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 (ie 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

Use the AHI Discussion Thread on the AHK forums

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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.

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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.

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Setup

1. Download and install the Interception Driver
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 libraries and files needed for AHI.
3. Extract both x86 and x64 folders from the library folder in interception.zip into the lib folder that was created in step (2).
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. If you do not know the VID/PID of your device, use the included Monitor app to find it. 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.
6. Edit one of the example remapping scripts, replacing the VID/PID(s) with that of your device and run it to make sure it works.
7. (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.

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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 := InterceptionWrapper()

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(...)

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.

Subscribing to Keyboard keys

Subscribe to a key on a specific keyboard SubscribeKey(<deviceId>, <scanCode>, <block>, <callback>)

Interception.SubscribeKey(keyboardId, GetKeySC("1"), true, Func("KeyEvent"))
return

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

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

Subscribing to Mouse Buttons

SubscribeMouseButton(<deviceId>, <button>, <block>, <callback>)
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 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) SubscribeMouseMove(<deviceId>, <block>, <callback>)
For Mouse Movement, the callback is passed two ints - x and y.

Interception.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

Interception.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.
Interception.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

Interception.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:
Interception.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:
Interception.SendMouseButtonEventAbsolute(<mouseId>, <button>, <state>, <x>, <y>)

Sending Mouse Movement

Relative

To send Relative (Normal) mouse movement, use:
Interception.SendMouseMove(<mouseId>, <x>, <y>)

Absolute

To sent Absolute mouse movement, use:
Interception.SendMouseMoveAbsolute(<mouseId>, <x>, <y>)
Note that Absolute mode will probably not work with FPS style mouse-aim games.

Monitor App

ToDo: Add recording of monitor app