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Updated: How to reduce QWidget nesting in PyQt code?

Updated Question
I think my original quandary might be a result of the structure of my PyQt app. The way I've approached creating a GUI is to divide the larger widget into smaller pieces, each given their own class until the parts are simple enough. Because of this, I end up with a ton of nesting, as a large widget holds instances of smaller widgets, and those hold their own even smaller widgets. It makes it hard to navigate data around the app.
How should a PyQt app be structured so that it is simple to understand in code and yet has a structure containing very little nesting? I haven't found many examples of this around, so I'm sort of stuck. The code example in my original question shows a pretty good example of the structure I'm currently using, which has a large amount of nesting.
Info on program
The GUI is used to create a set of parameters for running a test. The options in each setting should correspond to a binary number, and all of the binary numbers indicated by each set of options are collected, formed into a single sequence of binary numbers, and passed on. Changes to settings do not have to be carried over between sessions, as each new session will most likely correspond to a new test (and thus a new set of choices for settings).
The basic flow of the app should be that upon opening it, all available settings (about 20 total) are set to their default values. A user can go through and change whatever settings they would like, and once they're done they can press a "Generate" button to gather all of the binary numbers corresponding to the settings and create the command. It would be very helpful to have a live preview of individual bits that updates as settings are changed, which is why updates must be immediate.
Some settings are dependent on other; for instance, Setting A has 4 options, and if option 3 is selected, Setting B should be made visible, otherwise it is invisible.
Original Question
I'm definitely a beginner to PyQt, so I don't quite know if I've worded my question correctly, but here goes. I've got a GUI wherein I'm attempting to take a bunch of different settings, keep track of what number was selected from each setting, and then pass the number up to an object that keeps track of all of the numbers from all of the settings. The trouble is that I don't know the best way to get all the individual settings values up my tree of classes, so to speak. Here's the structure of my GUI so far:
Bottom: individual custom QWidgets, each responsible for a single setting. Each has a signal that fires whenever the value it returns changes.
Middle: a QWidget containing ~7-10 individual settings each. These collect settings into related groups.
Top: a QTabWidget that places each instance of a setting group into an individual tab. This widget also contains an object that should ideally collect all of the settings from individual groups into it.
My question is how do I get the values from the bottom layer signals to the top layer widget? My only idea is to connect all of the signals from those small setting widgets to a signal in the middle layer, and connect the middle layer signal to something in the top layer. This sort of chaining seems crazy, though.
I'm running PyQt5 and Python 3.7.
Here's some stripped down code which hopefully shows what I want to do.
class TabWindow(QTabWidget):
def __init__(self):
super().__init__()
self.tabs = [SettingsGroup1, SettingsGroup2, SettingsGroup3]
self.setting_storage = { # dictionary is where I'd like to store all settings values
# 'setting name': setting value
}
for tab in self.tabs:
self.addTab(tab, 'Example')
class SettingsGroup(QWidget):
def __init__(self):
super().__init__()
# not shown: layout created for widget
self.settings = []
def add_to_group(self, new_setting):
self.settings.append(new_setting)
# not shown: add setting to the layout
class SettingsGroup1(SettingsGroup):
def __init__(self):
super().__init__()
self.add_to_group([Setting1, Setting2, Setting3])
class SettingsGroup2(SettingsGroup):...
class SettingsGroup3(SettingsGroup):...
class Setting(QWidget):
val_signal = pyqtSignal([int], name='valChanged')
def __init__(self, name):
self.val = None
self.name = name
def set_val(self, new_val):
self.val = new_val
self.val_signal.emit(self.val) # <-- the signal I want to pass up
class Setting1(Setting):
def __init__(self, name):
super().__init__(name)
# not shown: create custom setting layout/interface
class Setting2(Setting):...
class Setting3(Setting):...
I use a lot of inheritance (SettingsGroup -> SettingsGroup1, 2, 3) because each subclass will have its own functions and internal dependencies that are unique to it. For each Setting subclass, for instance, there is a different user interface.
Thanks for any help provided!

EDIT: The question has been updated in the meantime, I've added a solution that's more specific at the bottom of this answer.
I feel like this question is slightly "opinion based", but since I've had my share of similar situations I'd like to propose my suggestions. In these situations it's important to understand that there's not one good way to do things, but many ways to do it wrong.
Original answer
An idea could be to create a common signal interface for every "level", which will get that signal and send it back to its parent by adding its own name to keep track of the setting "path"; the topmost widget will then evaluate the changes accordingly.
In this example every tab "group" has its own valueChanged signal, which includes the group name, setting name and value; the source signal is fired from the "source" (a spinbox, in this case), then it follows its parents which, in turn "add" their name in turn.
Keep in mind that you can also just use a generalized pyqtSignal(object) for every parent and connect it with widget.valueChanged.connect(self.valueChanged), and then track its group and setting by walking by self.sender() parents backwards.
As a final notice, if you are using these values for application settings, remember that Qt already provides the QSettings API, which can be used as a common and OS-transparent interface for every configuration you need to set (and remember between sessions) in your application. I implemented it in the example, but I suggest you to read its documentation to better understand how it works.
import sys
from PyQt5 import QtCore, QtWidgets
class SettingWidget(QtWidgets.QWidget):
valueChanged = QtCore.pyqtSignal(int)
def __init__(self, name):
super().__init__()
self.settings = QtCore.QSettings()
self.val = 0
self.name = name
layout = QtWidgets.QVBoxLayout()
self.setLayout(layout)
layout.addWidget(QtWidgets.QLabel(self.name))
self.spinBox = QtWidgets.QSpinBox()
layout.addWidget(self.spinBox)
self.spinBox.valueChanged.connect(self.set_val)
def set_val(self, new_val):
if self.val != new_val:
self.val = new_val
self.valueChanged.emit(self.val)
# enter a setting group, ensuring that same name settings won't
# be mismatched; this allows a single sub level setting only
self.settings.beginGroup(self.parent().name)
self.settings.setValue(self.name, new_val)
# leave the setting group. THIS IS IMPORTANT!!!
self.settings.endGroup()
class SettingWidget1(SettingWidget):
def __init__(self):
super().__init__('Setting1')
class SettingWidget2(SettingWidget):
def __init__(self):
super().__init__('Setting2')
class SettingWidget3(SettingWidget):
def __init__(self):
super().__init__('Setting3')
class SettingsGroup(QtWidgets.QWidget):
# create two signal signatures, the first sends the full "path",
# while the last will just send the value
valueChanged = QtCore.pyqtSignal([str, str, int], [int])
def __init__(self, name):
super().__init__()
self.name = name
layout = QtWidgets.QHBoxLayout()
self.setLayout(layout)
def add_to_group(self, new_setting):
widget = new_setting()
# emit both signal signatures
widget.valueChanged.connect(
lambda value, name=widget.name: self.valueChanged.emit(
self.name, name, value))
widget.valueChanged.connect(self.valueChanged[int])
self.layout().addWidget(widget)
class SettingsGroup1(SettingsGroup):
def __init__(self):
super().__init__('Group1')
self.add_to_group(SettingWidget1)
self.add_to_group(SettingWidget2)
class SettingsGroup2(SettingsGroup):
def __init__(self):
super().__init__('Group2')
self.add_to_group(SettingWidget3)
class TabWidget(QtWidgets.QTabWidget):
def __init__(self):
QtWidgets.QTabWidget.__init__(self)
self.settings = QtCore.QSettings()
self.tabs = [SettingsGroup1, SettingsGroup2]
self.settingsDict = {}
for tab in self.tabs:
widget = tab()
self.addTab(widget, widget.__class__.__name__)
widget.valueChanged[str, str, int].connect(self.valueChangedFullPath)
widget.valueChanged[int].connect(self.valueChangedOnly)
def valueChangedFullPath(self, group, setting, value):
# update the settings dict; if the group key doesn't exist, create it
try:
self.settingsDict[group][setting] = value
except:
self.settingsDict[group] = {setting: value}
settingsData = [group, setting, value]
print('Full path result: {}'.format(settingsData))
# Apply setting from here, instead of using the SettingWidget
# settings.setValue() option; this allows a single sub level only
# self.applySetting(data)
def valueChangedOnly(self, value):
parent = sender = self.sender()
# sender() returns the last signal sender, so we need to track down its
# source; keep in mind that this is *not* a suggested approach, as
# tracking the source might result in recursion if the sender's sender
# is not one of its children; this system also has issues if you're
# using a Qt.DirectConnection from a thread different from the one that
# emitted it
while parent.sender() in sender.children():
parent = sender.sender()
widgetPath = []
while parent not in self.children():
widgetPath.insert(0, parent)
parent = parent.parent()
settingsData = [w.name for w in widgetPath] + [value]
print('Single value result: {}'.format(settingsData))
# similar to valueChangedFullPath(), but with this implementation more
# nested "levels" can be used instead
# self.applySetting(settingsData)
def applySetting(self, settingsData):
# walk up to the next to last of settingsData levels, assuming they are
# all parent group section names
for count, group in enumerate(settingsData[:-2], 1):
self.settings.beginGroup(group)
# set the setting name settingsData[-2] to its value settingsData[-1]
self.settings.setValue(*settingsData[-2:])
for g in range(count):
self.settings.endGroup()
if __name__ == '__main__':
app = QtWidgets.QApplication(sys.argv)
# set both Organization and Application name to make settings persistent
app.setOrganizationName('StackOverflow')
app.setApplicationName('Example')
w = TabWidget()
w.show()
sys.exit(app.exec_())
Alternate solution, based on updated answer
Since the answer has become more specific in its update, I'm adding another suggestion.
As far as we can understand now, you don't need that level of "nested" classes, but more specifically designed code that can be reused according to your purposes. Also, since you're using binary based data, it makes things a bit (pun intended) easier, as long as you know how bit operation works (which I assume you do) and the setting "widgets" don't require specific GUI customization.
In this example I created just one "setting" class and one "group" class, and their instancies are created only according to their names and default values.
import sys
from PyQt5 import QtCore, QtWidgets
defaultValues = '0010101', '1001010', '000111'
# set bit lengths for each setting; be careful in ensuring that each
# setting group has the full default value bit length!
groups = [
['Group 1', [1, 3, 2, 1]],
['Group 2', [1, 2, 2, 1, 1]],
['Group 1', [2, 1, 2, 1]],
]
class BinaryWidget(QtWidgets.QFrame):
changed = QtCore.pyqtSignal()
def __init__(self, name, index, defaults='0'):
QtWidgets.QFrame.__init__(self)
self.setFrameShape(self.StyledPanel|self.Sunken)
layout = QtWidgets.QGridLayout()
self.setLayout(layout)
self.index = index
self.defaults = defaults
self.buttons = []
# use the "defaults" length to create buttons
for i in range(len(defaults)):
value = int(defaults[i], 2) & 1
# I used QToolButtons as they're usually smaller than QPushButtons
btn = QtWidgets.QToolButton()
btn.setText(str(value))
layout.addWidget(btn, 1, i)
btn.setCheckable(True)
btn.setChecked(value)
btn.toggled.connect(self.changed)
# show the binary value on change, just for conveniency
btn.toggled.connect(lambda v, btn=btn: btn.setText(str(int(v))))
self.buttons.append(btn)
layout.addWidget(QtWidgets.QLabel(name), 0, 0, 1, layout.columnCount())
def value(self):
# return the correct value of all widget's buttons; they're reversed
# because of how bit shifting works
v = 0
for i, btn in enumerate(reversed(self.buttons)):
v += btn.isChecked() << i
# bit shift again, according to the actual "setting" bit index
return v << self.index
def resetValues(self):
oldValue = self.value()
self.blockSignals(True)
for i, value in enumerate(self.defaults):
self.buttons[i].setChecked(int(self.defaults[i], 2) & 1)
self.blockSignals(False)
newValue = self.value()
# emit the changed signal only once, and only if values actually changed
if oldValue != newValue:
self.changed.emit()
class Group(QtWidgets.QWidget):
changed = QtCore.pyqtSignal()
def __init__(self, name, defaults=None, lenghts=None):
QtWidgets.QWidget.__init__(self)
layout = QtWidgets.QHBoxLayout()
self.setLayout(layout)
self.name = name
self.bitLength = 0
self.widgets = []
if defaults is not None:
self.addOptions(defaults, lenghts)
def value(self):
v = 0
for widget in self.widgets:
v += widget.value()
return v
def addOption(self, name, index, default='0'):
widget = BinaryWidget(name, index, default)
self.layout().addWidget(widget)
self.widgets.append(widget)
widget.changed.connect(self.changed)
self.bitLength += len(default)
def addOptions(self, defaults, lenghts = None):
if lenghts is None:
lenghts = [1] * len(defaults)
# reverse bit order for per-setting indexing
defaultsIndex = 0
bitIndex = len(defaults)
for i, l in enumerate(lenghts):
self.addOption(
'Setting {}'.format(i + 1),
bitIndex - l,
defaults[defaultsIndex:defaultsIndex + l])
bitIndex -= l
defaultsIndex += l
def resetValues(self):
for widget in self.widgets:
widget.resetValues()
class Tester(QtWidgets.QWidget):
def __init__(self):
QtWidgets.QWidget.__init__(self)
layout = QtWidgets.QGridLayout()
self.setLayout(layout)
self.tabWidget = QtWidgets.QTabWidget()
layout.addWidget(self.tabWidget)
resultLayout = QtWidgets.QHBoxLayout()
layout.addLayout(resultLayout, layout.rowCount(), 0, 1, layout.columnCount())
self.tabs = []
self.labels = []
for (group, lenghts), defaults in zip(groups, defaultValues):
tab = Group(group, defaults, lenghts)
self.tabWidget.addTab(tab, group)
tab.changed.connect(self.updateResults)
self.tabs.append(tab)
tabLabel = QtWidgets.QLabel()
self.labels.append(tabLabel)
resultLayout.addWidget(tabLabel)
self.resetButton = QtWidgets.QPushButton('Reset values')
layout.addWidget(self.resetButton)
self.resetButton.clicked.connect(lambda: [tab.resetValues() for tab in self.tabs])
self.updateResults()
def values(self):
return [tab.value() for tab in self.tabs]
def updateResults(self):
for value, tab, label in zip(self.values(), self.tabs, self.labels):
label.setText('''
{0}: <span style="font-family:monospace;">{1} <b>{1:0{2}b}</b></span>
'''.format(tab.name, value, tab.bitLength))
if __name__ == '__main__':
app = QtWidgets.QApplication(sys.argv)
w = Tester()
w.show()
sys.exit(app.exec_())

How to undo an edit of a QListWidgetItem in PySide/PyQt?

Short version
How do you implement undo functionality for edits made on QListWidgetItems in PySide/PyQt?
Hint from a Qt tutorial?
The following tutorial written for Qt users (c++) likely has the answer, but I am not a c++ person, so get a bit lost: Using Undo/Redo with Item Views
Longer version
I am using a QListWidget to learn my way around PyQt's Undo Framework (with the help of an article on the topic). I am fine with undo/redo when I implement a command myself (like deleting an item from the list).
I also want to make the QListWidgetItems in the widget editable. This is easy enough: just add the ItemIsEditable flag to each item. The problem is, how can I push such edits onto the undo stack, so I can then undo/redo them?
Below is a simple working example that shows a list, lets you delete items,and undo/redo such deletions. The application displays both the list and the the undo stack. What needs to be done to get edits onto that stack?
Simple working example
from PySide import QtGui, QtCore
class TodoList(QtGui.QWidget):
def __init__(self):
QtGui.QWidget.__init__(self)
self.setAttribute(QtCore.Qt.WA_DeleteOnClose)
self.initUI()
self.show()
def initUI(self):
self.todoList = self.makeTodoList()
self.undoStack = QtGui.QUndoStack(self)
undoView = QtGui.QUndoView(self.undoStack)
buttonLayout = self.buttonSetup()
mainLayout = QtGui.QHBoxLayout(self)
mainLayout.addWidget(undoView)
mainLayout.addWidget(self.todoList)
mainLayout.addLayout(buttonLayout)
self.setLayout(mainLayout)
self.makeConnections()
def buttonSetup(self):
#Make buttons
self.deleteButton = QtGui.QPushButton("Delete")
self.undoButton = QtGui.QPushButton("Undo")
self.redoButton = QtGui.QPushButton("Redo")
self.quitButton = QtGui.QPushButton("Quit")
#Lay them out
buttonLayout = QtGui.QVBoxLayout()
buttonLayout.addWidget(self.deleteButton)
buttonLayout.addStretch()
buttonLayout.addWidget(self.undoButton)
buttonLayout.addWidget(self.redoButton)
buttonLayout.addStretch()
buttonLayout.addWidget(self.quitButton)
return buttonLayout
def makeConnections(self):
self.deleteButton.clicked.connect(self.deleteItem)
self.quitButton.clicked.connect(self.close)
self.undoButton.clicked.connect(self.undoStack.undo)
self.redoButton.clicked.connect(self.undoStack.redo)
def deleteItem(self):
rowSelected=self.todoList.currentRow()
rowItem = self.todoList.item(rowSelected)
if rowItem is None:
return
command = CommandDelete(self.todoList, rowItem, rowSelected,
"Delete item '{0}'".format(rowItem.text()))
self.undoStack.push(command)
def makeTodoList(self):
todoList = QtGui.QListWidget()
allTasks = ('Fix door', 'Make dinner', 'Read',
'Program in PySide', 'Be nice to everyone')
for task in allTasks:
todoItem=QtGui.QListWidgetItem(task)
todoList.addItem(todoItem)
todoItem.setFlags(QtCore.Qt.ItemIsSelectable | QtCore.Qt.ItemIsEnabled)
return todoList
class CommandDelete(QtGui.QUndoCommand):
def __init__(self, listWidget, item, row, description):
super(CommandDelete, self).__init__(description)
self.listWidget = listWidget
self.string = item.text()
self.row = row
def redo(self):
self.listWidget.takeItem(self.row)
def undo(self):
addItem = QtGui.QListWidgetItem(self.string)
addItem.setFlags(QtCore.Qt.ItemIsSelectable | QtCore.Qt.ItemIsEnabled)
self.listWidget.insertItem(self.row, addItem)
if __name__ == "__main__":
import sys
app = QtGui.QApplication(sys.argv)
myList=TodoList()
sys.exit(app.exec_())
Note I posted an earlier version of this question at QtCentre.

That tutorial you mentioned is really not very helpful. There are indeed many approaches to undo-redo implementation for views, we just need to choose the simplest one. If you deal with small lists, the simpliest way is to save all data on each change and restore full list from scratch on each undo or redo operation.
If you still want atomic changes list, you can track user-made edits with QListWidget::itemChanged signal. There are two problems with that:
Any other item change in the list will also trigger this signal, so you need to wrap any code that changes items into QObject::blockSignals calls to block unwanted signals.
There is no way to get previous text, you can only get new text. The solution is either save all list data to variable, use and update it on change or save the edited item's text before it's edited. QListWidget is pretty reticent about its internal editor state, so I decided to use QListWidget::currentItemChanged assuming that user won't find a way to edit an item without making is current first.
So this is the changes that will make it work (besides adding ItemIsEditable flag in two places):
def __init__(self):
#...
self.todoList.itemChanged.connect(self.itemChanged)
self.todoList.currentItemChanged.connect(self.currentItemChanged)
self.textBeforeEdit = ""
def itemChanged(self, item):
command = CommandEdit(self.todoList, item, self.todoList.row(item),
self.textBeforeEdit,
"Rename item '{0}' to '{1}'".format(self.textBeforeEdit, item.text()))
self.undoStack.push(command)
def currentItemChanged(self, item):
self.textBeforeEdit = item.text()
And the new change class:
class CommandEdit(QtGui.QUndoCommand):
def __init__(self, listWidget, item, row, textBeforeEdit, description):
super(CommandEdit, self).__init__(description)
self.listWidget = listWidget
self.textBeforeEdit = textBeforeEdit
self.textAfterEdit = item.text()
self.row = row
def redo(self):
self.listWidget.blockSignals(True)
self.listWidget.item(self.row).setText(self.textAfterEdit)
self.listWidget.blockSignals(False)
def undo(self):
self.listWidget.blockSignals(True)
self.listWidget.item(self.row).setText(self.textBeforeEdit)
self.listWidget.blockSignals(False)

I would do it like this:
Create a custom QItemDelegate and use these two signals:
editorEvent
closeEditor
On editorEvent: Save current state
On closeEditor: Get new state and create a QUndoCommand that set the new state for Redo and the old state for Undo.

Each time you verify and accept the new text of the item, save it as list item data. Quasi-semi-pseudo-code:
OnItemEdited(Item* item)
{
int dataRole{ 32 }; //or greater (see ItemDataRole documentation)
if (Validate(item->text()) {
item->setData(dataRole, item->text());
} else { //Restore previous value
item->setText(item->data(dataRole).toString());
}
}
I'm sorry if it looks too much like C++.

PySide One slot to multiple widgets

I am creating a small app in python using PySide. I read lines from a text file and display each line in a separate QLineEdit Widget. Each "entry" has 2 line edits and 2 QPushButtons. For every line I add those widgets. My problem is that I set a signal-slot for the QPushButtons, but when all the "entries" are generated, only the last entries QPushButtons connects to the slot. May someone please help me.
Here is my code
class ItemLogger(QtGui.QMainWindow, Ui.Ui_MainWindow):
def __init__(self, parent = None):
super(ItemLogger, self).__init__(parent)
self.setupUi(self)
self.parseBossItem()
self.comboBox.currentIndexChanged.connect(self.parseBossItem)
self.increase.clicked.connect(self.add_subtract)
def add_subtract(self):
initial = 1
print "kajskasdjflsdkjflk"
def addRow(self, item):
self.frame = QtGui.QFrame()
self.layout = QtGui.QHBoxLayout()
self.itemName = QtGui.QLineEdit(item)
self.itemName.setReadOnly(True)
self.itemCount = QtGui.QLineEdit()
self.itemCount.setText("0")
self.itemCount.setMaximumWidth(40)
self.decrease = QtGui.QPushButton("-")
self.increase = QtGui.QPushButton("+")
self.layout.addWidget(self.itemName)
self.layout.addWidget(self.itemCount)
self.layout.addWidget(self.decrease)
self.layout.addWidget(self.increase)
self.frame.setLayout(self.layout)
self.verticalLayout_3.addWidget(self.frame)
def parseBossItem(self):
if self.comboBox.currentText() == "Item_1":
item_list = open("BossItems/Random_Item")
for line in item_list.readlines():
self.addRow(line)
if self.comboBox.currentText() == "Item_2":
item_list = open("BossItems/Random_Item_2")
for line in item_list.readlines():
self.addRow(line)

This is because you only connected the last entry.
Here is what you are actually doing:
You add row for item 1, and assign button widgets to self.decrease, self.increase.
You add row for item 2, replacing values of self.decrease, self.increase by newly created widgets.
You connect self.increase, which is now the last added widget.
If you don't need access to you widgets after their creation, you should consider using local variables (e.g. without self) and connecting the signal inside the addRow function.
If you need to keep track of widget references, then you could add them to an array:
# Somewhere in __init__ or in parseBossItem
self.increase = []
# in addRow
self.increase.append(QtGui.QPushButton("+"))
self.layout.addWidget(self.increase[-1])
self.increase[-1].clicked.connect(self.add_subtract)
# and so on...
To use the same slot form different senders, you need to identify who sent the signal. You could do something like this:
def onIncrease(self):
button = self.sender()
if isinstance(button, QtGui.QPushButton):
buttonName = button.text()
if buttonName == 'name of button 1':
self.itemCount[0].setText(str(int(self.itemCount[0])+1))
elif buttonName == 'name of button 2':
...
Off course, this is assuming you put each QLineEdit in the array self.itemCount.
Since all your buttons have the same name, we need to use another approach.
# in addRow
self.increase.clicked.connect(lambda: self.onIncrease(itemCount))
def onIncrease(self, edit):
edit.setText(str(int(edit.text()+1))

PyGI emulating set_attribute / appropriate signal to emit?

I have an existing project that I'm trying to build a GUI around (using PyGI + Gtk3). There are some native objects that I need to extend slightly to make them renderable. I've boiled the problem down to the simplified code here:
# Simplified Equivalent Code
from gi.repository import GObject
from gi.repository import Gtk
from gi.repository import GdkPixbuf
# Pre-existing, complex object
class Move(object):
def __init__(self, color):
self.color = color
# Pre-existing, complex object
class Block(object):
def __init__(self,move=None,**kwds):
self.move = move
# New object created to help render a Block
class BlockGui(Block):
pixbufs = {
'empty' : GdkPixbuf.Pixbuf.new_from_file('block_empty.png'),
'red' : GdkPixbuf.Pixbuf.new_from_file('block_red.png'),
'blue' : GdkPixbuf.Pixbuf.new_from_file('block_blue.png'),
}
def __setattr__(self, name, value):
super(BlockGui, self).__setattr__(name, value)
if name == 'move':
print "Need to emit a signal here"
def get_pixbuf(self):
try:
return BlockGui.pixbufs[self.move.color]
except AttributeError:
return BlockGui.pixbufs['empty']
class BlockRenderer(Gtk.CellRendererPixbuf):
__gproperties__ = {
'block' : (GObject.TYPE_PYOBJECT,
'block to render',
'the block object to be rendered',
GObject.PARAM_READWRITE)
}
def __init__(self):
GObject.GObject.__init__(self)
self.block = None
def do_set_property(self, prop, value):
# What is a GParamBoxed? Should I be checking if prop == 'block' from it somehow?
if isinstance(value, BlockGui):
self.block = value
self.set_property('pixbuf', self.block.get_pixbuf())
GObject.type_register(BlockRenderer)
def destroy(widget, data=None):
Gtk.main_quit()
# Normally do not have access to this assignment
def on_clicked(widget, liststore, treeview):
treeiter = liststore.get_iter(2)
block = liststore.get_value(treeiter, 1)
block.move = Move('red')
def main():
# 3x5 so this demo window has some size
fmt = [GObject.TYPE_PYOBJECT] * 3
liststore = Gtk.ListStore(*fmt)
for r in xrange(5):
liststore.append([BlockGui() for x in xrange(3)])
treeview = Gtk.TreeView(liststore)
for c in xrange(3):
col = Gtk.TreeViewColumn(str(c))
treeview.append_column(col)
cell = BlockRenderer()
col.pack_start(cell, True)
col.add_attribute(cell, 'block', c)
button = Gtk.Button("Change Color!")
button.connect('clicked', on_clicked, liststore, treeview)
vbox = Gtk.VBox()
vbox.add(treeview)
vbox.add(button)
window = Gtk.Window(Gtk.WindowType.TOPLEVEL)
window.connect('destroy', destroy)
window.add(vbox)
window.show_all()
Gtk.main()
if __name__ == '__main__':
main()
When the current code is run, clicking the button yields no immediate result, but running the mouse over the changed row will cause the center square to turn red (as the hover over the row triggers a refresh). Normally, when a 'proper' GObject has a set_attribute called, it will emit some signals to notify the widgets containing it to re-render.
I need to know which signal that emits, to whom it's emitted, and how to emulate that behavior.

If you know the widget that must be redrawn, then you can just call queue_draw(), queue_draw_region() or queue_draw_area() for that widget. That will invalidate that window area and it will be redrawn. If you want more fine grained control, you might want to use Gtk.DrawingArea.
You might want to check the documentation for The GTK+ Drawing Model.

Undo and Redo in an Tkinter Entry widget?

Is there a way to add undo and redo capabilities in Tkinter Entry widgets or must I use single line Text widgets for this type of functionality?
If the latter, are there any tips I should follow when configuring a Text widget to act as an Entry widget?
Some features that might need tweaking include trapping the Return KeyPress, converting tab keypresses into a request to change focus, and removing newlines from text being pasted from the clipboard.

Check the Tkinter Custom Entry. I have added Cut, Copy, Paste context menu, and undo redo functions.
# -*- coding: utf-8 -*-
from tkinter import *
class CEntry(Entry):
def __init__(self, parent, *args, **kwargs):
Entry.__init__(self, parent, *args, **kwargs)
self.changes = [""]
self.steps = int()
self.context_menu = Menu(self, tearoff=0)
self.context_menu.add_command(label="Cut")
self.context_menu.add_command(label="Copy")
self.context_menu.add_command(label="Paste")
self.bind("<Button-3>", self.popup)
self.bind("<Control-z>", self.undo)
self.bind("<Control-y>", self.redo)
self.bind("<Key>", self.add_changes)
def popup(self, event):
self.context_menu.post(event.x_root, event.y_root)
self.context_menu.entryconfigure("Cut", command=lambda: self.event_generate("<<Cut>>"))
self.context_menu.entryconfigure("Copy", command=lambda: self.event_generate("<<Copy>>"))
self.context_menu.entryconfigure("Paste", command=lambda: self.event_generate("<<Paste>>"))
def undo(self, event=None):
if self.steps != 0:
self.steps -= 1
self.delete(0, END)
self.insert(END, self.changes[self.steps])
def redo(self, event=None):
if self.steps < len(self.changes):
self.delete(0, END)
self.insert(END, self.changes[self.steps])
self.steps += 1
def add_changes(self, event=None):
if self.get() != self.changes[-1]:
self.changes.append(self.get())
self.steps += 1

Disclaimer: these are just thoughts that come into my mind on how to implement it.
class History(object):
def __init__(self):
self.l = ['']
self.i = 0
def next(self):
if self.i == len(self.l):
return None
self.i += 1
return self.l[self.i]
def prev(self):
if self.i == 0:
return None
self.i -= 1
return self.l[self.i]
def add(self, s):
del self.l[self.i+1:]
self.l.append(s)
self.i += 1
def current(self):
return self.l[self.i]
Run a thread that every X seconds (0.5?) save the state of the entry:
history = History()
...
history.add(stringval.get())
You can also set up events that save the Entry's status too, such as the pressure of Return.
prev = history.prev()
if prev is not None:
stringvar.set(prev)
or
next = history.next()
if next is not None:
stringvar.set(next)
Beware to set locks as needed.

Update on using this method for Undo/Redo:
I am creating a GUI with lot of frames and each contains at least ten or more 'entry' widgets.
I used the History class and created one history object for each entry field that I had. I was able to store all entry widgets values in a list as done here.
I am using 'trace' method attached to each entry widget which will call 'add' function of History class and store each changes. In this way, I was able to do it without running any thread separately.
But the biggest drawback of doing this is, we cannot do multiple undos/redos with this method.
Issue:
When I trace each and every change of the entry widget and add that to the list, it also 'traces' the change that happens when we 'undo/redo' which means we cannot go more one step back. once u do a undo, it is a change that will be traced and hence the 'undo' value will be added to the list at the end. Hence this is not the right method.
Solution:
Perfect way to do this is by creating two stacks for each entry widget. One for 'Undo' and one for 'redo'. When ever there is a change in entry, push that value into the undo stack. When user presses undo, pop the last stored value from the undo stack and importantly push this one to the 'redo stack'. hence, when the user presses redo, pop the last value from redo stack.

Based on Evgeny's answer with a custom Entry, but added a tkinter StringVar with a trace to the widget to more accurately track when changes are made to its contents (not just when any Key is pressed, which seemed to add empty Undo/Redo items to the stack). Also added a max depth using a Python deque.
If we're changing the contents of the Entry via code rather than keyboard input, we can temporarily disable the trace (e.g. see in the undo method below).
Code:
class CEntry(tk.Entry):
def __init__(self, master, **kw):
super().__init__(master=master, **kw)
self._undo_stack = deque(maxlen=100)
self._redo_stack = deque(maxlen=100)
self.bind("<Control-z>", self.undo)
self.bind("<Control-y>", self.redo)
# traces whenever the Entry's contents are changed
self.tkvar = tk.StringVar()
self.config(textvariable=self.tkvar)
self.trace_id = self.tkvar.trace("w", self.on_changes)
self.reset_undo_stacks()
# USE THESE TO TURN TRACE OFF THEN BACK ON AGAIN
# self.tkvar.trace_vdelete("w", self.trace_id)
# self.trace_id = self.tkvar.trace("w", self.on_changes)
def undo(self, event=None): # noqa
if len(self._undo_stack) <= 1:
return
content = self._undo_stack.pop()
self._redo_stack.append(content)
content = self._undo_stack[-1]
self.tkvar.trace_vdelete("w", self.trace_id)
self.delete(0, tk.END)
self.insert(0, content)
self.trace_id = self.tkvar.trace("w", self.on_changes)
def redo(self, event=None): # noqa
if not self._redo_stack:
return
content = self._redo_stack.pop()
self._undo_stack.append(content)
self.tkvar.trace_vdelete("w", self.trace_id)
self.delete(0, tk.END)
self.insert(0, content)
self.trace_id = self.tkvar.trace("w", self.on_changes)
def on_changes(self, a=None, b=None, c=None): # noqa
self._undo_stack.append(self.tkvar.get())
self._redo_stack.clear()
def reset_undo_stacks(self):
self._undo_stack.clear()
self._redo_stack.clear()
self._undo_stack.append(self.tkvar.get())