Summary

This PR adds support for a horizontal scrollbar in the editor, allowing users to scroll horizontally when line wrapping is disabled and content extends beyond the viewport. The horizontal scrollbar can be toggled on/off via the command palette or keybindings, and its visibility is configurable through the editor config.

Key Changes

• Horizontal Scrollbar Rendering: Added render_horizontal_scrollbar() method to render a horizontal scrollbar at the bottom of each split pane. The scrollbar thumb position reflects the current horizontal scroll position (left_column).

• Layout Updates: Modified SplitLayout struct to include horizontal_scrollbar_rect and updated split_layout() to calculate proper dimensions for both vertical and horizontal scrollbars, accounting for their visibility.

• Configuration Options: Added two new config options:

  • show_vertical_scrollbar (default: true) - controls vertical scrollbar visibility
  • show_horizontal_scrollbar (default: false) - controls horizontal scrollbar visibility

• Toggle Actions: Implemented toggle_vertical_scrollbar() and toggle_horizontal_scrollbar() methods with appropriate status messages.

• Mouse Input Handling:

  • Added support for native ScrollLeft/ScrollRight mouse events
  • Added Shift+ScrollUp/Down for horizontal scrolling
  • Implemented click handling on horizontal scrollbar track to jump to position

• Horizontal Scroll Logic: Added handle_horizontal_scroll() method that respects line wrap settings (no horizontal scrolling when wrapping is enabled).

• Command & Keybinding Support: Added new actions ToggleVerticalScrollbar and ToggleHorizontalScrollbar with command definitions and menu items.

• Comprehensive E2E Tests: Added horizontal_scrollbar.rs test suite covering:

  • Horizontal scrollbar visibility with long lines
  • Behavior with line wrapping enabled
  • Toggle functionality for both scrollbars
  • Config-based visibility settings
  • Split view scenarios

Notable Implementation Details

• The horizontal scrollbar is only rendered when line wrapping is disabled; when wrapping is enabled, an empty track is shown
• Scrollbar thumb size and position are calculated based on the ratio of visible width to total content width
• The implementation respects the estimated_line_length config for calculating content width
• Horizontal scrollbar areas are tracked in CachedLayout for mouse hit testing
• Localization strings added for toggle actions and status messages

https://claude.ai/code/session_016vmwKbd4BuvUJ34u6pViTi