Canvas ‒ A Smart Contracts Parachain

⚠️ Note: Canvas was moved into the Cumulus repo. Please check there for the current version.

This is a node implementation of Canvas, a Substrate parachain for smart contracts.

If you have any questions, feel free to talk to us on Element or on Discord (in the ink_smart-contracts channel).

Developing Smart Contracts for Canvas

This node is based on the cumulus/parachain-template, which we configured to use Substrate's smart contracts module ‒ the contracts pallet. This contracts pallet takes smart contracts as WebAssembly blobs and defines an API for everything a smart contract needs (storage access, …). As long as a programming language compiles to WebAssembly and there exists an implementation of this API in it, you can write a smart contract for this pallet ‒ and thus for Canvas ‒ in that language.

This is a list of languages you can currently choose from:

• Parity's ink! for Rust
• ask! for Assembly Script
• The Solang compiler for Solidity

There are also different user interfaces and command-line tools you can use to deploy or interact with contracts:

• Canvas UI
• polkadot-js

If you are looking for a quickstart, we can recommend ink!'s Guided Tutorial for Beginners.

Rococo Deployment

We have a live deployment of the Canvas parachain on Rococo ‒ a testnet for Polkadot and Kusama parachains. You can interact with the network through Polkadot JS Apps, click here for a direct link to Canvas.

The Canvas parachain uses the Rococo relay chain's native token (ROC) instead of having its own token. Due to this you'll need ROC in order to deploy contracts on Canvas.

As a first step, you should create an account. See here for a detailed guide.

As a second step, you have to get ROC testnet tokens through the Rococo Faucet. This is a chat room in which you need to write:

!drip YOUR_SS_58_ADDRESS:1002

The number 1002 is the parachain id of Canvas on Rococo, by supplying it the faucet will teleport ROC tokens directly to your account on the parachain.

If everything worked out, the teleported ROC tokens will show up under the "Accounts" tab for Canvas.

Once you have ROC on Canvas you can deploy a contract as you would normally. If you're unsure about this, our guided tutorial will clarify that for you in no time.

Run it Locally

Installation

You need to have executables of both Polkadot and Canvas.

Binary releases can be found here: Polkadot releases, Canvas releases.

Alternatively you can install (or build) the projects yourself:

• cargo install --git https://github.com/paritytech/polkadot.git --force --locked
• cargo install --git https://github.com/paritytech/canvas.git --force --locked

The --locked flag makes the installation (or build) use the same versions as the Cargo.lock in those repositories ‒ ensuring that the last known-to-work version of the dependencies is used.

Launching

Starting this project is best done using the polkadot-launch tool ‒ it starts Polkadot and registers the Canvas parachain on it automatically.

To use polkadot-launch you must ensure that you're using Node.js v14.x or newer. If you're on macOS, you must also ensure that your machine's firewall is disabled. You can do this by going to "System Preferences" > "Security & Privacy" > "Firewall" and ensuring that it's off.

Now that you have the prerequisites:

1. Install it with yarn global add polkadot-launch or npm i polkadot-launch -g
2. Check that the paths in polkadot-launch/config.json point to the polkadot and canvas executables
3. Launch the network with polkadot-launch polkadot-launch/config.json

At this point you should be able to use Polkadot JS Apps to connect to the Polkadot relay chain nodes as well as the Canvas collator.

Building from source

Follow the official installation steps to set up all Substrate prerequisites.

Afterwards you can install this node via

git clone https://github.com/paritytech/canvas.git
cd canvas/
cargo build --release --locked 

Substrate Compatibility

The latest confirmed working Substrate commit which will then be used is 3aecef7ee350db9cf53369481ebd1cee26ecc7ff.

Unstable Features

If you're the type of person that likes to drink your soup before it cools, you might also be wondering about how to activate unstable pallet-contracts features. To do this you can run the previous installation command with the following flag: --features contracts-unstable-interface.