Why does this game loop stop my process from responding?

Question

I implemented a fixed time step loop for my C# game. All it does at the moment is make a square bounce around the screen. The problem I'm having is that when I execute the program, I can't close it from the window's close button and the cursor is stuck on the "busy" icon. I have to go into Visual Studio and stop the program manually.

Here's the loop at the moment:

public void run()
    {
        int updates = 0;
        int frames = 0;
        double msPerTick = 1000.0 / 60.0;
        double threshhold = 0;
        long lastTime = getCurrentTime();
        long lastTimer = getCurrentTime();


        while (true)
        {
            long currTime = getCurrentTime(); 
            threshhold += (currTime - lastTime) / msPerTick;
            lastTime = currTime;

            while (threshhold >= 1)
            {
                update();
                updates++;
                threshhold -= 1;                                     
            }

            this.Refresh();
            frames++;

            if ((getCurrentTime() - lastTimer) >= 1000)
            {          
                this.Text = updates + " updates and " + frames + " frames per second";
                updates = 0;
                frames = 0;
                lastTimer += 1000;
            }
        }
    }

Why is this happening?

Answer 1

You need to handle windows events in order to get things like the close button and mouse interaction to work.

Either set up an event poll in your game loop or a callback function to handle events.

Answer 2

I think your window isn't responding because its message loop isn't handled. If that's the case and since you are using WinForms, adding Application.DoEvents(); somewhere inside your main loop should fix that. (The standard Application.Run() won't work because it's creating its own loop, so yours won't be executed until the window is closed.)

I expect your old Main method (when using timers) looked something like this (the VS standard template):

public static void Main(string[] args) {
    Form1 f = new Form1();
    Application.EnableVisualStyles();
    Application.Run(); // this handled the message loop for you
}

whereas your new Main method should look something like this:

public static void Main(string[] args) {
    Form1 f = new Form1();
    f.run(); // you need to handle the message loop on your own in there
}

Of course, replace Form1 with your corresponding Form class.

For more information, see the relevant documentation.

Answer 3

You are using C# so chances are that all the window message loops are already being handled by WinForms or WPF (if you are using one of those), so I don't think that is the problem. However since it did work when using a timer I think the problem is that you just don't give the application (or windows) time to handle the events since your loop is running as fast as possible because of while(true). Just add Thread.Sleep(0) to the bottom of your loop. This will cause the thread to yield so the rest of the application can do some processing until the Windows Thread Scheduler restarts the thread again.