!Develop
!Release

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

!A GIF showing how to split a polygon

Install

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

or use CDN:

`html

`

Usage

`js
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.

$3

Splitting polygons are done using the polygon-splitter package. which is pretty nit but has some issues and quirks. if you specify a lineWidth option other than zero (0) another algorithm is used which doesn't have does 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.

$3

`diff

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