Re: Image display problems in Gnus

[storm@cua.dk (Kim F. Storm)]

Jason Rumney <jasonr@gnu.org> writes:

> Kim F. Storm wrote:
>> This causese problems for the redisplay engine when it tries to figure
>> out where to display the cursor -- and it ends up displaying it at
>> some position which is not visible in the window.
>>
>> This triggers the recenting code in redisplay which wants the cursor
>> position to be displayed in the window.  But this still results in
>> the cursor in some invalid position....
>>
>> .. and finally, the redisplay has some code which catches this
>> anomaly and displays the cursor in the upper left corner of the window
>> instead.
>>   
> Where is the code that catches this? I have been trying to investigate
> a Windows specific bug listed in FOR-RELEASE the last couple of days,
> where the same seems to be happening with the splash screen image,
> except Emacs never catches it and it keeps looping. I can see that on
> X, Emacs catches it as you explain there.

I don't think it is X specific.

I'm not 100% sure, but I think it is this code in xdisp.c:

  /* Consider the following case: Window starts at BEGV, there is
     invisible, intangible text at BEGV, so that display starts at
     some point START > BEGV.  It can happen that we are called with
     PT somewhere between BEGV and START.  Try to handle that case.  */
  if (w->cursor.vpos < 0)
    {
      struct glyph_row *row = w->current_matrix->rows;
      if (row->mode_line_p)
	++row;
      set_cursor_from_row (w, row, w->current_matrix, 0, 0, 0, 0);
    }


It just seems to be triggered by some other special case where
displaying an image at the end of the window causes the cursor
to be placed "outside the window".

-- 
Kim F. Storm <storm@cua.dk> http://www.cua.dk