Re: Redisplay problems with invisible text at the beginning of a line.

[Lute Kamstra]

address@hidden (Kim F. Storm) writes:

> Can you pls. check whether there are still problems?   

All the display problems I mentioned are gone.  Thank you very much!

  Lute.


> Lute Kamstra <address@hidden> writes:
>> 
>> This concerns not only cvs Emacs 21.3.50 but also released Emacs 21.1
>> and 21.3.  The bugs are slightly different for the released Emacsen,
>> though.
>> 
>> Currently, I'm writing a major mode that uses an invisible character
>> at the beginning of each line to store some data.  This results in a
>> number of redisplay problems.  A good way to reproduce three of them
>> is as follows:
>> 
>> Create a buffer in a window and make sure that the buffer is
>> significantly larger that the window.  (Opening the tutorial with C-h
>> t will do nicely.)
>> 
>> Move point to the first character of a nonempty line in the bottom
>> half of the window.
>> 
>> Evaluate (put-text-property (point) (+ (point) 1) 'invisible t) to
>> make the first character of the line invisible.
>> 
>> Type C-u 0 C-l (to invoke recenter).
>> 
>> What I would expect to see now is that the line the point is in would
>> become the first line of the window and that point would not move.
>> However, this is not the case.  Bug number 1:
>> 
>> A. For Emacs 21.1 and 21.3 the following happens.  The line point is
>>    in, that is, the line starting with the invisible character,
>>    becomes the first line of the window and point moves to the
>>    beginning of the line in the middle of the window.
>> 
>> B. For Emacs 21.3.50 the following happens.  The line point is in
>>    becomes the middle line of the window (as if C-l had been typed
>>    without a prefix).
>> 
>> To see bug number 2, make sure that the line starting with the
>> invisible character is the top line of the window and that point is in
>> the line just after the top line.
>> 
>> Now type C-a followed by C-p.  I would expect that point would just
>> move to the beginning of the top line.  This does happen, but the
>> window is also redisplayed and the line point is in is now shown in
>> the middle of the window.
>> 
>> For Emacs 21.1 under X (I can't test 21.3 or 21.3.50 under X at the
>> moment) bug number 3 now occurs that does not happen on a console (-nw
>> option).  The line starting with the invisible character that is shown
>> in the middle of the window is followed by a copy of itself.  So the
>> line line starting with the invisible character is displayed *twice*.
>> Typing C-l at this time causes the copy to go away.