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.

#Row-selection checkbox column

Separate from the anchor/focus selection above, rs-grid supports an opt-in row-selection checkbox column, with a per-row checkbox and a tri-state header checkbox ("select all"). Unlike the row-number gutter, it is not a fixed/pinned band — it's the first column of the scrollable region, so it scrolls away with the data on horizontal scroll, just like a regular column.

let model = GridModelBuilder::new(columns, data)
    .row_selection_checkboxes(true)
    .build();

Checked state is tracked separately from SelectionState, by physical row id (not display position), so it survives sorting and filtering:

// Toggle a single row (by logical/display index)
grid_state.apply(GridCommand::ToggleRowChecked(3));

// Toggle the header checkbox — checks or unchecks every row
// currently passing the active filter (or every row, if unfiltered)
grid_state.apply(GridCommand::ToggleAllFilteredChecked);

// Show/hide the column at runtime
grid_state.apply(GridCommand::SetShowCheckboxColumn(true));

// Change its width — the checkbox stays centered, so this also
// controls the visual margin around it
grid_state.apply(GridCommand::SetCheckboxColumnWidth(60.0));

CheckboxTriState (Checked / Unchecked / Indeterminate) describes the header checkbox's state — Indeterminate when some but not all rows in scope are checked. Clicking an indeterminate header checks every row in scope rather than unchecking them.

On GridCanvas (the browser integration):