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https://github.com/mhsattarian/mapbox-gl-draw-snap-mode

Custom mode for Mapbox GL Draw that adds snapping ability while drawing features.
https://github.com/mhsattarian/mapbox-gl-draw-snap-mode

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Custom mode for Mapbox GL Draw that adds snapping ability while drawing features.

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README

        

# Mapbox-GL Draw Snap Mode

[![npm](https://img.shields.io/npm/v/mapbox-gl-draw-snap-mode?color=green)](https://www.npmjs.com/package/mapbox-gl-draw-snap-mode)

Custom mode for [Mapbox GL Draw](https://github.com/mapbox/mapbox-gl-draw) that adds snapping ability while drawing features.
It provides options to show guiding lines, control snapping sensibility, and whether to snap to midpoints on each segment.

## Demo

See a full example in the docs folder, or check at the [**Demo**](https://mhsattarian.github.io/mapbox-gl-draw-snap-mode).

![a GIF showing usage demo](docs/demo.gif)

## Install

```shell
npm i mapbox-gl-draw-snap-mode
```

or use CDN:

```html

```

## Usage

```js
import {
SnapPolygonMode,
SnapPointMode,
SnapLineMode,
SnapModeDrawStyles,
SnapDirectSelect,
} from "mapbox-gl-draw-snap-mode";
// or global variable mapboxGlDrawSnapMode when using script tag

const draw = new MapboxDraw({
modes: {
...MapboxDraw.modes,
draw_point: SnapPointMode,
draw_polygon: SnapPolygonMode,
draw_line_string: SnapLineMode,
direct_select: SnapDirectSelect,
},
// Styling guides
styles: SnapModeDrawStyles,
userProperties: true,
// Config snapping features
snap: true,
snapOptions: {
snapPx: 15, // defaults to 15
snapToMidPoints: true, // defaults to false
snapVertexPriorityDistance: 0.0025, // defaults to 1.25
},
guides: false,
});

map.addControl(draw, "top-right");

draw.changeMode("draw_polygon");
```

### options

#### `snapPx`

The min distnace (in pixels) where snapping to the line/segments would take effect.

#### `snapToMidPoints`

Controls whether to snap to line/segments midpoints (an imaginary point in the middle of each segment) or not.

#### `snapVertexPriorityDistance`

The min distance (in Kilometers) from each vertex, where snapping to that vertex would take priority over snapping to line/segments.

#### `overlap`

Defaults to `true`. When creating polygons, if `false`, will use `turf.difference` on all overlapping polygons to create a polygon that does not overlap existing ones.

### Changing settings

Changing settings would take effect while snapping imidiately, so you can control snapping behaivior using `draw.options.snap`, like so:

```js
// turn snapping off
draw.options.snap = false;

// and back on
draw.options.snap = true;
```

> Snapping can also be disabled holding `Alt (Option)` key.

You can also create a [custom mapbox-gl draw toolbar](https://github.com/mapbox/mapbox-gl-draw/issues/874#issuecomment-470591089) to control this, take a look at the [example in the `docs` directory](/docs/index.html#L122).

## Developing and testing

Install dependencies, start the dev server:

```bash
npm install
npm start
```

to preview, change `docs/index.html` as so:

```diff
-
+
```

> Remember to revert this change before `git push`.

## Publishing

To GitHub and NPM:

```
npm version (major|minor|patch)
git push --tags
git push
npm publish
```

## Acknowledgement

This project is heavily inspired by [this work](https://github.com/mapbox/mapbox-gl-draw/issues/865) by [@davidgilbertson](https://github.com/davidgilbertson) and [`leaflet-geoman` project](https://github.com/geoman-io/leaflet-geoman).