kde-extraapps/gwenview/app/preloader.cpp

// vim: set tabstop=4 shiftwidth=4 expandtab:
/*
Gwenview: an image viewer
Copyright 2008 Aurélien Gâteau <agateau@kde.org>

This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License
as published by the Free Software Foundation; either version 2
of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Cambridge, MA 02110-1301, USA.

*/
// Self
#include "preloader.moc"

// Qt

// KDE
#include <KDebug>

// Local
#include <lib/document/documentfactory.h>

namespace Gwenview
{

#undef ENABLE_LOG
#undef LOG
//#define ENABLE_LOG
#ifdef ENABLE_LOG
#define LOG(x) kDebug() << x
#else
#define LOG(x) ;
#endif

struct PreloaderPrivate
{
    Preloader* q;
    Document::Ptr mDocument;
    QSize mSize;

    void forgetDocument()
    {
        // Forget about the document. Keeping a reference to it would prevent it
        // from being garbage collected.
        QObject::disconnect(mDocument.data(), 0, q, 0);
        mDocument = 0;
    }
};

Preloader::Preloader(QObject* parent)
: QObject(parent)
, d(new PreloaderPrivate)
{
    d->q = this;
}

Preloader::~Preloader()
{
    delete d;
}

void Preloader::preload(const KUrl& url, const QSize& size)
{
    LOG("url=" << url);
    if (d->mDocument) {
        disconnect(d->mDocument.data(), 0, this, 0);
    }

    d->mDocument = DocumentFactory::instance()->load(url);
    d->mSize = size;
    connect(d->mDocument.data(), SIGNAL(metaInfoUpdated()),
            SLOT(doPreload()));

    if (d->mDocument->size().isValid()) {
        LOG("size is already available");
        doPreload();
    }
}

void Preloader::doPreload()
{
    if (!d->mDocument) {
        return;
    }

    if (d->mDocument->loadingState() == Document::LoadingFailed) {
        LOG("loading failed");
        d->forgetDocument();
        return;
    }

    if (!d->mDocument->size().isValid()) {
        LOG("size not available yet");
        return;
    }

    qreal zoom = qMin(
                     d->mSize.width() / qreal(d->mDocument->width()),
                     d->mSize.height() / qreal(d->mDocument->height())
                 );

    if (zoom < Document::maxDownSampledZoom()) {
        LOG("preloading down sampled, zoom=" << zoom);
        d->mDocument->prepareDownSampledImageForZoom(zoom);
    } else {
        LOG("preloading full image");
        d->mDocument->startLoadingFullImage();
    }
    d->forgetDocument();
}

} // namespace