The GDK Broadway backend provides support for displaying GTK applications in a web browser, using HTML5 and web sockets.

Broadway was written as an experiment and is not the most actively developed backend. It supports the features that were required of GDK backends in GTK 4.0, but may not be up-to-date with the latest developments.

Using GTK with Broadway

To run your application under Broadway, first run the broadway server, gtk-broadwayd, that ships with GTK:

gtk4-broadwayd :5

The server expects the colon-prefixed display number as a commandline argument.

Then point your web browser at http://127.0.0.1:8085.

Once the Broadway server is running, you can start your applications like this:

GDK_BACKEND=broadway BROADWAY_DISPLAY=:5 gtk4-demo

Multiple applications can be presented in the same web browser window.

Broadway-specific environment variables

BROADWAY_DISPLAY

Specifies the Broadway display number. The default display is 0.

The display number determines the port to use when connecting to a Broadway application via the following formula:

port = 8080 + display