Image display problems in Gnus

Image display problems in Gnus

[Kim F. Storm]

David Kastrup <dak@gnu.org> writes:

Ref: [Reiner Steib] [AUCTeX-devel] toolbar-x.el modifies global value of `tool-bar-map'

> Ok, this mail behaves _really_ weird with regard to images.  Hopefully
> you are using gnus as a mail reader (and the geometry is suitable
> similar to mine).

I don't see the problem, but perhaps it is because your signature
was appended to the original mail.

However, I know there is a problem with images at the end of a message
in Gnus article buffers!

It is somehow related to the image being shown as part of an overlay
on the last newline character in the buffer (or some such), followed by another overlay covering the rest of the article (the signature).
I didn't quite figure out what Gnus does though.

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.

I've been trying hard to find a way to fix that, but as I said in my
message about the recent fixes to improve image scrolling, it works
for "normal images" ... and I should have added under "normal
circumstances".  

I think this may be easier to fix this in Gnus than in redisplay!!

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

Re: Image display problems in Gnus

[Jason Rumney]

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.

Re: Image display problems in Gnus

[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

Re: Image display problems in Gnus

[Kim F. Storm]

storm@cua.dk (Kim F. Storm) writes:

> I've been trying hard to find a way to fix that, but as I said in my
> message about the recent fixes to improve image scrolling, it works
> for "normal images" ... and I should have added under "normal
> circumstances".  

I have just installed a small fix to produce_image_glyph which seems
to fix the behavior in Gnus.

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

Re: Image display problems in Gnus

[Jason Rumney]

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Kim F. Storm wrote:
> storm@cua.dk (Kim F. Storm) writes:
>
>   
>> I've been trying hard to find a way to fix that, but as I said in my
>> message about the recent fixes to improve image scrolling, it works
>> for "normal images" ... and I should have added under "normal
>> circumstances".  
>>     
>
> I have just installed a small fix to produce_image_glyph which seems
> to fix the behavior in Gnus.
>   
This seems to have fixed the following bug from FOR-RELEASE as well:

** Markus Gritsch's report about Emacs looping on Windoze with the 
following...



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