DllCall

DllCall is a function in AutoHotkey that enables calling functions exported by DLLs from inside a script. It provides a bridge to native code, making it possible to invoke Windows API functions and functions in other libraries without writing separate DLL wrappers. DllCall supports both Windows API calls and calls to non-system DLLs, making it a versatile tool for extending AutoHotkey with unmanaged code.

How it works: DllCall takes the name of the DLL function to call as its first argument, followed by a sequence of type specifiers and corresponding values. The first type specifier is the return type, and the subsequent pairs describe each parameter’s type and value. Type specifiers can denote common C/C++ types such as Int, UInt, Ptr, Str, and Double, as well as pointers and buffers. Strings may be passed as ANSI (Str) or Unicode (WStr) depending on the function’s expectations, and pointers (Ptr) are used for buffers and complex arguments. The exact syntax can vary by AutoHotkey version, but the general form is: DllCall(FunctionName, ReturnType, Arg1Type, Arg1, Arg2Type, Arg2, ...).

Example: DllCall("User32.dll\MessageBoxA", "UInt", 0, "Str", "Hello", "Str", "Title", "UInt", 0) calls the Windows MessageBoxA function and returns a user-specified result.

Example with a custom DLL: DllCall("MyLib.dll\ComputeSum", "Int", 0, "Int", a, "Int", b) passes two integers to a function and receives an integer result.

Cautions: Incorrect type declarations or mismatched calling conventions can cause crashes or memory errors. Properly handling buffers, Unicode vs ANSI strings, and pointer lifetimes is important for safe use.