QCompleter Custom Completion Rules

Question

I'm using Qt4.6 and I have a QComboBox with a QCompleter in it.

The usual functionality is to provide completion hints (these can be in a dropdown rather than inline - which is my usage) based on a prefix. For example, given

chicken soup
chilli peppers
grilled chicken

entering ch would match chicken soup and chilli peppers but not grilled chicken.

What I want is to be able to enter ch and match all of them or, more specifically, chicken and match chicken soup and grilled chicken.
I also want to be able to assign a tag like chs to chicken soup to produce another match which is not just on the text's content. I can handle the algorithm but,

Which of QCompleter's functions do I need to override?
I'm not really sure where I should be looking...

Answer 1

Based on @j3frea suggestion, here is a working example (using PySide). It appears that the model needs to be set every time splitPath is called (setting the proxy once in setModel doesn't work).

combobox.setEditable(True)
combobox.setInsertPolicy(QComboBox.NoInsert)

class CustomQCompleter(QCompleter):
    def __init__(self, parent=None):
        super(CustomQCompleter, self).__init__(parent)
        self.local_completion_prefix = ""
        self.source_model = None

    def setModel(self, model):
        self.source_model = model
        super(CustomQCompleter, self).setModel(self.source_model)

    def updateModel(self):
        local_completion_prefix = self.local_completion_prefix
        class InnerProxyModel(QSortFilterProxyModel):
            def filterAcceptsRow(self, sourceRow, sourceParent):
                index0 = self.sourceModel().index(sourceRow, 0, sourceParent)
                return local_completion_prefix.lower() in self.sourceModel().data(index0).lower()
        proxy_model = InnerProxyModel()
        proxy_model.setSourceModel(self.source_model)
        super(CustomQCompleter, self).setModel(proxy_model)

    def splitPath(self, path):
        self.local_completion_prefix = path
        self.updateModel()
        return ""


completer = CustomQCompleter(combobox)
completer.setCompletionMode(QCompleter.PopupCompletion)
completer.setModel(combobox.model())

combobox.setCompleter(completer)

Answer 2

Unfortunately, the answer is currently that it's not possible. To do that you'd need to duplicate much of the functionality of QCompleter in your own application (Qt Creator does that for its Locator, see src/plugins/locator/locatorwidget.cpp for the magic if you're interested).

Meanwhile you could vote on QTBUG-7830, which is about making it possible to customize the way completion items are matched, like you want. But don't hold your breath on that one.

Answer 3

Thanks Thorbjørn, I actually did solve the problem by inheriting from QSortFilterProxyModel.

The filterAcceptsRow method must be overwritten and then you just return true or false depending on whether or not you want that item displayed.

The problem with this solution is that it only hides items in a list and so you can never rearrange them (which is what I wanted to do to give certain items priority).

[EDIT]
I thought I'd throw this into the solution since it's [basically] what I ended up doing (because the above solution wasn't adequate). I used http://www.cppblog.com/biao/archive/2009/10/31/99873.html:

#include "locationlineedit.h"
#include <QKeyEvent>
#include <QtGui/QListView>
#include <QtGui/QStringListModel>
#include <QDebug>

LocationLineEdit::LocationLineEdit(QStringList *words, QHash<QString, int> *hash, QVector<int> *bookChapterRange, int maxVisibleRows, QWidget *parent)
: QLineEdit(parent), words(**&words), hash(**&hash)
{
listView = new QListView(this);
model = new QStringListModel(this);
listView->setWindowFlags(Qt::ToolTip);

connect(this, SIGNAL(textChanged(const QString &)), this, SLOT(setCompleter(const QString &)));
connect(listView, SIGNAL(clicked(const QModelIndex &)), this, SLOT(completeText(const QModelIndex &)));

this->bookChapterRange = new QVector<int>;
this->bookChapterRange = bookChapterRange;
this->maxVisibleRows = &maxVisibleRows;

listView->setModel(model);
}

void LocationLineEdit::focusOutEvent(QFocusEvent *e)
{
listView->hide();
QLineEdit::focusOutEvent(e);
}
void LocationLineEdit::keyPressEvent(QKeyEvent *e)
{
int key = e->key();
if (!listView->isHidden())
{
    int count = listView->model()->rowCount();
    QModelIndex currentIndex = listView->currentIndex();

    if (key == Qt::Key_Down || key == Qt::Key_Up)
    {
    int row = currentIndex.row();
    switch(key) {
    case Qt::Key_Down:
        if (++row >= count)
        row = 0;
        break;
    case Qt::Key_Up:
        if (--row < 0)
        row = count - 1;
        break;
    }

    if (listView->isEnabled())
    {
        QModelIndex index = listView->model()->index(row, 0);
        listView->setCurrentIndex(index);
    }
    }
    else if ((Qt::Key_Enter == key || Qt::Key_Return == key || Qt::Key_Space == key) && listView->isEnabled())
    {
    if (currentIndex.isValid())
    {
        QString text = currentIndex.data().toString();
        setText(text + " ");
        listView->hide();
        setCompleter(this->text());
    }
    else if (this->text().length() > 1)
    {
        QString text = model->stringList().at(0);
        setText(text + " ");
        listView->hide();
        setCompleter(this->text());
    }
    else
    {
        QLineEdit::keyPressEvent(e);
    }
    }
    else if (Qt::Key_Escape == key)
    {
    listView->hide();
    }
    else
    {
    listView->hide();
    QLineEdit::keyPressEvent(e);
    }
}
else
{
    if (key == Qt::Key_Down || key == Qt::Key_Up)
    {
    setCompleter(this->text());

    if (!listView->isHidden())
    {
        int row;
        switch(key) {
        case Qt::Key_Down:
        row = 0;
        break;
        case Qt::Key_Up:
        row = listView->model()->rowCount() - 1;
        break;
        }
        if (listView->isEnabled())
        {
        QModelIndex index = listView->model()->index(row, 0);
        listView->setCurrentIndex(index);
        }
    }
    }
    else
    {
    QLineEdit::keyPressEvent(e);
    }
}
}

void LocationLineEdit::setCompleter(const QString &text)
{
if (text.isEmpty())
{
    listView->hide();
    return;
}
/*
This is there in the original but it seems to be bad for performance
(keeping listview hidden unnecessarily - havn't thought about it properly though)
*/
//    if ((text.length() > 1) && (!listView->isHidden()))
//    {
//        return;
//    }


model->setStringList(filteredModelFromText(text));


if (model->rowCount() == 0)
{
    return;
}

int maxVisibleRows = 10;
// Position the text edit
QPoint p(0, height());
int x = mapToGlobal(p).x();
int y = mapToGlobal(p).y() + 1;
listView->move(x, y);
listView->setMinimumWidth(width());
listView->setMaximumWidth(width());
if (model->rowCount() > maxVisibleRows)
{
    listView->setFixedHeight(maxVisibleRows * (listView->fontMetrics().height() + 2) + 2);
}
else
{
    listView->setFixedHeight(model->rowCount() * (listView->fontMetrics().height() + 2) + 2);
}
listView->show();
}

//Basically just a slot to connect to the listView's click event
void LocationLineEdit::completeText(const QModelIndex &index)
{
QString text = index.data().toString();
setText(text);
listView->hide();
}

QStringList LocationLineEdit::filteredModelFromText(const QString &text)
{
QStringList newFilteredModel;

    //do whatever you like and fill the filteredModel

return newFilteredModel;
}

Answer 4

Use filterMode : Qt::MatchFlags property. This property holds how the filtering is performed. If filterMode is set to Qt::MatchStartsWith, only those entries that start with the typed characters will be displayed. Qt::MatchContains will display the entries that contain the typed characters, and Qt::MatchEndsWith the ones that end with the typed characters. Currently, only these three modes are implemented. Setting filterMode to any other Qt::MatchFlag will issue a warning, and no action will be performed. The default mode is Qt::MatchStartsWith.

This property was introduced in Qt 5.2.

Access functions:

Qt::MatchFlags  filterMode() const
void    setFilterMode(Qt::MatchFlags filterMode)

Answer 5

You can get around QTBUG-7830 as mentioned above by providing custom role and making completion on that role. In the handler of that role, you can do the trick to let QCompleter know that item is there. This will work if you also override filterAcceptsRow in your SortFilterProxy model.

Answer 6

Building on the answer of @Bruno, I am using the standard QSortFilterProxyModel function setFilterRegExp to change the search string. In this way no sub-classing is necessary.

It also fixes a bug in @Bruno's answer, which made the suggestions vanish for some reasons once the input string got corrected with backspace while typing.

class CustomQCompleter(QtGui.QCompleter):
    """
    adapted from: http://stackoverflow.com/a/7767999/2156909
    """
    def __init__(self, *args):#parent=None):
        super(CustomQCompleter, self).__init__(*args)
        self.local_completion_prefix = ""
        self.source_model = None
        self.filterProxyModel = QtGui.QSortFilterProxyModel(self)
        self.usingOriginalModel = False

    def setModel(self, model):
        self.source_model = model
        self.filterProxyModel = QtGui.QSortFilterProxyModel(self)
        self.filterProxyModel.setSourceModel(self.source_model)
        super(CustomQCompleter, self).setModel(self.filterProxyModel)
        self.usingOriginalModel = True

    def updateModel(self):
        if not self.usingOriginalModel:
            self.filterProxyModel.setSourceModel(self.source_model)

        pattern = QtCore.QRegExp(self.local_completion_prefix,
                                QtCore.Qt.CaseInsensitive,
                                QtCore.QRegExp.FixedString)

        self.filterProxyModel.setFilterRegExp(pattern)

    def splitPath(self, path):
        self.local_completion_prefix = path
        self.updateModel()
        if self.filterProxyModel.rowCount() == 0:
            self.usingOriginalModel = False
            self.filterProxyModel.setSourceModel(QtGui.QStringListModel([path]))
            return [path]

        return []

class AutoCompleteComboBox(QtGui.QComboBox):
    def __init__(self, *args, **kwargs):
        super(AutoCompleteComboBox, self).__init__(*args, **kwargs)

        self.setEditable(True)
        self.setInsertPolicy(self.NoInsert)

        self.comp = CustomQCompleter(self)
        self.comp.setCompletionMode(QtGui.QCompleter.PopupCompletion)
        self.setCompleter(self.comp)#
        self.setModel(["Lola", "Lila", "Cola", 'Lothian'])

    def setModel(self, strList):
        self.clear()
        self.insertItems(0, strList)
        self.comp.setModel(self.model())

    def focusInEvent(self, event):
        self.clearEditText()
        super(AutoCompleteComboBox, self).focusInEvent(event)

    def keyPressEvent(self, event):
        key = event.key()
        if key == 16777220:
            # Enter (if event.key() == QtCore.Qt.Key_Enter) does not work
            # for some reason

            # make sure that the completer does not set the
            # currentText of the combobox to "" when pressing enter
            text = self.currentText()
            self.setCompleter(None)
            self.setEditText(text)
            self.setCompleter(self.comp)

        return super(AutoCompleteComboBox, self).keyPressEvent(event)

Update:

I figured that my previous solution worked until the string in the combobox matched none of the list items. Then the QFilterProxyModel was empty and this in turn reseted the text of the combobox. I tried to find an elegant solution to this problem, but I ran into problems (referencing deleted object errors) whenever I tried to change something on self.filterProxyModel. So now the hack is to set the model of self.filterProxyModel everytime new when its pattern is updated. And whenever the pattern does not match anything in the model anymore, to give it a new model that just contains the current text (aka path in splitPath). This might lead to performance issues if you are dealing with very large models, but for me the hack works pretty well.

Update 2:

I realized that this is still not the perfect way to go, because if a new string is typed in the combobox and the user presses enter, the combobox is cleared again. The only way to enter a new string is to select it from the drop down menu after typing.

Update 3:

Now enter works as well. I worked around the reset of the combobox text by simply taking it off charge when the user presses enter. But I put it back in, so that the completion functionality remains in place. If the user decides to do further edits.

Answer 7

This page now has been viewed over 14k times and referenced by many other posts on SO. It seems that people are creating and setting a new proxy model every time when splitPath is called, which is completely unnecessary (and expensive for large models). We just need to set the proxy model once in setModel.

As @bruno mentioned:

It appears that the model needs to be set every time splitPath is called (setting the proxy once in setModel doesn't work).

That is because if we don't invalidate the current filtering, the proxy model won't update internally. Just make sure to invalidate any current filtering or sorting on the proxy model and then you will be able to see the updates:

    def splitPath(self, path):
        self.local_completion_prefix = path
        self.proxyModel.invalidateFilter()  # invalidate the current filtering
        self.proxyModel.invalidate()  # or invalidate both filtering and sorting
        return ""

This is available since Qt 4.3, see https://doc.qt.io/qt-5/qsortfilterproxymodel.html#invalidateFilter

Answer 8

Easiest solution with PyQt5 :

from PyQt5.QtCore import Qt
from PyQt5.QtWidgets import QCompleter

completer = QCompleter()
completer.setFilterMode(Qt.MatchContains)