AutoHotInterception

AutoHotInterception (AHI) allows you to execute AutoHotkey code in response to events from a specific keyboard or mouse, whilst (optionally) blocking the native functionality (i.e. stopping Windows from seeing that keyboard or mouse event).
In other words, you can use a key on a second (or third, or fourth...) keyboard to trigger AHK code, and that key will not be seen by applications. You can use the same key on multiple keyboards for individual actions.
Keyboard Keys, Mouse Buttons and Mouse movement (Both Relative and Absolute modes) are supported.

AHI uses the Interception driver by Francisco Lopez

Getting Help

AHI Discussion Thread on the AHK forums

Discord Channel

WARNING

TAKE CARE when using this code. Because Interception is a driver, and sits below windows proper, blocking with Interception goes so deep that it can even block CTRL+ALT+DEL etc. As such, it is entirely possible to lock up all input, or at least make life a little difficult.
In general, worst-case scenario would require use of the reset button.
For example, using Subscription Mode with block enabled will totally block that key from working on that keyboard. So if you block Ctrl on your only keyboard, you just blocked CTRL+ALT+DEL.
The best insurance policy is to have another keyboard or mouse handy, one that you don't block.
Be wary of making scripts using this code run on startup. Know how to enter "Safe Mode" in windows and disable startup of the scripts. Know mouse alternatives to emergency keyboard actions (Right click on clock for Task Manager!)
As they say - With great power comes great responsibility.
If this all scares you and you don't really understand it, then TL/DR is you should probably stick to "Context Mode", it's safer.

Device IDs / VIDs PIDs etc

Interception identifies unique devices by an ID. This is a number from 1..20.
Devices 1-10 are always keyboards
Devices 11-20 are always mice
This ID scheme is totally unique to Interception, and IDs may change as you plug / unplug devices etc.
On PC, devices are often identified by VendorID (VID) and ProductID (PID). These are identifiers baked into the hardware at time of manufacture, and are identical for all devices of the same make / model.
Most AHI functions (eg to Subscribe to a key etc) use an Interception ID, so some handy functions are provided to allow you to find the (current) Interception ID of your device, given a VID / PID.
If you are unsure of what the VID / PID of your device is (or even if Interception can see it), you can use the included Monitor script to find it.

You will need to know the VID / PID of at least one of your devices in order to do anything with AHI.

Monitor App

This handy tool allows you to check if AHI is working, and also to find the VID/PID or DeviceHandle of your devices.
You can use the handy "Copy" buttons to copy the VID/PID or DeviceHandle of the device to the clipboard.
When using the monitor app, DO NOT tick all devices at once, as if it crashes, it will lock up all devices. Instead, tick one at a time and see if it your device.

Known Issues

If you unplug / replug a device, or go into hibernate and resume, the Interception ID of a device will increase by 1.
If the ID of a device goes above 10 (For keyboards) or 20 (For Mice), The device will completely cease to function until the next reboot - not only in AutoHotInterception, but in Windows also.
There is nothing I can do to fix this issue, it is a limitation of the Interception driver

Setup

1. Download and install the Interception Driver
   Note that you must run install-interception.exe at an admin command prompt (Not double-click it) - once you do so, it will instruct you to execute install-interception.exe /install to actually perform the install.
   Here is a GIF showing the process:
   
2. Download an AHI release from the releases page and extract it to a folder.
   DO NOT use the "Clone or Download" link on the main page.
   This is the folder where (at least initially) you will be running scripts from.
   It contains a number of sample .ahk scripts and a lib folder, which contains all the AHI libraries.
3. In the Interception installer zip, there is a library folder containing x86 and x64 folders.
   Copy both of these folders into the AHI lib folder that you created in step (3) - the folder structure should end up looking like:

AHI Root Folder
	Monitor.ahk
	etc...
	Lib
		AutoHotInterception.ahk
		AutoHotInterception.dll
		CLR.ahk
		Unblocker.ps1
		etc..
		x86
			interception.dll
		x64
			interception.dll

4. Right-click Unblocker.ps1 in the lib folder and select Run as Admin.
   This is because downloaded DLLs are often blocked and will not work.
   This can be done manually by right clicking the DLLs, selecting Properties, and checking a "Block" box if it exists.
5. Edit one of the example remapping scripts, replacing the VID/PID(s) with that of your device (Use the Monitor app to find it) and run it to make sure it works.
6. (Optional) The contents of the lib folder can actually be placed in one of the AutoHotkey lib folders (eg My Documents\AutoHotkey\lib - make it if it does not exist), and the #include lines of the sample scripts changed to #include <AutoHotInterception>, to enable your AHI scripts to be in any folder, without each needing it's own copy of the library files.

Usage

Initializing the Library

Include the library

#Persistent ; (Interception hotkeys do not stop AHK from exiting, so use this)
#include Lib\AutoHotInterception.ahk

Initialize the library

global AHI := new AutoHotInterception()

Note
The AHI variable is an AHK class that makes it easy to interact with the AutoHotInterception DLL (Which itself then interacts with the Interception dll). For example, it wraps GetDeviceList() to make it return a normal AHK array. Most of the time you will not need it.
For advanced users, if you wish to directly communicate with the AHI DLL (eg for best possible performance), you can call AHI.Instance instead of AHI for most functions (eg when sending of synthesized input using SendMouseMove).

AHI := new AutoHotInterception()
AHI.Instance.SendMouseMove(...)

Misc Commands

SetState

SetState(true|false)
Turns on or off all subscriptions (Starts on)
Where true is on, false is off.
eg AHI.SetState(false)

Finding Device IDs

USB Devices

In most cases, you will want to hard-wire a script to a specific VID/PID - in this instance, use one of the following methods.
For all these methods, if you have multiple identical VID/PID devices, you can specify an instance (Starts from 1).

GetDeviceId

AHI.GetDeviceId(<isMouse>, <VID>, <PID> [,<instance = 1>] )
Where isMouse is true if you wish to find a mouse, or false if you wish to find a keyboard.
eg AHI.GetDeviceId(false, 0x04F2, 0x0112) to find a keyboard with VID 0x04F2 and PID 0x0112

GetKeyboardId

AHI.GetKeyboardId(<VID>, <PID> [,<instance = 1>] )

GetMouseId

AHI.GetMouseId(<VID>, <PID> [,<instance = 1>] )

PS/2 and other Legacy devices (Can also apply to Laptops)

Some devices (eg older machines with PS/2 interfaces, or some laptops) may not use USB, so these will not have a VID and PID.
In this case, use the monitor app (Or GetDeviceList()) to findle out the "Handle" of your device, and get it's ID from that.

GetDeviceIdFromHandle

AHI.GetDeviceIdFromHandle(<isMouse>, <handle> [,<instance = 1>] )
This works in the same way as GetDeviceId above, except you pass a string containing the handle.
eg AHI.GetDeviceIdFromHandle(false, "ACPI\PNP0303") to find a keyboard with the handle ACPI\PNP0303

GetKeyboardIdFromHandle

AHI.GetKeyboardIdFromHandle(<handle> [,<instance = 1>] )

GetMouseIdFromHandle

AHI.GetMouseIdFromHandle(<handle> [,<instance = 1>] )

Getting a list of devices

If you wish to get a list of all available devices, you can call AHI.GetDeviceList(), which will return an array of DeviceInfo objects, each of which has the following properties:

Id
isMouse
Vid
Pid
Handle

Input Detection

AHI has two input detection modes - Context Mode and Subscription Mode, and both can be used simultaneously.

Context mode

Context mode is so named as it takes advantage of AutoHotkey's Context Sensitive Hotkeys.
As such, only Keyboard Keys and Mouse Buttons are supported in this mode. Mouse Movement is not supported.

In context mode, you create a Context Manager object which turns on/off a set of AHK hotkeys for you.
You wrap your hotkeys in an #if block which is controlled by the manager.

Create a Context Manager for the keyboard or mouse, pass it the Interception ID of the device.
Then Create your hotkeys, wrapped in an #if block that checks the .IsActive property of your Context Manager

(Complete, working script)

#include Lib\AutoHotInterception.ahk

keyboard1Id := AHI.GetKeyboardId(0x04F2, 0x0112)
cm1 := AHI.CreateContextManager(keyboard1Id)

#if cm1.IsActive	; Start the #if block
::aaa::JACKPOT
1:: 
	ToolTip % "KEY DOWN EVENT @ " A_TickCount
	return
	
1 up::
	ToolTip % "KEY UP EVENT @ " A_TickCount
	return
#if			; Close the #if block

Subscription mode

In Subscription mode, you bypass AHK's hotkey system completely, and Interception notifies you of key events via callbacks.
All forms of input are supported in Subscription Mode.
Subscription Mode overrides Context Mode - that is, if a key on a keyboard has been subscribed to with Subscription Mode, then Context Mode will not fire for that key on that keyboard.
Each Subscribe endpont also has a corresponding Unsubscribe endpoint, which removes the subscription and any block associated with it.

Subscribing to Keyboard keys

Subscribe to a specific key on a specific keyboard

SubscribeKey(<deviceId>, <scanCode>, <block>, <callback>, <concurrent>)
UnsubscribeKey(<deviceId>, <scanCode>) eg
AHI.SubscribeKey(keyboardId, GetKeySC("1"), true, Func("KeyEvent"))

Callback function is passed state 0 (released) or 1 (pressed)

KeyEvent(state){
	ToolTip % "State: " state
}

Parameter <concurrent> is optional and is false by default meaning that all the events raised for that key will be handled sequentially (i.e. callback function will be called on a single thread). If set to true, a new thread will be created for each event and the callback function will be called on it.

Subscribe to all keys on a specific keyboard

SubscribeKeyboard(<deviceId>, <block>, <callback>, <concurrent>)
eg
AHI.SubscribeKeyboard(keyboardId, true, Func("KeyEvent"))

Callback function is passed scancode of pressed key and state

KeyEvent(code, state){
	ToolTip % "Keyboard Key - Code: " code ", State: " state
}

Subscribing to Mouse Buttons

Subscribing to a specific button on a specific mouse

SubscribeMouseButton(<deviceId>, <button>, <block>, <callback>, <concurrent>)
UnsubscribeMouseButton(<deviceId>, <button>)
Where button is one of:

0: Left Mouse
1: Right Mouse
2: Middle Mouse
3: Side Button 1
4: Side Button 2
5: Mouse Wheel (Vertical)
6: Mouse Wheel (Horizontal)

For Mouse Wheel events, the <state> parameter will be 1 for Wheel Up / Right and -1 for Wheel Down / Left

Otherwise, usage is identical to SubscribeKey

Subscribing to all buttons on a specific mouse

SubscribeMouseButtons(<deviceId>, <block>, <callback>, <concurrent>)
eg
AHI.SubscribeMouseButtons(mouseId, true, Func("MouseButtonEvent"))

Callback function is passed ID (See above) of pressed button and state

MouseButtonEvent(code, state){
	ToolTip % "Mouse Button - Code: " code ", State: " state	
}

Subscribing to Mouse Movement

Warning! When Subscribing to mouse movement, you will get LOTS of callbacks.
Note the CPU usage of the demo Monitor app.
AutoHotkey is not good for handling heavy processing in each callback (eg updating a GUI, like the monitor app does).
Keep your callbacks short and efficient in this mode if you wish to avoid high CPU usage.

Relative Mode

Relative mode is for normal mice and most trackpads.
Coordinates will be delta (change)
Each endpoint has two naming variants for convenience, they both do the same.

SubscribeMouseMove(<deviceId>, <block>, <callback>, <concurrent>)
SubscribeMouseMoveRelative(<deviceId>, <block>, <callback>, <concurrent>)
UnsubscribeMouseMove(<deviceId>)
UnsubscribeMouseMoveRelative(<deviceId>)
For Mouse Movement, the callback is passed two ints - x and y.

AHI.SubscribeMouseMove(mouseId, false, Func("MouseEvent"))

MouseEvent(x, y){
	[...]
}

Absolute Mode

Absolute mode is used for Graphics Tablets, Light Guns etc.
Coordinates will be in the range 0..65535
SubscribeMouseMoveAbsolute(<deviceId>, <block>, <callback>, <concurrent>)
UnsubscribeMouseMoveAbsolute(<deviceId>)
Again, the callback is passed two ints - x and y.

AHI.SubscribeMouseMoveAbsolute(mouseId, false, Func("MouseEvent"))

MouseEvent(x, y){
	[...]
}

Synthesizing Output

Note that these commands will work in both Context and Subscription modes
Also note that you can send as any device, regardless of whether you have subscribed to it in some way or not.

Sending Keyboard Keys

You can send keys as a specific keyboard using the SendKeyEvent method.
AHI.SendKeyEvent(<keyboardId>, <scanCode>, <state>)
scanCode = the Scan Code of the key
state = 1 for press, 0 for release
keyboardId = The Interception ID of the keyboard

AHI.SendKeyEvent(keyboardId, GetKeySC("a"), 1)

If you subscribe to a key using Subscription mode with the block parameter set to true, then send a different key using SendKeyEvent, you are transforming that key in a way which is totally invisible to windows (And all apps running on it), and it will respond as appropriate. For example, AHK $ prefixed hotkeys will not be able to tell that this is synthetic input, and will respond to it.

Sending Mouse Buttons

You can send clicks and other mouse button events with:
AHI.SendMouseButtonEvent(<mouseId>, <button>, <state>)
Where button is the button index, as used in SubscribeMouseButton

When Sending Mouse Wheel events, set <state> to 1 for Wheel Up / Right and -1 for Wheel Down / Left.

If you are working in Absolute mode (eg with a graphics tablet or light guns), you can send mouse button events at specific coordinates using:
AHI.SendMouseButtonEventAbsolute(<mouseId>, <button>, <state>, <x>, <y>)

Sending Mouse Movement

Relative

To send Relative (Normal) mouse movement, use:
AHI.SendMouseMove(<mouseId>, <x>, <y>)
X and Y are not setting the absolute cursor position, they are altering current position
Note that x and y are not in pixels, they are in "Mickeys"

Absolute

To sent Absolute mouse movement, use:
AHI.SendMouseMoveAbsolute(<mouseId>, <x>, <y>)
Note that Absolute mode will probably not work with FPS style mouse-aim games.
Note that Absolute mouse move uses coordinates in the range 0..65535 which are NOT screen coordinates. If, for example, you have one 1920x1080 monitor, then divide 65535 by 1920 to find the x position on your screen. This 65535 coordinate space maps to all your screens however, so if you have multiple monitors, further maths will be required.

Moving the Mouse Cursor

To move the mouse cursor to a specific screen or window coordinate, use:
AHI.MoveCursor(<x>, <y> [, <coordMode>, <mouseId>])
coordMode is optional and is the CoordMode to use (Will switch back to current CoordMode after) - Defaults to "Screen".
mouseId is optional and the ID of the mouse to use (Defaults to ID 11 - the first mouse)
eg
AHI.MoveCursor(100, 200) - move to 100, 200 Screen position using mouse ID 11
AHI.MoveCursor(100, 200, "Window") - move to 100, 200 Window position using mouse ID 11
AHI.MoveCursor(100, 200, , 12) - move to 100, 200 Screen position using mouse ID 12

Compiling scripts

AHI scripts can be compiled (Right click the script and select "Compile")
All required DLLs will be packed inside the EXE, so only the EXE needs to be distributed
When the EXE is run, the Lib folder will be created with the required DLLs