[Visualpython-users] VPython 5.61: crosshairs in graphs, bug fixes

With the new VPython 5.61 available at vpython.org you can drag the
mouse across a graph and see crosshairs with the (x,y) value of the
crosshair position, to make it possible to read locations accurately
off the graph. No change is needed to existing programs to get this
behavior.

If you use the controls module (buttons, sliders, menus), you no
longer need to call interact() inside a loop. For backward
compatibility the interact() function is still present but now does
nothing.

A long-standing inconsistency in the label object has been fixed. The
background of a label object's box is now by default the same as
scene.background. You can also set the label's background color.

There are bug fixes to materials.bricks, thanks to Kadir Haldenbilen,
and a bug fix to the machinery that lets VPython run even if the
Polygon and font modules are unavailable (though in this case you
can't use extrusion or text objects).

Bruce Sherwood

P.S. In the course of this work I was surprised to discover what seems
to be a long-standing bug on the Mac. In programs that open two
graphics windows, occasionally (maybe 1% of the time) the second
window fails to open and, even more exciting, Python statements stop
being executed! The first window remains active, and you can zoom and
spin. Be on the lookout for such behavior on the Mac. It would be
great if there were some program that failed every time. As it is, the
failure happens so seldom that it is difficult to debug.

I first noticed this in the graphtest.py example program and thought I
must have broken something in the process of enabling crosshairs, but
then I found the problem was present in older versions, and in
programs that don't create graphing windows.