These bindings were newly started in August 2024. The bindings are complete for QtCore, QtGui, QtWidgets, QtMultimedia, QtMultimediaWidgets, QtSpatialAudio, QtPrintSupport, QtSvg, QtScript, QtNetwork, QtWebkit, QtWebChannel, QtWebEngine, QScintilla, ScintillaEdit, there is subclassing support, and there is a uic/rcc implementation. But, the bindings may be immature in some ways. Please try out the bindings and raise issues if you have trouble.
Yes. You must also meet your Qt license obligations: either use Qt dynamically-linked dll/so/dylib files under the LGPL, or, purchase a Qt commercial license for static linking.
The first time MIQT is used, your `go build` would take [about 10 minutes](https://github.com/mappu/miqt/discussions/65). But after that, any `go build` is very fast.
If you are compiling your app with a one-shot `docker run` command, the compile speed can be improved if you also bind-mount the Docker container's `GOCACHE` directory: `-v $(pwd)/container-build-cache:/root/.cache/go-build`
- [therecipe/qt](https://github.com/therecipe/qt) is the most mature Qt binding for Go.
- It works by making IPC calls to a separate C++ binary downloaded at runtime from a site under the maintainer's control. This may be less performant than calling Qt directly.
- Because of the LGPL license, it's [extremely difficult to make a proprietary app](https://github.com/therecipe/qt/wiki/FAQ#can-i-make-a-proprietary-app-with-this-binding-). See also their [issue 259](https://github.com/therecipe/qt/issues/259).
- [kitech/qt.go](https://github.com/kitech/qt.go) is another mature Qt binding for Go.
- Unfortunately, it's also using the LGPL license.
- [go-qamel/qamel](https://github.com/go-qamel/qamel) is an MIT-licensed Qt binding for Go.
- Unfortunately, it only supports QML, not Qt Widgets.
The `QByteArray`, `QString`, `QList<T>`, `QVector<T>`, `QMap<K,V>`, `QHash<K,V>` types are projected as plain Go `[]byte`, `string`, `[]T`, and `map[K]V`. Therefore, you can't call any of the Qt type's methods, you must use some Go equivalent method instead.
- Go strings are internally converted to QString using `QString::fromUtf8`. Therefore, the Go string must be UTF-8 to avoid [mojibake](https://en.wikipedia.org/wiki/Mojibake). If the Go string contains binary data, the conversion would corrupt such bytes into U+FFFD (<28>). On return to Go space, this becomes `\xEF\xBF\xBD`.
- The iteration order of a Qt QMap/QHash will differ from the Go map iteration order. QMap is iterated by key order, but Go maps and QHash iterate in an undefined internal order.
Where Qt returns a C++ object by value (e.g. `QSize`), the binding may have moved it to the heap, and in Go this may be represented as a pointer type. In such cases, a Go finalizer is added to automatically delete the heap object. This means code using MIQT can look basically similar to the Qt C++ equivalent code.
- You can also override virtual methods like PaintEvent in the same way. Your callback `func()` receives `super()` as a first argument that can be used to call the base class implementation.
Qt class inherited types are projected as a Go embedded struct. For example, to pass a `var myLabel *qt.QLabel` to a function taking only the `*qt.QWidget` base class, write `myLabel.QWidget`.
- When a Qt subclass adds a method overload (e.g. `QMenu::addAction(QString)` vs `QWidget::addAction(QAction*)`), the base class version is shadowed and can only be called via `myQMenu.QWidget.AddAction(QAction*)`.
The Go runtime migrates goroutines between OS threads, but Qt expects fixed OS threads to be used for each QObject. When you first call `qt.NewQApplication` in MIQT, that will be considered the [Qt main thread](https://doc.qt.io/qt-6/thread-basics.html#gui-thread-and-worker-thread) and will automatically signal the Go runtime to bind to a fixed OS thread using `runtime.LockOSThread()`.
### Q6. Can I use Qt Designer and the Qt Resource system?
MIQT has a custom implementation of Qt `uic` and `rcc` tools, to allow using [Qt Designer](https://doc.qt.io/qt-5/qtdesigner-manual.html) for form design and resource management. After running the `miqt-uic` and `miqt-rcc` tools once, you can rebuild any changes using the convenient `go generate` command.
MIQT uses `pkg-config` to find all used Qt libraries. Every Qt library should have a definition file in `.pc` format, which provides CGO with the necessary `CXXFLAGS`/`LDFLAGS`. Your Qt development environment already included the necessary `.pc` definition files.
You can use the `PKG_CONFIG_PATH` environment variable to override where CGO looks for `.pc` files. [Read more »](pkg-config/README.md)
export GOROOT=/ucrt64/lib/go # Needed only if this is the first time installing Go in MSYS2. Otherwise it would be automatically applied when opening a new Bash terminal.
# Install Qt
pacman -S mingw-w64-ucrt-x86_64-qt5-base # For Qt 5
pacman -S mingw-w64-ucrt-x86_64-qt6-base # For Qt 6
- Note: the MSYS2 `qt5-base` package [is built to use `libicu`](https://github.com/msys2/MINGW-packages/blob/master/mingw-w64-qt5-base/PKGBUILD#L241), whereas the Fsu0413 Qt packages are not. [ICU is included by default with Windows 10 1703 and later](https://devblogs.microsoft.com/oldnewthing/20210527-00/?p=105255). If you are targeting older versions of Windows, then when using MSYS2, your distribution size including `.dll` files will be larger.
Static linking is also available by installing the `mingw-w64-ucrt-x86_64-qt5-static` package and building with `--tags=windowsqtstatic`. The static build will also be smaller as it [does not link to `libicu`](https://github.com/msys2/MINGW-packages/blob/master/mingw-w64-qt5-static/PKGBUILD#L280).
3. Copy necessary Qt LGPL libraries and plugin files.
See FAQ Q3 for advice about docker performance.
To add an icon and other properties to the .exe, you can use [the go-winres tool](https://github.com/tc-hib/go-winres). See the `examples/windowsmanifest` for details.
Installing `qt@5` from Homebrew may be very slow if Homebrew chooses to do a from-source build instead of a binary Bottle build, particularly owing to QtWebEngine (Chromium).
For repeated builds, only steps 3 and 6 are needed. If you customize the `AndroidManifest.xml` file or images, they will be used for the next `androiddeployqt` run.
