'Annotation' of lines in a QTextEdit

[fullmetalcoder]

as far as in understand from the api, the margins are still part of the control's responsibility.

The margins are indeed drawn by the scroll area and to paint anything on them it is highly recommened to use a custom layout. Custom is important here because it implies using setViewportMargins() from the layout (actually a public wrapper function but it does not make such a difference).

t

he problem i am facing, is that when i get the paint callback called, i am trying to create a QPainter, it complains that it's not created on the paintEvent() event.

i hope something see's what i am missing.

QPainter MUST be initialized on viewport()!!! Indeed (nearly) *ALL* events recieved by a QAbstractScrollArea are redirected from its viewport... Besides it is generally a bad idea to draw the margins from the widget paint event... You should consider placing this code in another widget which would be parented to the editor and managed by the aforementioned custom layout. FYI I made such a custom layout, inspired of Qt 4 Border Layout example, for use with the next version of QCodeEdit.

Also I hope you consider me as a little more than "something"...

[elcuco]

I did not understand your first comment, but I disagree with you on the second comment:

As far as I understand from the code (I looked inside the sources of Qt), the QScrollArea is composed from a a layout in which they stick in 2 scroll bars, and a viewport. The viewport is what we see as the texteditor, the corner widget will sit generally on the right buttom corner, between the scroll bars.

The function discussed in this thread will make a margin for the central widget (the viewport). This is why my code before was not working: the main widget (which contains the main layout, which contains the scroll bars and the text editor) was nto drawn: only the view port.

I think that the parts outside of the margins should be handeled by a special widget inserted to the scroll area. Not sure how yet, even tough I have seen code which uses this API.

[fullmetalcoder]

The function discussed in this thread will make a margin for the central widget (the viewport). This is why my code before was not working: the main widget (which contains the main layout, which contains the scroll bars and the text editor) was nto drawn: only the view port.

Correct me if I'm wrong but I don't think the viewport can be drawn without the scroll area (thus scroll bars) being painted... The only quirk is that widget placed in the margins are NOT updated when the scroll bars move... You MUST explicitely connect the QSlider::valueChanged(int) signal to your panel widgets (widgets put in the margins).

I think that the parts outside of the margins should be handeled by a special widget inserted to the scroll area. Not sure how yet, even tough I have seen code which uses this API.

You've seen my code? Well, I'd be happy to know how... The last snippet I'm working on are not even available yet on SVN and the previous versions of QCodeEdit did not make use of setViewportMargins()... As with any other widget I don't quite see how you could play with the internals of QAbstractScrollArea... If you're interested in the layout code I guess I can post it...

[wysota]

FMC: If you managed to insert a "margin widget" into a scroll area, could you please present a minimal code that accomplishes that? We might be going in circles here and I'm really interested in finding a solution.

[fullmetalcoder]

FMC: If you managed to insert a "margin widget" into a scroll area, could you please present a minimal code that accomplishes that? We might be going in circles here and I'm really interested in finding a solution.

Minimal? well... my code is not really minimal because the layout used has some complexities and I use a custom class, QPanel (inheriting from QWidget). As I don't feel like spending too much time on trimming down my code so I'll give you a layout-less sample... Fell free to ask for the layout code if you want something a little more flexible but then don't expect something that will work out of box...

So here comes the minimum (not very handy nor fully functionnal but works...) :

#include <QPainter>
#include <QPaintEvent>
 
#include <QTextEdit>
#include <QTextBlock>
#include <QTextLayout>
 
#include <QScrollBar>
#include <QApplication>
 
class SampleArea : public QTextEdit
{
	public:
		SampleArea(QWidget *p = 0)
		 : QTextEdit(p)
		{
			QString txt =  "eat me...\ndrink me...\n";
 
			for ( int i = 0; i < 8; ++i )
				txt += txt;
 
			document()->setPlainText(txt);
		}
 
		inline void setMargins(int l, int r, int t, int b)
		{ setViewportMargins(l, r, t, b); }
};
 
class SamplePanel : public QWidget
{
	public:
		SamplePanel(SampleArea *a)
		 : QWidget(a), m_area(a)
		{
			setFixedWidth(50);
			setFixedHeight(a->height());
 
			connect(a->verticalScrollBar()	, SIGNAL( valueChanged(int) ),
					this					, SLOT  ( update() ));
 
			a->setMargins(50, 0, 0, 0);
		}
 
	protected:
		virtual void paintEvent(QPaintEvent *e)
		{
			e->accept();
 
			QPainter p(this);
 
			int m_lineNumber = 1;
			const QFontMetrics fm = fontMetrics();
			const int ascent = fontMetrics().ascent() + 1;
			QTextBlock block = m_area->document()->begin();
			int contentsY = m_area->verticalScrollBar()->value();
			qreal pageBottom = contentsY + m_area->viewport()->height();
 
			for ( ; block.isValid(); block = block.next(), ++m_lineNumber )
			{
				QTextLayout* layout = block.layout();
				QPointF position = layout->position();
				const QRectF boundingRect = layout->boundingRect();
 
				if ( position.y() + boundingRect.height() < contentsY )
					continue;
 
				if ( position.y() > pageBottom )
					break;
 
				const QString txt = QString::number( m_lineNumber );
 
				p.drawText(width() - fm.width(txt) - 2, qRound(position.y()) - contentsY + ascent, txt);
			}
		}
 
	private:
		SampleArea *m_area;
};
 
int main (int argc, char **argv)
{
	QApplication app(argc, argv);
 
	SampleArea area;
	SamplePanel panel(&area);
 
	area.show();
 
	return app.exec();
}

#include <QPainter>
#include <QPaintEvent>

#include <QTextEdit>
#include <QTextBlock>
#include <QTextLayout>

#include <QScrollBar>
#include <QApplication>

class SampleArea : public QTextEdit
{
	public:
		SampleArea(QWidget *p = 0)
		 : QTextEdit(p)
		{
			QString txt =  "eat me...\ndrink me...\n";
			
			for ( int i = 0; i < 8; ++i )
				txt += txt;
			
			document()->setPlainText(txt);
		}
		
		inline void setMargins(int l, int r, int t, int b)
		{ setViewportMargins(l, r, t, b); }
};

class SamplePanel : public QWidget
{
	public:
		SamplePanel(SampleArea *a)
		 : QWidget(a), m_area(a)
		{
			setFixedWidth(50);
			setFixedHeight(a->height());
			
			connect(a->verticalScrollBar()	, SIGNAL( valueChanged(int) ),
					this					, SLOT  ( update() ));
			
			a->setMargins(50, 0, 0, 0);
		}
		
	protected:
		virtual void paintEvent(QPaintEvent *e)
		{
			e->accept();
			
			QPainter p(this);
			
			int m_lineNumber = 1;
			const QFontMetrics fm = fontMetrics();
			const int ascent = fontMetrics().ascent() + 1;
			QTextBlock block = m_area->document()->begin();
			int contentsY = m_area->verticalScrollBar()->value();
			qreal pageBottom = contentsY + m_area->viewport()->height();
			
			for ( ; block.isValid(); block = block.next(), ++m_lineNumber )
			{
				QTextLayout* layout = block.layout();
				QPointF position = layout->position();
				const QRectF boundingRect = layout->boundingRect();
				
				if ( position.y() + boundingRect.height() < contentsY )
					continue;
				
				if ( position.y() > pageBottom )
					break;
				
				const QString txt = QString::number( m_lineNumber );
		
				p.drawText(width() - fm.width(txt) - 2, qRound(position.y()) - contentsY + ascent, txt);
			}
		}
		
	private:
		SampleArea *m_area;
};

int main (int argc, char **argv)
{
	QApplication app(argc, argv);
	
	SampleArea area;
	SamplePanel panel(&area);
	
	area.show();
	
	return app.exec();
}

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[marcel]

Here's one. Just two buttons and a graphics view.

The cpp:

#include "scrollarea.h"
#include <QGraphicsView>
#include <QWidget>
#include <QPushButton>
#include <QScrollBar>
 
#define DEFAULT_MARGIN 30
 
scroller::scroller(QWidget* parent/* =null */)
:QGraphicsView(parent)
{
    mLeftWidget = NULL;
    mTopWidget = NULL;
 
    setScene(new QGraphicsScene(this));
    scene()->setSceneRect(QRectF(0, 0, 3000.0f, 3000.0f)); //just for scrolling purposes
 
    QScrollBar* hbar = verticalScrollBar();
    QScrollBar* vbar = horizontalScrollBar();
    connect(hbar, SIGNAL(valueChanged(int)), this, SLOT(adjustMarginWidgets()));
    connect(vbar, SIGNAL(valueChanged(int)), this, SLOT(adjustMarginWidgets()));
    setViewportMargins(DEFAULT_MARGIN, DEFAULT_MARGIN, 0, 0 );
    createMarginWidgets();
}
 
scroller::~scroller()
{
 
}
 
void scroller::createMarginWidgets()
{
    mLeftWidget = new QPushButton("L", this);
    mTopWidget = new QPushButton("T", this);
 
    adjustMarginWidgets();
}
 
void scroller::adjustMarginWidgets()
{
    QRect viewportRect = viewport()->geometry();
    QRect lrect = QRect(viewportRect.topLeft(), viewportRect.bottomLeft());
    lrect.adjust(-DEFAULT_MARGIN, 0, 0, 0);
    mLeftWidget->setGeometry(lrect);
 
    QRect trect = QRect(viewportRect.topLeft(), viewportRect.topRight());
    trect.adjust(0, -DEFAULT_MARGIN, 0, 0);
    mTopWidget->setGeometry(trect);
}
 
void scroller::createCornerWidget()
{
 
}
 
void scroller::resizeEvent(QResizeEvent *e)
{
    QGraphicsView::resizeEvent(e);
    adjustMarginWidgets();
}

#include "scrollarea.h"
#include <QGraphicsView>
#include <QWidget>
#include <QPushButton>
#include <QScrollBar>

#define DEFAULT_MARGIN 30

scroller::scroller(QWidget* parent/* =null */)
:QGraphicsView(parent)
{
    mLeftWidget = NULL;
    mTopWidget = NULL;
    
    setScene(new QGraphicsScene(this));
    scene()->setSceneRect(QRectF(0, 0, 3000.0f, 3000.0f)); //just for scrolling purposes

    QScrollBar* hbar = verticalScrollBar();
    QScrollBar* vbar = horizontalScrollBar();
    connect(hbar, SIGNAL(valueChanged(int)), this, SLOT(adjustMarginWidgets()));
    connect(vbar, SIGNAL(valueChanged(int)), this, SLOT(adjustMarginWidgets()));
    setViewportMargins(DEFAULT_MARGIN, DEFAULT_MARGIN, 0, 0 );
    createMarginWidgets();
}

scroller::~scroller()
{

}

void scroller::createMarginWidgets()
{
    mLeftWidget = new QPushButton("L", this);
    mTopWidget = new QPushButton("T", this);
    
    adjustMarginWidgets();
}

void scroller::adjustMarginWidgets()
{
    QRect viewportRect = viewport()->geometry();
    QRect lrect = QRect(viewportRect.topLeft(), viewportRect.bottomLeft());
    lrect.adjust(-DEFAULT_MARGIN, 0, 0, 0);
    mLeftWidget->setGeometry(lrect);

    QRect trect = QRect(viewportRect.topLeft(), viewportRect.topRight());
    trect.adjust(0, -DEFAULT_MARGIN, 0, 0);
    mTopWidget->setGeometry(trect);
}

void scroller::createCornerWidget()
{
    
}

void scroller::resizeEvent(QResizeEvent *e)
{
    QGraphicsView::resizeEvent(e);
    adjustMarginWidgets();
}

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The header:

#pragma once
 
#include <QGraphicsView>
 
class QWidget;
class QPushButton;
 
class scroller : public QGraphicsView
{
    Q_OBJECT
public:
    scroller(QWidget* = NULL);
    ~scroller();
 
protected:
    virtual void resizeEvent(QResizeEvent *);
 
private slots:
    void adjustMarginWidgets();
 
private:
    void createMarginWidgets();
    void createCornerWidget();
    QPushButton *mLeftWidget;
    QPushButton    *mTopWidget;
};

#pragma once

#include <QGraphicsView>

class QWidget;
class QPushButton;

class scroller : public QGraphicsView
{
    Q_OBJECT
public:
    scroller(QWidget* = NULL);
    ~scroller();

protected:
    virtual void resizeEvent(QResizeEvent *);

private slots:
    void adjustMarginWidgets();

private:
    void createMarginWidgets();
    void createCornerWidget();
    QPushButton *mLeftWidget;
    QPushButton    *mTopWidget;
};

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You can just set this as the central widget in a main window, or whatever.

Regards