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README-LIB.md

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AutoHotkeyLib

This project includes the capability to compile as a dll, for hosting the interpreter in another application. This was added in 2022, and is not to be confused with the AutoHotkey.dll first created by tinku99 in 2009 and later developed by HotKeyIt (HotKeyIt/ahkdll) and thqby (thqby/AutoHotkey_H). In contrast with those projects, this dll aims to provide a more convenient interface for hosting the interpreter, behaving as close to base AutoHotkey as is practical.

The dll has two primary use cases:

  • Host and execute a script; in particular, allow the use of v1 code within a v2 process.
  • Examine a script without executing it; provide data for auto-complete, calltips, navigating to function definitions, etc.

The dll is Unicode-only; ANSI is currently unsupported.

Experimental

The syntax and behaviour described here may change between releases, without notice. Version numbers are purely for the base version of AutoHotkey and do not reflect the status of the Lib API.

Building

Select the Release.dll build configuration and appropriate platform to build the dll.

Use the Debug.dll configuration for debugging, but in the project settings, set the debug command line to the path of an exe which will load the dll. If both the dll and the exe are debug builds, it should be possible to debug both at once (even if they are not in the same project/directory).

Entry Points

The dll currently has two entry points.

Host

Creates and returns an instance of AutoHotkeyLib.

HRESULT Host(IDispatch **ppLib);

This can be used from AutoHotkey v2 as follows, where dll contains the path or filename:

if !hmod := DllCall("LoadLibrary", "str", dll, "ptr")
    throw OSError()
DllCall(dll "\Host", "ptr*", Lib := ComValue(9, 0), "hresult")

Lib then contains a COM object as described below.

The dll does not yet include the set of functions needed to implement a COM class factory, which would allow activation by means such as CoCreateInstance, ComObjCreate, ComObject or CreateObject (depending on the language/version). Such use would require registering the dll, whereas Host does not.

Main

Executes the script in the same way that AutoHotkey.exe would.

int Main(int argc, LPTSTR argv[]);

This was mainly for testing during early development, and is internally used by Lib.Main(CmdLine).

Lib API

The methods and properties exposed by the Lib object are defined in ahklib.idl, in the IAutoHotkeyLib interface. These are subject to change.

General:

  • ExitCode := Lib.Main(CmdLine) executes a command line more or less the same as AutoHotkey.exe would. If the script is persistent, it does not return. CmdLine must include "parameter 0" (which is normally the path of the exe), although its value is ignored. ExitCode is either 0 or 2 (CRITICAL_ERROR); ExitApp causes the whole program to terminate.
  • Lib.LoadFile(FileName) loads a script file but does not execute it. It can only be called once, unless the dll is unloaded and loaded again. The script is partially initialized for execution, but hotkeys are not manifested.
  • Lib.OnProblem(Callback) registers a callback to be called for each warning or error, including load-time errors (if registered before the script is loaded) and exceptions that aren't caught or handled by OnError. If a callback is set, the default error message is not shown. Callback receives a single parameter containing the thrown value or exception. If an exception object is created for warnings and errors that otherwise wouldn't have one, What is set to "Warn" or "Error".

Execution:

  • ExitCode := Lib.Execute() manifests hotkeys and excecutes the auto-execute section, then returns. Unlike Main, it does not initialize the command line arg variables or check for a previous instance of the script. Execute can be called multiple times. If this function is not called, it is possible to extract information about the script without executing it, or to execute specific functions without (or before) executing the auto-execute section.
  • Lib.Script returns an object which can be used to retrieve or set global variables (as properties) or call functions (as methods).

Informational:

  • Lib.Funcs, Lib.Vars and Lib.Labels return collections of objects describing functions, variables and labels. See IDescribeFunc, IDescribeVar, IDescribeLabel and IDescribeParam in ahklib.idl for usage. Collections use the IDispCollection interface, with Funcs, Vars and Labels accepting a name for Index and Params accepting a one-based index.

Not Implemented

Lib does not provide any means to enumerate classes. It can be done by enumerating global variable names with Lib.Vars, retrieving the classes from Lib.Script and inspecting them, but this carries some risk because invoking the class object may cause unknown script to execute.

There are many other ways that the API could be extended, either to extract information or to control how the script executes or integrates with its host.

Known Issues

Events that execute in a new pseudo-thread may cause undefined behaviour if Lib.Execute() was skipped.

A_AhkPath refers to the path of the current process, so attempts to use it to execute scripts may not behave as intended.

Functions and menu items which execute a command line derived from the path of the current executable may not behave as intended. This includes Reload.

Unloading/Reloading

Although the dll only supports loading one main script file, it is possible to execute or examine multiple scripts, one at a time, by unloading the dll and loading it again.

DllCall("FreeLibrary", "ptr", hmod)  ; hmod was previously returned by LoadLibrary

Before unloading the dll, release all external references to objects created by the dll and ensure the keyboard/mouse hook is uninstalled (such as by suspending hotkeys). If the keyboard/mouse hook is still installed, calling FreeLibrary generally will not unload the dll. Lib currently does not provide any way to remove the hooks explicitly, so in some cases (e.g. if #InstallKeybdHook was used) it may not be possible.