837577 - scrollbar arrows, arrow keys scroll by more than one line; not obvious pref.

Status: RESOLVED INCOMPLETE

(SeaMonkey :: MailNews: Message Display, defect)

Description

[Daniel B.]

User Agent: Mozilla/5.0 (X11; Linux i686 on x86_64; rv:18.0) Gecko/20100101 Firefox/18.0 SeaMonkey/2.15.1
Build ID: 20130118191211

Steps to reproduce:

I viewed a message all of whose lines were the same height (a plain-text message)
in the mail preview pane (the lower-right pane in the MailNews window).

Then I clicked on the vertical scrollbar buttons (and typed the up and down arrow keys).

(Knowing that some mouse-wheel scrolling changed recently, I opened 
about:config and looked for scrolling-related preference items by searching for
"scroll".  The only obvious candidate was toolkit.scrollbox.verticalScrollDistance, 
since its value was 3.)




Actual results:

The text scrolled vertically by three lines per click (or keypress).

(Changing the value of toolkit.scrollbox.verticalScrollDistance from 3 to 1 didn't
affect that scrolling.)


Expected results:

The text should have scrolled vertically one line per click (or keypress), as 
scrolling by scrollbar arrows works in many other things (e.g.:
- SeaMonkey's mail account and folders tree pane,
- SeaMonkey's mail messages list,
- SeaMonkey's bookmarks list panes,
- SeaMonkey's Preferences window's Category tree pane,
- Emacs, 
- Eclipse (at least several different kinds of list, tree, and text views)
- Windows Explorer's textual List and Details views,
- etc..


More generally, there should be an (easy) way to scroll a message by one line at 
a time.  The vertical scrollbar arrows and arrow keys are the standard way of doing
that. 

In SeaMonkey, they should still work that standard way even if mouse-wheel
scrolling is sped up for convenience of mouse-driven scrolling.

Comment 1

[Tony Mechelynck [:tonymec]]

Scrolling by three lines at a time seems to be intentional, see bug 725700 comment #0 and bug 725700 comment #10.

If the behaviour doesn't obey a change of preference, that's a possible bug; however, some layout preferences only take effect in a new window, or even after a restart.

Comment 2

[Daniel B.]

(In reply to Tony Mechelynck [:tonymec] from comment #1)
> Scrolling by three lines at a time seems to be intentional, see bug 725700
> comment #0 and bug 725700 comment #10.

Then that (that intent) is the bug (if it didn't include the ability for the 
user to configure that back to one line).

Apparently the reporters/authors compared SeaMonkey only to other browsers (to 
how they scroll text), rather than to the many other programs/UIs that scroll 
text.

Most other program let you scroll text up and down line by line, letting you
position the text vertically at any line boundary.  SeaMonkey shouldn't deny
that ability.  (Yes, I know that web pages, with variable line spacing and
non-textual content, means it's not so simple to define what one line of 
vertical distance is.)



> If the behaviour doesn't obey a change of preference, that's a possible bug; ...

Is that preference values supposed to control the type of scrolling I reported 
about?

Comment 3

[Rainer Bielefeld]

@Reporter:
toolkit.scrollbox.verticalScrollDistance' works as expected, changing value to 1 iwll have vertical scroll destance of 1 text row as result.
What exactly is the intention of this report?

Comment 4

[Rainer Bielefeld]

No response, so I close this one for now.

@Reporter: Please feel free to reopen this Bug if you still can reproduce the problem with a current SeaMonkey version and a current OS and if you can contribute a step by step instruction due to <https://developer.mozilla.org/en-US/docs/Mozilla/QA/Bug_writing_guidelines>  (containing every key press and every mouse click) how to reproduce the problem reliably.