58435 - tree rows not painted when threaded messages arrive, and user scrolls up|down

Status: RESOLVED WONTFIX

(Core :: XUL, defect, P3)

Description

[John Morrison]

This bug is to document the bug that hyatt and I saw late on Friday night/
Saturday morning in the mailnews threadPane.

The following only applies to the condition where the user is in threaded
mode in mailnews, and receives a message that is part of an existing thread.
Independent messages arriving while in threaded mode, and independent or 
threaded messages arriving if not in threaded mode, do not trigger this 
bug. 

Steps to reproduce:

0) Set your 'biff' interval to be 1min. Quit and restart mailnews.
   Adjust your mail filters so that messages from '[e-mail]'
   go into the Inbox folder (or some folder where they will reliably
   be filtered to).

1) Send yourself two messages titled "Foo test" and read them.

2) Put the threadPane into threaded mode and sort by subject.

3) Scroll down to the folder for "Foo test" messages and expand it.

4) Set the scroll position so that the last message visible in the 
   threadPane is the message following the "Foo Test" folder. Read
   that message so the message and headers are loaded into the 
   messagePane.

   e.g., 
            Find out ...
            Flying away ...
          V Foo test
              Foo test
            Friday's meeting ...
          -----------------------------^^^------------------------

5) Page up one time, by clicking on the scrollbar above the thumb.

6) Select one of the messages that are now visible in the threadPane.

7) Send yourself, e.g. 5,  messages in rapid succession (from
   the Unix command line 'mail -s "Foo test" [e-mail]'; then 
   enter "blah blah", hit CR, enter a single period '.', then CR, and hit 
   CR when prompted for a CC: list).

8) Wait for biff to fetch these messages. When they have arrived, click
   once below the scrollbar thumb to page back down to see the "Foo test"
   folder.

Actual results: 
  It seems to depend somewhat on the number of messages that arrive, and 
  the number of messages visible in the threadPane, but ... the tree scrolls
  down the previous last visible message "Friday's meeting" which is now
  greater than the number of visible rows in the threadPane, due to the 
  arrival of the 5 messages in the "Foo test" folder. 

  When this occurs, many of the rows are not painted. However, the scrollbar
  is not out-of-synch, and the user can recover by simply scrolling until the
  view returns to normal.

  Note: this can happen when 1 message in a thread arrives, or when 10 messages
  arrive in a thread. 

  It also happens if you are 2 or 5 "PageUps" away from the folder
  that gets the incoming message. In this case, the first PageDown will show
  unpainted lines, but after that everything comes back in synch. (This really
  means that using threaded mode is exposed to this bug every time a message 
  arrives that is part of an existing thread -- a common scenario).

  All of this also applies when the current view is below the folder that
  will receive the incoming message.

  (I also guess, but did not check that this would also happen on
   other sort criteria, for the threaded view).
  
Expected results: 
  The view should scroll down one threadPane's worth of rows, so that the 
  new last message visible, is the next "Foo test" message in the thread.

In the end, after mucking with pageup and pagedown a bit, the user will 
always (in my experience) recover a usable threadPane, but since this will
happen on every threaded message arrival, it will be an annoying problem
for the user.

The behaviour described above is in a win2k trunk build pulled ~11:30pm 
Friday, Oct 27 -- with the addition of the patch on bug 57139.

In the current candidate build on win2k, this bug is not observed. So, 
this bug is part of a tradeoff -- we get some other fixes that people 
want but it will introduce this behaviour. Marking rtm, in the hope
that there may still be magic in hyatt's fingers. :-]

Comment 1

[John Morrison]

One other note: this only occurs on Pageup/pagedown. Scrolling by single line
clicking on the scrollbarbutton, or by dragging the thumb do not result in 
these unpainted lines.

Comment 2

[Peter Trudelle]

[rtm-]/future

Comment 3

[Peter Trudelle]

back to untargetted for triage

Comment 4

[Peter Trudelle]

resolving as wontfix, dropping active support for trees, please switch over to
using outliner.