setRasterOp Equivalent

[vermarajeev]

And here is the code that I want....

#include "setrasteroptest.h"
#include <QMouseEvent>
#include <QPainter>
 
//Program to draw a straight line using Qt4
//constructor 
setRasterOpTest::setRasterOpTest(QWidget *parent, Qt::WFlags flags)
	: QFrame(parent, flags)
{
	ui.setupUi(this);
	QColor color( Qt::white );
	QPalette palette;
	palette.setColor(backgroundRole(), color);
	setPalette(palette);
	setMouseTracking(true);	
	m_bflag = false;
}
 
setRasterOpTest::~setRasterOpTest()
{}
 
void setRasterOpTest::mousePressEvent( QMouseEvent *e ){ 
	if (e->button() == Qt::LeftButton){       
		m_firstpt = e->pos();
		m_lastpt = e->pos();  
	}
}
 
void setRasterOpTest::mouseMoveEvent( QMouseEvent *e ){
	if ((e->buttons() & Qt::LeftButton) ){
		m_lastpt = e->pos(); 	
		m_bflag = true;
		update();    
	}
}
 
void setRasterOpTest::mouseReleaseEvent(QMouseEvent *e){
	if (e->button() == Qt::LeftButton )	{
		m_lastpt = e->pos();
		m_vectorLine << QLine( m_firstpt, m_lastpt ); 
		update();
	}
}
 
void setRasterOpTest::paintEvent(QPaintEvent *e){	
	QPainter painter(this);
	painter.setPen( Qt::black );	
	painter.drawLines( m_vectorLine ); 
 
	if( m_bflag ){
		painter.drawLine( m_firstpt, m_lastpt );
		m_bflag = false;
	}
}

#include "setrasteroptest.h"
#include <QMouseEvent>
#include <QPainter>

//Program to draw a straight line using Qt4
//constructor 
setRasterOpTest::setRasterOpTest(QWidget *parent, Qt::WFlags flags)
	: QFrame(parent, flags)
{
	ui.setupUi(this);
	QColor color( Qt::white );
	QPalette palette;
	palette.setColor(backgroundRole(), color);
	setPalette(palette);
	setMouseTracking(true);	
	m_bflag = false;
}

setRasterOpTest::~setRasterOpTest()
{}

void setRasterOpTest::mousePressEvent( QMouseEvent *e ){ 
	if (e->button() == Qt::LeftButton){       
		m_firstpt = e->pos();
		m_lastpt = e->pos();  
	}
}

void setRasterOpTest::mouseMoveEvent( QMouseEvent *e ){
	if ((e->buttons() & Qt::LeftButton) ){
		m_lastpt = e->pos(); 	
		m_bflag = true;
		update();    
	}
}

void setRasterOpTest::mouseReleaseEvent(QMouseEvent *e){
	if (e->button() == Qt::LeftButton )	{
		m_lastpt = e->pos();
		m_vectorLine << QLine( m_firstpt, m_lastpt ); 
		update();
	}
}

void setRasterOpTest::paintEvent(QPaintEvent *e){	
	QPainter painter(this);
	painter.setPen( Qt::black );	
	painter.drawLines( m_vectorLine ); 

	if( m_bflag ){
		painter.drawLine( m_firstpt, m_lastpt );
		m_bflag = false;
	}
}

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Thanks wysota!!!!

[wysota]

What is the m_bflag for? No matter what it is, you use it incorrectly. You surely shouldn't zero the flag in a paint event.

[vermarajeev]

What is the m_bflag for? No matter what it is, you use it incorrectly. You surely shouldn't zero the flag in a paint event.

Hi wysota,
The m_bflag helps me to see the line on mouseMove. Without this the line is not visible when I move the mouse.

I have attached the complete solution.

Let me know if I'm doing anything wrong.

Thanks

[wysota]

What happens if you drag a line and suddenly some window from another application pops up obscuring a part of your widget? A paint event will come and as your flag will be set to false by the previous paint event, the "dynamic" line will not be redrawn. Instead you should clear the flag in mouseReleaseEvent. And don't use the flag - just clear m_lastPt - it'll return true on QPoint::isNull() call. Then it's only a matter of checking that point in the paint event and drawing the line only if isNull() returns false. Just look at one of my previous examples.