Imagine you're in an operating system development team, and you're in charge of designing how a given application would handle its windows and controls. Not the actual drawing of elements, but how to set up a window and react to events.


In Windows, the answers are a tree of objects, where things like buttons and input boxes are the same as the windows they are in, distinguished only by their class and styles, and events are done by a message pump -- the application spins a loop, checking for new system messages and responding to them.

For example, a button could be created by the CreateWindow system call, specifying that it needs to be a button by class, and returning the window handle for it. In the message pump, the message for being clicked is found, and the target handle matches the one CreateWindow returned, so we know that the button was clicked.

This system works fine for procedural languages, and can be mapped into OOP -- just look at MFC and .Net.


The question is, how would you do it? This is your OS, so anything goes. Surprise me.

So basically, the entire GUI is made of webpage?

Neat.


Update: we discussed this on IRC just now and I feel this should be posted for posterity's sake. To get a language-agnostic nature, I've suggested to replace the Javascript-style onFoo attributes with a Win32-inspired message pump. The application would spin around waiting for events as in Win32, and each event would specify its own nature (clicked, closed, paint, drag-drop stuff...) and the target, which could be either a vague identifier ("this window") or an element's ID attribute.

<window title="Test window" resizable="no"> <!-- Ignoring layout for clarity --> <button id="increase">Increase power</button> <label id="currentPower">Power: 0%</label> </window> ... while (true) { while (HaveEvents()) { event e = CheckEvents(); switch (e.type) { case EV_CLICKED: if (e.target == "increase") { power += 20; //prepare the new text here some way, I dunno, sprintf? SetText("currentPower", newText); } break; case EV_CLOSING: //no need to use target -- buttons and labels can't close, so this has to be the window. e.cancel = true; //don't let them close the window because mine is an evil laugh. break; } } }

Here's a practical demonstration I came up with. The screenshot is a mockup, and is missing one element but whatever.

http://helmet.kafuka.org/liliwin_sample1.rar

Could you post a snippet of actual code? Also, how would you solve the problem of language-agnosticism?

And the part where it doesn't have to be in C, which is what "languag-agnostic" means?


Minimalist theme mockup of the hypothetical LiliOS. I'm thinking, a given window ought to be able to change the theme it wants to use, but defaults to a system-wide setting. So in that shot, you might imagine opening the sample app's "Theme" menu and selecting a Motif theme, which would switch the whole window to an approximation of Motif, while bsnes and the rest of the system remain set to Minimal.