Building Desktop Apps With Deno

Aug 13, 2023

Deno 1.36 brings a small, but powerful, upgrade to deno compile.

A new --no-terminal flag can now be used with deno compile. If the compiled binary is run on Windows, this flag will prevent the terminal window from being opened. — Deno can now compile executables on Windows that link to the Windows subsystem.

Now, developers can compile native binaries on Windows that don’t depend on a console window! This flag changes the WIndows subsystem your application links to, giving access to libraries specifically built for desktop, an air of legitimacy, and a more-private stdout.

What are Windows Subsystems?

According to René Nyffenegger, Windows consists of multiple subsystems that all expose subsets of a base Windows executive system service. If you’re a developer on Windows, chances are you’ve heard of a few.

Native–used for device drivers and native Windows processes
Windows (GUI)
Console
OS2 CUI
Posix CUI
Native 9x driver
Windows CE
EFI application
EFI driver with boot services
EFI driver with run-time services
EFI ROM image
XBOX
Windows boot application

Each subsystem gives your application access to specific libraries and access to system resources. Since console and GUI (Graphic User Interface) apps are inherently different, linking the appropriate subsystem is crucial when building your executable. According to Nyffenegger, linking to the Windows subsystem not only doesn’t spawn a console window, but provides your application access to libraries for detecting mouse movement, putting multiple windows side-by-side, and other desktop-specific tasks.

I want to show you how you can build a small desktop app with Deno, and the effects of this new compiler flag.

Building a Desktop App with Deno

import { Webview } from "https://deno.land/x/webview@0.7.6/mod.ts";

const html = `
  <html>
  <body>
    <h1>Hello from deno v${Deno.version.deno}</h1>
  </body>
  </html>
`;

const webview = new Webview();

webview.navigate(`data:text/html,${encodeURIComponent(html)}`);
webview.run();

Above is a simple script for launching a desktop app with Deno. You can save the following deno.jsonc to copy the various build options I’d like to demonstrate.

{
  "tasks": {
    "build-dev": "deno compile -Ar --unstable --allow-ffi main.ts",
    "build": "deno compile -Ar --no-terminal --unstable --allow-ffi main.ts",
    "dev": "deno run -Ar --unstable --allow-ffi --watch main.ts",
    "start": "deno run -Ar --unstable --allow-ffi main.ts"
  }
}

Running any of these commands will result in the following window.

Running the build scripts will result in a static binary. It’s not perfect, and you can’t modify the icon or other resources without third-party tools, but it’s a start of a Deno desktop ecosystem to rival Electron. With deno compile and FFI, desktop apps with Deno are cross-compliable and as capable as any app utilizing the OS’s native web view.

Ham Typed

Discussion about this post