Show/Hide height animation with SetFixedSize

[mnunberg]

I've been trying for quite a while now to have a window which automatically shrinks to the size of its widgets, and whose child widgets' hide/show operations will be animated.

So far I've managed to get a window which will shrink, using window.layout().setSizeConstraint(QLayout.SetFixed Size) - and then overriding the widget's sizeHint (see the code).

I have been experimenting with different sizePolicies on the widget and different sizeConstraints on the encapsulating layouts -- needless to say, they have each had slightly different (and horrible) results. Here is my code -- in which the animation doesn't work at all:

#!/usr/bin/env python
 
from PyQt4.QtGui import *
from PyQt4.QtCore import *
import sys
 
connect = QObject.connect
 
app = QApplication(sys.argv)
 
def print_qsize(sz, title=""):
    print title, "W: ", sz.width(), " H: ", sz.height()
 
class ResizingWindow(QMainWindow):
    def __init__(self, parent=None):
        QMainWindow.__init__(self, parent)
        centralwidget = QWidget(self)
        self.setCentralWidget(centralwidget)
        layout = QVBoxLayout()
        centralwidget.setLayout(layout)
 
        checkbox1 = QCheckBox("Show First Widget", self)
        checkbox2 = QCheckBox("Show Second Widget", self)
        textedit1 = QPlainTextEdit(self)
        textedit2 = QPlainTextEdit(self)
 
        layout.addWidget(checkbox1)
        layout.addWidget(textedit1)
        layout.addWidget(checkbox2)
        layout.addWidget(textedit2)
 
        connect(checkbox1, SIGNAL("toggled(bool)"), lambda b: self.hide_resize(textedit1, b))
        connect(checkbox2, SIGNAL("toggled(bool)"), lambda b: self.hide_resize(textedit2, b))
 
        self.modify_widget(textedit1)
        self.modify_widget(textedit2)
        textedit1.hide()
        textedit2.hide()
 
        self.layout().setSizeConstraint(QLayout.SetFixedSize)
 
    def modify_widget(self, widget):
        #this is needed so that the widget 'inherits' the existing size of the
        #layout rather than forcing the layout to expand even further.. don't ask
        #me how this works
        def sizeHint():
            return QSize(1, 1)
        widget.sizeHint = sizeHint
 
    def hide_resize(self, widget, show=True):
        if show:
            #this doesn't work
            widget.resize(widget.width(), 1)
            widget.show()
 
            #neither does this
            widget.resize(widget.width(), 1)
 
            #and neither do these:
            a = QPropertyAnimation(widget, "height", widget)
            a.setStartValue(1)
            a.setEndValue(100)
            a.setDuration(250)
            a.start()
        else:
            widget.hide()
 
mw = ResizingWindow()
mw.show()
app.exec_()

#!/usr/bin/env python

from PyQt4.QtGui import *
from PyQt4.QtCore import *
import sys

connect = QObject.connect

app = QApplication(sys.argv)

def print_qsize(sz, title=""):
    print title, "W: ", sz.width(), " H: ", sz.height()

class ResizingWindow(QMainWindow):
    def __init__(self, parent=None):
        QMainWindow.__init__(self, parent)
        centralwidget = QWidget(self)
        self.setCentralWidget(centralwidget)
        layout = QVBoxLayout()
        centralwidget.setLayout(layout)
        
        checkbox1 = QCheckBox("Show First Widget", self)
        checkbox2 = QCheckBox("Show Second Widget", self)
        textedit1 = QPlainTextEdit(self)
        textedit2 = QPlainTextEdit(self)
        
        layout.addWidget(checkbox1)
        layout.addWidget(textedit1)
        layout.addWidget(checkbox2)
        layout.addWidget(textedit2)
                
        connect(checkbox1, SIGNAL("toggled(bool)"), lambda b: self.hide_resize(textedit1, b))
        connect(checkbox2, SIGNAL("toggled(bool)"), lambda b: self.hide_resize(textedit2, b))
        
        self.modify_widget(textedit1)
        self.modify_widget(textedit2)
        textedit1.hide()
        textedit2.hide()
        
        self.layout().setSizeConstraint(QLayout.SetFixedSize)
            
    def modify_widget(self, widget):
        #this is needed so that the widget 'inherits' the existing size of the
        #layout rather than forcing the layout to expand even further.. don't ask
        #me how this works
        def sizeHint():
            return QSize(1, 1)
        widget.sizeHint = sizeHint
        
    def hide_resize(self, widget, show=True):
        if show:
            #this doesn't work
            widget.resize(widget.width(), 1)
            widget.show()
            
            #neither does this
            widget.resize(widget.width(), 1)
            
            #and neither do these:
            a = QPropertyAnimation(widget, "height", widget)
            a.setStartValue(1)
            a.setEndValue(100)
            a.setDuration(250)
            a.start()
        else:
            widget.hide()
            
mw = ResizingWindow()
mw.show()
app.exec_()

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My question is how to make the animation here work? I'm quite sure it involves a magic combination of sizeConstraints and sizePolicy settings, and maybe even a wrapping container widget -- but I haven't found the right combination yet.

Update: Trying to animate the size property rather than just the height yields some results, however I prefer to only dabble with the height, as I would like to leave the width managed by other things - it would be a pain to go through all the layouts and their margins, and then set that width manually by calculating the size of the top-most widget, then subtracting the margins of the layouts

Also, it seems that the animation only works on the widget, but not the window itself (which would be really nice) -- so e.g. the window first expands the full (allowed?) size, and then the widget animates (improperly though)