commit 7219836b03f169f9ea69e4dfdf3f35dfdba80ab0
parent 111ca020e8a8bc480663afb62f2006e35b732320
Author: Sebastiano Tronto <sebastiano@tronto.net>
Date: Fri, 4 Apr 2025 16:21:22 +0200
Added blog post
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1 file changed, 100 insertions(+), 0 deletions(-)
diff --git a/src/blog/2025-04-04-qt-minimal/qt-minimal.md b/src/blog/2025-04-04-qt-minimal/qt-minimal.md
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+# Getting started with QT, without the nonsense
+
+At work I have recently (yesterday) ended working on a big project and
+I am now waiting for a new assignment. While I wait, I decided that I
+should take some time to learn something that could be useful both at
+work and for my personal projects. After some thought, I settled on QT
+development with C++.
+
+Any tutorial on this topic tells you to start by downloading QT Creator,
+an full-blown IDE, and set up a new project from there. In a few clicks
+you'll have a couple of source code files and a CMakeLists.txt full of
+[CMake](https://nl.wikipedia.org/wiki/CMake) magic. Ready to go!
+
+But there is a problem. I don't like full-blown IDEs (although admittedly
+QT Creator seems quite snappy), and I don't like being locked into specific
+tools such as CMake. I tried to look online how to set up a QT project
+without these, but I could not find anything, so I had to figure it out on
+my own. And then I wrote this post so you don't have have to waste your
+time like I did :)
+
+You can find the source code for this tiny project
+[here](https://git.tronto.net/minimal-qt) (or
+[here](https://github.com/sebastianotronto/minimal-qt)) if you have bad
+tase and prefer github over my [self-hosted](../2022-11-23-git-host/)
+git instance. If you just want to try it out you can run, from the
+project's main folder:
+
+```
+make && run
+```
+
+But keep reading if you want to understand how this works!
+
+## 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.
+
+## 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
+```
