thumbnails example improved for the use case of having many items
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@ -16,11 +16,14 @@
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#include <QskObjectCounter.h>
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#include <QskPushButton.h>
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#include <QskScrollArea.h>
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#include <QskQuick.h>
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#include <QskWindow.h>
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#include <QGuiApplication>
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#include <QPainter>
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#define HIDE_NODES 1
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const int gridSize = 20;
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const int thumbnailSize = 150;
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@ -65,12 +68,23 @@ class Thumbnail : public QskPushButton
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Thumbnail( const QColor& color, int shape, QQuickItem* parentItem )
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: QskPushButton( parentItem )
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{
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using namespace SkinnyShapeFactory;
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const QSizeF size( thumbnailSize, thumbnailSize );
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QskGraphic graphic;
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setGraphic( thumbnailGraphic( color, shape, size ) );
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setFixedSize( size );
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setFlat( true );
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}
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private:
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QskGraphic thumbnailGraphic( const QColor& color,
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int shape, const QSizeF& size ) const
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{
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const auto path = SkinnyShapeFactory::shapePath(
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static_cast< SkinnyShapeFactory::Shape >( shape ), size );
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QskGraphic graphic;
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QPen pen( Qt::black, 3 );
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pen.setJoinStyle( Qt::MiterJoin );
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pen.setCosmetic( true );
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@ -80,13 +94,10 @@ class Thumbnail : public QskPushButton
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painter.setPen( pen );
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painter.setBrush( color );
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painter.drawPath( shapePath( static_cast< Shape >( shape ), size ) );
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painter.drawPath( path );
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painter.end();
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setGraphic( graphic );
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setFixedSize( size );
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setFlat( true );
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return graphic;
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}
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};
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@ -104,7 +115,67 @@ class IconGrid : public QskLinearBox
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for ( int row = 0; row < gridSize; row++ )
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( void ) new Thumbnail( randomColor(), randomShape(), this );
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}
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#if HIDE_NODES
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/*
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When having too many nodes, the scene graph becomes horribly slow.
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So we explicitely hide all items outside the visible area
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( see updateVisibilities below ) and make use of the DeferredUpdate and
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CleanupOnVisibility features of QskQuickItem.
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*/
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setSize( sizeConstraint() );
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updateLayout(); // so that every item has its initial geometry
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for ( int i = 0; i < count(); i++ )
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{
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if ( auto item = qobject_cast< QskControl* > ( itemAtIndex( i ) ) )
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{
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// to support the optimizations in ScrollArea::updateVisibilities
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item->setLayoutHint( RetainSizeWhenHidden, true );
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item->setVisible( false );
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}
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}
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#endif
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}
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#if HIDE_NODES
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void updateVisibilities( const QRectF& viewPort )
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{
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if ( !isEmpty() && viewPort != m_viewPort )
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{
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setItemsVisible( m_viewPort, false );
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setItemsVisible( viewPort, true );
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m_viewPort = viewPort;
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}
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}
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private:
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void setItemsVisible( const QRectF& rect, bool on )
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{
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const int dim = dimension();
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// we know, that all items have the same size
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const auto itemSize = qskItemSize( itemAtIndex( 0 ) );
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const int rowMin = rect.top() / ( itemSize.height() + spacing() );
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const int rowMax = rect.bottom() / ( itemSize.height() + spacing() );
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const int colMin = rect.left() / ( itemSize.width() + spacing() );
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const int colMax = rect.right() / ( itemSize.height() + spacing() );
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for ( int row = rowMin; row <= rowMax; row++ )
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{
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for ( int col = colMin; col <= colMax; col++ )
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{
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if ( auto item = itemAtIndex( row * dim + col ) )
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item->setVisible( on );
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}
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}
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}
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QRectF m_viewPort;
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#endif
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};
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class ScrollArea : public QskScrollArea
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@ -129,6 +200,29 @@ class ScrollArea : public QskScrollArea
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setBoxShapeHint( HorizontalScrollHandle, 8 );
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setFlickRecognizerTimeout( 300 );
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connect( this, &QskScrollView::scrollPosChanged,
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this, &ScrollArea::updateVisibilities );
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}
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protected:
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void geometryChanged( const QRectF& newRect, const QRectF& oldRect ) override
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{
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QskScrollArea::geometryChanged( newRect, oldRect );
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updateVisibilities();
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}
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private:
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void updateVisibilities()
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{
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#if HIDE_NODES
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const auto box = static_cast< IconGrid* >( scrolledItem() );
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if ( box )
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{
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const QRectF viewPort( scrollPos(), viewContentsRect().size() );
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box->updateVisibilities( viewPort );
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}
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#endif
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}
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};
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@ -153,6 +247,8 @@ int main( int argc, char* argv[] )
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This example also shows, that blocking of the scene graph node creation
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( QskControl::DeferredUpdate + QskControl::CleanupOnVisibility )
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could be improved to also respect being inside the window or a clip region.
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To have a similar effect with what is possible today, the code
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explicitely hide/show(s) the buttons out/inside the viewport.
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But here we only want to demonstrate how QskScrollArea works.
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*/
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