The objective:
I'm writing a Gui front-end for a Matplotlib-based library for nested samples (pip install anesthetic if you want to have a look).
How I would go about it in C++: My previous experience with QML was a C++ program, where instead of going into QML to find a canvas to render to, I created a C++ object, registered it in QML's type system, and had it behave as a QtQuick controls widget. As far as I know this is the recommended way of doing things: have all the rendering be done in QML, and have all the business-end-logic in C++.
THe best approach and why I can't do it: This approach doesn't work here. AFAIK you can only implement custom QML using C++, and I need for the program to be pure-ish Python (for others to be able to maintain it) some JS is accessible and QML is pretty easy to understand and edit, so I had no objections (C++ was a hard no).
what I got working: I have a working implementation of what I want. It was all in one file. So, naturally I wanted to split the canvas to which I'm drawing to into a separate file: figure.qml. Trouble is, I can't seem to find the object by that name whenever it's loaded from a separate file (the next step is to use a Loader, because the Figure is quite clunky).
I have a two-file project with view.qml being the root, and a component in Figure.qml.
The trouble is, it only works if I load the thing with objectName: "component" in view.qml and not in Component.qml.
So how does one findChild in Pyside for an objectName that's in a different .qml file?
MWE:
main.py
import sys
from pathlib import Path
from matplotlib_backend_qtquick.backend_qtquickagg import FigureCanvasQtQuickAgg
from matplotlib_backend_qtquick.qt_compat import QtGui, QtQml, QtCore
def main():
app = QtGui.QGuiApplication(sys.argv)
engine = QtQml.QQmlApplicationEngine()
displayBridge = DisplayBridge()
context = engine.rootContext()
qmlFile = Path(Path.cwd(), Path(__file__).parent, "view.qml")
engine.load(QtCore.QUrl.fromLocalFile(str(qmlFile)))
win = engine.rootObjects()[0]
if win.findChild(QtCore.QObject, "figure"):
print('success') # This fails
app.exec_()
view.qml
import QtQuick.Controls 2.12
import QtQuick.Windows 2.12
ApplicationWindow{
Figure {
}
}
Figure.qml
import QtQuick.Controls 2.12
import QtQuick 2.12
Component{
Rectangle{
objectName: "figure"
}
}
Component is used to define a QML element, it does not instantiate it, therefore you cannot access the object. Creating a Figure.qml is equivalent to creating a Component, and you are creating a Component inside another Component.
The solution is not to use Component:
Figure.qml
import QtQuick.Controls 2.12
import QtQuick 2.12
Rectangle{
objectName: "figure"
}
But it is not recommended to use objectName since, for example, if you create multiple components, how will you identify which component it is? o If you create the object after a time T, or use Loader or Repeater you will not be able to apply that logic. Instead of them it is better to create a QObject that allows obtaining those objects:
from PySide2 import QtCore
import shiboken2
class ObjectManager(QtCore.QObject):
def __init__(self, parent=None):
super().__init__(parent)
self._qobjects = []
#property
def qobjects(self):
return self._qobjects
#QtCore.Slot(QtCore.QObject)
def add_qobject(self, obj):
if obj is not None:
obj.destroyed.connect(self._handle_destroyed)
self.qobjects.append(obj)
print(self.qobjects)
def _handle_destroyed(self):
self._qobjects = [o for o in self.qobjects if shiboken2.isValid(o)]
# ...
object_manager = ObjectManager()
context = engine.rootContext()
context.setContextProperty("object_manager", object_manager)
qmlFile = Path(Path.cwd(), Path(__file__).parent, "view.qml")
engine.load(QtCore.QUrl.fromLocalFile(str(qmlFile)))
# ...
import QtQuick.Controls 2.12
import QtQuick 2.12
Rectangle{
Component.onCompleted: object_manager.add_qobject(this)
}
Related
I am trying to write my own QQuickItems that use the SceneGraph to draw shapes as if it the parent Item was a Canvas. I am using PySide6 and Python. During my attempts I found a bug in PySide6, which was earlier reported. I downloaded the patch that fixed it and it seems to be ok now (https://bugreports.qt.io/browse/PYSIDE-1345).
My program now compiles and runs, but the node is not painted. If I understand the documentation correctly, I need to do three things to have a custom QQuickItem painted:
Inherit from QQuickItem
Override updatePaintNode
Set the ItemHasContents flag
I did all that, registered my type, added it in QML and made sure it has non-zero dimensions. Unfortunately, it still does not get paited. I do not know what to do next.
Here's the minimal working example:
main.py
# This Python file uses the following encoding: utf-8
import os
from pathlib import Path
import sys
from PySide6.QtGui import QGuiApplication, QColor
from PySide6.QtQml import QQmlApplicationEngine, qmlRegisterType
from PySide6.QtQuick import QQuickItem, QSGGeometryNode, QSGGeometry, QSGFlatColorMaterial
class JustItem(QQuickItem):
def __init__(self, parent=None):
super().__init__(parent)
self.setFlag(QQuickItem.ItemHasContents)
def updatePaintNode(self, node, update_data):
if node is None:
node = QSGGeometryNode()
geometry = QSGGeometry(QSGGeometry.defaultAttributes_Point2D(), 4)
geometry.setDrawingMode(QSGGeometry.DrawTriangles)
vertex_data = geometry.vertexDataAsPoint2D()
vertex_data[0].set(10, 10)
vertex_data[1].set(100, 10)
vertex_data[2].set(100, 100)
vertex_data[3].set(10, 100)
material = QSGFlatColorMaterial()
material.setColor(QColor(255, 0, 0, 127))
node.setGeometry(geometry)
node.setMaterial(material)
return node
if __name__ == "__main__":
qmlRegisterType(JustItem, "PythonTypes", 1, 0, "JustItem")
app = QGuiApplication(sys.argv)
engine = QQmlApplicationEngine()
engine.load(os.fspath(Path(__file__).resolve().parent / "main.qml"))
if not engine.rootObjects():
sys.exit(-1)
sys.exit(app.exec())
And QML:
import QtQuick
import QtQuick.Window
import PythonTypes 1.0
Window {
width: 640
height: 480
visible: true
title: qsTr("Hello World")
JustItem {
}
}
The result is an empty white window. When I resize it, it segfaults.
This is a bug in PySide 2. Currently it is not possible to draw your custom QQuickItems in PySide 2.
The bug is discussed in more detail here: https://forum.qt.io/topic/116585/qsggeometry-does-not-work-on-pyside2/16
There's also a bug report, which has a proposed fix. The fix causes segmentation fault: https://bugreports.qt.io/browse/PYSIDE-1345
Unfortunately, if you want to draw custom QQuickItems you either need to write them in C++ or use another GUI framework entirely.
I am running code on a Windows 7 VM with Qt Creator and I am getting a module "material" is not installed error when running my code. It is initialized with Python 3.8 using Pyside6. My Qt Creator is version 4.15.0
This is the QML code:
import QtQuick 2.0
import QtQuick.Controls 2.12
Item {
width: 640
height: 480
visible: true
Rectangle {
id: rectangle
x: 232
y: 220
width: 200
height: 200
color: "#c96565"
}
}
This is the Python script: It is a modified version of one of the example default scripts.
import os
import sys
import urllib.request
import json
from pathlib import Path
import PySide6.QtQml
from PySide6.QtQuick import QQuickView
from PySide6.QtCore import QStringListModel, Qt, QUrl
from PySide6.QtGui import QGuiApplication
if __name__ == '__main__':
#Set up the application window
app = QGuiApplication(sys.argv)
view = QQuickView()
view.setResizeMode(QQuickView.SizeRootObjectToView)
#Load the QML file
qml_file = Path(__file__).parent / "main.qml"
view.setSource(QUrl.fromLocalFile(os.fspath(qml_file.resolve())))
#Show the window
if view.status() == QQuickView.Error:
sys.exit(-1)
view.show()
#execute and cleanup
app.exec()
del view
I didn't use Qt Quick Control elements in the QMl yet though. Even if I do have a Quick Control elements there the same thing happens. However, if I remove/comment out the import statement for Qt Quick Controls below, the application runs fine. I've tried changing the version number next to quick controls too without success.
UPDATE: It seems that not being able to find the module is a path issue, so I brute forced the path into the qml file by adding this line to the top: import "./Controls.2" as QtQuickControls
And I copied pasted the Controls.2 folder that is nested in the PySide6 folder into the root directory of this project. The error I get now is
The plugin <filepath to qtquickcontrols2plugin.dll> uses incompatible Qt library. <5.15.0> [release] import "./Controls.2" as QtQuickControls
I figured it out: I don't need to brute force the path in; in the .pydevproject file of your python project, make sure you add in the full path to PySide6 because for some reason the system cannot find it without the path.
Something like this:
<pydev_pathproperty name="org.python.pydev.PROJECT_EXTERNAL_SOURCE_PATH">
<path>\path\to\your\python\venv\or\folder\Lib\site-packages\PySide6</path>
</pydev_pathproperty>
If that doesn't work, try calling the Material module directly:
import QtQuick.Controls.Material 2.12
I have a problem with Toolbar when I use the qml file with PyQt5. The result is not the seem : no background image when mouse is over, image no resize automatically.
I want to know if it's normal.
How can I do for have the same result with PyQt5
The result with qmlscene:
The result with Python:
Thanks you for your help.
File : _test.py
from PyQt5.QtCore import (
pyqtProperty,
pyqtSignal,
pyqtSlot,
QAbstractListModel,
QModelIndex,
QObject,
Qt,
QTimer,
)
from PyQt5.QtGui import QGuiApplication
from PyQt5.QtQml import QQmlApplicationEngine
from PyQt5.QtQuick import QQuickView
class MainWindow(QObject):
def __init__(self, parent=None):
super().__init__(parent)
if __name__ == "__main__":
import sys
app = QGuiApplication(sys.argv)
engine = QQmlApplicationEngine()
engine.quit.connect(app.quit)
main_window = MainWindow()
engine.load("_test.qml")
if not engine.rootObjects():
sys.exit(app.exec_())
sys.exit(app.exec())
File : _test.qml
import QtQuick 2.4
import QtQuick.Layouts 1.1
import QtQuick.Controls 1.3
import QtQuick.Controls.Styles 1.3
ApplicationWindow {
width: 500
height: 200
visible: true
ToolBar {
Layout.fillWidth: true
RowLayout {
anchors.fill: parent
ToolButton {
//width: parent.height
anchors.margins: 4
iconSource: "ico/abacus.png"
}
ToolButton {
width: parent.height
Image {
source: "ico/quitter.png"
anchors.fill: parent
anchors.margins: 4
}
}
ToolButton {
width: parent.height
iconSource: "ico/start.png"
anchors.margins: 4
}
ToolButton {
width: parent.height
Image {
source: "ico/stop.png"
anchors.fill: parent
anchors.margins: 4
}
}
}
}
}
Analyzing the source code of qmlscene and testing with the --apptype option I get the following:
qmlscene _test.qml --apptype gui
qmlscene _test.qml --apptype widgets
So analyzing the fundamental difference is that QApplicacion is being used and not QGuiApplication, so internally it should activate some flag that scales the icons.
Considering the above, the solution is:
from PyQt5.QtCore import QUrl
from PyQt5.QtWidgets import QApplication
from PyQt5.QtQml import QQmlApplicationEngine
if __name__ == "__main__":
import os
import sys
app = QApplication(sys.argv)
engine = QQmlApplicationEngine()
current_dir = os.path.dirname(os.path.realpath(__file__))
file = os.path.join(current_dir, "_test.qml")
engine.load(QUrl.fromLocalFile(file))
if not engine.rootObjects():
sys.exit(-1)
sys.exit(app.exec_())
According to the docs of Qt Quick Controls 1:
Note: We are using QApplication and not QGuiApplication in this
example. Though you can use QGuiApplication instead, doing this will
eliminate platform-dependent styling. This is because it is relying on
the widget module to provide the native look and feel.
So it seems that the scaling of the icons is part of the style of the platform.
Each type of project requires a QXApplication:
Console application: You can use any of the 3 types of QXApplication, but using QCoreApplication is the most optimal since the other QXApplication require that they have a window system that in that case is an unnecessary requirement.
QML Application: It requires at least one QGuiApplication, but for certain ones such as the need to use the styles of each platform it is necessary to use QApplication.
Qt Widgets Application: A QApplication is necessary because QWidgets use the styles of each platform.
The fact that sizes change, is this a problem of QtQuick.Controls 1?
Yes, one of the main differences between QQC1 and QQC2 is that the first one is developed to support desktop platforms so you use the styles, unlike the second one that is designed for embedded systems where the main objective is performance. For more information read Differences with Qt Quick Controls 1
Conclusions:
If you want your GUI made with QML to respect the styles of your desktop platform then you must use QQC1 with QApplication.
If your goal is that the style of your application does not respect the style of the desktop in addition to wanting more performance you should use QQC2 with QGuiApplication.
I am fairly new to Qt/PyQt and currently struggling with some basic functionality. What I'm trying to do is, to dynamically load QML-Views (*.qml) files from python and replace specific content on the fly. For example a checkbox gets checked and part of my current view is replaced with another qml file. First I wanted to provide this logic via PyQt, but it seems a StackView is a better idea (multiple qml files in pyqt).
However, in this case I am not able to inject properties into my QML files. I am only able to inject a property into the rootContext. That however limits the usage of my QML-Views since I can only use one view (of the same type) at once. I would like to inject properties dynamically into QML-Views and make them only visible to this particular view. In this case I can use the same view more than once with more than one object in the back-end to catch the signals.
Here is my SimpleMainWindow.qml file (the main view:
import QtQuick 2.9
import QtQuick.Window 2.2
import QtQuick.Controls 2.3
import QtQuick.Controls 1.4
ApplicationWindow {
id: window
visible: true
width: 640
height: 480
title: qsTr("Hello World")
objectName : "WINDOW"
property ApplicationWindow appWindow : window
}
And here the file I try to load (TestViewButton.qml):
import QtQuick 2.9
import QtQuick.Controls 1.4
Button {
id: test
text: "test"
objectName : "Button"
onClicked: {
configurator.sum(1, 2)
configurator.info("TestOutput")
}
}
Python file loading QML-View (Component)
from PyQt5.QtCore import QObject, QUrl
from PyQt5.QtGui import QGuiApplication
from PyQt5.QtQml import QQmlApplicationEngine, QQmlComponent
if __name__ == "__main__":
app = QGuiApplication(sys.argv)
engine = QQmlApplicationEngine()
engine.load("qml/SimpleMainWindow.qml")
engine.quit.connect(app.quit)
rootWindow = engine.rootObjects()[0].children()[0].parent()
# create component
component = QQmlComponent(engine)
component.loadUrl(QUrl("qml/TestViewButton.qml"))
configurator = SignalHandler()
component.setProperty("configurator", configurator)
itm = component.create()
itm.setParentItem(rootWindow.children()[0])
itm.setProperty("configurator", configurator)
app.exec_()
And the python object that I use to handle the signals from the view (SignalHandler.py):
from PyQt5.QtCore import QObject, pyqtSlot
class SignalHandler(QObject):
#pyqtSlot(int, int)
def sum(self, arg1, arg2):
print("Adding two numbers")
#pyqtSlot(str)
def info(self, arg1):
print("STR " + arg1)
The button loads fine (by the way, is there a better way to identify the parent I want to add my button to, wasn't having any look with findChild). What is not working is the component.setProperty.... part. If I set the property in the rootContext of the engine it works fine (the SignalHandler methods are called). Already checked similar topics (like Load a qml component from another qml file dynamically and access that component's qml type properties ...)
Is this possible, or am I getting something wrong here?
thanks
From what I understand, you want to load the configuration object only in TestViewButton.qml and it is not visible in SimpleMainWindow.qml.
To do this TestViewButton.qml must have its own QQmlContext when it is loaded and is not the rootContext().
To test my response and observe that behavior we will create a similar button that tries to use the configurator, if this is pressed it should throw an error noting that the property does not exist but if the button loaded is pressed by the QQmlComponent should do its job normally.
qml/SimpleMainWindow.qml
import QtQuick 2.9
import QtQuick.Window 2.2
import QtQuick.Controls 2.3
import QtQuick.Controls 1.4
ApplicationWindow {
id: window
visible: true
width: 640
color: "red"
height: 480
title: qsTr("Hello World")
Button {
x: 100
y: 100
text: "ApplicationWindow"
onClicked: {
console.log("ApplicationWindow")
configurator.sum(1, 2)
configurator.info("TestOutput")
}
}
}
As I commented previously I added the component with a new context:
if __name__ == "__main__":
app = QGuiApplication(sys.argv)
engine = QQmlApplicationEngine()
configurator = SignalHandler()
engine.load("qml/SimpleMainWindow.qml")
engine.quit.connect(app.quit)
rootWindow = engine.rootObjects()[0]
content_item = rootWindow.property("contentItem")
context = QQmlContext(engine)
component = QQmlComponent(engine)
component.loadUrl(QUrl("qml/TestViewButton.qml"))
itm = component.create(context)
context.setContextProperty("configurator", configurator)
itm.setProperty("parent", content_item)
sys.exit(app.exec_())
At the end we get the following output:
qml: Component
Adding two numbers
STR TestOutput
qml: ApplicationWindow
file:///xxx/qml/SimpleMainWindow.qml:20: ReferenceError: configurator is not defined
qml: Component
Adding two numbers
STR TestOutput
qml: ApplicationWindow
file:///xxx/qml/SimpleMainWindow.qml:20: ReferenceError: configurator is not defined
Where we observe the desired behavior. The complete example can be found in the following link.
Building off this Pyside tutorial:
http://qt-project.org/wiki/PySide_QML_Tutorial_Advanced_1
http://qt-project.org/wiki/PySide_QML_Tutorial_Advanced_2
http://qt-project.org/wiki/PySide_QML_Tutorial_Advanced_3
http://qt-project.org/wiki/PySide_QML_Tutorial_Advanced_4
I am attempting to do everything in Python and not have any java script.
The only difficulty I've run into is when calling the createObject() method of a QDeclarativeComponent which is described nicely as a "Dynamic Object Management" here:
http://qt-project.org/doc/qt-4.8/qdeclarativedynamicobjects.html
So here is a bare bones example that causes the error:
import sys
from PySide.QtCore import *
from PySide.QtGui import *
from PySide.QtDeclarative import *
class MainWindow(QDeclarativeView):
def __init__(self, parent=None):
super(MainWindow, self).__init__(parent)
self.setWindowTitle("Main Window")
# Renders game screen
self.setSource(QUrl.fromLocalFile('game2.qml'))
# QML resizes to main window
self.setResizeMode(QDeclarativeView.SizeRootObjectToView)
# a qml object I'd like to add dynamically
self.component = QDeclarativeComponent(QDeclarativeEngine(), QUrl.fromLocalFile("Block2.qml"))
# check if were ready to construct the object
if self.component.isReady():
# create the qml object dynamically
dynamicObject = self.component.createObject(self.rootObject())
if __name__ == '__main__':
# Create the Qt Application
app = QApplication(sys.argv)
# Create and show the main window
window = MainWindow()
window.show()
# Run the main Qt loop
sys.exit(app.exec_())
With main window QML file contents ("game2.qml"):
import QtQuick 1.0
Rectangle {
id: screen
width: 490; height: 720
SystemPalette { id: activePalette }
}
And QML object I'd like to dynamically construct ("Block2.qml"):
import QtQuick 1.0
Rectangle {
id: block
}
When I run this code, it crashes at:
dynamicObject = self.component.createObject(self.rootObject())
with:
TypeError: Unknown type used to call meta function (that may be a signal): QScriptValue
I understand the parent must be a QObject but otherwise I'm not entirely sure from the docs what more it should constitute:
http://srinikom.github.io/pyside-docs/PySide/QtDeclarative/QDeclarativeComponent.html
This isn't an issue in C++ according to:
https://qt-project.org/forums/viewthread/7717
It is clearly only an issue in Pyside currently.
Any idea what might be causing this issue? Potential bug?
A work around is to rely on javascript for object creation while everything else is python. In this implementation you pass the qml file of the component and its parent to the javascript implementation that creates the component. It does a basic construction of the object. Would be ideal having pure python solution though for brevity.
import sys
from PySide.QtCore import *
from PySide.QtGui import *
from PySide.QtDeclarative import *
class MainWindow(QDeclarativeView):
def __init__(self, parent=None):
super(MainWindow, self).__init__(parent)
self.setWindowTitle("Main Window")
# Renders game screen
self.setSource(QUrl.fromLocalFile('game2.qml'))
# QML resizes to main window
self.setResizeMode(QDeclarativeView.SizeRootObjectToView)
# a qml object I'd like to add dynamically
parent = self.rootObject()
view = QDeclarativeView()
view.setSource(QUrl.fromLocalFile("comp_create.qml"))
block = view.rootObject().create("Block2.qml", parent)
print block
block.x = 100
block.y = 200
# prove that we created the object
print block.x, block.y
if __name__ == '__main__':
# Create the Qt Application
app = QApplication(sys.argv)
# Create and show the main window
window = MainWindow()
window.show()
# Run the main Qt loop
sys.exit(app.exec_())
The only added QML is a component creator that uses javascript to create objects since Pyside currently wont work ("comp_create.qml"):
import QtQuick 1.0
Item {
id: creator
function create(qml_fname, parent) {
// for a given qml file and parent, create component
var comp = Qt.createComponent(qml_fname);
if (comp.status == Component.Ready) {
// create the object with given parent
var ob = comp.createObject(parent);
if (ob == null) {
// Error Handling
console.log("Error creating object");
}
return ob
} else if (component.status == Component.Error) {
// Error Handling
console.log("Error loading component:", component.errorString());
}
else {
component.statusChanged.connect(finishCreation);
}
return null
}
}
Note, borrowed this code mostly from:
http://qt-project.org/doc/qt-4.8/qdeclarativedynamicobjects.html