My Development Blog

My Development experiences

Multiple Input Devices – Controlling the accelerator pedal

Posted by ipwright83 on April 27, 2012

My work machine has a couple of input devices, mainly to try and reduce the onset of RSI. I’ve got an EM500 Ergonomic Computer Mouse and a Logitech MX600 Laser Mouse


The Ergonomic mouse by the way is brilliant and really helps prevent RSI ensuring that you’re wrist is better supported and more naturally placed. There was one significant problem with it however, the sensitivity was much less than my MX600. This meant if ever myself or a fellow developer wanted to use the MX600 on my machine there was a speed conflict. Either the MX600 had the speed of a Ferrari and you had to be very careful not to twitch the accelerator pedal too much, or the EM500 had the speed of a tortoise.

Changing the speed of the mice in control panel quickly became a hassle, so I had a quick look around to see if there were any applications that would automatically switch it based on the device. I found one but unfortunately it cost $15 and therefore would have been a lot of hassle getting it ordered. I figured it surely can’t be that hard to write my own can it?


I started off by looking for libraries – it’s always better reusing existing code than writing something from scratch. I quickly came across RawInputSharp which is a port of a C++ library for monitoring mouse input. I had an attempt at getting the demo’s in the library working, the compiled version worked fine, but whenever I tried to built it from source it just wouldn’t work. I left it alone and came back to it a few weeks later and discovered the problem was due to the build configuration (the target platform if I remember off the top of my head). I got it all working and was then able to register for mouse events.

public void MouseSpeedSwitch(){
   // Register for the mice
   this.mouseInput = new RawMouseInput();

A little special handling later to fire the necessary updates:

/// Handle the Mouse Move Events and Update the Mouse Speed 
protected const int WM_INPUT = 0x00FF; 
protected override void WndProc(ref Message m) 
   switch (m.Msg) 
      case WM_INPUT: // Read in new mouse values. 
         if (this.mouseInput != null) 
    base.WndProc(ref m); 

At this point I had mouse events and the ID’s of the devices every time I moved a mouse within my application. I made a minor change to the original library which suddenly switched the application to detecting mouse events globally in the operating system, regardless of whether the mouse was in my application or not. Brilliant!

public void RegisterForWM_INPUT(IntPtr hwndTarget) 
   rid.usUsagePage = 0x01;
   rid.usUsage = 0x02; //mouse
   rid.dwFlags = 0x00000100; // Register for events outside the current window

Things were starting to look good at this point. A few simple methods later to retrieve the names of mice from the registry and update the mouse speed and the application was almost complete. I then wrote a little very simple UI so I could use my application:

Once added into the Startup folder in the start menu, I no longer needed to worry about changing the speed of my mouse. Everything would be done automatically 🙂

Feel free to download the application, it’s free to use for both personal and commercial use – currently hosted here.


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