COM API mode

What is translated > Routines > Translation modes > COM API mode

This translation mode is used for native COM interface methods and functions that follow the COM binary interface (ABI).

It generates code compatible with standard COM interfaces such as IUnknown, IDropTarget, and similar Windows COM APIs.

Characteristics

Calling convention

Portable compilers (MSVC, GCC, Clang):

__stdcall (or equivalent, e.g. STDMETHODCALLTYPE)

C++Builder:

__stdcall

Return type

Typically HRESULT

COM methods usually report success or failure via the return value.

Interfaces

Passed as raw pointers:

IUnknown*

IDataObject*

other COM interface pointers

No Delphi interface wrappers are used in this mode.

Parameters

var / out -> pointer (T*)

This follows the standard COM pattern of returning values through pointer parameters.

Types

Strong use of COM and Windows types, such as:

HRESULT

BSTR

VARIANT

SAFEARRAY

GUID, IID, CLSID

Standard Delphi types are replaced with their API equivalents where appropriate.

General Behavior

Example

Delphi

function DragEnter(

  const DataObj: IDataObject;

  grfKeyState: Longint;

  pt: TPoint;

  var dwEffect: Longint

): HResult; stdcall;

C++ (Portable)

HRESULT __stdcall DragEnter(

    IDataObject* DataObj,

    DWORD grfKeyState,

    POINTL pt,

    DWORD* pdwEffect);

C++ (C++Builder)

HRESULT __stdcall DragEnter(

    IDataObject* DataObj,

    DWORD grfKeyState,

    POINTL pt,

    DWORD* pdwEffect);

Notes

This mode is selected when a method clearly follows native COM patterns, such as:

Important Distinction

A class may implement a COM interface but still contain Delphi-style helper methods.

Only methods that match the native COM ABI are translated in COM API mode.

This page belongs to the Delphi2Cpp Documentation