Zenity as a simple GUI

There has been a lot of discussion about GUIs and it will be incredibly cool to have Boyd Multerer’s Scenic framwork when he releases it. In the interim (or perhaps for simpler tasks), I’ve discovered that Zenity is actually not half bad to use. Not pretty, but functional. Although originally for Linux, a Mac version available from MacPorts. Not having found any mention of it by searching for Forums, I wanted to share in case anyone else might find it useful.

By “discovered”, I mean that I found Andrei Clinciu’s great post at https://andreiclinciu.net/article/zenity-gui-for-elixir/ and the links therein. Just to give a flavor, here is an example that takes a list of keywords, ensures they are unique and in alphabetic order, presents the list to the user as a check list and then returns the checked words as a list.

My example is more brute force that Andrei’s because some of the arguments to be sent required quotes and I was having a terrible time getting that to work (I am very much a beginner at Elixir and not primarily a developer.)

The desired command to be sent is as follows:

/opt/local/bin/zenity --list --checklist --column "Delete?" --column "Keywords" --separator=":" "FALSE" "Cat" "FALSE" "Furry dog" "FALSE" "Horse" 2>/dev/null

which I built programmatically and then just passed to Port.open as a blob. Zenity sometimes emits an irritating GTK+ warning, which I’d chosen to sent to /dev/null for simplicity. Obviously, in real use, kw_input would come from some external source.

Even I can tell that the structure of this example is horrid, but I hope it illustrates the Zenity-specific aspects adequately. Sometimes it’s nice to just be able to kludge a shell command together for what you need.

Would love to hear of other alternatives, especially for low-complexity use cases like this.

Glenn

defmodule Zenity do
  @zenity "/opt/local/bin/zenity"

  def do_it do
    kw_input = ["Cat", "Furry Dog", "Cat", "Horse"]

    kw_for_cmd =
      kw_input
      |> MapSet.new()
      |> Enum.sort()
      |> Enum.flat_map(fn x -> [~s("FALSE"), ~s("#{x}")] end)
      |> Enum.join(" ")

    cmds =
      ~s(#{@zenity} --list --checklist --column "Delete?" --column "Keywords" --separator=":" #{kw_for_cmd} 2>/dev/null)

    exec(cmds)
  end

  defp exec(cmd) do
    port = Port.open({:spawn, cmd}, [:stream, :binary, :exit_status, :hide, :use_stdio])

    port
    |> handle_output
    |> listify
  end

  defp handle_output(port, data \\ "") do
    receive do
      {^port, {:data, data}} ->
        handle_output(port, data)

      {^port, {:exit_status, status}} ->
        {data, status}
    end
  end

  defp listify({_, 1}) do
    IO.puts("Operation cancelled")
  end

  defp listify({"", 0}) do
    IO.puts("Nothing selected")
  end

  defp listify({kw_list, 0}) do
    kw_list
    |> String.trim_trailing("\n")
    |> String.split(":")
  end

end

Zenity.do_it