Exercise 1: First Terra Draw Implementation

Let's create a basic Terra Draw setup with MapLibre GL JS. Update your src/routes/+page.svelte:

Basic TerraDraw setup

Firstly, we can setup Terra Draw without any UI interaction.

Open +page.svelte, add the following codes in the <script> tag section just under the other imports.

import { TerraDraw, TerraDrawRectangleMode } from 'terra-draw'
import { TerraDrawMapLibreGLAdapter } from 'terra-draw-maplibre-gl-adapter';

let draw: TerraDraw | undefined;

Then update the existing onMount() method to also intialize the TerraDraw library after the MapLibre map is created.

onMount(() => {
    // Add codes in the last section of onMount after the map initialization

    draw = new TerraDraw({
        // Using the MapLibre Adapter
        adapter: new TerraDrawMapLibreGLAdapter({ map }),

        // Add the Rectangle Mode
        modes: [new TerraDrawRectangleMode()],
    });

    // Have to wait maplibre to load map style before starting to draw
    map.once('load', () => {
        // Start drawing
        draw.start();
        draw.setMode("rectangle");
    })
})

You can draw a rectangle polygon on the map like below.

Figure 1: Terra Draw Rectangle Mode without UI interactions

Testing Your Implementation

1. Save your changes and the Vite development server should automatically reload
2. Open your browser to http://localhost:5173
3. Test drawing - click on the map to create rectangles

Example code

The above example code is available at example/without-ui branch.

What's Next?

Now that you have a working Terra Draw implementation without UI, let's add more Terra Draw modes with UI buttons.