Re: [matplotlib-devel] Re: PS backend wish list

[John H. <jdh...@ac...>]

>>>>> "Matt" == Matt Newville <new...@ca...> writes:

    Matt> I like Darren's and Paul's suggestion (set line properties
    Matt> once, then have the ticks be a simple list of pen up / pen
    Matt> down).  I believe major and minor ticks would need to have
    Matt> different properties, but it's still only 2 set of
    Matt> properties. I understand that this might mean a significant
    Matt> redesign, but the performance boost might be worth it.

I would bet dollars to doughnuts (careful here, Perry still owes me a
doughnut!) that almost all of the tick cost comes from laying out the
text of the ticks and not in drawing the tick lines themselves -- Arnd
posted some hotshot profile of this earlier, but I don't remember the
exact results).

I agree ticks (and text in general) are too expensive.  In my
experience, this is usually only starts a problem in animated plots
(do you have another use case in mind?).  I think we might be able to
work around this particular problem by supporting the drawing of only
a subset of the artists in the scene.  I imagine something like the
following is workable.

  line, = ax.plot(blah)

  dynamic = (line,)  # a list of artists to animate
  # draws everything but artists in dynamic and caches Axes bbox to bitmap
  ax.animate_prepare( dynamic) 

  while 1:
     line.set_data(blah)
     # blits the axes background cache and renders only the artists in dynamic
     ax.animate()  


I'm not opposed to a redesign of the Tick drawing if there are
appreciable gains to be had, but my guess is we may get more bang for
the buck in special casing the typical text layout (angle=0.0, no
mathtext, no unicode) and handling dynamic updates more intelligently.

JDH