Canva Apps SDK starter kit

Welcome to the Apps SDK starter kit for Canva's app development platform. 🎉

This repo contains everything you need to get an app up and running in a matter of minutes, including a boilerplate project and lots of examples. The complete documentation for the platform is at canva.dev/docs/apps.

Note: The starter kit and documentation assumes some experience with TypeScript and React.

Requirements

Node.js v18 or v20.10.0
npm v9 or v10

Note: To make sure you're running the correct version of Node.js, we recommend using a version manager, such as nvm. The .nvmrc file in the root directory of this repo will ensure the correct version is used once you run nvm install.

Quick start

git clone git@github.com:canva-sdks/canva-apps-sdk-starter-kit.git
cd canva-apps-sdk-starter-kit
npm install

Using the boilerplate

Step 1: Start the local development server

The src directory contains the boilerplate of an app.

To start the boilerplate's development server, run the following command:

npm start

The server becomes available at http://localhost:8080.

The app's source code is in the src/app.tsx file.

Step 2: Preview the app

The local development server only exposes a JavaScript bundle, so you can't preview an app by visiting http://localhost:8080. You can only preview an app via the Canva editor.

To preview an app:

Create an app via the Developer Portal.
Select App source > Development URL.
In the Development URL field, enter the URL of the development server.
Click Preview. This opens the Canva editor (and the app) in a new tab.
Click Open. (This screen only appears when using an app for the first time.)

The app will appear in the side panel.

(Optional) Step 3: Enable Hot Module Replacement

By default, every time you make a change to an app, you have to reload the entire app to see the results of those changes. If you enable Hot Module Replacement (HMR), changes will be reflected without a full reload, which significantly speeds up the development loop.

Note: HMR does not work while running the development server in a Docker container.

To enable HMR:

Navigate to an app via the Your apps.
Select Configure your app.
Copy the value from the App origin field. This value is unique to each app and cannot be customized.
In the starter kit's directory, open the .env file.
Set the CANVA_APP_ORIGIN environment variable to the value copied from the App origin field:
```
CANVA_APP_ORIGIN=# YOUR APP ORIGIN GOES HERE
```
Set the CANVA_HMR_ENABLED environment variable to true:
```
CANVA_HMR_ENABLED=true
```
Restart the local development server.
Reload the app manually to ensure that HMR takes effect.

Previewing apps in Safari

By default, the development server is not HTTPS-enabled. This is convenient, as there's no need for a security certificate, but it prevents apps from being previewed in Safari.

Why Safari requires the development server to be HTTPS-enabled?

Canva itself is served via HTTPS and most browsers prevent HTTPS pages from loading scripts via non-HTTPS connections. Chrome and Firefox make exceptions for local servers, such as localhost, but Safari does not, so if you're using Safari, the development server must be HTTPS-enabled.

To learn more, see Loading mixed-content resources.

To preview apps in Safari:

Start the development server with HTTPS enabled:

# Run the main app
npm start --use-https

# Run an example
npm start <example-name> --use-https

Navigate to https://localhost:8080.
Bypass the invalid security certificate warning:
Click Show details.
Click Visit website.
In the Developer Portal, set the app's Development URL to https://localhost:8080.

You need to bypass the invalid security certificate warning every time you start the local server. A similar warning will appear in other browsers (and will need to be bypassed) whenever HTTPS is enabled.

Running an example's backend

Some examples have a backend. This backend is defined in the example's backend/server.ts file, automatically starts when the npm start command is run, and becomes available at http://localhost:3001.

To run examples that have a backend:

Navigate to the Your apps page.
Copy the ID of an app from the App ID column in the apps table.

In the starter kit's .env file, set CANVA_APP_ID to the ID of the app.

For example:

CANVA_APP_ID=AABBccddeeff
CANVA_APP_ORIGIN=#
CANVA_BACKEND_PORT=3001
CANVA_FRONTEND_PORT=8080
CANVA_BACKEND_HOST=http://localhost:3001
CANVA_HMR_ENABLED=FALSE

Start the example:
```
npm start fetch
```

The ID of the app must be explicitly defined because it's required to send and verify HTTP requests. If you don't set up the ID in the .env file, an error will be thrown when attempting to run the example.

Customizing the backend host

If your app has a backend, the URL of the server likely depends on whether it's a development or production build. For example, during development, the backend is probably running on a localhost URL, but once the app's in production, the backend needs to be exposed to the internet.

To more easily customize the URL of the server:

Open the .env file in the text editor of your choice.
Set the CANVA_BACKEND_HOST environment variable to the URL of the server.
When sending a request, use BACKEND_HOST as the base URL:
```
const response = await fetch(`${BACKEND_HOST}/custom-route`);
```
Note: BACKEND_HOST is a global constant that contains the value of the CANVA_BACKEND_HOST environment variable. The variable is made available to the app via webpack and does not need to be imported.
Before bundling the app for production, update CANVA_BACKEND_HOST to point to the production backend.

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