Add simple Qt example

[aurelienrb]

• I use CMake presets, that help reduce the amount of scripts need in CI, but require a recent CMake version (>= 3.20)
  • typically options such as BUILD_WITH_ASAN etc... are set to ON via a preset dedicated to CI builds
• Therefore I added a script to install a recent cmake version on Linux distros
  • ./scripts/install_recent_cmake.sh
• The code should compile with fairly old Qt5 versions and the latest Qt6
  • apt-get install -qq ninja-build qt5-default libqt5x11extras5-dev
• On Windows with MSVC, a high level of warnings is being configured, and warnings are treated as errors
• I tried to showcase various aspects to Qt on purpose (rather than using things existing in std C++): text translation, QDirIterator, QtConcurrent, signal/slots in a multithreaded context, embeded resources (images), Qt asserts and logs, ...
• I applied the clang-format style already exisint in the project
• I use camelCase convention, in a way quite similar to what Qt does
• I use a PCH that include many std headers and all QtCore (requires CMake >= 3.16)
• I was a bit surprised to find the source code in the tools dir rather than a src dir, but why not
• Basically the demo app allows to:
  • scan (in the background) a folder for some log file patterns (*.log, log*.txt)
  • read those files (in the background) in order to count their number of lines
  • highlight in red the files that contain the word "error" in their name
  • select one of those file (mark it in bold) and display its content in a basic text editor (read only)

IMO, a key element in such an application is the text viewer. here I use a QTextEdit, but for a real log viewer app this class is not powerful enough, in terms of capacity to display huge log files, line numbers, customize line colors, etc... So I think a special widget has to be developed for that purpose. And I think it will apply to any GUI toolkit being used. And it can be a tricky task depending on the toolkit being used. I managed to quickly do a skeleton with Qt, with very good performances. But failed with Dear ImGui. I think OpenGL based toolkits are not well suited to build such text intensive widgets. At least that's the feeling I got from my experiments.

[aurelienrb]

CMake 3.20 required for the presets

[mm-s]

I think this is aligned and serve as a example towards showing up a time-series of events.

[mm-s]

I meged it in my fork mm-s/DebugVision.git

[mm-s]

I think this is aligned and serve as a example towards showing up a time-series of events.
Merged in mm-s/DebugVision

[mm-s]

  Could not find a package configuration file provided by "QT" with any of
  the following names:

    Qt6Config.cmake
...

Cmake should write an include file called config.h defining the macro
HAVE_QT 1|0

writing 0 or 1 depending on whether qt is available in the system or not, or --without-qt is selected

At most CMake shall report that the system is configured without Qt, but currently it fails with error

[aurelienrb]

At most CMake shall report that the system is configured without Qt, but currently it fails with error

It can, but I configured the search for Qt to be REQUIRED
I should be able to allow it to ignore the failure and then fail gracefully with a manual message asking to install it