[qt5-base] Fix hardcoded absolute paths in DLLs

[claudiofantacci]

This PR changes the configuration parameters for the qt5-base port in order to fix #3248.

In order for the DLL to have the proper hardcoded absolute paths in the DLL, the deployment path, i.e. CURRENT_INSTALLED_DIR, must be passed at configure time instead of the intermediate vcpkg installation path, i.e. CURRENT_PACKAGES_DIR.

A thoroughful discussion can be found, and is still in progress, in #3248.

Fixes #3248

[claudiofantacci]

Ping for the present issue.
Please also have a look at issue #3248 that reports a discussion about Qt and vcpkg.

[claudiofantacci]

Apologise for this new ping, my colleagues and I are just wondering whether this PR will be ever merged or not, just to take proper actions internally since issue #3248 is relevant for us.

[MikeGitb]

Isn't CURRENT_PACKAGES_DIR the directory where cmake gets the data from when I use -DCMAKE_TOOLCHAIN_FILE=VCPKG_ROOT/scripts/buildsystems/vcpkg.cmake ?

Would that still work?

[claudiofantacci]

Hi @MikeGitb, CMake looks for libraries in CURRENT_INSTALLED_DIR (i.e. <VCPKG folder>/installed/<arch>-windows folder) by using vcpkg toolchain.

This is the main problem when using Qt libraries as they have hardcoded paths into the DLL that are set to CURRENT_PACKAGES_DIR and not CURRENT_INSTALLED_DIR, as you can see from the patch I propose in this PR.

[claudiofantacci]

This PR has been ignored for over 4 months now, and I would just like to understand the point of view of the maintainers about consuming Qt in a project outside the vcpkg build tree.
As of now, I have problem using it without shipping a qt.conf file.
Thanks!

[ras0219-msft]

Thanks for the PR and sorry for such a long merge delay!

[huangqinjin]

There's no ${CURRENT_INSTALLED_DIR}/debug/qml installed . qmldir in debug mode should also point to ${CURRENT_INSTALLED_DIR}/qml.

[claudiofantacci]

There's no ${CURRENT_INSTALLED_DIR}/debug/qml installed . qmldir in debug mode should also point to ${CURRENT_INSTALLED_DIR}/qml.

Hi @huangqinjin, thanks for pointing out this issue.
debug/qml was already present in the portfile and I left it unultered.
I can double check this as soon as I get back to office and submit a fix asap.

[tronical]

This PR has been ignored for over 4 months now, and I would just like to understand the point of view of the maintainers about consuming Qt in a project outside the vcpkg build tree.
As of now, I have problem using it without shipping a qt.conf file.

Given that the paths presented at configure time are coded straight into Qt5Core.dll, I think you have only two options for a truly relocatable application binary:

1. Install qt.conf next to the application, see http://doc.qt.io/qt-5/qt-conf.html
2. Use windeployqt with a target path, that will patch Qt5Core.dll (binary wise) and change the prefix in there. Then use the Qt Install Framework to create an installer, which may also patch the binary at installation time on the user site.

I kind of prefer the first option, but both are valid depending on the use-case.

[claudiofantacci]

Thanks @tronical, we actually use the second solution here 😄

The change that I proposed in this PR was to address a problem located only in vcpkg were you could not remove the Qt build folder because the hardcoded path were pointing to the build folder and not the installation folders.