Selection#

rs-grid uses an anchor/focus selection model. The anchor is where the selection started; the focus is where it currently ends. Shift-click extends the selection from the anchor to a new focus.

#SelectionState

SelectionState tracks two positions:

Each position can refer to a cell, a row, or a column. Mixed granularity (anchor on a cell, focus on a row) is not supported.

#Commands

// Select a single cell
grid_state.apply(GridCommand::SelectCell { row: 0, col: 2 });

// Extend selection (shift-click equivalent)
grid_state.apply(GridCommand::ExtendSelection { row: 5, col: 2 });

// Select an entire row
grid_state.apply(GridCommand::SelectRow { row: 3 });

// Select an entire column
grid_state.apply(GridCommand::SelectColumn { col: 1 });

// Clear selection
grid_state.apply(GridCommand::ClearSelection);

#Hit-testing

Given a pixel coordinate (x, y) relative to the canvas, hit-testing returns the cell under the cursor:

let hit = grid_state.hit_test(x, y);
// Returns Option<HitResult> with { row: u64, col: usize }

Hit-testing uses the same precomputed column offset array as the viewport, giving O(log n) performance. Row hit-testing is O(1) with uniform row height.

#Rendering the selection

SceneBuilder reads SelectionState and emits ScenePrimitive::Rect entries with the selection highlight color for every selected cell in the viewport.