qt_exp

Bootstrapping QT into Bazel

TLDR

1. Install QT if it does not exist.
2. Run setup_qt.sh
3. bazel build //...

Hermetic on not

Integrating a moderate size repo with CMake or makefile is relatively easy - example. QT is quite different. It has multiple submodules and configuration. For configuration and build is still needs certain dependencies on the machine.

I do not know how a full hermetic QT build in Bazel would even work. But if it does then the build would take considerable time. But even if such a build succeeds, there is a need for QT goodies on the local machine, and so what's the point of hermetic build?

Self-hermetic

Given an existing QT installation on local machine, it is just a matter of setup symlinks to include and shared libraries. To make symlinking before build ended up tricky. Bazel genrule wants to list all include files and not just a directory. There are other multiple ways other than genrule but it quickly became convoluted.

The easiest way of setting up QT on Ubuntu with Bazel integration

1. sudo apt update
   sudo apt install qt6-base-dev qt6-tools-dev \
    qt6-tools-dev-tools qt6-base-examples \
    qtbase6-doc-html qt6-declarative-dev \
    qt6-declarative-dev-tools
   

2. ./setup_qt
3. Adjust copts if needed

The other types of installing QT through online installer or through sources is problematic. Qt must be installed under /usr and not under /usr/local or home directory the reason being is that Bazel copts requires \usr directory (or maybe opts, I haven't tried that) and not home directory and even not /usr/local.

With this setup it is the simplest and the most straightforward way to integrate with Bazel.

Integration QML with Bazel

Quick and dirty solution is to run_rcc.sh before main binary which generates resource file stub. It requires qml file be a part of binary data.