Background in stockchart example

[wooosh]

Hi,

I'm playing with the stockchart example and trying to change the background color of the plot. I'm using
setCanvasBackground(QColor(Qt::red)) in the Plot::Plot() constructor but all this does is that it draws a border of 1px width next to the right and bottom axis. Could someone explain to me what I am doing wrong, please?

9908

[Cah]

Look into the method void Plot::populate() and comment out the gridItem.

Thus...

void Plot::populate()
{
GridItem *gridItem = new GridItem();
#if 0
gridItem->setOrientations( Qt::Horizontal );
#endif
gridItem->attach( this );

...
}

Becomes

void Plot::populate()
{
//GridItem *gridItem = new GridItem();
//#if 0
//gridItem->setOrientations( Qt::Horizontal );
//#endif
//gridItem->attach( this );

...
}

Of course you still need to send setCanvasBackground() to the instance of Plot.

[Uwe]

Could someone explain to me what I am doing wrong, please?
You copied code from a Qwt example without trying to understand it: the red background is covered by a plot item that draws the chess board.
Remove the grid item from your copy and you have what you want.

Uwe

[Cah]

A quick update...

The suggestion to comment out the grid code forces you to live without the grid. I assume that that was ok. If it's not Then do the following:-

In the constructor GridItem::GridItem() initialize the QPalette instance m_palette.

f.e

GridItem::GridItem():
QwtPlotItem( QwtText( "Grid" ) ),
m_orientations( Qt::Horizontal | Qt::Vertical ),
m_gridAttributes( AutoUpdate | FillCanvas ),
m_isXMinEnabled( false ),
m_isYMinEnabled( false )
{
...
m_palette.setBrush(QPalette::Base, QColor(255, 0, 0));
m_palette.setBrush(QPalette::AlternateBase , QColor(200, 0, 0));

}

[wooosh]

Hi,

thanks a lot for your answers.
I did not expect the GridItem to draw the chessboard but just a grid. I thought the chessboard was some default 'no color set' background. I'm new to this.. thanks again.

Added after 5 minutes:


A quick update...

The suggestion to comment out the grid code forces you to live without the grid. I assume that that was ok. If it's not Then do the following:-
}

I found this to work well for me:

QwtPlotGrid *grid = new QwtPlotGrid();
grid->setItemAttribute(grid->Legend, false);
grid->setItemAttribute(grid->AutoScale, true);
grid->setPen(QColor(Qt::gray), 0.0, Qt::PenStyle::DotLine);

[Uwe]

grid->setItemAttribute(grid->AutoScale, true);
This line doesn't hurt as a QwtPlotGrid has no bounding rectangle to affect the autoscaler - but enabling autoscaling for this type of grid is probably not what you want.

Uwe