2.5 KiB
| title | date | draft | tags | ||||
|---|---|---|---|---|---|---|---|
| Binding QML with Python: PyViewer | 2021-08-29T12:53:19+02:00 | false |
|
PyViewer is a example project which implements a simple image browser / viewer in a scrollable grid array. This main objective here was using QML to define a graphical layout and bind it to a python code-base. Note that this code base is compatible with both Pyside2 and Pyside6. This is because while Pyside6 is preferred it is not readily available on all platforms. Running Pyside6 instead only recommend the qml library version requirements to omitted.
Please take a look at the git repository for exact implementation details. A brief summary of this interaction is presented below.
Emitting QML Calls
Creating a QObject and adding PySide2.QtCore.Slot decorators to its methods
will allow a python object to be added to the qml context as a referenceable
object. For example here we add "viewer" to the qml context which is a
"PyViewer" python object.
pyviewer = PyViewer()
engine.rootContext().setContextProperty("viewer", pyviewer)
This way we can call the object's python procedure "update_tag_filter" from within the QML script as follows:
viewer.update_tag_filter(false);
Further using the PySide2.QtCore.Property decorator further allows us to call
states in our python object and manipulate them as it were a qml object.
viewer.path.split("::")
Emitting Python Calls
Once this context is working we can create a PySide2.QtCore.Signal object to
call QML methods from within the python context. A python procedure could then
"emit" this signal and thereby prompt any connected qml methods.
self.path_changed.emit()
In the qml contect we can connect the signals from the python "viewer" object to a qml function call "swipe.update_paths" for example.
viewer.path_changed.connect(swipe.update_paths)
Downside
Debugging and designing QML in this environment is limited since the pyside python library does not support all available QML/QT6 functionality. In most cases you are looking at C++ Qt documentation for how the pyside data-types and methods are supposed to behave without good hinting.
Also the variety in data types that can be passed from one context to the other is constrained although in this case I was able to manage with strings and byte objects.
Other Notes: TODO
ImageCms.profileToProfile(img, 'USWebCoatedSWOP.icc',
'sRGB Color Space Profile.icm', renderingIntent=0, outputMode='RGB')