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Using Pushover with Common Lisp

Pushover is a small app that let’s you push notifications to your phone in a very simple and elegant way. It’s available on both Android and iOS.

It’s great for all those small things that you’d otherwise feel too lazy to write a proper app for. I’ve used to for receiving notifications of when a build breaks, when people push commit to a certain repository and a bunch of other stuff.

(defparameter *pushover-url*

(defun pushover (message user token)
  "Returns 200 if everything went well,
   4xx if your input was invalid and
   500 if pushover.net is having problems"

  (let ((content-type
        (content (concatenate 'string
                              "message=" message
                              "&user="   user
                              "&token="  token)))
    (car (trivial-http:http-post
          *pushover-url* content-type content))))

As you can see from this example that I hacked together in CL, they’ve got a great API that’s super easy to use.

A roadmap for Shoes 4

A couple of weeks ago we posted a roadmap for Shoes 4 on the shoes-mailing list. I figured that it might be a good idea to post it here as well, since everyone isn’t subscribed to the mailing list and it might be a good idea for crawling purposes.

  • 4.0.0-pre1

    • run all examples in the example folder
  • 4.0.0-pre2

    • update the built-in manual
  • 4.0.0

    • upload the gem to RubyGems.org
    • redesign the Shoes website
    • packaging support
  • 4.0.1 (or 4.0.2)

    • be able to run Hackety Hack

Visual programming and why it sucks

A favourite subject for Ph.D. dissertations in software engineering is graphical, or visual programming. […] Nothing even convincing, much less exciting, has yet emerged from such efforts. I am persuaded that nothing will.

Frederick Brooks The Mythical Man Month

tl;dr: It gets messy. Fast.

Not too long ago I was having lunch with a friend I hadn’t talked to in a while. He had been to a conference organized by the game development industry where he saw a company demo a visual programming tool for the Unity engine (I’m not 100% sure, but I think it was PlayMaker).

The tool allowed you to instead of having to painstakingly type out commands, simply drag a couple of boxes on a workspace, select some options and draw arrows between them. It’s worked very much like schematic tools used for programming FPGAs.

On the surface the idea seemed great and the demos were more than impressive. Instead of having to remember syntax and method names, you could simply browse through a list and find what you were looking for. Yet, I was still not convinced.

The basic problem is, as Frederick Brooks brings up in his book, that flowcharts are a very poor abstraction of software structure. They work fine for simple, trivial programs like the demos that the company showed my friend. But let’s be honest: very little software in the real world outside of a spreadsheet document is actually that simple.

Visual programming reminds me of this time when we designed and built a 4-bit computer out of nothing but NAND-gates in university. We started out with a few full adders and the schematic looking nice and clean. But as we kept on adding functionality the number boxes and the number of wires connecting the different boxes together grew to a horrifying amount. What was once a simple schematic had turned into a horrible abomination that was impossible, even for its creators, to get a grasp of. I know that it can be hard to return to code that you’ve written after a few months of not looking at it; but a schematic? That’s something I wouldn’t even consider doing.

The fact that text works better in the long run is something people discovered a long time ago in other fields. That’s why VHDL Verilog is more popular than the schematic based approaches I mentioned before. Graphical stuff at the abstraction level that we have to deal with in software just gets too messy too fast. Modularization does solve some of the problems, but it’s too hard to do right and it’s too hard to clean up after someone has done it wrong.

So is visual programming all bad? Well, no. It does bring with it a few benefits.

As I mentioned before, not having a syntax or an API that you have to memorize is great. Especially for people that aren’t programmers or interested in programming. It also works well when you’ve got good modules that make your program seem trivial. I suspect that for the sort of games/applications that PlayMaker’s users are creating, it works more than just well. And from what I understand, PlayMaker also supports a hybrid approach where you can still write the code and interface it with the visual code. Perhaps this brings out the best of both worlds?

Contributing to Shoes4

Let me start off by saying that if you’re unfamiliar with the project, you should first have a look at Tobias Pfeiffer’s presentation. Shoes is a great little cross-platform GUI library/DSL for Ruby and Tobias does a great job of explaining what’s new in Shoes 4 and why you should care.

But before we start, let me just show you an example of why Shoes rocks. Here are two versions of the code for displaying a window with the text “Hello, world!”. The first is written in Java and the second in Ruby using Shoes.


import org.eclipse.swt.SWT;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Shell;
import org.eclipse.swt.widgets.Text;

public class SWTHelloWorld {
  public static void main (String [] args) {
    Display display = new Display ();
    Shell shell = new Shell(display);
    Text helloWorldTest = new Text(shell, SWT.NONE);
    helloWorldTest.setText("Hello, world!");
    shell.open ();
    while (!shell.isDisposed ()) {
      if (!display.readAndDispatch ()) display.sleep ();
      display.dispose ();
Shoes 4/Ruby

Shoes.app do
  para "Hello, world!"


In the following blog post I’m going to walk you through implementing a style for the list box element and by the end of it you should have the knowledge necessary to submit your first Shoes commit.

I’m going to assume that you have some familiarity with JRuby and RSpec, but even if you don’t most of the code is pretty easy to get a grasp of.

Please note that the code presented below isn’t written to be particularly eloquent, but to be easy for a newcomer to the project to understand.

Code Tour

The first thing you need do is head on over to the project’s Github repository and create your own fork. If you’re unfamiliar with git or Github, there are already excellent tutorials out there that will help get you started.

Basically there are just two folders that you need to worry about; specand lib. spec contains the Shoes-spec. In it there are two folders, shoes and swt_shoes. The first folder contains the spec for the DSL part of Shoes and should be somewhat language agnostic while the second folder contains very implementation specific tests. lib has two subfolders that function in the same manner. The language agnostic stuff is in lib/shoes, while the swt-stuff is in lib/shoes/swt.

The user’s program calls functions in lib/shoes/element_methods.rb, which in turn call the different classes found in lib/shoes that load the actual backend classes (right now in lib/shoes/swt/ or mock) by calling Shoes.configuration.backend. Shoes.configuration can be found in lib/shoes/configuration.rb and is responsible for loading the correct backend.

There’s a more info about the structure in the project wiki.

Implementing your first feature

We’re going to start off by implementing the :choose style for the list box. It is described more closely in the manual. When we’re done, the following code will create a window with a simple list box and the item “cat” pre-chosen.

Shoes.app do
  para "Here's a list box:"
  list_box :items => ["cat", "hat"], :choose => "cat"

The first thing we will do is open up spec/swt/list_box_spec.rb and add the following lines.

The manual states that the list box is supposed to have a method called choose that “Selects the option in the list box that matches the string given by item”. Let’s start off by implementing that feature. First, let’s make sure that list box actually has a method with that name.

  it { should respond_to :choose }

Now type in rake spec and make sure that the test fails. Did it fail? Good! Now, let’s actually create choose.


def choose(item)


Run the spec again and make sure that it passes. Please note that our choose-method doesn’t actually do anything yet. Let’s continue defining what we expect from it in the spec.


it "should call @gui.choose when we choose something" do
           should_receive(:choose).with "Wine"
  subject.choose "Wine"

def choose(item)
  @gui.choose item

All we’ve done now is basically just made sure that shoes/list_box calls @gui.choose, when something calls its choose-method. In the future, we might want this method to check and make sure that item actually is a part of items. I leave this as an exercise to the reader. ;–)

Now let’s open up the swt part of the spec and finish what we started. Judging from the javadoc what we need to do is call setText on the SWT combo-object (@real). So basically we want to make sure that we call @real.text=value (thanks to JRuby, the same thing as @real.setText(value)) when we call choose.


it { should respond_to :choose }

it "should set the text when we call choose" do
  real.should_receive(:text=).with "Bacon"
  subject.choose "Bacon"

def choose(item)
  @real.text = item

Now we just need to make sure that list_box actually responds to the :choose-option.


def initialize(parent, opts = {}, blk = nil)
  # …
  self.choose opts[:choose] if opts.has_key? :choose

And we’re done! Easy, right?

What’s next?

The best way to get acquainted with the code and the easiest features to implement are styles. To get started with that just take a look at the manual and try to figure out what styles aren’t yet implemented, and then simply add them.

I would caution you to stay away from Text_block.rb for a while. Most of the styles for that class are dependent on custom layout managers that haven’t been written yet.

Another great place to look for what needs to be done is the issue tracker on Github.

Other Resources

The following resources should be quite handy if you’re looking to help out.