CMake: vcpkg-qt takes precedence over onlineinstaller-qt

[tuli]

Hi,

I am using the standard autogenerated CMake-template, with vpckg.
Thus I have this line at the very top:

set(CMAKE_TOOLCHAIN_FILE "C:/vcpkg/scripts/buildsystems/vcpkg.cmake" CACHE STRING "")

set(CMAKE_TOOLCHAIN_FILE "C:/vcpkg/scripts/buildsystems/vcpkg.cmake" CACHE STRING "")

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Everything works fine when I open this in QtCreater 8 and build it.
For Kits, I have 5.15 and 6.2 installed from the online installer. I configure both in QtCreator and can then switch between them in the build menu.


This works fine ... as long as no Qt is installed in vcpkg. If I install "qtbase" vcpkg package (which contains Qt 6.3), then the build will *always* use this Qt installation, no matter what I select in Qt Creator (even when I select Qt 5.15).


How can I resolve this situation so that CMake prefers the online installer Kits from QtCreator over the vcpkg package?

[d_stranz]

Somewhere, either in the CMakelists.txt file that Qt Creator makes for your project, or perhaps in the vcpkg.cmake toolchain file, there will be a find_package() command that loads the Qt references. This find_package() command takes an optional "version" argument that appears after the package name. There is also a "REQUIRED" argument which causes CMake to fail if the package can't be found.

There are some predefined constants that are passed in to the Qt package finder in CMake, one of which is QT_DEFAULT_MAJOR_VERSION. See the discussion here, especially the part about setting the value to either 5 or 6 before the find_package() command is called if you have mixed projects.

You will probably have to modify your CMakelists.txt file to define this appropriately. Qt Creator has a "%(Qt:Version)" variable which I assume changes with the kit, but I don't have any idea how to reference this from within CMake.

CMake can also take optional command line arguments that pass variables into CMake. I don't use Qt Creator much, especially not with CMake, so I do not know how Qt Creator invokes CMake. If you can specify a command line argument on a kit by kit basis, then that is where you could set a value for the QT_DEFAULT_MAJOR_VERSION variable.

vpckg

Thanks for this. I had no idea it existed and it looks like it could be useful. Sort of Microsoft's answer for the C++ world to Python's pip and conda I suppose.