COMDirect2D

COMDirect2D is a software library that provides a COM-based API wrapper around Direct2D, Microsoft's hardware-accelerated 2D graphics API. It enables legacy COM clients to render 2D graphics with the performance of Direct2D without rewriting rendering code. By exposing COM interfaces that map to Direct2D objects, COMDirect2D allows developers using languages that interoperate with COM (such as C++, C#, VB6) to create render targets, brushes, and geometry.

Internally it implements a set of COM-visible interfaces that mirror Direct2D concepts: factory, render targets, brushes, geometry, and bitmap resources. Each COM object wraps the corresponding Direct2D object, forwarding calls to the Direct2D runtime, managing lifetimes via COM reference counting, and handling error translation. The library typically integrates with DirectWrite for text rendering and uses the Direct2D render pipeline for anti-aliasing and hardware acceleration.

Typical usage involves initializing the COM library, creating a Direct2D-compatible factory through the COM layer, creating render targets associated with a window or bitmap, selecting brushes and geometry, and issuing begin-end draw calls. The API is designed to be source-compatible with COM-based code patterns, using HRESULT results and COM interface querying for object creation.

It is targeted at Windows platforms where Direct2D is supported. While it reduces the barrier for migrating COM-based apps to Direct2D, some advanced Direct2D features may not have exact equivalents in the COM wrapper, and performance is subject to the overhead of the COM abstraction. Compatibility with managed runtimes depends on the environment's COM interop facilities.

See also: Direct2D, DirectWrite, COM, Windows Graphics Programming.