Towards Juno 0.7

Quite a few changes are coming with Juno 0.7 (which will be compatible with the upcoming Julia 0.7).

Workspace Pane

The workspace pane is now a bit faster and there are a few quality of life improvements:

  • Workspace items can be fuzzy-filtered by name.
  • There’s buttons for selecting the current module and refreshing the workspace pane.
  • Rendering performance is better now – displaying all of Base doesn’t nearly take as long and doesn’t slow the rest of Atom to a crawl.


Plot Pane

Most of these changes are relevant to package authors, but the UI has seen a few improvements as well.

Previous versions of Juno provided a history of plots, as long as those were images and nothing else. This is now also the case for interactive plots.

The plot pane picks up show methods with image/xxx mimetypes, so there’s no need to depend on Juno.jl and define custom render methods any more. These images are displayed with basic pan and zoom capabilities:

basic plot

It’s also possible to provide a show method for the application/juno+plotpane mime type, which allows rendering of arbitrary HTML in a <webview> element.

rich plot

Note that you can use arbitrary data URLs in your custom show method; if whatever is printed to io does not start with data: then Juno falls back to data:text/html (which is what happens in the above screenshot).

Since it is possible to exectue arbitrary JS code in a webview a package can set up communication channels between Julia and the plot pane in whatever way it’s authors want. The transition to this new display system also resulted in the removal of Blink.jl from the Juno stack, which significantly improves load times at the cost of packages having to set up the aforementioned communication themselves.

All show methods whose return values end up in the plot pane are called with two (for now) custom IOContext keys:

  • :juno_plotsize is an Array of the plot pane’s current width/height in pixels. See Juno.plotsize for more info.
  • :juno_colors returns a Dict{String, UInt32} which contains a few named colors used by the current Atom syntax theme. See Juno.syntaxcolors for more info.

Progress Meters

The integrated progress display now makes use of the shiny new logging functionality in Base. This means that there’s no need to depend on Juno.jl anymore for getting a progress bar – it’s sufficicent to send a log message of an arbitrary level (though I’d recommend -1 or smaller so it’s not picked up by the default logger and spams the REPL) with a progress argument:

@logmsg -1 "making progress" progress=0.5 # or progress=NaN, or progress="done"

For convenience, Juno.jl does still expose progress and @progress, which work the same as in previous versions (but still use the debugging framework internally).

See here for additional docs (until those find their way into the official Juno docs).

Terminal Integration

Juno’s terminal integration has steadily gotten better as well – mostly due to improvements to improvements to the underlying xterm.js library:

  • Styling changes are applied to terminals instantly (no need to restart Atom when changing from a dark to a light theme).
  • Default colors are much more readable on light backgrounds. They’ll most likely be customizable in the near future.
  • A terminal’s tab title reflects what is going on in the terminal (as long as the shell sends the appropriate escape sequences, that is).
  • Link detection works even with wrapped lines.



TreeViews.jl provides a uniform API for defining, well, tree views. It also ships a renderer for the REPL, while Juno provides one for rich inline display. This makes it possible for package authors to drop any dependencies on the Juno stack and still get pretty rendering for their custom types:


The REPL renderer still needs a bit of work (and tests), but the actual API works pretty well already and is only 7 LoC plus documentation.

This package was inspired by Steven G. Johnson (@stevengj) in Juno.jl#91.


Unfortunately I didn’t yet make much progress on updating Traceur.jl to work on Julia 0.7 – mostly because ASTInterpreter2.jl is a rather complex package. I’m pretty confident I’ll make some progress on this during the next week though.