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# textedit.cpp Example File
tools/customcompleter/textedit.cpp

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     ** This file is part of the examples of the Qt Toolkit.
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     ** General Public License version 2.1 as published by the Free Software
     ** Foundation and appearing in the file LICENSE.LGPL included in the
     ** packaging of this file.  Please review the following information to
     ** ensure the GNU Lesser General Public License version 2.1 requirements
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     ** Alternatively, this file may be used under the terms of the GNU
     ** General Public License version 3.0 as published by the Free Software
     ** Foundation and appearing in the file LICENSE.GPL included in the
     ** packaging of this file.  Please review the following information to
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     #include "textedit.h"
     #include <QCompleter>
     #include <QKeyEvent>
     #include <QAbstractItemView>
     #include <QtDebug>
     #include <QApplication>
     #include <QModelIndex>
     #include <QAbstractItemModel>
     #include <QScrollBar>

     TextEdit::TextEdit(QWidget *parent)
     : QTextEdit(parent), c(0)
     {
         setPlainText(tr("This TextEdit provides autocompletions for words that have more than"
                         " 3 characters. You can trigger autocompletion using ") +
                         QKeySequence("Ctrl+E").toString(QKeySequence::NativeText));
     }

     TextEdit::~TextEdit()
     {
     }

     void TextEdit::setCompleter(QCompleter *completer)
     {
         if (c)
             QObject::disconnect(c, 0, this, 0);

         c = completer;

         if (!c)
             return;

         c->setWidget(this);
         c->setCompletionMode(QCompleter::PopupCompletion);
         c->setCaseSensitivity(Qt::CaseInsensitive);
         QObject::connect(c, SIGNAL(activated(QString)),
                          this, SLOT(insertCompletion(QString)));
     }

     QCompleter *TextEdit::completer() const
     {
         return c;
     }

     void TextEdit::insertCompletion(const QString& completion)
     {
         if (c->widget() != this)
             return;
         QTextCursor tc = textCursor();
         int extra = completion.length() - c->completionPrefix().length();
         tc.movePosition(QTextCursor::Left);
         tc.movePosition(QTextCursor::EndOfWord);
         tc.insertText(completion.right(extra));
         setTextCursor(tc);
     }

     QString TextEdit::textUnderCursor() const
     {
         QTextCursor tc = textCursor();
         tc.select(QTextCursor::WordUnderCursor);
         return tc.selectedText();
     }

     void TextEdit::focusInEvent(QFocusEvent *e)
     {
         if (c)
             c->setWidget(this);
         QTextEdit::focusInEvent(e);
     }

     void TextEdit::keyPressEvent(QKeyEvent *e)
     {
         if (c && c->popup()->isVisible()) {
             // The following keys are forwarded by the completer to the widget
            switch (e->key()) {
            case Qt::Key_Enter:
            case Qt::Key_Return:
            case Qt::Key_Escape:
            case Qt::Key_Tab:
            case Qt::Key_Backtab:
                 e->ignore();
                 return; // let the completer do default behavior
            default:
                break;
            }
         }

         bool isShortcut = ((e->modifiers() & Qt::ControlModifier) && e->key() == Qt::Key_E); // CTRL+E
         if (!c || !isShortcut) // dont process the shortcut when we have a completer
             QTextEdit::keyPressEvent(e);

         const bool ctrlOrShift = e->modifiers() & (Qt::ControlModifier | Qt::ShiftModifier);
         if (!c || (ctrlOrShift && e->text().isEmpty()))
             return;

         static QString eow("~!@#$%^&*()_+{}|:\"<>?,./;'[]\\-="); // end of word
         bool hasModifier = (e->modifiers() != Qt::NoModifier) && !ctrlOrShift;
         QString completionPrefix = textUnderCursor();

         if (!isShortcut && (hasModifier || e->text().isEmpty()|| completionPrefix.length() < 3
                           || eow.contains(e->text().right(1)))) {
             c->popup()->hide();
             return;
         }

         if (completionPrefix != c->completionPrefix()) {
             c->setCompletionPrefix(completionPrefix);
             c->popup()->setCurrentIndex(c->completionModel()->index(0, 0));
         }
         QRect cr = cursorRect();
         cr.setWidth(c->popup()->sizeHintForColumn(0)
                     + c->popup()->verticalScrollBar()->sizeHint().width());
         c->complete(cr); // popup it up!
     }