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)

[wysota]

Trying with size policies and size constraints is not a good solution. You should just implement your own layout.

[mnunberg]

I poked around a bit at this idea, but I don't see how it will help me with the animation part, - I've only managed to see that the layout's setGeometry is called whenever a widget is shown/hidden.. I tried to play around with that a bit, (some nasty animation stuff with setGeometry, which didn't work, and didn't seem the right way to do it anyway)
Can you give some pointers?

[wysota]

If you implement your own layout you are a master of allocating space for all the managed widgets. You can gradually (i.e. using a timer) increase the size hint returned by the layout to make your main widget grow and you can use setGeometry to manage where the child widgets go. You can also hide/show widgets as you see fit. Of course then you won't be able to show()/hide() those widgets directly or it would break your layout - you'd have to add appropriate API for that in your layout class.

[norobro]

Not sure if this is what you are after or not, but I got the animation to work using the "geometry" property.

I couldn't get it to work using "height" either. Could it be because "height" is constant (int height () const), Wysota?

#!/usr/bin/env python
# -*- coding: utf-8 -*-
 
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()
 
 
        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)
        centralwidget.setLayout(layout)                
        connect(checkbox1, SIGNAL("toggled(bool)"), lambda b: self.hide_resize(textedit1, b))
        connect(checkbox2, SIGNAL("toggled(bool)"), lambda b: self.hide_resize(textedit2, b))
 
        textedit1.hide()
        textedit2.hide()
 
        self.layout().setSizeConstraint(QLayout.SetFixedSize)
 
    def hide_resize(self, widget, show=True):
        if show:
            widget.setVerticalScrollBarPolicy(Qt.ScrollBarAlwaysOff)    #got some flicker as the widget was growing without this
            widget.show()
            a = QPropertyAnimation(widget, "geometry", widget)
            a.setStartValue(QRect(widget.geometry().x(),widget.geometry().y(),0,0))     #use widget's original (x,y) 
            a.setEndValue(QRect(widget.geometry().x(),widget.geometry().y(),256,192))   
            a.setDuration(250)
            a.start()
        else:
            widget.hide()
 
mw = ResizingWindow()
mw.show()
app.exec_()

#!/usr/bin/env python
# -*- coding: utf-8 -*-

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()
        
        
        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)
        centralwidget.setLayout(layout)                
        connect(checkbox1, SIGNAL("toggled(bool)"), lambda b: self.hide_resize(textedit1, b))
        connect(checkbox2, SIGNAL("toggled(bool)"), lambda b: self.hide_resize(textedit2, b))
        
        textedit1.hide()
        textedit2.hide()
        
        self.layout().setSizeConstraint(QLayout.SetFixedSize)
        
    def hide_resize(self, widget, show=True):
        if show:
            widget.setVerticalScrollBarPolicy(Qt.ScrollBarAlwaysOff)    #got some flicker as the widget was growing without this
            widget.show()
            a = QPropertyAnimation(widget, "geometry", widget)
            a.setStartValue(QRect(widget.geometry().x(),widget.geometry().y(),0,0))     #use widget's original (x,y) 
            a.setEndValue(QRect(widget.geometry().x(),widget.geometry().y(),256,192))   
            a.setDuration(250)
            a.start()
        else:
            widget.hide()
            
mw = ResizingWindow()
mw.show()
app.exec_()

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HTH

[mnunberg]

norobo: Your solution works fine, save for the problem that the resizing of the main window itself is not animated - which is also my goal.

I have managed to come up with my own crappy layout implementation. It *works* and does everything i *want* it to, but there must be a better way

a sample run gives me:

increment is  0.5
increment is  0.5
show, going for height 125
got begin 0 end 125 step 0.5
amount_grown is 124
hides
amount_shrunk is 0
show, going for height 125
got begin 0 end 125 step 0.5
amount_grown is 124
hides
amount_shrunk is 0
show, going for height 125
got begin 0 end 125 step 0.5
amount_grown is 124
show, going for height 125
got begin 0 end 125 step 0.5
amount_grown is 124
hides
amount_shrunk is 0
show, going for height 125
got begin 0 end 125 step 0.5
amount_grown is 124
hides
amount_shrunk is 0
show, going for height 125
got begin 0 end 125 step 0.5
amount_grown is 124
 
real	0m13.645s
user	0m2.369s
sys	0m1.193s

increment is  0.5
increment is  0.5
show, going for height 125
got begin 0 end 125 step 0.5
amount_grown is 124
hides
amount_shrunk is 0
show, going for height 125
got begin 0 end 125 step 0.5
amount_grown is 124
hides
amount_shrunk is 0
show, going for height 125
got begin 0 end 125 step 0.5
amount_grown is 124
show, going for height 125
got begin 0 end 125 step 0.5
amount_grown is 124
hides
amount_shrunk is 0
show, going for height 125
got begin 0 end 125 step 0.5
amount_grown is 124
hides
amount_shrunk is 0
show, going for height 125
got begin 0 end 125 step 0.5
amount_grown is 124

real	0m13.645s
user	0m2.369s
sys	0m1.193s

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-- way too much CPU time for this

The updated code is:

#!/usr/bin/env python
# -*- coding: utf-8 -*-
 
from PyQt4.QtGui import *
from PyQt4.QtCore import *
import sys
 
connect = QObject.connect
 
app = QApplication(sys.argv)
 
def copy_size(size):
    return QSize(size.width(), size.height())
 
def xfloat_range(begin,end,step):
    print "got begin", begin, "end", end, "step", step
    while begin < end:
        yield begin
        begin += step
 
def xfloat_range_decrement(begin, end, step):
    while begin > end and begin > 0:
        yield begin
        begin -= step
 
 
def print_qsize(sz, title=""):
    print title, "W: ", sz.width(), " H: ", sz.height()
 
class AnimatedLayout(QHBoxLayout):
    def __init__(self, child, size, parent = None):
        QHBoxLayout.__init__(self, parent)
        self._name = ""
 
        child.sizeHint = lambda: QSize()
        child.setSizePolicy(QSizePolicy.Preferred, QSizePolicy.Ignored)
 
        self.child = child
        self.addWidget(child)
        self.mandated_size = QSize(size.height(), 0)
        self.preferred_size = size
 
        self.setContentsMargins(0,0,0,0)
        self.setSpacing(0)
 
        self.duration = 250
 
        self.amount_grown = 0
        self.amount_shrunk = 0
        self.generator = None
 
        self.timer = QTimer(self)
        self.child.setVisible(True)
 
        self.show = self.startShow
        self.hide = self.startHide
        self.child.show = self.show
        self.child.hide = self.hide
 
        print "increment is ", self.increment
 
    @property
    def increment(self):
        return float(float(self.preferred_size.height())/float(self.duration))
 
    def setGeometry(self, rect):
        #print_qsize(rect.size(), self._name)
        super(type(self), self).setGeometry(rect)
 
    def sizeHint(self):
        return self.mandated_size
 
    def setAnimationDuration(self, msecs):
        self.duration = msecs
 
    def timer_fire_show(self):
        if not self.generator:
            raise Exception("Generator not initialized!")
        try:
            h = int(self.generator.next())
            #print h
            if h > self.amount_grown:
                self.mandated_size.setHeight(h)
                self.amount_grown = h
                self.update()
        except StopIteration:
            #finished:
            print "amount_grown is", self.amount_grown
            self.timer.stop()
            #do any cleanup, just a final check
            self.mandated_size = copy_size(self.preferred_size)
            self.update()
            QObject.disconnect(self.timer, SIGNAL("timeout()"), self.timer_fire_show)
            del self.generator
 
    def startShow(self):
        print "show, going for height", self.preferred_size.height()
        #start an animation here using a timer that will update both our sizeHint
        #as well as the widget's size accordingly
        self.generator = xfloat_range(0, self.preferred_size.height(), self.increment)
        QObject.connect(self.timer, SIGNAL("timeout()"), self.timer_fire_show)
        self.amount_grown = 0
        self.timer.start(1)
 
    def timer_fire_hide(self):
        if not self.generator:
            raise Exception("Generator not initialized")
        try:
            h = int(self.generator.next())
            #print h
            if h < self.amount_shrunk:
                self.mandated_size.setHeight(h)
                self.amount_shrunk = h
                self.update()
        except StopIteration:
            print "amount_shrunk is", self.amount_shrunk
            self.timer.stop()
            self.mandated_size.setHeight(0)
            self.update()
            QObject.disconnect(self.timer, SIGNAL("timeout()"), self.timer_fire_hide)
 
    def startHide(self):
        print "hides"
        self.generator = xfloat_range_decrement(self.preferred_size.height(), 0, self.increment)
        QObject.connect(self.timer, SIGNAL("timeout()"), self.timer_fire_hide)
        self.amount_shrunk = self.preferred_size.height()
        self.timer.start(1)
 
    def setVisible(self, b):
        "convenience method"
        if b:
            self.startShow()
        else:
            self.startHide()        
 
class ResizingWindow(QMainWindow):
    def __init__(self, parent=None):
        QMainWindow.__init__(self, parent)
        self.layout().setSizeConstraint(QLayout.SetFixedSize)
 
        centralwidget = QWidget(self)
        self.setCentralWidget(centralwidget)
        layout = QVBoxLayout()
 
 
        checkbox1 = QCheckBox("Show First Widget", self)
        checkbox2 = QCheckBox("Show Second Widget", self)
        textedit1 = QPlainTextEdit(self)
        textedit2 = QPlainTextEdit(self)
 
        anim_wrapper1 = AnimatedLayout(textedit1, QSize(150, 125))
        anim_wrapper1._name = "anim_wrapper1"
        self.anim_wrapper1 = anim_wrapper1
        anim_wrapper2 = AnimatedLayout(textedit2, QSize(150, 125))
        anim_wrapper2._name = "anim_wrapper2"
        self.anim_wrapper2 = anim_wrapper2
 
 
        layout.addWidget(checkbox1)
        layout.addLayout(anim_wrapper1)
        layout.addWidget(checkbox2)
        layout.addLayout(anim_wrapper2)
        centralwidget.setLayout(layout)
 
        connect(checkbox1, SIGNAL("toggled(bool)"), anim_wrapper1.setVisible)
        connect(checkbox2, SIGNAL("toggled(bool)"), anim_wrapper2.setVisible)            
mw = ResizingWindow()
mw.show()
app.exec_()

#!/usr/bin/env python
# -*- coding: utf-8 -*-

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

connect = QObject.connect

app = QApplication(sys.argv)

def copy_size(size):
    return QSize(size.width(), size.height())

def xfloat_range(begin,end,step):
    print "got begin", begin, "end", end, "step", step
    while begin < end:
        yield begin
        begin += step
        
def xfloat_range_decrement(begin, end, step):
    while begin > end and begin > 0:
        yield begin
        begin -= step

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

class AnimatedLayout(QHBoxLayout):
    def __init__(self, child, size, parent = None):
        QHBoxLayout.__init__(self, parent)
        self._name = ""
        
        child.sizeHint = lambda: QSize()
        child.setSizePolicy(QSizePolicy.Preferred, QSizePolicy.Ignored)
        
        self.child = child
        self.addWidget(child)
        self.mandated_size = QSize(size.height(), 0)
        self.preferred_size = size

        self.setContentsMargins(0,0,0,0)
        self.setSpacing(0)
        
        self.duration = 250
        
        self.amount_grown = 0
        self.amount_shrunk = 0
        self.generator = None
        
        self.timer = QTimer(self)
        self.child.setVisible(True)
        
        self.show = self.startShow
        self.hide = self.startHide
        self.child.show = self.show
        self.child.hide = self.hide
        
        print "increment is ", self.increment
    
    @property
    def increment(self):
        return float(float(self.preferred_size.height())/float(self.duration))
    
    def setGeometry(self, rect):
        #print_qsize(rect.size(), self._name)
        super(type(self), self).setGeometry(rect)
    
    def sizeHint(self):
        return self.mandated_size
    
    def setAnimationDuration(self, msecs):
        self.duration = msecs
        
    def timer_fire_show(self):
        if not self.generator:
            raise Exception("Generator not initialized!")
        try:
            h = int(self.generator.next())
            #print h
            if h > self.amount_grown:
                self.mandated_size.setHeight(h)
                self.amount_grown = h
                self.update()
        except StopIteration:
            #finished:
            print "amount_grown is", self.amount_grown
            self.timer.stop()
            #do any cleanup, just a final check
            self.mandated_size = copy_size(self.preferred_size)
            self.update()
            QObject.disconnect(self.timer, SIGNAL("timeout()"), self.timer_fire_show)
            del self.generator
    
    def startShow(self):
        print "show, going for height", self.preferred_size.height()
        #start an animation here using a timer that will update both our sizeHint
        #as well as the widget's size accordingly
        self.generator = xfloat_range(0, self.preferred_size.height(), self.increment)
        QObject.connect(self.timer, SIGNAL("timeout()"), self.timer_fire_show)
        self.amount_grown = 0
        self.timer.start(1)
    
    def timer_fire_hide(self):
        if not self.generator:
            raise Exception("Generator not initialized")
        try:
            h = int(self.generator.next())
            #print h
            if h < self.amount_shrunk:
                self.mandated_size.setHeight(h)
                self.amount_shrunk = h
                self.update()
        except StopIteration:
            print "amount_shrunk is", self.amount_shrunk
            self.timer.stop()
            self.mandated_size.setHeight(0)
            self.update()
            QObject.disconnect(self.timer, SIGNAL("timeout()"), self.timer_fire_hide)
    
    def startHide(self):
        print "hides"
        self.generator = xfloat_range_decrement(self.preferred_size.height(), 0, self.increment)
        QObject.connect(self.timer, SIGNAL("timeout()"), self.timer_fire_hide)
        self.amount_shrunk = self.preferred_size.height()
        self.timer.start(1)
    
    def setVisible(self, b):
        "convenience method"
        if b:
            self.startShow()
        else:
            self.startHide()        
    
class ResizingWindow(QMainWindow):
    def __init__(self, parent=None):
        QMainWindow.__init__(self, parent)
        self.layout().setSizeConstraint(QLayout.SetFixedSize)
        
        centralwidget = QWidget(self)
        self.setCentralWidget(centralwidget)
        layout = QVBoxLayout()
        
        
        checkbox1 = QCheckBox("Show First Widget", self)
        checkbox2 = QCheckBox("Show Second Widget", self)
        textedit1 = QPlainTextEdit(self)
        textedit2 = QPlainTextEdit(self)
        
        anim_wrapper1 = AnimatedLayout(textedit1, QSize(150, 125))
        anim_wrapper1._name = "anim_wrapper1"
        self.anim_wrapper1 = anim_wrapper1
        anim_wrapper2 = AnimatedLayout(textedit2, QSize(150, 125))
        anim_wrapper2._name = "anim_wrapper2"
        self.anim_wrapper2 = anim_wrapper2
        
        
        layout.addWidget(checkbox1)
        layout.addLayout(anim_wrapper1)
        layout.addWidget(checkbox2)
        layout.addLayout(anim_wrapper2)
        centralwidget.setLayout(layout)
        
        connect(checkbox1, SIGNAL("toggled(bool)"), anim_wrapper1.setVisible)
        connect(checkbox2, SIGNAL("toggled(bool)"), anim_wrapper2.setVisible)            
mw = ResizingWindow()
mw.show()
app.exec_()

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[mnunberg]

Well, I've reworked a cleaner example, but this one jitters, and it doesn't seem to work in my actual code -- I get the children widgets in their own windows?:

#!/usr/bin/env python
# -*- coding: utf-8 -*-
 
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 AnimatedLayout(QLayout):
    STATE_HIDDEN, STATE_VISIBLE, STATE_ANIMATING = range(3)
 
    def __init__(self, child, size, parent = None):
        super(type(self),self).__init__(parent)
        self._name = ""
 
        child.setSizePolicy(QSizePolicy.Preferred, QSizePolicy.Fixed)
        #self.setSizeConstraint(QLayout.SetFixedSize)
 
        self.child = child
        self.mandated_size = QSize(size.width(), 0)
        self.preferred_size = size
 
        self.setContentsMargins(0,0,0,0)
        self.setSpacing(0)
 
        self.duration = 250
        self.child.setVisible(True)
 
        self.show = self.startShow
        self.hide = self.startHide
        self.child.show = self.show
        self.child.hide = self.hide
        self.child.setVisible = self.setVisible
 
        self.child_state = self.STATE_VISIBLE
 
    #these two segfaulted if i tried to do anything legit with them?
    def count(self):
        return 0
    def itemAt(self, index):
        return None    
 
    def setGeometry(self, rect):
        if not self.child_state in (self.STATE_ANIMATING, self.STATE_VISIBLE):
            return
        #super(type(self), self).setGeometry(rect)
        self.child.setGeometry(rect)
 
    def sizeHint(self):
        return self.mandated_size
        #return self.child.sizeHint()
 
    def setAnimationDuration(self, msecs):
        self.duration = msecs
 
    def startShow(self):
        self._start_animation(True)
    def startHide(self):
        self._start_animation(False)
 
    def _start_animation(self, show=True):
        a = QPropertyAnimation(self.child, "geometry", self)
        g = self.child.geometry()
        g.setHeight(0)
        a.setStartValue(g)
        g.setHeight(self.preferred_size.height())
        a.setEndValue(g)
        a.setEasingCurve(QEasingCurve.OutQuad)
        a.setDuration(self.duration)
        def valueChanged(qv):
            r = qv.toRect()
            self.mandated_size.setHeight(r.height())
            self.update()
        connect(a, SIGNAL("valueChanged(QVariant)"), valueChanged)
 
        if not show:
            a.setDirection(a.Backward)
            connect(a, SIGNAL("finished()"), lambda: setattr(self, "child_state", self.STATE_HIDDEN))
        else:
            a.setDirection(a.Forward)
            connect(a, SIGNAL("finished()"), lambda: setattr(self, "child_state", self.STATE_VISIBLE))        
        a.start(a.DeleteWhenStopped)
 
 
    def setVisible(self, b):
        "convenience method"
        if b:
            self.startShow()
        else:
            self.startHide()        
 
class ResizingWindow(QMainWindow):
    def __init__(self, parent=None):
        QMainWindow.__init__(self, parent)
        self.layout().setSizeConstraint(QLayout.SetFixedSize)
 
        centralwidget = QWidget(self)
        self.setCentralWidget(centralwidget)
        layout = QVBoxLayout()
 
 
        checkbox1 = QCheckBox("Show First Widget", self)
        checkbox2 = QCheckBox("Show Second Widget", self)
        textedit1 = QPlainTextEdit(self)
        textedit2 = QPlainTextEdit(self)
        textedit1.setVerticalScrollBarPolicy(Qt.ScrollBarAlwaysOff)
        textedit2.setVerticalScrollBarPolicy(Qt.ScrollBarAlwaysOff)
 
        anim_wrapper1 = AnimatedLayout(textedit1, QSize(150, 125))
        anim_wrapper1._name = "anim_wrapper1"
        self.anim_wrapper1 = anim_wrapper1
        anim_wrapper2 = AnimatedLayout(textedit2, QSize(150, 125))
        anim_wrapper2._name = "anim_wrapper2"
        self.anim_wrapper2 = anim_wrapper2
 
 
        layout.addWidget(checkbox1)
        layout.addLayout(anim_wrapper1)
        layout.addWidget(checkbox2)
        layout.addLayout(anim_wrapper2)
        centralwidget.setLayout(layout)
 
        connect(checkbox1, SIGNAL("toggled(bool)"), anim_wrapper1.setVisible)
        connect(checkbox2, SIGNAL("toggled(bool)"), anim_wrapper2.setVisible)            
mw = ResizingWindow()
mw.show()
app.exec_()

#!/usr/bin/env python
# -*- coding: utf-8 -*-

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 AnimatedLayout(QLayout):
    STATE_HIDDEN, STATE_VISIBLE, STATE_ANIMATING = range(3)
    
    def __init__(self, child, size, parent = None):
        super(type(self),self).__init__(parent)
        self._name = ""
        
        child.setSizePolicy(QSizePolicy.Preferred, QSizePolicy.Fixed)
        #self.setSizeConstraint(QLayout.SetFixedSize)
        
        self.child = child
        self.mandated_size = QSize(size.width(), 0)
        self.preferred_size = size

        self.setContentsMargins(0,0,0,0)
        self.setSpacing(0)
        
        self.duration = 250
        self.child.setVisible(True)
        
        self.show = self.startShow
        self.hide = self.startHide
        self.child.show = self.show
        self.child.hide = self.hide
        self.child.setVisible = self.setVisible
        
        self.child_state = self.STATE_VISIBLE
    
    #these two segfaulted if i tried to do anything legit with them?
    def count(self):
        return 0
    def itemAt(self, index):
        return None    
        
    def setGeometry(self, rect):
        if not self.child_state in (self.STATE_ANIMATING, self.STATE_VISIBLE):
            return
        #super(type(self), self).setGeometry(rect)
        self.child.setGeometry(rect)
    
    def sizeHint(self):
        return self.mandated_size
        #return self.child.sizeHint()
    
    def setAnimationDuration(self, msecs):
        self.duration = msecs
            
    def startShow(self):
        self._start_animation(True)
    def startHide(self):
        self._start_animation(False)
    
    def _start_animation(self, show=True):
        a = QPropertyAnimation(self.child, "geometry", self)
        g = self.child.geometry()
        g.setHeight(0)
        a.setStartValue(g)
        g.setHeight(self.preferred_size.height())
        a.setEndValue(g)
        a.setEasingCurve(QEasingCurve.OutQuad)
        a.setDuration(self.duration)
        def valueChanged(qv):
            r = qv.toRect()
            self.mandated_size.setHeight(r.height())
            self.update()
        connect(a, SIGNAL("valueChanged(QVariant)"), valueChanged)
        
        if not show:
            a.setDirection(a.Backward)
            connect(a, SIGNAL("finished()"), lambda: setattr(self, "child_state", self.STATE_HIDDEN))
        else:
            a.setDirection(a.Forward)
            connect(a, SIGNAL("finished()"), lambda: setattr(self, "child_state", self.STATE_VISIBLE))        
        a.start(a.DeleteWhenStopped)

    
    def setVisible(self, b):
        "convenience method"
        if b:
            self.startShow()
        else:
            self.startHide()        
    
class ResizingWindow(QMainWindow):
    def __init__(self, parent=None):
        QMainWindow.__init__(self, parent)
        self.layout().setSizeConstraint(QLayout.SetFixedSize)
        
        centralwidget = QWidget(self)
        self.setCentralWidget(centralwidget)
        layout = QVBoxLayout()
        
        
        checkbox1 = QCheckBox("Show First Widget", self)
        checkbox2 = QCheckBox("Show Second Widget", self)
        textedit1 = QPlainTextEdit(self)
        textedit2 = QPlainTextEdit(self)
        textedit1.setVerticalScrollBarPolicy(Qt.ScrollBarAlwaysOff)
        textedit2.setVerticalScrollBarPolicy(Qt.ScrollBarAlwaysOff)
        
        anim_wrapper1 = AnimatedLayout(textedit1, QSize(150, 125))
        anim_wrapper1._name = "anim_wrapper1"
        self.anim_wrapper1 = anim_wrapper1
        anim_wrapper2 = AnimatedLayout(textedit2, QSize(150, 125))
        anim_wrapper2._name = "anim_wrapper2"
        self.anim_wrapper2 = anim_wrapper2
        
        
        layout.addWidget(checkbox1)
        layout.addLayout(anim_wrapper1)
        layout.addWidget(checkbox2)
        layout.addLayout(anim_wrapper2)
        centralwidget.setLayout(layout)
        
        connect(checkbox1, SIGNAL("toggled(bool)"), anim_wrapper1.setVisible)
        connect(checkbox2, SIGNAL("toggled(bool)"), anim_wrapper2.setVisible)            
mw = ResizingWindow()
mw.show()
app.exec_()

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[junky]

I have same kind of problem and would like to resize window when i hide a widget from layout(so this will give user dock kind of experience), this can be easily done by setting layout property QLayout::setSizeConstraint(QLayout::SetFixedSize), but then i can't resize window.

so is there any way where i can re size window without loosing dock kind of effect when i hide or show child widget from layout.

Please note that i don't want to implement re size event handling.
thanks.