Are physical and programmatic keypresses handled differently by either .NET or the OS

Firstly some background information...

I have a C# .NET application that runs on a slate pc i.e. no physical keyboard. We are using the on-screen keyboard built into Windows XP Tablet edition to populate TextBox controls on a form. Ther开发者_如何转开发e is no special key press handling for the form (although other components of the UI do handle key presses).

Occasionally the on-screen keyboard will stop registering some key presses. The form still has focus and the cursor remains in the text box. Repeatedly tapping a key will eventually cause the character to be displayed. Our application uses a number of busy processing threads however it is far from 100% CPU utilisation.

When this behaviour occurs it remains that way until our application is restarted, after which the keyboard behaves normally. The problem does not occur at all when a USB keyboard is attached and used for input.

I'm interested in what differences there are between physical and programmatic key presses? Do programmatic key presses generate hardware interrupts as a physical keyboard would? Could .NET be handling each type differently?

Any suggestions that could help debug the problem would be much appreciated!

I've never worked with the tablet version of the XP OSK, but I have used the XP Embedded version. As far as I could tell the Windows API was sending key presses to .NET and MFC applications the same way. In fact, if I recall correctly, there was no way for us to tell the difference between the two programatically. As far as I know an OSK will not cause a hardware interrupt, however the virtual-key code will be sent to application-level programs in the exact same manner as a physical one.

Unless you are running a custom driver or something (that has access to the hardware layer), it sounds like it may not be your application that is causing the problem.

If you haven't already, I would check that the touchscreen has the latest drivers and is properly calibrated. I'd also check that the OSK has all the latest updates from Microsoft.