Can force the axis' backbone extend to align with the edge of the canvas?

[Uwe]

For both questions the same answer: you have to remove the grid layout that is used in the PlotMatrix class and implement a new method

void PlotMatrix::layoutPlots( const QRect &rect )
{
  // calculate and assign the geometries of your plots here
  ...
}

void PlotMatrix::layoutPlots( const QRect &rect )
{
  // calculate and assign the geometries of your plots here
  ...
}

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In PlotMatrix::resizeEvent() and some other places that have an effect on the size of your plots you have to call:

layoutPlots( contentsRect() );

layoutPlots( contentsRect() );

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As you probably want to have the same size for the canvases ( not the plots ! ) you have to subtract the sizeHints() of the scales, legends and titles ( QwtPlot is a composite widget ! ).

Uwe