Frame regions and insets

Fit a selection

import JAPAN from "@johnmorrisdotca/chizu/divisions/jp";
import { focusRegionFit, regionCentre, wholeMapBox, boxToViewBox } from "@johnmorrisdotca/chizu";
console.log(focusRegionFit(JAPAN,"47")?.zoom,regionCentre(JAPAN,"47"));
console.log(boxToViewBox(wholeMapBox(JAPAN)),focusRegionFit(JAPAN,"unknown"));

3 { x: 315, y: 560 }
0 0 1000 1133 null

Okinawa and other outlying islands are drawn in inset boxes. The framing helpers follow where a region is drawn, so a selected inset stays in view. focusRegionFit and regionCentre return null for a null or unknown region code. focusBox and zoomToFit fall back to the whole map when nothing matches; that is a useful reset, not evidence that the input code matched.

Pan a wrapping world

MAP_ZOOM_LEVELS is a ten-step ladder. stepMapZoom clamps at its ends. The world’s east/west edge wraps, so zoomBox can overhang its horizontal seam; wrapOffsets describes the copies needed for the window. Country maps are clamped by default. Geographic longitude/latitude uses projectPoint and unprojectPoint; inset positions describe the drawing instead.

The detailed framing reference retains the geometry and fit examples.