thumbnails example improved for the use case of having many items

This commit is contained in:
Uwe Rathmann 2020-01-17 13:58:36 +01:00
parent fe98439bd6
commit f654da28c0
1 changed files with 104 additions and 8 deletions

View File

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