The test inserts the following text:

   A: *
   B: ?
   C: *?
   D: ?*
   E: *?*
   F: ?*?
   G: ??

The `*' and `?' characters have `invisibile' properties
with a value of `t', so I expect to see none of them.

The `?' characters all have `display' properties with a
value of "!" (one of them has "$" instead, for clarity).
This, I believe, _should_ be irrelevant.

In other words, I expect to see the following:

   A:
   B:
   C:
   D:
   E:
   F:
   G:

The actual result I get is this:

   A:
   B: ?
   C:
   D: ?
   E:
   F: ?
   G: ?!

Those exclamation marks should not be there.  What they all
have in common is that none of them are preceded by
invisible characters _without_ `display' properties.

That is, a character with both `invisible' and `display'
properties appears to display correctly (i.e., not at all)
if and only if it is preceded by an invisible character
without a `display' property.

I get the same (AFAICS) erroneous results if I put an image
or some space instead of a string on the `display' property.

-- 
Daniel Brockman <daniel@brockman.se>