[PyQt] model/view/delegate: data() method called too many times? Performance problem

[TP]

Hi everybody,

I use model/view/delegate architecture of Qt.
I have a problem of slowness in a small example given below. Run the script
from a terminal to see all standard output.
Try to play with the tree: expand items, click on cells, etc. You will find
that the function "data" is called all the time by Qt. Too many times, I
think. For example, we get on standard output sequences as:

data, col=1, row=2
data, col=1, row=2
data, col=1, row=2
data, col=1, row=2
data, col=1, row=2
data, col=1, row=2
data, col=1, row=2

which means that the data function is called several times for the same
cell! Why? It slows down a lot my "real world" application, which is much
more complicated than this simple script.

How to modify this "greedy" behavior of Qt?

Thanks a lot

Julien


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

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


class CustomProxyModel( QSortFilterProxyModel ):

    def filterAcceptsRow( self
            , source_row
            , source_parent_index ):

        return True


class TreeROModel( QAbstractItemModel ):


    def __init__( self
            , parent = None ):

        super( TreeROModel, self ).__init__( parent )
        self.root = "toto"
        self.children = [
                "coco"
                , "line 1" ]
        self.children_offirstline = [
                "coucou" ]
        self.columncount = 2



    def rowCount( self, parent ):

        node = self.nodeFromIndex( parent )
        if node == self.root:
            return len( self.children )
        elif node == "coco":
            return 1
        else:
            return 0


    def columnCount( self, QModelIndex = None ):

        return 2
        return self.columncount


    def data( self, index, role ):

        content = None
        col = index.column()
        row = index.row()
        print "data, col=%i, row=%i" % (col, row)
        if role == Qt.DisplayRole:
            if col == 0:
                content = self.nodeFromIndex( index )
            elif row == 0:
                content = len( self.children ) - 1

            else:
                content = "nothing in this item"

        elif role == Qt.TextAlignmentRole:

            if col == 0:
                content = int( Qt.AlignTop|Qt.AlignLeft )
            else:
                content = int( Qt.AlignTop|Qt.AlignRight )

        if content != None:
            return QVariant( content )
        else:
            # default choice
            return QVariant()




    def index( self, row, column, parent_index ):

        parent = self.nodeFromIndex( parent_index )
        if parent == "coco":
            child = self.children_offirstline[0]
        else:
            child = self.children[ row ]
        index = self.createIndex( row
                , column
                , child )

        return index



    def nodeFromIndex( self, index ):

        if index.isValid():
            node = index.internalPointer()
            return node
        else:
            node = self.root
            return node


    def parent( self, child_index ):

        node = self.nodeFromIndex( child_index )
        if node == "coucou":
            index = self.createIndex( 0, 0, self.root )
            return index
        else:
            return QModelIndex()


    def allIndex( self ):

        yield QModelIndex()
        index = self.createIndex( 0, 0, self.children[0] )
        yield index
        index = self.createIndex( 0, 0, self.children_offirstline[0] )
        yield index



class TreeROWidget( QWidget ):



    def __init__( self
            , TreeROModel_
            , title = None
            , parent = None ):

        super( TreeROWidget, self ).__init__( parent )

        # central tree view
        self.view = QTreeView( parent )
        self.view.setSelectionBehavior( QTreeView.SelectItems )

        # central tree model
        self.model = TreeROModel_
        self.proxyModel = CustomProxyModel()
        self.proxyModel.setSourceModel( self.model )

        self.view.setModel( self.proxyModel )
        self.view.setAlternatingRowColors( True )


        self.connect( self.view, SIGNAL( "clicked(QModelIndex)" )
                , self.cellClicked )

        # layout
        vboxlayout = QVBoxLayout()
        hboxlayout = QHBoxLayout()
        vboxlayout.addLayout( hboxlayout )
        vboxlayout.addWidget( self.view )
        self.setLayout( vboxlayout )

        self.show()


    def cellClicked( self, qmodelindex ):

        if qmodelindex.isValid():
            qmodelindex = self.proxyModel.mapToSource( qmodelindex )
            print qmodelindex.internalPointer()



class TreeWidget( TreeROWidget ):

    def __init__( self
            , TreeROModel_
            , title = None
            , parent = None ):

        super( TreeWidget, self ).__init__( parent = parent
                , TreeROModel_ = TreeROModel_
                , title = title )



if __name__ == "__main__":

    def add_col():

        for index in widget.model.allIndex():
            print index, index.internalPointer()
            widget.model.beginInsertColumns( index, 2, 2 )
            widget.model.endInsertColumns()

    def add_row():

        index = QModelIndex()
        l = len( widget.model.children )
        widget.model.beginInsertRows( index, l, l )
        widget.model.children.append( "toto %i" % l )
        print widget.model.children
        widget.model.endInsertRows()

    app = QApplication( sys.argv )
    dialog = QDialog( )
    dialog.resize( 750, 550 )

    widget = TreeWidget( TreeROModel() )

    vboxlayout = QVBoxLayout( dialog )
    vboxlayout.addWidget( widget )
    dialog.setLayout( vboxlayout )
    dialog.show()
    widget.view.resizeColumnToContents( 0 )
    widget.view.resizeColumnToContents( 1 )

    pushbutton1 = QPushButton( "Add column in line 1" )
    pushbutton2 = QPushButton( "Add row" )
    vboxlayout.addWidget( pushbutton1 )
    vboxlayout.addWidget( pushbutton2 )

    QObject.connect( pushbutton1, SIGNAL( "clicked()" )
            , add_col )
    QObject.connect( pushbutton2, SIGNAL( "clicked()" )
            , add_row )

    app.exec_()



-- 
python -c "print ''.join([chr(154 - ord(c)) for c in '*9(9&(18%.\
9&1+,\'Z4(55l4('])"

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