How to make QTextCursor::WordUnderCursor include more characters or larger words

I'm trying to show a tooltip when the cursor is over a keyword in a text editor using:

QTextCursor cursor = cursorForPosition(pos);
cursor.select(QTextCursor::WordUnderCursor);

This works well, but the definition of a word does not fit my needs. For example, the keyword \abcde is recognized as 2 words, \ and abcde. Similarly, the word a1:2 is recognized in three parts a1, : and 1.

Basically, what I'd like is to change the behavior, such as a word is defined as a set of characters separated by space.

I tried QTextCursor::BlockUnderCursor, but it does the same as QTextCursor::LineUnderCursor and returns the entire line.

Solution

Here's a way to select words separated by a space when a text cursor's position changes.

It basically works this way:

Check if the current cursor is selecting (QTextCursor::anchor and QTextCursor::position have different values), and set the custom cursor's position accordingly.
Go forward until you reach the end or a space.
Store the last position reached.
Go back until you reach the start or a space.
Select from where the cursor stopped until the position previously stored as the end.
The result is the fetched selection.

void Form::on_textEdit_cursorPositionChanged()
{
    //prevent infinite loop in case text is added manually at start
    if(textCursor().position()<0)
            return;

    QTextCursor cursor(ui->textEdit->textCursor());
    int end;

    //prevent cursor from being anchored when the normal cursor is selecting
    if(ui->textEdit->textCursor().anchor()!=ui->textEdit->textCursor().position())
    {
        cursor.setPosition(ui->textEdit->textCursor().position());
    }

    //I'm checking for new line using QChar(8233)
    //you might have to change that depending on your platform
    while(!cursor.atEnd() &&
          (ui->textEdit->document()->characterAt(cursor.position())!=' ' && ui->textEdit->document()->characterAt(cursor.position())!=QChar(8233)))
    {
        cursor.movePosition(QTextCursor::NextCharacter, QTextCursor::MoveAnchor);
    }

    end=cursor.position();

    while(!cursor.atStart() &&
          (ui->textEdit->document()->characterAt(cursor.position()-1)!=' ' && ui->textEdit->document()->characterAt(cursor.position()-1)!=QChar(8233)))
    {
        cursor.movePosition(QTextCursor::PreviousCharacter, QTextCursor::MoveAnchor);
    }

    cursor.movePosition(QTextCursor::NextCharacter, QTextCursor::KeepAnchor,end-cursor.position());

    QString result = cursor.selectedText();
}

Demonstration: