issues with cmake build system

[JPeterMugaas]

I have two big issues with the cmake build for DirectX-Headers when building for mingw-w64 in MSYS2 (a CygWin derivative).

1. The CMakeLists.txt file needs to be updated to fix that rpc number issue so libraries such as DirectXTex can be built in mingw. DirectXTex uses CMake's "find_package" and that fails if only Meson was used to build the DirectX-Headers. I have created a patch to fix that issue for CMakeLists.txt and it's simply a line such as "elseif((CMAKE_CXX_COMPILER_ID STREQUAL "GNU") OR (CMAKE_CXX_COMPILER_ID STREQUAL "Clang"))" in the "if (NOT WIN32)" block.

2. The CMakeLists.txt needs to generate a "DirectX-Headers.pc" pkg-config file just like the building with Meson does. That is how Mesa's build script can detect the presence of the DirectX-Headers. and I suspect that other build systems such as Autoconf do something similar with package config files.

Incidentally, I noticed an inconsistency between what is done with Meson and CMake. If you build with mesa, one of the two static libraries is "ibd3dx12-format-properties.a" but if you build with CMake, that file is "libDirectX-Headers.a".

[jenatali]

If you build with mesa, one of the two static libraries is "ibd3dx12-format-properties.a" but if you build with CMake, that file is "libDirectX-Headers.a".

Right, CMake's concept of a static library with header dependencies isn't something that meson really has. So for CMake, we just say that the DirectX-Headers static library is the dependency that's exported, and the additional includes are a PUBLIC property of that, but for meson, a dependency object is needed. The dependency object is named DirectX-Headers and includes the include paths and references to the relevant C++ files as static libraries.

[walbourn]

The introduction of DirectX-Headers.pc breaks VCPKG:

warning: There should be no absolute paths, such as the following, in an installed package:
  D:\vcpkg\packages\directx-headers_x64-windows
  D:\vcpkg\installed
  D:\vcpkg\buildtrees\directx-headers
  D:\vcpkg\downloads
Absolute paths were found in the following files:
  D:\vcpkg\packages\directx-headers_x64-windows\debug\lib\pkgconfig\DirectX-Headers.pc
  D:\vcpkg\packages\directx-headers_x64-windows\lib\pkgconfig\DirectX-Headers.pc
error: Found 1 post-build check problem(s). To submit these ports to curated catalogs, please first correct the portfile: D:\vcpkg\ports\directx-headers\portfile.cmake