[Qt-interest] Calculating text size in QLineEdit

[Andre Somers]

Hi,

Op Di, 8 maart, 2011 11:10 am, schreef Matthias Paul:
>
> -------- Original-Nachricht --------
>> Datum: Tue, 8 Mar 2011 10:20:23 +0100
>> Von: "Andre Somers" <andre at familiesomers.nl>
>> An: "\'qt-interest at trolltech.com\'" <qt-interest at trolltech.com>
>> Betreff: Re: [Qt-interest] Calculating text size in QLineEdit
>
>> Op Di, 8 maart, 2011 10:06 am, schreef Matthias Paul:
>> > Hello!
>> >
>> > I created a QLineEdit subclass, which automatically displays a
>> truncated
>> > text if the original text is too long for the widget's size, so that
>> > there's no need to scroll for the user. Instead a tooltip with full
>> text
>> > is displayed.
>> >
>> > QFontMetrics calculates the size required for the displayed text based
>> on
>> > QWidget's size() (provided by ResizeEvent). Still, I cannot figure out
>> how
>> > to get the the text label size _minus_ widget's borders and margins.
>> Guess
>> > I have to use QStyle somehow, so can someone give me a hint please?
>>
>> Perhaps you can use QStyle::subElementRect, using
>> QStyle::SE_LineEditContents for the element argument, and a style option
>> initialized with your line edit widget as the style option? That should
>> give you the rect that is available to draw the text.
>>
>> André
>>
>
> Hello André!
>
> Thank you for your reply!
>
> The subelementRect() always returns an invalid QRect, although the
> QLineEdit is displayed and has content in it.
>
> That's what I tried: (typos included)
> --------------------------------------------------
> void
> TruncatedLineEdit::resizeEvent(
>     QResizeEvent * resizeEvent) {
>
>   QLineEdit::resizeEvent(resizeEvent);
>
>   qDebug() << "QWidget's size (by event):" << resizeEvent->size();
>   QStyleOption option;
>   option.initFrom(this);
>   qDebug() << "QWidget's content rect (by style):"
>            << this->style()->subElementRect(
>                   QStyle::SE_LineEditContents,
>                   &option,
>                   this);
>   // do smth with size information
> }
> --------------------------------------------------
>
> The output is:
> --------------------------------------------------
> QWidget's size (by event): QSize(246, 22)
> QWidget's content rect (by style): QRect(0,0 0x0)
> --------------------------------------------------
>
>
> Is it because QLineEdit has no user-style set to it? QLineEdit has been
> set with usual calls like setFont(), setReadOnly() and setObjectName().

I would have expected your code to work. I don't know why it doesn't.
Sorry! Perhaps you can check QLineEdit's sources to find out how QLineEdit
itself determines the rect to draw the text in?

André