controls/QskDirtyItemFilter.cpp

static inline bool qskIsUpdateBlocked(
    const QQuickItem * item
)

static inline void qskBlockDirty(
    QQuickItem * item,
    bool on
)

/******************************************************************************
 * QSkinny - Copyright (C) 2016 Uwe Rathmann
 * This file may be used under the terms of the QSkinny License, Version 1.0
 *****************************************************************************/

#include "QskDirtyItemFilter.h"
#include "QskQuickItem.h"


#include <private/qquickitem_p.h>
#include <private/qquickwindow_p.h>


static inline bool qskIsUpdateBlocked( const QQuickItem* item )
{
    if ( !item->isVisible() )
    {
        if ( auto qskItem = qobject_cast< const QskQuickItem* >( item ) )
            return qskItem->testUpdateFlag( QskQuickItem::DeferredUpdate );
    }

#if 0
    /*
        Blocking items, that are outside the window would be easy,
        but we have not yet found a performant way to send update notifications
        when an item enters/leaves the window. TODO ...
     */
    else if ( const auto control = qskControlCast( item ) )
    {
        const QRectF itemRect( item->mapToScene( QPointF() ), item->size() );
        const QRectF sceneRect( 0, 0, item->window()->width(), item->window()->height() );

        return !itemRect.intersects( sceneRect );
    }
#endif

    return false;
}

static inline void qskBlockDirty( QQuickItem* item, bool on )
{
    if ( qskIsUpdateBlocked( item ) )
        QQuickItemPrivate::get( item )->componentComplete = !on;

    const auto children = item->childItems();
    for ( auto child : children )
        qskBlockDirty( child, on );
}

namespace
{
    class ResetBlockedDirtyJob final : public QRunnable
    {
      public:
        inline ResetBlockedDirtyJob( QQuickWindow* window )
            : m_window( window )
        {
        }

        void run() override
        {
            qskBlockDirty( m_window->contentItem(), false );
        }

      private:
        const QQuickWindow* m_window;
    };
}

QskDirtyItemFilter::QskDirtyItemFilter( QObject* parent )
    : QObject( parent )
{
}

QskDirtyItemFilter::~QskDirtyItemFilter()
{
}

void QskDirtyItemFilter::addWindow( QQuickWindow* window )
{
    if ( m_windows.contains( window ) )
        return;

    m_windows.insert( window );

    /*
        Depending on the configration the scene graph runs on
        a different thread and we need a direct connection to
        filter the dirty list in the scene graph thread.

        As QObject::sender() is not valid, when using a direct
        connection between different threads, we need an
        extra lambda to pass window as parameter.
     */

    connect( window, &QQuickWindow::beforeSynchronizing,
        window, [ this, window ] { beforeSynchronizing( window ); },
        Qt::DirectConnection );

    connect( window, &QObject::destroyed,
        this, [ this, window ] { m_windows.remove( window ); } );
}

void QskDirtyItemFilter::beforeSynchronizing( QQuickWindow* window )
{
    filterDirtyList( window, qskIsUpdateBlocked );

    if ( QQuickWindowPrivate::get( window )->renderer == nullptr )
    {
        /*
            In this specific initial situation QQuickWindow updates
            the dirtyList after emitting "beforeSynchronizing".
            So we need a special hack setting/resetting componentComplete
            to avoid having all items in the dirtyList.
         */
        qskBlockDirty( window->contentItem(), true );

        window->scheduleRenderJob( new ResetBlockedDirtyJob( window ),
            QQuickWindow::AfterSynchronizingStage );
    }
}

void QskDirtyItemFilter::filterDirtyList(
    QQuickWindow* window, bool ( *isBlocked )( const QQuickItem* ) )
{
    if ( window == nullptr )
        return;

    auto d = QQuickWindowPrivate::get( window );
    for ( auto item = d->dirtyItemList; item != nullptr; )
    {
        auto nextItem = QQuickItemPrivate::get( item )->nextDirtyItem;

        if ( isBlocked( item ) )
            QQuickItemPrivate::get( item )->removeFromDirtyList();

        item = nextItem;
    }
}