KMessageBox preferred size algorithm

[Urs Wolfer]

On Friday 11 August 2006 20:35, mauricio at tabuleiro.com wrote: 
> Hi. 
Hi
> I came across some layout issues when using KMessageBox, with longer 
> text being cut, usually half a line on the bottom or half a character at
> left. This was happening with several screens of KGoldrunner and were
> reported as sighted in KBlackbox as well (new KDE 4 ports, using QGV).
>
> I traced the problem to a commit 40 days ago in kmessagebox.cpp (commit
> 559160), where an extra 10 pixel margin was removed. I restored the
> previous behavior, which was the same used in KDE3. The svn commit log for
> kmessagebox.cpp (today) includes more information.
>
> However, I would like to find a more definitive solution to this problem.
> The line in question is now
>
> label2->setFixedSize(QSize(pref_width + 10, pref_height + 10));
>
> And pref_width and pref_height are calculated in a routine just above its
> usage, reproduced below for your convenience. Notice that the
> Q3SimpleRichText widget is never used, it is just set with the same text
> used in the label (qt_text) and used only to calculate the best geometry,
> as Q3SimpleRichText has the widthused() property.
>
>   // Calculate a proper size for the text.
>     {
>        Q3SimpleRichText rt(qt_text, dialog->font());
>        QRect d = KGlobalSettings::desktopGeometry(dialog);
>
>        pref_width = d.width() / 3;
>        pref_height = label2->heightForWidth(pref_width);
>
>        rt.setWidth(pref_width);
>        int used_width = rt.widthUsed();
>        pref_height = rt.height();
>        if (3*pref_height > 2*d.height())
>        {
>           // Very high dialog.. make it wider
>           pref_width = d.width() / 2;
>           rt.setWidth(pref_width);
>           used_width = rt.widthUsed();
>           pref_height = rt.height();
>        }
>        if (used_width <= pref_width)
>        {
>           while(true)
>           {
>              int new_width = (used_width * 9) / 10;
>              rt.setWidth(new_width);
>              int new_height = rt.height();
>              if (new_height > pref_height)
>                 break;
>              used_width = rt.widthUsed();
>              if (used_width > new_width)
>                 break;
>           }
>           pref_width = used_width;
>        }
>        else
>        {
>           if (used_width > (pref_width *2))
>              pref_width = pref_width *2;
>           else
>              pref_width = used_width;
>        }
>    }
>
> What would be the correct way to calculate this without using the
> intermediary Q3SimpleRichText, preferrably using the QLabel that will be
> displayed directly? I am still getting used to setting layouts in code.
> Until now all my usage of Qt was based on Designer .ui files, and things
> usually "just worked" right for me, without the need to tweak the size
> hints or anything like that.

There was in another file the same preferred size algorithm. It has been 
ported some time ago. Probably this can help you:
http://websvn.kde.org/trunk/KDE/kdelibs/kio/kio/passdlg.cpp?rev=527457&sortby=author&view=diff&r1=527457&r2=527456&p1=trunk/KDE/kdelibs/kio/kio/passdlg.cpp&p2=/trunk/KDE/kdelibs/kio/kio/passdlg.cpp
(Commit: 527457 File: kio/passdlg.cpp)

Bye
urs
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