PySide: Difference between revisions

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[http://en.wikipedia.org/wiki/PyQt PyQt] is a python module that allows python applications to create, access and modify [http://en.wikipedia.org/wiki/Qt_(toolkit) Qt] applications. You can use it for example to create your own Qt programs in python, or to access and modify the interface of a running qt application, like FreeCAD.
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==Introduction== <!--T:28-->
By using the PyQt module from inside FreeCAD, you have therefore full control over its interface. You can for example:
* Add your own panels, widgets and toolbars
* Add or hide elements to existing panels
* Change, redirect or add connections between all those elements


<!--T:29-->
PyQt has an extensive [http://www.riverbankcomputing.co.uk/static/Docs/PyQt4/html/classes.html API documentation], and there are many tutorials on the net to teach you how it works.
[[PySide|PySide]] is a library that allows you to use the cross-platform graphical user interface (GUI) toolkit Qt with [[Python|Python]]. Qt is a C++ collection of libraries, so its components are normally available from C++, but with the help of PySide, we can use the same components from Python. This means that every complex graphical interface that we can image that can be created in C++, can also be created and modified in Python. An advantage of using Python is that Qt interfaces can be developed and tested live, as we don't need to compile the source files.


<!--T:54-->
If you want to work on the FreeCAD interface, the very first thing to do is create a reference to the FreeCAD main window:
When you [[Installing|install]] FreeCAD, you should get both Qt and PySide as part of the package. If you are [[Compiling|compiling]] yourself, then you must verify that these two libraries are installed, in order for FreeCAD to run correctly. Of course, PySide will only work if Qt is present.


<!--T:55-->
import sys
In the past, FreeCAD used PyQt, another Qt binding for Python, but in 2013 ([https://github.com/FreeCAD/FreeCAD/commit/1dc122dc9a 1dc122dc9a]) the project migrated to PySide because it has a more permissible [[licence|license]].
from PyQt4 import QtGui
app = QtGui.qApp
mw = app.activeWindow()


<!--T:56-->
Then, you can for example browse through all the widgets of the interface:
For more information see:
* [http://en.wikipedia.org/wiki/PySide Wikipedia:PySide]
* [http://qt-project.org/wiki/Differences_Between_PySide_and_PyQt Differences Between PySide and PyQt]


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for child in mw.children():
[[File:PySideScreenSnapshot1.jpg]] [[File:PySideScreenSnapshot2.jpg]]
print 'widget name = ', child.objectName(), ', widget type = ', child
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{{Caption|Examples created with PySide. Left: a simple dialog. Right: a more complex dialog with graphs.}}


== PySide in FreeCAD with Qt5 == <!--T:47-->
The widgets in a Qt interface are usually nested into "containers" widgets, so the children of our main window can themselves contain other children. Depending on the widget type, there are a lot of things you can do. Check the API documentation to see what is possible.


<!--T:48-->
Adding a new widget, for example a dockWidget (which can be placed in one of FreeCAD's side panels) is easy:
FreeCAD was developed to be used with Python 2 and Qt4. As these two libraries became obsolete, FreeCAD transitioned to Python 3 and Qt5. In most cases this transition was done without needing to break backwards compatibility.


<!--T:49-->
myWidget = QtGui.QDockWidget()
Normally, the {{incode|PySide}} module provides support for Qt4, while {{incode|PySide2}} provides support for Qt5. However, in FreeCAD, there is no need to use {{incode|PySide2}} directly, as a special {{incode|PySide}} module is included to handle Qt5.
mw.addDockWidget(QtCore.Qt.RightDockWidgetArea,myWidget)


<!--T:50-->
You could then add stuff directly to your widget:
This {{incode|PySide}} module is located in the {{incode|Ext/}} directory of an installation of FreeCAD compiled for Qt5.
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{{Code|code=
/usr/share/freecad/Ext/PySide
}}
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myWidget.setObjectName("my Nice New Widget")
This module just imports the necessary classes from {{incode|PySide2}}, but places them in the {{incode|PySide}} namespace. This means that in most cases the same code can be used with both Qt4 and Qt5, as long as it imports the single {{incode|PySide}} module.
myWidget.resize(QtCore.QSize(300,100)) # sets size of the widget
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label = QtGui.QLabel("Hello World", myWidget) # creates a label
{{Code|code=
label.setGeometry(QtCore.QRect(50,50,200,24)) # sets its size
PySide2.QtCore -> PySide.QtCore
label.setObjectName("myLabel") # sets its name, so it can be found by name
PySide2.QtGui -> PySide.QtGui
PySide2.QtSvg -> PySide.QtSvg
PySide2.QtUiTools -> PySide.QtUiTools
}}
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<!--T:52-->
But a preferred method is to create a UI object which will do all of the setup of your widget at once. The big advantage is that such an UI object can be [[Dialog creation|created graphically]] with the Qt Designer program. A typical object generated by Qt Designer is like this:
The only unusual aspect is that the {{incode|PySide2.QtWidgets}} classes are placed in the {{incode|PySide.QtGui}} namespace.
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{{Code|code=
PySide2.QtWidgets.QCheckBox -> PySide.QtGui.QCheckBox
}}
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== Real examples of PySide use == <!--T:58-->
class myWidget_Ui(object):
def setupUi(self, myWidget):
myWidget.setObjectName("my Nice New Widget")
myWidget.resize(QtCore.QSize(300,100).expandedTo(myWidget.minimumSizeHint())) # sets size of the widget
self.label = QtGui.QLabel(myWidget) # creates a label
self.label.setGeometry(QtCore.QRect(50,50,200,24)) # sets its size
self.label.setObjectName("label") # sets its name, so it can be found by name
def retranslateUi(self, draftToolbar): # built-in QT function that manages translations of widgets
myWidget.setWindowTitle(QtGui.QApplication.translate("myWidget", "My Widget", None, QtGui.QApplication.UnicodeUTF8))
self.label.setText(QtGui.QApplication.translate("myWidget", "Welcome to my new widget!", None, QtGui.QApplication.UnicodeUTF8))


<!--T:38-->
To use it, you just need to apply it to your freshly created widget like this:
* [[PySide Beginner Examples]], hello world, announcements, enter text, enter number.
* [[PySide Intermediate Examples]], window sizing, hiding widgets, popup menus, mouse position, mouse events.
* [[PySide Advanced Examples]], many widgets.


<!--T:39-->
myNewFreeCADWidget = QtGui.QDockWidget() # create a new dckwidget
The examples of PySide are divided into 3 parts, differentiated by level of exposure to PySide, Python and the FreeCAD internals. The first page has an overview on PySide; the second and third pages are mostly code examples at different levels.
myNewFreeCADWidget.ui = myWidget_Ui() # load the Ui script
myNewFreeCADWidget.ui.setupUi(myNewFreeCADWidget) # setup the ui
FCmw.addDockWidget(QtCore.Qt.RightDockWidgetArea,myNewFreeCADWidget) # add the widget to the main window


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It is expected that these examples are useful to get started, and afterwards the user can consult other resources online, or the official documentation.


== Documentation == <!--T:59-->
{{languages | {{es|PyQt/es}} {{ru|PyQt/ru}} {{se|PyQt/se}} }}


<!--T:60-->
[[Category:Poweruser Documentation]]
There are some differences in handling of widgets in Qt4 (PySide) and Qt5 (PySide2). The programmer should be aware of these incompatibilities, and should consult the official documentation if something doesn't seem to work as expected in a given platform. Nevertheless, Qt4 is considered obsolete, so most development should target Qt5 and Python 3.

<!--T:61-->
The PySide documentation refers to the Python-style classes; however, since Qt is originally a C++ library, the same information should be available in the corresponding C++ reference.
* [https://doc.qt.io/qtforpython/modules.html Qt Modules] available from PySide2 (Qt5).
* [https://doc.qt.io/qt-5/modules-cpp.html All Qt classes by module] in Qt5 for C++.
* [https://deptinfo-ensip.univ-poitiers.fr/ENS/pyside-docs/index.html Qt Modules] available from PySide (Qt4).

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Revision as of 20:17, 15 May 2020

Introduction

PySide is a library that allows you to use the cross-platform graphical user interface (GUI) toolkit Qt with Python. Qt is a C++ collection of libraries, so its components are normally available from C++, but with the help of PySide, we can use the same components from Python. This means that every complex graphical interface that we can image that can be created in C++, can also be created and modified in Python. An advantage of using Python is that Qt interfaces can be developed and tested live, as we don't need to compile the source files.

When you install FreeCAD, you should get both Qt and PySide as part of the package. If you are compiling yourself, then you must verify that these two libraries are installed, in order for FreeCAD to run correctly. Of course, PySide will only work if Qt is present.

In the past, FreeCAD used PyQt, another Qt binding for Python, but in 2013 (1dc122dc9a) the project migrated to PySide because it has a more permissible license.

For more information see:

Examples created with PySide. Left: a simple dialog. Right: a more complex dialog with graphs.

PySide in FreeCAD with Qt5

FreeCAD was developed to be used with Python 2 and Qt4. As these two libraries became obsolete, FreeCAD transitioned to Python 3 and Qt5. In most cases this transition was done without needing to break backwards compatibility.

Normally, the PySide module provides support for Qt4, while PySide2 provides support for Qt5. However, in FreeCAD, there is no need to use PySide2 directly, as a special PySide module is included to handle Qt5.

This PySide module is located in the Ext/ directory of an installation of FreeCAD compiled for Qt5.

/usr/share/freecad/Ext/PySide

This module just imports the necessary classes from PySide2, but places them in the PySide namespace. This means that in most cases the same code can be used with both Qt4 and Qt5, as long as it imports the single PySide module.

PySide2.QtCore -> PySide.QtCore
PySide2.QtGui -> PySide.QtGui
PySide2.QtSvg -> PySide.QtSvg
PySide2.QtUiTools -> PySide.QtUiTools

The only unusual aspect is that the PySide2.QtWidgets classes are placed in the PySide.QtGui namespace.

PySide2.QtWidgets.QCheckBox -> PySide.QtGui.QCheckBox

Real examples of PySide use

The examples of PySide are divided into 3 parts, differentiated by level of exposure to PySide, Python and the FreeCAD internals. The first page has an overview on PySide; the second and third pages are mostly code examples at different levels.

It is expected that these examples are useful to get started, and afterwards the user can consult other resources online, or the official documentation.

Documentation

There are some differences in handling of widgets in Qt4 (PySide) and Qt5 (PySide2). The programmer should be aware of these incompatibilities, and should consult the official documentation if something doesn't seem to work as expected in a given platform. Nevertheless, Qt4 is considered obsolete, so most development should target Qt5 and Python 3.

The PySide documentation refers to the Python-style classes; however, since Qt is originally a C++ library, the same information should be available in the corresponding C++ reference.