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python - Connect action in QMainWindow with method of view's delegate (PySide/Qt/PyQt)

I have a QTreeView displaying data from a QStandardItemModel. One of the columns of the tree is displayed with a delegate that lets the user edit and display rich text. Below is a SSCCE that limits the editing to bold (with keyboard shortcut).

When the user is editing one of the items, how can I set it up so that in addition to toggling boldness with keyboard shortcut (CTRL-B), the user can also toggle it using the toolbar icon?

enter image description here

Thus far, the keyboard shortcut works great (you can double click, edit text, and CTRL-B will toggle bold). However, I haven't figured out how to connect the bold button in the toolbar to the appropriate slot:

    self.boldTextAction.triggered.connect(self.emboldenText)

where I have this just sitting there doing nothing:

def emboldenText(self):
    print "Make selected text bold...How do I do this?"

Things would be easy if the main window's central widget was the text editor: I could directly invoke the text editor's toggle bold method. Unfortunately, the text editor is only generated transiently by the tree view's delegate when the user double-clicks to start editing the tree.

That is, we have this complicated relationship:

QMainWindow -> QTreeView -> Delegate.CreateEditor -> QTextEdit.toggleBold()

How do I access toggleBold() from within the main window for use by the toolbar action, especially given that the editor is only created temporarily when opened by the user?

I realize this may not be a PySide/Qt question as much as a Python/OOP question, so I've included additional potentially relevant tags. Any help with improving my word choice/jargon would be appreciated too.

SSCCE

#!/usr/bin/env python

import platform
import sys
from PySide import QtGui, QtCore


class MainTree(QtGui.QMainWindow):
    def __init__(self, tree, parent = None):
        QtGui.QMainWindow.__init__(self)
        self.setAttribute(QtCore.Qt.WA_DeleteOnClose) 
        self.setCentralWidget(tree)
        self.createStatusBar()
        self.createBoldAction()
        self.createToolbar()
        self.tree = tree
        #self.htmlDelegate = self.tree.itemDelegateForColumn(1)

    def createStatusBar(self):                          
        self.status = self.statusBar()
        self.status.setSizeGripEnabled(False)
        self.status.showMessage("In editor, keyboard to toggle bold")

    def createToolbar(self):
        self.textToolbar = self.addToolBar("Text actions")
        self.textToolbar.addAction(self.boldTextAction)

    def createBoldAction(self):
        self.boldTextAction = QtGui.QAction("Bold", self)
        self.boldTextAction.setIcon(QtGui.QIcon("boldText.png"))
        self.boldTextAction.triggered.connect(self.emboldenText)
        self.boldTextAction.setStatusTip("Make selected text bold")

    def emboldenText(self):
        print "Make selected text bold...How do I do this? It's stuck in RichTextLineEdit"

class HtmlTree(QtGui.QTreeView):
    def __init__(self, parent = None):    
        QtGui.QTreeView.__init__(self)
        model = QtGui.QStandardItemModel()
        model.setHorizontalHeaderLabels(['Task', 'Priority'])
        rootItem = model.invisibleRootItem()
        item0 = [QtGui.QStandardItem('Sneeze'), QtGui.QStandardItem('Low')]
        item00 = [QtGui.QStandardItem('Tickle nose'), QtGui.QStandardItem('Low')]
        item1 = [QtGui.QStandardItem('Get a job'), QtGui.QStandardItem('<b>High</b>')]
        item01 = [QtGui.QStandardItem('Call temp agency'), QtGui.QStandardItem('<b>Extremely</b> <i>high</i>')]
        rootItem.appendRow(item0)
        item0[0].appendRow(item00) 
        rootItem.appendRow(item1)
        item1[0].appendRow(item01)
        self.setModel(model)
        self.expandAll()
        self.resizeColumnToContents(0)
        self.setToolTip("Use keyboard to toggle bold")
        self.setItemDelegate(HtmlPainter(self))

class HtmlPainter(QtGui.QStyledItemDelegate):
    def __init__(self, parent=None):
        QtGui.QStyledItemDelegate.__init__(self, parent)

    def paint(self, painter, option, index):
        if index.column() == 1: 
            text = index.model().data(index) #default role is display (for edit consider fixing Valign prob)
            palette = QtGui.QApplication.palette()
            document = QtGui.QTextDocument()
            document.setDefaultFont(option.font)
            #Set text (color depends on whether selected)
            if option.state & QtGui.QStyle.State_Selected:  
                displayString = "<font color={0}>{1}</font>".format(palette.highlightedText().color().name(), text) 
                document.setHtml(displayString)
            else:
                document.setHtml(text)
            #Set background color
            bgColor = palette.highlight().color() if (option.state & QtGui.QStyle.State_Selected)
                     else palette.base().color()
            painter.save()

            painter.fillRect(option.rect, bgColor)
            document.setTextWidth(option.rect.width())
            offset_y = (option.rect.height() - document.size().height())/2
            painter.translate(option.rect.x(), option.rect.y() + offset_y) 
            document.drawContents(painter)
            painter.restore()
        else:
            QtGui.QStyledItemDelegate.paint(self, painter, option, index)          

    def sizeHint(self, option, index):
        fm = option.fontMetrics
        if index.column() == 1:
            text = index.model().data(index)
            document = QtGui.QTextDocument()
            document.setDefaultFont(option.font)
            document.setHtml(text)
            return QtCore.QSize(document.idealWidth() + 5, fm.height())
        return QtGui.QStyledItemDelegate.sizeHint(self, option, index)


    def createEditor(self, parent, option, index):
        if index.column() == 1:
            editor = RichTextLineEdit(parent)
            editor.returnPressed.connect(self.commitAndCloseEditor)
            return editor
        else:
            return QtGui.QStyledItemDelegate.createEditor(self, parent, option,
                                                    index)

    def commitAndCloseEditor(self):
        editor = self.sender()
        if isinstance(editor, (QtGui.QTextEdit, QtGui.QLineEdit)):
            self.commitData.emit(editor)
            self.closeEditor.emit(editor, QtGui.QAbstractItemDelegate.NoHint)


class RichTextLineEdit(QtGui.QTextEdit):

    returnPressed = QtCore.Signal()

    def __init__(self, parent=None):
        QtGui.QTextEdit.__init__(self, parent)
        self.setLineWrapMode(QtGui.QTextEdit.NoWrap)
        self.setTabChangesFocus(True)
        self.setVerticalScrollBarPolicy(QtCore.Qt.ScrollBarAlwaysOff)
        self.setHorizontalScrollBarPolicy(QtCore.Qt.ScrollBarAlwaysOff)
        fontMetrics = QtGui.QFontMetrics(self.font())
        h = int(fontMetrics.height() * (1.4 if platform.system() == "Windows"
                                   else 1.2))
        self.setMinimumHeight(h)
        self.setMaximumHeight(int(h * 1.2))
        self.setToolTip("Press <b>Ctrl+b</b> to toggle bold")

    def toggleBold(self):
        self.setFontWeight(QtGui.QFont.Normal
                if self.fontWeight() > QtGui.QFont.Normal else QtGui.QFont.Bold)

    def sizeHint(self):
        return QtCore.QSize(self.document().idealWidth() + 5,
                     self.maximumHeight())

    def minimumSizeHint(self):
        fm = QtGui.QFontMetrics(self.font())
        return QtCore.QSize(fm.width("WWWW"), self.minimumHeight())

    def keyPressEvent(self, event):
        '''This just handles all keyboard shortcuts, and stops retun from returning'''
        if event.modifiers() & QtCore.Qt.ControlModifier:
            handled = False
            if event.key() == QtCore.Qt.Key_B:
                self.toggleBold()
                handled = True
            if handled:
                event.accept()
                return
        if event.key() in (QtCore.Qt.Key_Enter, QtCore.Qt.Key_Return):
            self.returnPressed.emit()
            event.accept()
        else:
            QtGui.QTextEdit.keyPressEvent(self, event)


def main():
    app = QtGui.QApplication(sys.argv)
    myTree = HtmlTree()
    #myTree.show()
    myMainTree = MainTree(myTree)
    myMainTree.show()
    sys.exit(app.exec_())

if __name__ == "__main__":
    main()

Note for those that want the Full Tree Experience, with the button in the toolbar, here it is you can put it in the same folder as the script (change the name to boldText.png:

enter image description here

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I think from a design point of view the top window is a sort of global. You have already described a behaviour which is treating it in that way and (as ekhumoro has said) that pretty much requires you to provide access to that top window to the editor.

One very simple way to do that is to call parent.window() in the createEditor method. Maybe something like:

parent.window().boldTextAction.triggered.connect(editor.toggleBold)

That seems to work for me.


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