# A minimal QT application, without the nonsense

This repository contains a minimal QT application that can be compiled
without using CMake or QT Creator.

## Requirements

* A C++ compiler (tested with GCC 14.2.1 and Clang 19.1.7, both on Linux-x86_64)
* QT libraries and headers
* The QT development tools `moc` and `uic`

On Fedora Linux they are contained in the `qt6-qtbase-devel` package.
I have not tested this on other operating systems.

## tl;dr

If you just want to try out this program you can run (if you have `make` installed)

```
make && ./run
```

## Explanation

Following the most basic QT Creator template, there are 4 source code files:

* `main.cpp`: the main source file
* `mainwindow.h`: the header file for the main window of the application
* `mainwindow.cpp`: the C++ source for the main window
* `mainwindow.ui`: the UI file with an XML description of the main window

The compilation is done in 3 steps:

1. Pre-process `mainwindow.h` with `moc` to obtain `moc_mainwindow.cpp`
2. Compile `mainwindow.ui` with `uic` to obtain `ui_mainwindow.h`
3. Compile the C++ files, including `moc_mainwindow.cpp`

The `Makefile` implements these three steps.

The first two steps are straightforward: first you need to locate the
`moc` and `uic` commands. They are usually in the QT installation
folder - for example I have them in `/usr/lib64/qt/libexec`. Then run:

```
/usr/lib64/qt/libexec/moc mainwindow.h > moc_mainwindow.cpp
/usr/lib64/qt/libexex/uic mainwindow.ui > ui_mainwindow.h
```

These steps can be skipped if one prefers to write the `moc_` and `ui_`
files directly, removing the dependency on the two tools.

For the last step, one needs to include the header files and link with
the QT libraries.

On my system the header files are in `/usr/include/qt6`. This means I
need to add the option `-I /usr/include/qt6` to my `g++` command. This
project also requires headers contained in a subfolder of this,
so I will add a second `-I` option (see the full command below).

As for the shared libraries, in my case they are installed in a system
folder that is scanned by default by the linker, so I don't have to
specify the path.  We need the files `libQt6Widgets.so`, `libQt6Core.so`
and `libQt6Gui.so`, which we can include with
`-lQt6Widgets -lQt6Core -lQt6Gui`. If your linker does not find them,
locate them and include their folder with `-L /path/to/the/folder`.

So the command for step 3 becomes:

```
g++ main.cpp mainwindow.cpp moc_mainwindow.cpp \
	-I /usr/include/qt6 -I /usr/include/qt6/QtWidgets \
	-lQt6Widgets -lQt6Core -lQt6Gui
	-o run
```

And finally you can enjoy your new app:

```
./run
```