How to draw lines

This sample demonstrates how to create a plugin that adds colored lines to the user's document.

Prerequisites

• Basic knowledge of HTML, CSS, and JavaScript
• Quick Start Tutorial
• Debugging Tutorial

Development Steps

1. Prepare your plugin scaffold

First, edit the manifest file for the plugin you created in our Quick Start Tutorial.

Replace the uiEntryPoints field of the manifest with the following:

"uiEntryPoints": [
    {
        "type": "menu",
        "label": "Create lines",
        "commandId": "createLinesCommand"
    }
]

If you're curious about what each entry means, see the manifest documentation, where you can also learn about all manifest requirements for a plugin to be published in the XD Plugin Manager.

Then, update your main.js file, mapping the manifest's commandId to a handler function.

Replace the content of your main.js file with the following code:

function createLinesCommand(selection) {
    // The body of this function is added later
}

module.exports = {
    commands: {
        createLinesCommand
    }
};

The remaining steps in this tutorial describe additional edits to the main.js file.

2. Require in XD API dependencies

For this tutorial, we just need access to two XD scenegraph classes and one XD module.

Add the following lines to the top of your main.js file:

// Add this to the top of your main.js file
const { Line, Color } = require("scenegraph");
const commands = require("commands");

Now the Line and Color classes and commands module are required in and ready to be used.

3. Create a helper function

Our plugin is going to assigning random colors to the lines we create!

Add the lines of code below to your file:

function randomColor() {
    const hexValues = ['00', '33', '66', '99', 'CC', 'FF'];
    const color = "#" + Array.from({ length: 3 }, _ => hexValues[Math.floor(Math.random() * hexValues.length)]).join("");
    return color;
}

This function returns a web-friendly color hex value (e.g., `"#FFFFFF"). This is just straight-up JavaScript; there's nothing specific to XD plugin APIs to cover here.

4. Create line data

In this step, we're going to add a little more plain-old JavaScript. This time we'll add a data structure that will set us up to draw lines with the XD plugin API in the next step.

Add this code to your file:

const lineData = [
    { startX: 100, startY: 110, endX: 210, endY: 233 },
    { startX: 210, startY: 233, endX: 320, endY: 156 },
    { startX: 320, startY: 156, endX: 400, endY: 300 },
    { startX: 400, startY: 300, endX: 500, endY: 120 }
]

A couple of things to note:

• In this example, the each line's startX and startY matches the former line's endX and endY. This ensures lines are connected to each other. But they don't have to connect; feel free to modifiy the data as you wish!
• The data structure here is important to note:
  • lineData is an array. This gives us a way to store coordinates for multiple lines. We'll loop over this array in the next step.
  • The array contains multiple objects that will be passed, one at a time, to the Line API.
  • Since we're drawing lines, each object has a start and end coordinates for X and Y.

5. Create the main function

In this step, we'll build out the main function, createLinesCommand, that we added in the first step. Each of the numbered comments are explained below the code:

function createLinesCommand(selection) {            // [1]

    let lines = [];                                 // [2]

    lineData.forEach(data => {                      // [3]
        const line = new Line();                    // [4.i]

        line.setStartEnd(                           // [4.ii]
            data.startX,
            data.startY,
            data.endX,
            data.endY
        );

        line.strokeEnabled = true;                  // [4.iii]
        line.stroke = new Color(randomColor());     // [4.iv]
        line.strokeWidth = 3;                       // [4.v]

        lines.push(line);                           // [4.vi]

        selection.editContext.addChild(line)        // [4.vii]
    });

    selection.items = lines;                        // [5]
    commands.group();                               // [6]
}

1. This function only needs the first contextual argument, selection, which gives access to the selection object inside XD.
2. Create an empty array to contain all the Line objects we'll create. This array will be used in a later step.
3. Loop over the lineData array, getting an individual data object each time through the loop.
4. For each data object:
   1. Create a new instance of Line.
   2. Use the Line object's setter, .setStartEnd, to set the line data from our data object.
   3. Set the strokeEnabled property to true in order to draw a stroke for the line.
   4. Set the stroke color using the randomColor helper function.
   5. Set the width of the stroke using strokeWidth property.
   6. Append the line object into the lines array.
   7. Insert the line into the edit context using the selection.editContext.addChild method. This step adds the line to the document's scenegraph.
5. Now that all of the Line objects have been added to the scenegraph, set the document's current selection to be those Line objects.
6. Use the group command to combine all of the currently-selected objects (the Line objects) into a single group object.

6. Run the plugin

After saving all of your changes, reload the plugin in XD and run it. The result should be similar to the following:

Next Steps

Want to expand on what you learned here? Have a look at these references to see options for customizing this sample plugin:

• Line
• Color
• Commands

Ready to explore further? Take a look at our other resources:

• Tutorials
• Sample code repos