Drawing a line on a QWidget

Question

I'm attempting to create a widget that consists of of a single horizontal black line. This widget will be placed in a QGridLayout such that it takes up the entire row, thus acting as a separator. As the widget upon which the layout is installed is resized, I'd like the line to change it's size to keep up. I've checked out a number of options, including QLine, QGraphicsView and QImage, but I can't seem to get the line drawn, never mind get it to resize.

I'm implementing this in it's own class so I can reuse it as and when it's needed. Can anyone please help me with this?

#include "startMenuSectionFooter.h"

#include <QtGui>

StartMenuSectionFooter::StartMenuSectionFooter( QWidget *parent )
  : QWidget( parent )
{
  layout = new QHBoxLayout( this );
}

void StartMenuSectionFooter::paintEvent( QPainEvent *e )
{
  QPointF p1 = QPointF( parentWidget()->height(), 0 );
  QPointF p2 = QPointF( parentWidget()->height(), parentWidget()->width() );

  QPainter painter( this );
  painter.setRenderHint( QPainter::Antialiasing, true );
  painter.setPen( QPen( Qt::black, 10 ) );

  painter.drawLine( p1, p2 );
}

In this case, parent is the parentQWidget upon which the QGridLayout mentioned earlier is installed.

#ifndef START_MENU_SECTION_FOOTER_H
#define START_MENU_SECTION_FOOTER_H

#include <QWidget>

class QHBoxLayout;
class QPainEvent;

class StartMenuSectionFooter : public QWidget
{
  Q_OBJECT

  QBHoxLayout *layout;

  void paintEvent( QPainEvent *e );

public:
  StartMenuSectionFooter( QWidget *parent = NULL );
};

#endif

can you show us a screenshot of what it looks like so far? AFAIK, I don't think you can make a widget take up multiple locations in a QGridLayout, a better approach might be to make a horizontal line and put it in each column (same row) — eqzx, Jun 19 '12 at 19:21
Have you tried using a QFrame with the frame shape set to HLine? — RA., Jun 19 '12 at 19:22
@RA, that's exactly what I was looking for, thanks :) If you write it in as an answer, I'll go ahead and accept. — , Jun 19 '12 at 19:26

score 12 · Accepted Answer · answered Jun 19 '12 at 19:31

The simplest way to create a horizontal line in Qt is to use a QFrame with the frameShape property set to QFrame::HLine. You can then place this frame in your grid layout with the appropriate column span. Here's a simple, contrived example:

QFrame* myFrame = new QFrame();
myFrame->setFrameShape(QFrame::HLine);

const int NUMBER_OF_COLUMNS_IN_GRID = 4;
myGridLayout->addWidget(myFrame, 0, 0, 1, NUMBER_OF_COLUMNS_IN_GRID);

This should do everything you need it do to, including automatically resize when the parent layout resizes. You can also play with the frame's palette to show it in the desired color.

score 1 · Answer 2 · answered Mar 01 '16 at 03:53

1

You misspelled QPaintEvent. The mispelling means that your paintEvent() function does not override the base classes' paintEvent().

Because you never use the variable e of "QPainEvent", there is no syntax error.

answered Mar 01 '16 at 03:53

Colin Jensen

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Drawing a line on a QWidget

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