A code-generation toolchain that turns Microsoft DirectX MIDL definitions into a wire protocol for serializing DXGI / Direct3D 11 / Direct3D 12 COM calls between two processes (typically a guest and a host, e.g. a VM graphics stack).

The repository ships:

• a JSON registry derived from the DirectX MIDL files (npt_registry.json),
• a small set of Python generators that turn the registry into C headers for both ends of the wire (tools/),
• Mako templates that drive the generators (templates/),
• a Meson build that wires everything together and runs a roundtrip test suite (meson.build, tests/).

The protocol itself — command/reply framing, encoding rules, COM-handle representation, etc. — is documented in docs/neptune_command_serialization.txt.

All scripts live in tools/ and are normally driven by Meson; they can also be invoked directly.

Prerequisites:

• Python 3 with mako installed (only needed if Meson cannot find it via your distro packages).
• Meson ≥ 0.56.0 and Ninja.
• A C11 compiler.

meson setup builddir
ninja -C builddir
meson test -C builddir

The default Meson configuration generates code from npt_registry.json and npt_registry_overlay.json in the source tree. Both paths can be overridden:

meson setup builddir \
    -Djson=path/to/registry.json \
    -Doverlay=path/to/overlay.json

The build emits four custom-target groups into the build directory:

• npt_protocol_directx_types — Microsoft-layout C types header.
• npt_protocol_host — host (decoder + dispatch) headers, including shared npt_protocol_defs.h, npt_protocol_common_*, per-family headers, top-level function dispatch, and the umbrella npt_protocol_host.h.
• npt_protocol_guest — guest (encoder) headers, plus the umbrella npt_protocol_guest.h.
• npt_protocol_client — per-family COM client header + out-of-line .c bodies, the global IID→ctor table, and npt_client_families.txt. Compiled by the consumer (e.g. mesa), not by this repository.

npt_registry.json is checked in but to regenerate it from Windows SDKs:

pip install midl-classic
./tools/convert_midl.py -o npt_registry.json \
    dxgiformat.idl \
    dxgicommon.idl \
    dxgitype.idl \
    dxgi.idl \
    dxgi1_2.idl \
    dxgi1_3.idl \
    dxgi1_4.idl \
    dxgi1_5.idl \
    dxgi1_6.idl \
    d3dcommon.idl \
    d3d11.idl \
    d3d11_1.idl \
    d3d11_2.idl \
    d3d11_3.idl \
    d3d11_4.idl \
    d3d11on12.idl \
    d3d12.idl

All MIDL files must live in the same directory; pass them in dependency order (base types first). The conversion is idempotent — running it against the same inputs produces the same output.

Overlays are JSON documents that share the registry schema and are merged on top of npt_registry.json at every generator invocation. They carry information that cannot be expressed in MIDL and is too small to justify a fork of the SDK headers, for example:

• typedef base types ({"name": "DWORD", "primitive": "uint32_t"}),
• group/id assignments for top-level entry points like D3D11CreateDevice (top-level functions without a group/id are dropped from the wire),
• per-method tweaks such as skip_default: true to opt a method out of the generator's default thunk in favour of a hand-written one,
• per-parameter fixes (handle classification, input/output direction, array counts).

Multiple overlays can be passed; they are applied in order, and arrays of typed objects are merged by name (or by index for positional overrides). See docs/neptune_command_serialization.txt for the full merge rules.

When the generator encounters an interface whose GUID is not pinned in npt_interface_ids.json, it refuses to emit code. To allocate the next free id:

./tools/npt_allocate_interface_id.py ID3D11Foo aec22fb8-76f3-4639-9be0-28eb43a67a2e

The script is idempotent: repeated invocations with the same arguments print the existing id rather than re-allocating. Retired interfaces stay in the file with "retired": true so their slots are reserved forever.

tests/ builds a roundtrip executable that exercises every encode/decode pair via generator-emitted fixtures. Run it through Meson:

meson test -C builddir

The roundtrip test has a 120-second timeout and exits non-zero on the first mismatch.

Apache-2.0. See LICENSE.