bug#9854: Problem with emacs

[Glenn Morris]

Alexander wrote:

> When I'm working in emacs on various file types ( .cpp, .h ) sometimes
> the text I have just typed does not show as itself but the cursor
> moves forward and the text has in fact been typed into the buffer.
> Perhaps my problem is not clear to the reader; consider an event where
> one types text into any screen with a white background; as the word
> "apple" is typed, only "a     " shows up, or a variation thereof with
> corruption and distortion.

That sounds very odd.
Does this only happen with C mode?
Does it happen if you start emacs with `emacs -Q'?
After it has happened, if you do M-x font-lock-mode, do the missing
characters become visible?
When a character is invisible, please post the results of pressing
C-u C-x =
with point on the invisible character.