Scale color using Qwt::

[<qw...@ds...>]

The program I am working on needs to be able to draw
a QwtPlot subclass widget onto a QPixmap to be able
to double-buffer and draw things onto the graph.  I have
about 252 of these plots to draw and use.

I determined that the following code placed in this plotter
class would print onto a QPainter:

   print (painter, plotRect);

(I did read in the mailing list of the Qpixmap::grabWidget()
way of doing this, but it turned out to be really slow.)

The problem I faced with this approach (print method)
is that the background I chose is black and the routine
printScales() that print() calls also paints the scales
in black by default with this code (qwt_plot_print.cpp):

#if 1
    painter->setPen(Qt::black); // acisColor ????
#endif

That’s from 4.2rc1.  So I checked the CVS and the only
change was in the comment.

It would be nice if we had control over the color that the
scales are printed somehow.  I imagine this would not
be terribly difficult to implement as part of
the QwtScale class, using a call similar to setTitleColor(),
maybe setScaleColor() or setPen() -- this, in my mind,
includes the tick marks, and major tick labels).

What do you think?

In the mean time I changed the “#if 1” to “#if 0” (in
qwt_plot_print.cpp) and set the pen [color] outside
of printScales().

I replaced the simple print() call to this code, for simplicity,
and efficiency:

   // prepare for plotting
   updateAxes();
   updateLayout();

   // draw the canvas area:  grids, curves, markers - that stuff
   painter->translate (plotLayout()->canvasRect().x(),
                       plotLayout()->canvasRect().y());
   drawCanvas (painter);
   painter->resetXForm();

   // draw scales
   painter->setPen (white);
   drawScale (painter, xBottom);
   drawScale (painter, yLeft);

   return plotLayout()->canvasRect();

where drawScale() is:

   // from qwt_plot_print.cpp ... print()
   int startDist, endDist;
   axis (axisKey)->minBorderDist (startDist, endDist);
   int baseDist = axis (axisKey)->baseLineDist();

   printScale (painter, axisKey, startDist, endDist,
               baseDist, plotLayout()->scaleRect (axisKey));

Thank you,
Randy Evered