Using QAbstractItemDelegate to display a TGA from a database

[rakkar]

Actually, using a cache increased the performance enough I can use it. Here's the code

#ifndef __BYTE_ARRAY_AS_IMAGE_ITEM_DELEGATE_H_
#define __BYTE_ARRAY_AS_IMAGE_ITEM_DELEGATE_H_
 
#include <QItemDelegate>
#include <QTimer>
 
class ModelIndicesDeferredPainter;
 
// If an item is a byte array, wait 100 milliseconds, then load it as an image if possible.
class ByteArrayAsImageItemDelegate : public QItemDelegate
{
	Q_OBJECT
public:
	ByteArrayAsImageItemDelegate(QWidget *parent = 0) : QItemDelegate(parent) {}
 
	virtual void paint(QPainter *painter, const QStyleOptionViewItem &option,
		const QModelIndex &index) const;
 
	// This is needed because you can't emit events from paint() since paint() is const
	void SetDeferredPainter(ModelIndicesDeferredPainter *df) {deferredPainter=df;}
 
signals:
	void paintingDeferred(const QModelIndex& index);
 
protected:
	ModelIndicesDeferredPainter *deferredPainter;
};
 
class ModelIndicesDeferredPainter : public QObject
{
	Q_OBJECT
 
public:
	ModelIndicesDeferredPainter(QAbstractItemView *view, QObject *parent);
	bool paintLater(const QModelIndex& index);
 
	protected slots:
	void paintPendingIndexes();
 
protected:
	QModelIndexList indicesToPaint;
	QAbstractItemView *storedItemView;
 
	// Don't immediately load images. This way, if an image immediately goes out of viewable area, it is not drawn
	QTimer timer;
 
	// This is needed so we know not to just call paintLater() again from ByteArrayAsImageItemDelegate
	bool isPaintingLater;
};
 
 
#endif

#ifndef __BYTE_ARRAY_AS_IMAGE_ITEM_DELEGATE_H_
#define __BYTE_ARRAY_AS_IMAGE_ITEM_DELEGATE_H_

#include <QItemDelegate>
#include <QTimer>

class ModelIndicesDeferredPainter;

// If an item is a byte array, wait 100 milliseconds, then load it as an image if possible.
class ByteArrayAsImageItemDelegate : public QItemDelegate
{
	Q_OBJECT
public:
	ByteArrayAsImageItemDelegate(QWidget *parent = 0) : QItemDelegate(parent) {}

	virtual void paint(QPainter *painter, const QStyleOptionViewItem &option,
		const QModelIndex &index) const;

	// This is needed because you can't emit events from paint() since paint() is const
	void SetDeferredPainter(ModelIndicesDeferredPainter *df) {deferredPainter=df;}

signals:
	void paintingDeferred(const QModelIndex& index);

protected:
	ModelIndicesDeferredPainter *deferredPainter;
};

class ModelIndicesDeferredPainter : public QObject
{
	Q_OBJECT

public:
	ModelIndicesDeferredPainter(QAbstractItemView *view, QObject *parent);
	bool paintLater(const QModelIndex& index);

	protected slots:
	void paintPendingIndexes();

protected:
	QModelIndexList indicesToPaint;
	QAbstractItemView *storedItemView;

	// Don't immediately load images. This way, if an image immediately goes out of viewable area, it is not drawn
	QTimer timer;

	// This is needed so we know not to just call paintLater() again from ByteArrayAsImageItemDelegate
	bool isPaintingLater;
};


#endif

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#include "ByteArrayAsImageItemDelegate.h"
#include <QPainter>
#include <QBuffer>
#include <QImageReader>
#include <QAbstractItemView>
#include <QPixmapCache>
 
// From RakNet
#include "SuperFastHash.h"
 
void ByteArrayAsImageItemDelegate::paint(QPainter *painter, const QStyleOptionViewItem &option,
				   const QModelIndex &index) const
{
	const QVariant &v = index.data();
	if (v.type()==QVariant::ByteArray)
	{
		QByteArray ba = v.toByteArray();
		unsigned int hash = SuperFastHash(ba.data(),ba.length());
		QString hashKey;
		// Safer collision code commented out, in case I need it
		//hashKey.sprintf("%i%i%i",index.row(),index.column(),hash);
		// Faster, in case images are duplicated
		hashKey.sprintf("%i",hash);
		QPixmap pixmap;
		bool foundPixmap = QPixmapCache::find(hashKey, pixmap);
		bool paintLater;
		if (foundPixmap==false)
		{
			paintLater=deferredPainter->paintLater(index);
			if (paintLater==false)
			{
				// Load pixmap
				QBuffer buffer;
				buffer.setBuffer(&ba);
				buffer.open(QIODevice::ReadOnly);
				QImageReader qir;
				qir.setDevice(&buffer);
				QImage image;
				if (qir.read(&image))
				{
					pixmap = QPixmap::fromImage(image);
 
					// Save to cache
					QPixmapCache::insert(hashKey,pixmap);
				}
				else
				{
					// Not an image?
					QItemDelegate::paint(painter,option,index);
					return;
				}
			}
		}
 
		if (foundPixmap==true || paintLater==false)
		{
			// Paint
			QSize imageSize = pixmap.size();
			QRect drawRect;
			float scaleWidth, scaleHeight;
			float drawWidth, drawHeight;
			scaleWidth = (float) imageSize.width() / (float)option.rect.width();
			scaleHeight = (float)imageSize.height() / (float)option.rect.height();
			// Downscale by the larger of the two proportions
			if (scaleHeight > scaleWidth)
			{
				drawWidth=(float)imageSize.width()/scaleHeight;
				drawHeight=(float)imageSize.height()/scaleHeight;
			}
			else
			{
				drawWidth=(float)imageSize.width()/scaleWidth;
				drawHeight=(float)imageSize.height()/scaleWidth;
			}
 
			float centerX = (float)option.rect.left() + (float)option.rect.width()/2.0;
			float centerY = (float)option.rect.top() + (float)option.rect.height()/2.0;
			drawRect.setLeft(centerX-drawWidth/2.0);
			drawRect.setRight(centerX+drawWidth/2.0);
			drawRect.setTop(centerY-drawHeight/2.0);
			drawRect.setBottom(centerY+drawHeight/2.0);
			painter->drawPixmap(drawRect, pixmap);
		}
 
	}
	else
	{
		QItemDelegate::paint(painter,option,index);
	}
}
ModelIndicesDeferredPainter::ModelIndicesDeferredPainter(QAbstractItemView *view, QObject *parent)
: QObject(parent)
{
	storedItemView = view;
 
	timer.setSingleShot(true);
	timer.setInterval(100);
	connect(&timer, SIGNAL(timeout()),
		this, SLOT(paintPendingIndexes()));
	isPaintingLater=false;
}
 
bool ModelIndicesDeferredPainter::paintLater(const QModelIndex& index)
{
	if (isPaintingLater)
		return false;
 
	if (indicesToPaint.contains(index)==false)
	{
		indicesToPaint.append(index);
		timer.start();
	}
 
	return true;
}
 
void ModelIndicesDeferredPainter::paintPendingIndexes()
{
	// This flag is needed so ByteArrayAsImageItemDelegate::paint does not just call paintLater again()
	isPaintingLater=true;
 
	foreach(const QModelIndex& index, indicesToPaint)
		storedItemView->update(index);
	storedItemView->repaint();
 
	isPaintingLater=false;
 
	indicesToPaint.clear();
}

#include "ByteArrayAsImageItemDelegate.h"
#include <QPainter>
#include <QBuffer>
#include <QImageReader>
#include <QAbstractItemView>
#include <QPixmapCache>

// From RakNet
#include "SuperFastHash.h"

void ByteArrayAsImageItemDelegate::paint(QPainter *painter, const QStyleOptionViewItem &option,
				   const QModelIndex &index) const
{
	const QVariant &v = index.data();
	if (v.type()==QVariant::ByteArray)
	{
		QByteArray ba = v.toByteArray();
		unsigned int hash = SuperFastHash(ba.data(),ba.length());
		QString hashKey;
		// Safer collision code commented out, in case I need it
		//hashKey.sprintf("%i%i%i",index.row(),index.column(),hash);
		// Faster, in case images are duplicated
		hashKey.sprintf("%i",hash);
		QPixmap pixmap;
		bool foundPixmap = QPixmapCache::find(hashKey, pixmap);
		bool paintLater;
		if (foundPixmap==false)
		{
			paintLater=deferredPainter->paintLater(index);
			if (paintLater==false)
			{
				// Load pixmap
				QBuffer buffer;
				buffer.setBuffer(&ba);
				buffer.open(QIODevice::ReadOnly);
				QImageReader qir;
				qir.setDevice(&buffer);
				QImage image;
				if (qir.read(&image))
				{
					pixmap = QPixmap::fromImage(image);

					// Save to cache
					QPixmapCache::insert(hashKey,pixmap);
				}
				else
				{
					// Not an image?
					QItemDelegate::paint(painter,option,index);
					return;
				}
			}
		}

		if (foundPixmap==true || paintLater==false)
		{
			// Paint
			QSize imageSize = pixmap.size();
			QRect drawRect;
			float scaleWidth, scaleHeight;
			float drawWidth, drawHeight;
			scaleWidth = (float) imageSize.width() / (float)option.rect.width();
			scaleHeight = (float)imageSize.height() / (float)option.rect.height();
			// Downscale by the larger of the two proportions
			if (scaleHeight > scaleWidth)
			{
				drawWidth=(float)imageSize.width()/scaleHeight;
				drawHeight=(float)imageSize.height()/scaleHeight;
			}
			else
			{
				drawWidth=(float)imageSize.width()/scaleWidth;
				drawHeight=(float)imageSize.height()/scaleWidth;
			}

			float centerX = (float)option.rect.left() + (float)option.rect.width()/2.0;
			float centerY = (float)option.rect.top() + (float)option.rect.height()/2.0;
			drawRect.setLeft(centerX-drawWidth/2.0);
			drawRect.setRight(centerX+drawWidth/2.0);
			drawRect.setTop(centerY-drawHeight/2.0);
			drawRect.setBottom(centerY+drawHeight/2.0);
			painter->drawPixmap(drawRect, pixmap);
		}

	}
	else
	{
		QItemDelegate::paint(painter,option,index);
	}
}
ModelIndicesDeferredPainter::ModelIndicesDeferredPainter(QAbstractItemView *view, QObject *parent)
: QObject(parent)
{
	storedItemView = view;

	timer.setSingleShot(true);
	timer.setInterval(100);
	connect(&timer, SIGNAL(timeout()),
		this, SLOT(paintPendingIndexes()));
	isPaintingLater=false;
}

bool ModelIndicesDeferredPainter::paintLater(const QModelIndex& index)
{
	if (isPaintingLater)
		return false;

	if (indicesToPaint.contains(index)==false)
	{
		indicesToPaint.append(index);
		timer.start();
	}

	return true;
}

void ModelIndicesDeferredPainter::paintPendingIndexes()
{
	// This flag is needed so ByteArrayAsImageItemDelegate::paint does not just call paintLater again()
	isPaintingLater=true;

	foreach(const QModelIndex& index, indicesToPaint)
		storedItemView->update(index);
	storedItemView->repaint();

	isPaintingLater=false;

	indicesToPaint.clear();
}

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[wysota]

Why are you deferring anything? Not that I see what you are deferring...