[IPython-User] autoscrolling in html notebook

Brian Granger ellisonbg@gmail....
Sun Jan 22 15:39:53 CST 2012

Can you clarify the scroll up behavior you are asking about.  I just
tested a simple notebook and when I move up to the top cell it is at
the top of the scrolling area.  Do you sometimes see that it is not?
Are you asking for logic that does:

if cell 0 selected:
if cell -1 selected:
  scroll to bottom

I think I could add that but I would like to understand the problem a
bit better first.

2012/1/22 Zoltán Vörös <zvoros@gmail.com>:
> Hi Brian,
> Many thanks for your comments! I see that there is a serious obstacle here,
> and I agree that if one did what I was inquiring about, that could lead to
> some unexpected behaviour. It just so happened that I had never encountered
> those cases, so they didn't bug me. But your point is taken.
> However, the question about scrolling up could be still valid, couldn't it?
> When one is scrolling up, one does not expect output from anywhere, one just
> wants to get to the top of the page. This does not involve autoscrolling,
> for the user is doing it.
> Cheers,
> Zoltán
> On 01/22/2012 08:18 PM, Brian Granger wrote:
>> The situation is a bit more complex.  This past summer, I spent
>> probably 3-4 days working on the scrolling model for the notebook.  We
>> spent considerable time studying the scrolling behavior of different
>> applications.  It was one of the more difficult things to get right.
>> I can summarize the main issues and explain the model...
>> * The overarching theme in the scrolling model is that we put the use
>> in charge of the scrolling.  This means that we don't try to guess
>> when and where they want the notebook div to be scrolled, we let them
>> make that decision.
>> * The reason we went this route is that each time we tried to scroll
>> the notebook for them, we would sometimes guess wrong leading to very
>> frustrating behaviors - more frustrating than requiring the user to
>> scroll it themselves.  It also lead to glitches.
>> * One difficulty we faced is that browsers make scrolling decisions on
>> their own based on what element in a div is has focus.  We found that
>> when we tried to scroll the window, we ended up "arguing" with the
>> browsers built-in scrolling behavior.  We would scroll up, it would
>> scroll down - glitchy.  The only way out of this is to *completely*
>> take over the scrolling ourselves.  Getting that right would be
>> extremely difficult.
>> * The other, more fundamental issue, it the asynchronous behavior of
>> the notebook.  There *are* a few cases where we *do* currently scroll
>> the notebook for the user.  One case is after the last cell is
>> executed we scroll the notebook to the bottom.  You should then ask
>> "wait, then why doesn't my plot show!?"  The answer is that the
>> scroll-to-the-bottom is done after the code is submitted and the new
>> cell is created, but *before* the output is returned.  We have no
>> control over when the output arrives - it could be nearly instant, or
>> it could take 12 hours.  If we were to wait until output arrives and
>> then scroll it into view, users will be equally unhappy - the current
>> thing they were working on would scroll out of view.
>> Hope this clarifies the notebook scrolling.
>> Cheers,
>> Brian
>> 2012/1/20 Zoltán Vörös<zvoros@gmail.com>:
>>> Hi All,
>>> I was just wondering whether there is a trick to scroll to the bottom of
>>> the page in the html notebook. What I mean is the following: suppose
>>> that I have some code that produces a plot. The plot might very well be
>>> bigger than the screen. If I run the code, what happens is that the
>>> cursor jumps to the next cell, but that cell will be below the bottom of
>>> the browser. So, in effect, I don't see the cursor, nor the plot just
>>> created. Is there a way to make the browser scroll to the proper
>>> position? By the way, this happens in the opposite direction, too,
>>> namely, if I move up with the cursor pressing the "Up" arrow diligently,
>>> when I get to the first, cell, the browser does not move any more, even
>>> if the cursor is above the top of the visible field
>>> Cheers,
>>> Zoltán
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Brian E. Granger
Cal Poly State University, San Luis Obispo
bgranger@calpoly.edu and ellisonbg@gmail.com

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