Here's a todo list for DisplayTool, for the curious:

1.  Moving images around and resizing them can't be done when the images are
displayed at full size (the windows can be moved but this doesn't change
the value of the selection).  Perhaps it would be nice, but perhaps not.

2.  When the left mouse button is pressed inside the popup windows that display
the images, the window should get repositioned.  Right now the windows can
be repositioned by using the window frame, but since the frame has minimal
decor, it's not very easy to grab.

3.  The "Duplicate Image" function hasn't been implemented, although it's not
critical to the application.

4.  I've improved the memory usage a lot, but there is still room for improvement --
each cycle of loading in an input file and then clearing out the slides causes
the memory to grow monitonically.  It should grow the first time and then not
again if the same file is loaded up.

5.  Colormap idealizing for each slide should be done.  While the current slide is
displayed the ideal colormap for the next slide should be computed (and the
pixmaps should be created and XPutImage'ed into), and then when the next slide
is to be shown the current colormap should be freed the new one installed and
then call XCopyArea on the pixmaps for the next screen  -- fairly simple algorithm
for much better color performance.  Right now none of this is done, including
the pixmap buffering so there is a couple second delay in between the display
of each slide.