Viewport#

The viewport is the window into the grid data. Only cells that intersect the visible area are passed to the renderer, regardless of the total row or column count.

#ViewportState

ViewportState lives inside GridState and tracks four values:

Pixel values are in CSS pixels. The renderer applies the device pixel ratio (DPR) multiplier when issuing draw calls.

#Visible columns

Column offsets are precomputed and stored in a prefix-sum array. Given scroll_x and width, the first and last visible column are found with a binary search — O(log n) regardless of column count.

The same approach applies to rows using the row height and scroll_y.

#Row count limits

Row indices use u64. The practical limit with f64 scroll offsets is ~9 x 10^14 rows before floating-point precision degrades.

#Scrolling

Send a scroll command to update the viewport:

grid_state.apply(GridCommand::ScrollTo {
    x: new_scroll_x,
    y: new_scroll_y,
});

The web integration layer (rs-grid-web) translates browser wheel events into scroll commands automatically. DPR and pixel rounding are handled internally.

#Resize

When the canvas is resized (window resize, container resize), update the viewport dimensions:

grid_state.apply(GridCommand::Resize {
    width: new_width,
    height: new_height,
});

The Leptos component observes a ResizeObserver and dispatches this command automatically.