Improved font manager

This was an easy change to the font manager. You should see

    > it in CVS later today.


An unrelated bug I found in testing with one of my apps

In the font_manager

    def get_size_in_points(self, parent_size=None):
        """Convert text to point size"""
        if isinstance(self.__size, str):
            if self.__size == 'larger':
                size = int(self.__parent_size*1.2)
            elif self.__size == 'smaller':
                size = int(self.__parent_size/1.2)
                defsize = fontManager.get_default_size()
                size = defsize*font_scalings[self.__size]
            return size
            return self.__size

I sometimes get key error on font_scalings[self.__size] when
self.__size is a number, eg 10. From the code, it looks like you
intend self.__size to always be a relative size. I did a temporary
workaround along the lines of

                try: size = float(self.__size)
                except ValueError:
                    defsize = fontManager.get_default_size()
                    size = defsize*font_scalings[self.__size]
            return size

but this hack may be masking another bug so I thought you'd want to
look into it.

    > On a related issue, I noticed that the sizes of PS plots are
    > different depending on which backend is used first. If I
    > send a plot directly to the PS backend, I get a nice plot
    > (see the attachment Whereas, if I first
    > display the plot using TkAgg and then save it to PS, I get a
    > plot that is much larger than the display area (see the
    > attachment The text size in both plots
    > appears to be the same size, this would indicate an
    > incorrect scaling factor somewhere.

backend_tkagg needs to override FigureCanvasTkAgg.print_figure
following the lead of backend_gtkagg. The critical point is that dpi
must be set to 72 for backend_ps. Even though ps doesn't use DPI,
this value is used by the figure to compute the canvas size as
width*dpi and height*dpi, and this does affect backend_ps.

In FigureCanvaseGTKAgg.print_figure I save the orig dpi, set the
figure dpi to 72, print the figure, and then reset. I do the same
with other figure properties (eg, background color, so you can have a
different color background for printing and GUI).

It should be mostly a cut and paste from backend_gtkagg.