New PySide6 project does not show widgets

tilz0R

When you start new UI project in QtCreator 9.0.0, with PySide6.4.1, running the script won't load the widgets.
You have to manually call centralWidget().show() to get something on the screen.

Video recorded: https://www.youtube.com/watch?v=7_58210bylQ

Steps:

New project created and run is called to verify default status
Button is added and main layout is vertically oriented - > calling run does NOT show the button on the screen - but program taskbar is visible
python code must be updated to show central widget - > button (and the rest of UI) is now visible, but there is NO program taskbar visible
If both, widget.show() and widget.centralWidget().show() are both enabled, 2 windows appear.

Taskbar is visible only if I call widget.show() that turns main window on. But it does not display its content -> why?

How do we make full UI visible AND taskbar visible from PySide6 dynamic UI module example, with single window?

SGaist

One issue I can see is that you are creating a new QMainWindow that you want to embedded in your own QMainWindow subclass. While it's not an issue per se, it's not really something you would do.

From my perspective, your form.ui is the main widget of your application, so you should instantiate and use it directly rather than use your MainWindow in between. The load method of QUiLoader does not act in the same fashion as when you generate the code from the .ui file. It creates a new instance of the widget defined in that file nad if you give it a parent, then set it as parent of the newly created widget. You can see how it is used in the QUiLoader documentation details.

The UI files tutorial also shows the difference between the two approaches.

SGaist

Hi,

Can you provide a minimal script that shows this behaviour ?

tilz0R

Sure, here below is UI file and mainwindow.py.

You have to play with mainwindow python file. Enable widget.centralWidget().show() and/or widget.show() and observe how:

Taskbar is shown or not
One or 2 windows are visible
Button is displayed on the window or not

Target is to have 1 window, button displayed, taskbar icon visible. Code is below, or on Google Drive.

mainwindow.py

# This Python file uses the following encoding: utf-8
import os
from pathlib import Path
import sys

from PySide6.QtWidgets import QApplication, QMainWindow
from PySide6.QtCore import QFile
from PySide6.QtUiTools import QUiLoader


class MainWindow(QMainWindow):
    def __init__(self, parent=None):
        super().__init__(parent)
        self.load_ui()

    def load_ui(self):
        loader = QUiLoader()
        path = Path(__file__).resolve().parent / "form.ui"
        ui_file = QFile(path)
        ui_file.open(QFile.ReadOnly)
        loader.load(ui_file, self)
        ui_file.close()


if __name__ == "__main__":
    app = QApplication(sys.argv)
    widget = MainWindow()

    # Default generated code
    # does not show widgets
    #widget.centralWidget().show()
    widget.show()
    sys.exit(app.exec())

form.ui

<?xml version="1.0" encoding="UTF-8"?>
<ui version="4.0">
 <class>MainWindow</class>
 <widget class="QMainWindow" name="MainWindow">
  <property name="geometry">
   <rect>
    <x>0</x>
    <y>0</y>
    <width>606</width>
    <height>364</height>
   </rect>
  </property>
  <property name="windowTitle">
   <string>MainWindow</string>
  </property>
  <widget class="QWidget" name="centralwidget">
   <layout class="QVBoxLayout" name="verticalLayout">
    <item>
     <widget class="QPushButton" name="pushButton">
      <property name="text">
       <string>PushButton</string>
      </property>
     </widget>
    </item>
   </layout>
  </widget>
  <widget class="QMenuBar" name="menubar">
   <property name="geometry">
    <rect>
     <x>0</x>
     <y>0</y>
     <width>606</width>
     <height>24</height>
    </rect>
   </property>
   <widget class="QMenu" name="menuFile">
    <property name="title">
     <string>File</string>
    </property>
    <addaction name="actionOpen"/>
   </widget>
   <widget class="QMenu" name="menuHelp">
    <property name="title">
     <string>Help</string>
    </property>
    <addaction name="actionAbout"/>
   </widget>
   <addaction name="menuFile"/>
   <addaction name="menuHelp"/>
  </widget>
  <widget class="QStatusBar" name="statusbar"/>
  <action name="actionOpen">
   <property name="text">
    <string>Open</string>
   </property>
  </action>
  <action name="actionAbout">
   <property name="text">
    <string>About</string>
   </property>
  </action>
 </widget>
 <resources/>
 <connections/>
</ui>

tilz0R

@SGaist said in New PySide6 project does not show widgets:

Hi,

Can you provide a minimal script that shows this behaviour ?

Have you been able to check please?

SGaist

One issue I can see is that you are creating a new QMainWindow that you want to embedded in your own QMainWindow subclass. While it's not an issue per se, it's not really something you would do.

From my perspective, your form.ui is the main widget of your application, so you should instantiate and use it directly rather than use your MainWindow in between. The load method of QUiLoader does not act in the same fashion as when you generate the code from the .ui file. It creates a new instance of the widget defined in that file nad if you give it a parent, then set it as parent of the newly created widget. You can see how it is used in the QUiLoader documentation details.

The UI files tutorial also shows the difference between the two approaches.

tilz0R

But since the code is directly coming from QtCreator new project, shall we report this as a bug?

tilz0R

Changing the code to the one below, I finally have a window, with all widgets (top menu, status bar, ...) and windows taskbar icon!

# Extend from QObject
class MainWindow(QObject):
    def __init__(self):
        super(MainWindow, self).__init__()
        self.load_ui()

        self.window.show()

    def load_ui(self):
        loader = QUiLoader()
        path = Path(__file__).resolve().parent / "form.ui"
        ui_file = QFile(path)
        ui_file.open(QFile.ReadOnly)

        # Load window manually
        self.window = loader.load(ui_file)
        ui_file.close()

        # Now show the window
        self.window.show()

if __name__ == "__main__":
    app = QApplication(sys.argv)
    widget = MainWindow()
    sys.exit(app.exec())

Thanks for the support.

SGaist

In your case, MainWindow is just overkill. Just move the load_ui code in your main function.

Erriez

@tilz0R Related to: https://forum.qt.io/post/742517