Producing events

As mentioned in the first post, this system will continuously capture the mouse position and emit it as a series of events. At a later point, I plan to develop a web app, but for now, a simple console app will suffice.

After opening the solution in VSCode, we can see Producer.cs - the template for console applications in .NET 7.

Console.WriteLine("Hello, World!");

Since .NET 6, this is a valid C# program. This article explains a few relatively new features that make it possible to have a one-line program in .NET.

Before changing anything, we can execute the current code.

cd Producer
dotnet run

The output is as expected, Hello World! .

To get the mouse position, we can use the Windows API function called GetCursorPos and invoke it using the P/Invoke mechanism, which allows us to call platform-native functions from .NET code.

// MousePosition.cs
using System.Drawing;
using System.Runtime.InteropServices;

public class MousePosition
{
    private Point _lastPoint;
    private Point _currentPoint;

    public string GetNewPosition()
    {
        GetCursorPos(ref _currentPoint);

        if (_currentPoint != _lastPoint)
        {
            _lastPoint = _currentPoint;
            return $"[{_currentPoint.X}, {_currentPoint.Y}]";
        }
        else return string.Empty;
    }

    [DllImport("user32.dll")]
    static extern bool GetCursorPos(ref Point lpPoint);
}

We can repeatedly call GetCurrent() to get a stream of mouse positions and display them only in case there was a change.

// Program.cs 
var _mousePosition = new MousePosition();

while (true)
{
    var newPosition = _mousePosition.GetNewPosition();
    if (newPosition != string.Empty)
    {
        Console.WriteLine(newPosition);
    }
    await Task.Delay(100);
}

If we run the Producer again and move the mouse, we get a bunch of coordinates, up to 10 per second.

Now it's time to start thinking about the consumer.