.contains(position))
+                || self
+                    .files
+                    .is_some_and(|(area, _, _)| area.contains(position)))
+        {
+            return true;
+        }
        let editor = session.editor();
        if editor.diff().is_some() {
            let position = Position::new(mouse.column, mouse.row);
@@ -1817,8 +1919,16 @@ impl WheelPanels {
                    .find_map(|(area, focus)| area.contains(position).then_some(*focus))
            });
            if let Some(focus) = focus {
-                for _ in 0..3 {
-                    session.scroll_diff(focus, down);
+                if horizontal {
+                    let width =
+                        self.diff.as_ref().unwrap().text_widths[usize::from(focus == Focus::After)];
+                    if width > 0 {
+                        session.scroll_diff_horizontal(focus, down, usize::from(width));
+                    }
+                } else {
+                    for _ in 0..3 {
+                        session.scroll_diff(focus, down);
+                    }
                }
            }
            return true;
@@ -4016,12 +4126,18 @@ mod tests {
        };
        git(&["init", "-q"]);
        for index in 0..8 {
-            directory.file(&format!("file-{index}.txt"), "first\nsecond\nthird\n");
+            directory.file(
+                &format!("file-{index}.txt"),
+                &format!("{}\nsecond\nthird\n", "before.".repeat(30)),
+            );
        }
        git(&["add", "."]);
        git(&["commit", "-qm", "base"]);
        for index in 0..8 {
-            directory.file(&format!("file-{index}.txt"), "changed\nsecond\nthird\n");
+            directory.file(
+                &format!("file-{index}.txt"),
+                &format!("{}\nsecond\nthird\n", "after.".repeat(30)),
+            );
        }
        let mut session = EditorSession::open(Some(path), vec![], None).unwrap();
        let original = session.editor().lines().to_vec();
@@ -4054,6 +4170,30 @@ mod tests {
        let tree = regions[0].0;
        let before = regions[1].0;
        let after = regions[2].0;
+        let initial_focus = session.editor().diff().unwrap().focus;
+        let initial_cursor = session.editor().cursor();
+        assert!(viewports.scroll(
+            &mut session,
+            document_wheel(MouseEventKind::ScrollRight, before.x + 1, before.y + 1)
+        ));
+        terminal
+            .draw(|frame| viewports.draw_session(frame, &mut session))
+            .unwrap();
+        assert!(screen_text(&terminal).contains("ore.before."));
+        assert_eq!(session.editor().diff().unwrap().left_before, 3);
+        assert_eq!(session.editor().diff().unwrap().left_after, 0);
+        let mut shift = document_wheel(MouseEventKind::ScrollDown, after.x + 1, after.y + 1);
+        shift.modifiers = KeyModifiers::SHIFT;
+        assert!(viewports.scroll(&mut session, shift));
+        terminal
+            .draw(|frame| viewports.draw_session(frame, &mut session))
+            .unwrap();
+        assert!(screen_text(&terminal).contains("er.after."));
+        assert_eq!(session.editor().diff().unwrap().left_before, 3);
+        assert_eq!(session.editor().diff().unwrap().left_after, 3);
+        assert_eq!(session.editor().diff().unwrap().top, 0);
+        assert_eq!(session.editor().diff().unwrap().focus, initial_focus);
+        assert_eq!(session.editor().cursor(), initial_cursor);
        assert!(viewports.scroll(
            &mut session,
            document_wheel(MouseEventKind::ScrollDown, tree.x + 1, tree.y + 1),
@@ -7067,6 +7207,64 @@ end
        }
    }

+    #[test]
+    fn horizontal_wheel_preserves_selection_bounds_display_cells_and_survives_redraw() {
+        let directory = Directory::new();
+        let text = format!("abc\t界e\u{301}{}", "xyz".repeat(20));
+        let path = directory.file("wide.txt", &text);
+        let mut session = EditorSession::open(Some(path), vec![], None).unwrap();
+        session.handle(Input::Char('v'));
+        session.handle(Input::Char('l'));
+        let cursor = session.editor().cursor();
+        let selections = session.editor().selections();
+        let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(16, 6)).unwrap();
+        let mut viewports = BufferViewports::default();
+        terminal
+            .draw(|frame| viewports.draw_session(frame, &mut session))
+            .unwrap();
+        assert!(viewports.scroll(
+            &mut session,
+            document_wheel(MouseEventKind::ScrollRight, 0, 0)
+        ));
+        terminal
+            .draw(|frame| viewports.draw_session(frame, &mut session))
+            .unwrap();
+        assert_eq!(terminal.backend().buffer()[(3, 0)].symbol(), "界");
+        assert_eq!(terminal.backend().buffer()[(5, 0)].symbol(), "e\u{301}");
+        let mut shift = document_wheel(MouseEventKind::ScrollDown, 0, 0);
+        shift.modifiers = KeyModifiers::SHIFT;
+        assert!(viewports.scroll(&mut session, shift));
+        terminal
+            .draw(|frame| viewports.draw_session(frame, &mut session))
+            .unwrap();
+        assert_eq!(viewports.offsets[&session.editor().buffer_id()], (0, 6));
+        for _ in 0..100 {
+            viewports.scroll(&mut session, shift);
+        }
+        terminal
+            .draw(|frame| viewports.draw_session(frame, &mut session))
+            .unwrap();
+        assert_eq!(
+            viewports.offsets[&session.editor().buffer_id()].1,
+            display_column(&text, usize::MAX) + 1 - viewports.document.text_width
+        );
+        assert_eq!(session.editor().cursor(), cursor);
+        assert_eq!(session.editor().selections(), selections);
+        assert_eq!(session.editor().lines(), std::slice::from_ref(&text));
+        terminal.backend_mut().resize(100, 6);
+        terminal
+            .draw(|frame| viewports.draw_session(frame, &mut session))
+            .unwrap();
+        assert_eq!(viewports.offsets[&session.editor().buffer_id()], (0, 0));
+        assert!(screen_text(&terminal).contains("abc"));
+        session.handle(Input::Escape);
+        session.handle(Input::Char('l'));
+        terminal
+            .draw(|frame| viewports.draw_session(frame, &mut session))
+            .unwrap();
+        assert!(terminal.backend().cursor_visible());
+    }
+
    #[test]
    fn wheel_scrolls_rendered_document_three_rows_without_changing_any_selection() {
        let directory = Directory::new();