mapbox-gl-draw-split-polygon-mode

A custom mode for MapboxGL-Draw to split polygons based on a drawn lineString.

Check mapbox-gl-draw-split-line-mode For splitting lineStrings.

DEMO

Install

npm install mapbox-gl-draw-split-polygon-mode

or use CDN:

<script src="https://unpkg.com/mapbox-gl-draw-split-polygon-mode"></script>

Usage

import mapboxGl from "mapbox-gl";
import MapboxDraw from "@mapbox/mapbox-gl-draw";
import defaultDrawStyle from "@mapbox/mapbox-gl-draw/src/lib/theme.js";

import SplitPolygonMode, {
  drawStyles as splitPolygonDrawStyles,
} from "mapbox-gl-draw-split-polygon-mode";

const map = new mapboxgl.Map({
  container: "map",
  center: [-91.874, 42.76],
  zoom: 12,
});

draw = new MapboxDraw({
  userProperties: true,
  displayControlsDefault: false,
  modes: {
    ...SplitPolygonMode(MapboxDraw.modes),
  },
  styles: [...splitPolygonDrawStyles(defaultDrawStyle)],
  userProperties: true,
});

map.addControl(draw);

/// Activate the mode
draw.changeMode("split_polygon");

/// you can modify the behavior using these options:
draw.changeMode(
  "split_polygon",
  /** Default option values: */
  {
    highlightColor: "#222",
    lineWidth: 0,
    lineWidthUnit: "kilometers",
  }
);

The syntax used here is because mapbox-gl-draw-split-polygon-mode needs to modify the modes object and also the styles object passed to the mapbox-gl-draw. the reason is this package uses mapbox-gl-draw-passing-mode underneath (and adds this to modes object) and needs to modify the styles to show the selected feature.

also, take a look at the example in the demo directory. in this example mapbox-gl-draw-select-mode is used so users can select feature after clicking in the split icon in the toolbar and get a highlighting when hover each map feature.

Notes

Splitting polygons are done using the polygon-splitter package. which is pretty neat but has some issues and quirks. if you specify a lineWidth option other than zero (0) another algorithm is used which doesn't have those issues but creates a spacing between features so they can no longer become union.

Also, There is an issue in mapbox-gl-draw which causes multi-features to have the same properties object and therefor if you uncombine a multi-feature and try to split one of the pieces the whole multi-feature gets highlighted as the selected feature.

Upgrade from version 1

import mapboxGl from 'mapbox-gl';
import MapboxDraw from '@mapbox/mapbox-gl-draw';
+ import defaultDrawStyle from "https://unpkg.com/@mapbox/mapbox-gl-draw@1.3.0/src/lib/theme.js";

- import SplitPolygonMode from 'mapbox-gl-draw-split-polygon-mode';
- import mapboxGlDrawPassingMode from 'mapbox-gl-draw-passing-mode';

+ import SplitPolygonMode, {
+   drawStyles as splitPolygonDrawStyles,
+ } from "mapbox-gl-draw-split-polygon-mode";


draw = new MapboxDraw({
- modes: Object.assign(MapboxDraw.modes, {
-   splitPolygonMode: SplitPolygonMode,
-   passing_mode_line_string: mapboxGlDrawPassingMode(
-     MapboxDraw.modes.draw_line_string
-   ),
- }),
+ modes: {
+   ...SplitPolygonMode(MapboxDraw.modes),
+ },

+ styles: [...splitPolygonDrawStyles(defaultDrawStyle)],
  userProperties: true,
});

- draw.changeMode('splitPolygonMode');
+ draw.changeMode("split_polygon");

Development

use the command npm run dev. it will take advantage of vite to watch, serve, and build the package and the demo.

Acknowledgement

The main function responsible for cutting the features is from: https://gis.stackexchange.com/a/344277/145409

License

MIT © ReyhaneMasumi