QListView: keyboard navigation doesn't wrap when Wrapping is enabled

**mspacek** · 2nd February 2011, 01:19

Summary: with wrapping enabled in a QListView, if the cursor is at an edge of the list, keyboard navigation toward that edge does nothing.

Here's a wordier but more thorough description:

In TopToBottom flow mode with wrapping enabled, when the cursor is at the bottom of a column, hitting down doesn't navigate to the top of the next column. Similarly, when at the top of a column, hitting up doesn't navigate to the bottom of the previous column.

In LeftToRight flow mode with wrapping enabled, when the cursor is at the right edge of a row, hitting right doesn't navigate to the left edge of the next row. Similarly, when at the left edge of a row, hitting left doesn't navigate to the right edge of the previous row.

(Note that when I use the terms "row" and "column", these are sort of pseudo terms. With wrapping turned on, they look like rows and columns, but of course the list model itself is nothing but rows.)

I've looked around for any mention of this. All I found were these two separate posts, both with no responses:
http://www.qtcentre.org/threads/2168...w-keyboard-nav
http://www.qtcentre.org/threads/3501...pping-property

I'm using the stock Qt 4.7.0 with PyQt 4.7.4 from the Ubuntu 10.10 64-bit repos. Here's a minimal python program that demonstrates this behaviour:

Qt Code:

Switch view

import sys
from PyQt4 import QtCore, QtGui
from PyQt4.QtCore import Qt
 
class TestWindow(QtGui.QMainWindow):
    def __init__(self):
        QtGui.QMainWindow.__init__(self)
        self.list = TestListView(self)
        self.setCentralWidget(self.list)
        self.resize(500, 500)
 
class TestListView(QtGui.QListView):
    def __init__(self, parent):
        QtGui.QListView.__init__(self, parent)
        self.setModel(TestListModel(parent))
        self.setUniformItemSizes(True) # speeds up listview
        self.setFlow(QtGui.QListView.LeftToRight) # default is TopToBottom
        self.setWrapping(True) # default is False
 
class TestListModel(QtCore.QAbstractListModel):
    def __init__(self, parent):
        QtCore.QAbstractListModel.__init__(self, parent)
 
    def rowCount(self, parent=None):
        return 1000
 
    def data(self, index, role=Qt.DisplayRole):
        if role == Qt.DisplayRole and index.isValid():
            return index.row()
 
if __name__ == '__main__':
    app = QtGui.QApplication(sys.argv)
    win = TestWindow()
    win.show()
    sys.exit(app.exec_())

import sys
from PyQt4 import QtCore, QtGui
from PyQt4.QtCore import Qt

class TestWindow(QtGui.QMainWindow):
    def __init__(self):
        QtGui.QMainWindow.__init__(self)
        self.list = TestListView(self)
        self.setCentralWidget(self.list)
        self.resize(500, 500)

class TestListView(QtGui.QListView):
    def __init__(self, parent):
        QtGui.QListView.__init__(self, parent)
        self.setModel(TestListModel(parent))
        self.setUniformItemSizes(True) # speeds up listview
        self.setFlow(QtGui.QListView.LeftToRight) # default is TopToBottom
        self.setWrapping(True) # default is False

class TestListModel(QtCore.QAbstractListModel):
    def __init__(self, parent):
        QtCore.QAbstractListModel.__init__(self, parent)

    def rowCount(self, parent=None):
        return 1000

    def data(self, index, role=Qt.DisplayRole):
        if role == Qt.DisplayRole and index.isValid():
            return index.row()

if __name__ == '__main__':
    app = QtGui.QApplication(sys.argv)
    win = TestWindow()
    win.show()
    sys.exit(app.exec_())

To copy to clipboard, switch view to plain text mode

I'd argue that this behaviour is unexpected. Compact view and icon view in any file manager I've ever used wraps the cursor if it reaches an edge and if there's logically somewhere for it to go next. This makes the most of keyboard navigation.

Might this be considered a bug, or an unimplemented feature? Anyone know of any workarounds? The use case that I personally care about is LeftToRight flow mode with Wrapping enabled. I tried overriding QListView.KeyPressEvent() for left and right keys, like this:

Qt Code:

Switch view

def keyPressEvent(self, event):
    if event.key() == Qt.Key_Left:
        self.setCurrentIndex(self.moveCursor(self.MovePrevious, event.modifiers()))
    elif event.key() == Qt.Key_Right:
        self.setCurrentIndex(self.moveCursor(self.MoveNext, event.modifiers()))
    else:
        QtGui.QListView.keyPressEvent(self, event) # handle it as usual

def keyPressEvent(self, event):
    if event.key() == Qt.Key_Left:
        self.setCurrentIndex(self.moveCursor(self.MovePrevious, event.modifiers()))
    elif event.key() == Qt.Key_Right:
        self.setCurrentIndex(self.moveCursor(self.MoveNext, event.modifiers()))
    else:
        QtGui.QListView.keyPressEvent(self, event) # handle it as usual

To copy to clipboard, switch view to plain text mode

but that just moves the cursor up and down, not left and right. Using MoveLeft and MoveRight does what it says, but again doesn't wrap around the left or right edge, which is my original problem. Looking at the code in http://qt.gitorious.org/qt/qt/blobs/.../qlistview.cpp, "case MovePrevious" and "case MoveNext" are both empty in QListView::moveCursor. They both precede "case MoveUp" and "case MoveDown", which I presume in C++ means that's what they default to.

Thanks for any suggestions,

Martin