gsbischoff / usb-pen-injection

Sends and injects pointer input between computers using the WinAPI

USB Pen Injection

Uses the Windows API to slave the input of a pressure sensitive stylus from a Microsoft Surface and pipe it over USB (or some other protocol) for input on a separate computer without a touch display. (Work-In-Progress)

The initial implementation uses the UDP sockets from the Winsock API (with Winsock). USB or Bluetooth to come later.

Contents

PenClient.c and PenServer.c contain the sources of the program to recieve and inject input; and to capture and send input over a designated protocol. Currently, these send and recieve pen input using datagram/UDP sockets.

Point.c is for capturing Pen input using Pointer APIs. Currently, only WM_POINTER messages

Serial.c contains functions for serializing and deserializing the POINTER_PEN_INFO struct before and following transmission.

DieWithError.c and ResolveHost.c contain socket helper functions to print out correctly-formatted WinSock error messages and resolve input hostnames into IP addresses, respectively.

Testbeds

IOTest.c is for any scratchwork towards capturing and injecting pen input properly.

IOFinal.c contains only the code necessary for capturing the raw pen input using RawInput. No longer used for testing

Building

The client and server are built similarly to each other:

build.bat PenClient.c
build.bat PenServer.c

The test files have different dependencies that I've seperated into a seperate build script placed in their own directory:

build.bat IOTest.c
build.bat IOFinal.c

Notes/Current Issues

WM_INPUT messages can be recieved from a pen arbitrarily using the INPUTSINK attribute while registering the RI device -- however, once the RAWINPUT structure is returned from GetRawInputData(), we cannot place it back into a handle (using GlobalAlloc() or GlobalHandle()) to reinject into another context. Ideas:

• Try examining the HRAWINPUT of LPARAM to see if we can figure out how it is different from those we can make with the Global memory management functions. Said handles are not manageable with GlobalLock(), etc.

• See if WinTab has APIs for injection

Switch to using Pointer messages (can we capture all messages still as with INPUTSINK? Register pointers? No.)

• RegisterPointerDeviceNotifications() allows message-windows to recieve inputs telling when a pointer in put in range; however, the pointerId that is returned from GET_POINTERID_WPARAM() on those messages is invalid. ONLY when retrieving it through a WM_POINTERUPDATE message can you call GetPointerPenInfo(). Additionally, pointerIds are unique, each time the pen leaves and comes back in range, a new pointerId is returned.

• Must use a visible window.

• Can we get pressure and raw pen info using RAWINPUT (for which we have INPUTSINK attribute) and reinject it using the touch injection APIs?

Summary	Broadcast Globally	Inject?	Input sink?
RawInput	Yes	No	Yes
Pointers	Inject touch	Only touch	No
WinTab	?	?	?

There exist PenInjection APIs in C++/RT, but the only thing lost with TouchInjection is the eraser's functionality.