[Digikam-devel] [Bug 136855] Editing metadata on a few selected imagefiles and clicking forward or apply crashes digikam.

[Gilles Caulier]

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http://bugs.kde.org/show_bug.cgi?id=136855         




------- Additional Comments From caulier.gilles kdemail net  2006-11-08 09:34 -------
Andreas, 

When i said "good", i want mean "instructive" in fact (:=)))...

About the methods used in Exiv2iface from the MetadataEdit kipi-plugin, it's very simple. look the code from the slots used when we want save the changes in pictures metadata :

In Exif editor dialog, we have :

void EXIFEditDialog::slotApply()
{
    if (d->modified && !d->isReadOnly) 
    {
        d->captionPage->applyMetadata(d->exifData);
        ...
        KIPIPlugins::Exiv2Iface exiv2Iface;
        exiv2Iface.load((*d->currItem).path());
        exiv2Iface.setExif(d->exifData);
        exiv2Iface.save((*d->currItem).path());
        d->modified = false;
    }
}

d->modified and d->isReadOnly are just boolean variables. d->exifData is a bytearray to store metadata.

The IPTC code is similar than Exif :

void IPTCEditDialog::slotApply()
{
    if (d->modified && !d->isReadOnly) 
    {
        d->captionPage->applyMetadata(d->iptcData);
        ...
        KIPIPlugins::Exiv2Iface exiv2Iface;
        exiv2Iface.load((*d->currItem).path());
        exiv2Iface.setExif(d->iptcData);
        exiv2Iface.save((*d->currItem).path());
        d->modified = false;
    }
}

About to load metadata from pictures when user change current selected one to edit in MetadataEdit plugin, we have another slots for Exif :

void EXIFEditDialog::slotItemChanged()
{
    KIPIPlugins::Exiv2Iface exiv2Iface;
    exiv2Iface.load((*d->currItem).path());
    d->exifData = exiv2Iface.getExif();
    d->captionPage->readMetadata(d->exifData);
    ...
    d->isReadOnly = KIPIPlugins::Exiv2Iface::isReadOnly((*d->currItem).path()); 
    ...
}

... and for IPTC :

void IPTCEditDialog::slotItemChanged()
{
    KIPIPlugins::Exiv2Iface exiv2Iface;
    exiv2Iface.load((*d->currItem).path());
    d->iptcData = exiv2Iface.getIptc();
    d->captionPage->readMetadata(d->iptcData);
    ...
    d->isReadOnly = KIPIPlugins::Exiv2Iface::isReadOnly((*d->currItem).path()); 
    ...
}

The slotItemChanged() and slotApply() call the dialog page methods to get or set the matadata values on the Exif/IPTC bytearray. this is the readMetadata() and applyMetadata() methods. These one use too another instances of KIPIPlugins::Exiv2Iface class to use others methods relevant of tags manipulations. For example, in Exif Captions editor page, we have :

void EXIFCaption::readMetadata(QByteArray& exifData)
{
    ...
    KIPIPlugins::Exiv2Iface exiv2Iface;
    exiv2Iface.setExif(exifData);
    QString data;

    data = exiv2Iface.getExifTagString("Exif.Image.DocumentName", false);    
    ...
}

void EXIFCaption::applyMetadata(QByteArray& exifData)
{
    KIPIPlugins::Exiv2Iface exiv2Iface;
    exiv2Iface.setExif(exifData);

    if (d->documentNameCheck->isChecked())
        exiv2Iface.setExifTagString("Exif.Image.DocumentName", d->documentNameEdit->text());
    else
        exiv2Iface.removeExifTag("Exif.Image.DocumentName");
    ...
}

The both class instance are independant and there is no memory conflict here (checked with valgrind). Exiv2Iface do not use static member.

Other important note : this plugin do not use multithreading like in digiKam core. The crash is not relevant of an unthread-safe problem.

You can read all current plugin source code here :

http://websvn.kde.org/trunk/extragear/libs/kipi-plugins/metadataedit

and the Exiv2Iface class here :

http://websvn.kde.org/trunk/extragear/libs/kipi-plugins/common/exiv2iface

Gilles