PyQt5 QComboBox list items changing postion - python-2.7

Question

I am facing some issue with the display style of Qcombobox items. Currently am hardcoding the data to be shown in the combobox.
here is the code :
self.Dummy = QComboBox(self)
self.Dummy.setGeometry(200,600, 350, 50)
self.Dummy.setStyleSheet("QComboBox {background-color: white;border-style: outset;" border-width: 2px;border-radius: 5px;border-color: #448aff; font: 12px; min-width: 10em; padding: 3px;}")
self.Dummy.addItems(["-Select-", "2", "3","4","5","6","7","8","9","0","11",])
The issue is that the dropdown "list" postion keeps changing after each selection. Here is the image of the issue am facing.
Below is my combobox
The list contains items <-Select->,2,3,4,5,6,7,8,9,0,11 , where <-Select-> will be the first element shown.
Now when I click the box, the box list "down" the elements and suppose I selected '2'. Then, if I try to select another item, the list will be dropped in a "downwards" direction. see below
Now, say if selected the last element from the items, '11'. Now if I try to select a new item by clicking on the box, the list will be popped "up" instead of down. see below
What should be done to fix it ? I don't think its an issue with stylesheet, without it also, this issue is happening. The reason I need this to be fixed is that when the list is popping up, its covering the label above it

Answer 1

What you see is a behavior that is OS and style dependent.
To avoid it, the best way is to subclass QComboBox and overwrite showPopup(), then we call the base class implementation (which is responsible of showing, resizing and positioning the popup view) and move it if necessary.
class Combo(QtWidgets.QComboBox):
def showPopup(self):
super().showPopup()
# find the widget that contains the list; note that this is *not* the view
# that QComboBox.view() returns, but what is used to show it.
popup = self.view().window()
rect = popup.geometry()
if not rect.contains(self.mapToGlobal(self.rect().center())):
# the popup is not over the combo, there's no need to move it
return
# move the popup at the bottom left of the combo
rect.moveTopLeft(self.mapToGlobal(self.rect().bottomLeft()))
# ensure that the popup is always inside the edges of the screen
# we use the center of the popup as a reference, since with multiple
# screens the combo might be between two screens, but that position
# could also be completely outside the screen, so the cursor position
# is used as a fallback to decide on what screen we'll show it
done = False
for i, pos in enumerate((rect.center(), QtGui.QCursor.pos())):
for screen in QtWidgets.QApplication.screens():
if pos in screen.geometry():
screen = screen.geometry()
if rect.x() < screen.x():
rect.moveLeft(screen.x())
elif rect.right() > screen.right():
rect.moveRight(screen.right())
if rect.y() < screen.y():
rect.moveTop(screen.y())
elif rect.bottom() > screen.bottom():
# if the popup goes below the screen, move its bottom
# *over* the combo, so that the its current selected
# item will always be visible
rect.moveBottom(self.mapToGlobal(QtCore.QPoint()).y())
done = True
break
if done:
break
popup.move(rect.topLeft())
This can also be done without subclassing (for example if you have many combos, you created the UI from Designer and don't want to use promoted widgets), but you'll have to remember to change all referencies to the combo.
class MyWindow(QtWidgets.QWidget):
def __init__(self):
# ...
self.combo = QtWidgets.QComboBox()
self.combo.showPopup = self.showPopupAndCheck
def showPopupAndCheck(self):
QtWidgets.QComboBox.showPopup(self.combo)
popup = self.view().window()
rect = popup.geometry()
if not rect.contains(self.combo.mapToGlobal(self.combo.rect().center())):
# the popup is not over the combo, there's no need to move it
return
# change everything from self to self.combo
Alternatively, if you want to keep this behavior consistent through all your program without always using the subclass, you can use some sort of monkey patching hack.
The advantage is that any QComboBox you create (even when loading UI files or creating a combo at runtime) will always use the new behavior.
Important: this MUST be at the very beginning of the main file of your program, possibly just after the import section.
from PyQt5 import QtCore, QtGui, QtWidgets
def customShowPopup(self):
# we can't use super(), because we're not in the class definition, but
# calling the class method with "self" as first argument is practically the
# same thing; note the underscore!
QtWidgets.QComboBox._showPopup(self)
popup = self.view().window()
# ... go on, exactly as above
# create a new reference to the showPopup method, which is the one we've used
# in the function above
QtWidgets.QComboBox._showPopup = QtWidgets.QComboBox.showPopup
# overwrite the original reference with the new function
QtWidgets.QComboBox.showPopup = customShowPopup