Feature request: make panel splitters movable. Panels resizable by mouse

[phoenixway]

it will be great difference.

[louis030195]

I did some analysis on implementing this feature. Here's what I found:

Implementation Overview

The good news is most of the infrastructure already exists:

What's Already There

• Grid structure (frontends/rioterm/src/context/grid.rs): Tree-based layout with right, down, parent pointers
• Keyboard divider movement: move_divider_up/down/left/right() already working (lines 1355-1794)
• Mouse tracking: Position tracked in Mouse struct
• Split selection by mouse: select_current_based_on_mouse() already detects which split you click (line 450)
• Border rendering: 1px borders already drawn at split edges via create_border()

What Needs to Be Added

1. Divider hit-testing (~100 lines in grid.rs)

fn divider_at_position(&self, x: usize, y: usize) -> Option<DividerInfo> {
    // Check if (x, y) is within ~5-10px of a horizontal or vertical border
    // Return which two splits it separates + orientation (horizontal/vertical)
}

2. Drag state tracking (~30 lines)

struct DividerDrag {
    active: bool,
    orientation: Orientation, // Horizontal or Vertical
    adjacent_splits: (usize, usize), // keys of the two splits
    start_pos: (usize, usize),
}

3. Mouse event handling (~80 lines in application.rs)

• MouseInput (line 877): Start drag if clicking on divider
• CursorMoved (line 1011): If dragging, calculate delta and call existing move_divider_*
• On release: End drag state

4. Cursor icon changes (~10 lines)

• Set CursorIcon::RowResize when hovering horizontal dividers
• Set CursorIcon::ColResize when hovering vertical dividers

Key Insight

The resize logic already exists - move_divider_up/down/left/right functions handle all the complex tree manipulation, dimension updates, and terminal resize notifications. This feature is essentially just connecting mouse drag events to those existing functions.

Estimated Effort

Medium difficulty - probably 2-3 days for someone familiar with the codebase.

Happy to help with a PR if there's interest!

[raphamorim]

Sorry late reply, this should be fixed once #1335 is merged