Get incorrect widget size by window handle

Tim Tu

Test code:

#!/usr/bin/python3
import sys
from PySide6 import QtCore
from PySide6.QtWidgets import *
from PySide6.QtGui import *
from PySide6.QtCore import *


class Example(QWidget):
    def __init__(self):
        super(Example, self).__init__()
        self.initUI()

    def initUI(self):
        self.setWindowFlags(Qt.FramelessWindowHint)
        self.setGeometry(300, 100, 300, 200)
        print(self.size())


if __name__ == '__main__':
    app = QApplication(sys.argv)
    window = Example()
    window.show()
    sys.exit(app.exec_())

This problem only happen on PySide6 and PyQt6, there is no problem on PyQt5 and PySide2. So I think it's qt6's problem.

Axel Spoerl

Hi,

without seeing any relevant code, this answer is based on two assumptions:

the window system is Wayland (because xwininfo is used)
by "window handle", you mean QWidget::windowHandle() (not QWindow::handle(), which returns a QPlatformWindow * )

FramlessWindowHintproduces a borderless window, if supported by the window manager. There's no guarantee, however. QWindow::geometry()returns the window geometry exclusive of its frame (both in Qt 5 and Qt 6). The handling of window decorations has changed in the Qt Wayland implementation from Qt 5 to Qt 6. Without having any information about the Wayland configuration at hand, I can only suspect that a native window decoration is rendered regardless of the FramelessWindowHint. Probably because it would not be possible to close/resize the window otherwise. The difference of 13/8 pixels represents the window decoration.
You can figure that out by calling QPlatformWindow::frameMargins().

Cheers
Axel

Tim Tu

Thanks for your reply.
I think I should give you a specific example.

import os
import sys
from OCC.Core.BRepPrimAPI import BRepPrimAPI_MakeBox

from PySide6.QtWidgets import (
    QApplication,
    QMainWindow
)

from OCC.Display.backend import load_backend

load_backend("qt-pyside6")
import OCC.Display.qtDisplay as qtDisplay


class App(QMainWindow):
    def __init__(self):
        super().__init__()
        self.title = "PyQt5 / pythonOCC"
        self.left = 300
        self.top = 300
        self.width = 800
        self.height = 300
        self.initUI()

    def initUI(self):
        self.setWindowTitle(self.title)
        self.setGeometry(self.left, self.top, self.width, self.height)
        self.canvas = qtDisplay.qtViewer3d(self)
        self.setCentralWidget(self.canvas)
        self.canvas.InitDriver()
        self.display = self.canvas._display
        a_box = BRepPrimAPI_MakeBox(10.0, 20.0, 30.0).Shape()
        self.ais_box = self.display.DisplayShape(a_box)[0]
        self.display.FitAll()
        self.show()
        self.canvas.InitDriver()
        print(self.size())
        

if __name__ == "__main__":
    app = QApplication(sys.argv)
    ex = App()
    sys.exit(app.exec_())

(If you want to try this example, please install pythonocc-core conda install pythonocc-core)
PythonOCC depends on window handle to display in qt window.
547c3575-5e85-45d8-b958-9e20ddb1d59f-图片.png
It causes so issues.

Axel Spoerl

@Tim-Tu
What's is returned by yourWidget->windowHandle()->handle()->frameMargins()?

Tim Tu

@Axel-Spoerl

@Axel-Spoerl said in Get incorrect widget size by window handle:

What's is returned by yourWidget->windowHandle()->handle()->frameMargins()?

There is some thing wrong:

    print(self.windowHandle().Handle())
AttributeError: 'PySide6.QtGui.QWindow' object has no attribute 'Handle'

Did you means contentsMargins?
I have changed the test code:

##Author github user @Tanneguydv, 2021

import os
import sys
from OCC.Core.BRepPrimAPI import BRepPrimAPI_MakeBox

from PySide6.QtWidgets import (
    QApplication,
    QWidget,
    QVBoxLayout
)

from OCC.Display.backend import load_backend

load_backend("qt-pyside6")
import OCC.Display.qtDisplay as qtDisplay


class App(QWidget):
    def __init__(self):
        super().__init__()
        self.title = "PyQt5 / pythonOCC"
        self.left = 300
        self.top = 300
        self.width = 800
        self.height = 300
        self.initUI()

    def initUI(self):
        self.setWindowTitle(self.title)
        self.setGeometry(self.left, self.top, self.width, self.height)
        self.lay = QVBoxLayout()
        self.setLayout(self.lay)

        self.canvas = qtDisplay.qtViewer3d(self)
        self.lay.addWidget(self.canvas)
        self.canvas.InitDriver()
        self.display = self.canvas._display

        a_box = BRepPrimAPI_MakeBox(10.0, 20.0, 30.0).Shape()
        self.ais_box = self.display.DisplayShape(a_box)[0]
        self.display.FitAll()
        
        self.show()
        self.canvas.InitDriver()

        print(self.size())
        print(self.canvas.size())
        print(self.contentsMargins())
        print(self.canvas.contentsMargins())

if __name__ == "__main__":
    app = QApplication(sys.argv)
    ex = App()
    sys.exit(app.exec_())

The result:

Xw_Window created.
Display3d class successfully initialized.
#########################################
OpenGl information:
  GLvendor: AMD
  GLdevice: AMD Radeon Graphics (rembrandt, LLVM 15.0.7, DRM 3.52, 6.4.8-arch1-1)
  GLversion: 4.6 (Compatibility Profile) Mesa 23.1.5
  GLSLversion: 4.60
  Max texture size: 16384
  Max FBO dump size: 16384x16384
  Max combined texture units: 192
  Max MSAA samples: 8
  Viewport: 810x290
  Window buffer: RGB8 ALPHA8 DEPTH24 STENCIL8
  ResolutionRatio: 1
  FBO buffer: GL_SRGB8_ALPHA8 GL_DEPTH24_STENCIL8
PySide6.QtCore.QSize(800, 300)
PySide6.QtCore.QSize(778, 278)
<PySide6.QtCore.QMargins(0, 0, 0, 0) at 0x7f5581c95ec0>
<PySide6.QtCore.QMargins(0, 0, 0, 0) at 0x7f5581c95ec0>

Axel Spoerl

There is some thing wrong:
print(self.windowHandle().Handle())
AttributeError: 'PySide6.QtGui.QWindow' object has no attribute 'Handle'

handle(), not Handle().

Tim Tu

@Axel-Spoerl
Sorry, but there still has no attribute

    print(self.windowHandle().handle())
AttributeError: 'PySide6.QtGui.QWindow' object has no attribute 'handle'

JonB

@Axel-Spoerl
QWindow Class shows no sign of a (public at least, from C++, let alone Python) handle() method?

Axel Spoerl

@JonB
Hm, qwindow.cpp:2050-2070:

/*!
    Returns the platform window corresponding to the window.

    \internal
*/
QPlatformWindow *QWindow::handle() const
{
    Q_D(const QWindow);
    return d->platformWindow;
}

But...wait: It's a public method, documented as internal. That's why it doesn't show up in the documentation and maybe also not in python.

JonB

@Axel-Spoerl
:) And is it public? If so, either it's not documented, or maybe because of that it didn't get added into PySide/PyQt (since the OP shows it not working from Python)? The comment shows \internal....

And it returns a QPlatformWindow, which does not seem to be documented either, so maybe that's why it's not provided?? [It seems to have been mentioned in Qt 4.8 but not since then? :) ]

Axel Spoerl

@JonB
Messages crossed ;-)
It's indeed public.
QPlatformWindow also isn't documented and probably not available in PySide/PyQt.
Thanks, Jon, for the hint.

JonB

@Axel-Spoerl said in Get incorrect widget size by window handle:

It's indeed public.

I just added to my previous: The comment shows \internal....

Axel Spoerl

Nontheless, to conclude this thread somehow:
FramlessWindowHintis a hint and doesn't guarantee that window is really rendered frameless.
Native handles seem to get rendered in the case at hand. The pixel difference represents their size.
Given that my proposed way to confirm it doesn't work out in Python, looking at the physical window on the screen is the only way to confirm.