[webkit-dev] Adding "Scroll Padding" to allow scroll beyond the edge of the page (within some bounds)

[Robert Kroeger]

On Thu, Oct 6, 2011 at 2:02 PM, Antonio Gomes <tonikitoo at gmail.com> wrote:
> From what I tested on iOS5 Mobo Safari, it also overscroll's the
> overflow:scroll case (generally div's).
>
> On Thu, Oct 6, 2011 at 1:47 PM, Fady Samuel <fsamuel at chromium.org> wrote:
>>
>> Hi Anders,
>> At this point in time, we see no reason to allow for non-zero padding in
>> overflow:scroll regions because you can always just move the page into a
>> unobstructed area and then scroll through that overflow region.

I agree with Fady that the feature he describes only requires scroll
padding on the page. But would it be better from a code structure
viewpoint to actually add this functionality to ScrollableArea?

Rob.

>> Thanks,
>> Fady
>>
>> On Thu, Oct 6, 2011 at 1:43 PM, Anders Carlsson <andersca at apple.com>
>> wrote:
>>>
>>> Do you envision this being useful on overflow:scroll regions as well or
>>> is it just frames? If it's just frames, then it seems like something we
>>> could keep in ScrollView? (I haven't looked at the patch yet).
>>> - Anders
>>> On Oct 6, 2011, at 10:41 AM, Fady Samuel wrote:
>>>
>>> Hi Anders,
>>> Thanks for your reply.
>>> Yes, you are correct. This padding would be between the content and the
>>> overhang area.
>>> Thanks,
>>> Fady
>>> On Thu, Oct 6, 2011 at 1:32 PM, Anders Carlsson <andersca at apple.com>
>>> wrote:
>>>>
>>>> Hi Fady,
>>>> so if I'm understanding correctly, in the context of rubber-band
>>>> scrolling, this padding would be between the content and the overhang area?
>>>> As far as constrainsScrollingToContentEdge goes, I'd like to get rid of
>>>> it and just have two scroll functions, one that constrains to the content
>>>> edge and one that doesn't.
>>>> - Anders
>>>> On Oct 6, 2011, at 10:03 AM, Fady Samuel wrote:
>>>>
>>>> Hi all,
>>>>
>>>> We'd like to provide a general mechanism in WebKit for embedders to
>>>> scroll page content so that it is not hidden by embedder-provided UI
>>>> elements that overlap the page.
>>>>
>>>> In some cases, if a floating UI element overlaps the edge of the page,
>>>> we'd like to allow the embedder to scroll beyond the edge of the page to
>>>> allow the hidden content to move to an area that isn't overlapped by UI
>>>> elements. This feature is orthogonal to rubber band scrolling.
>>>>
>>>> One approach we considered taking is to allow the platform to set
>>>> "scroll padding" to a FrameView/ScrollableArea to allow scrolling beyond the
>>>> edge of the page.
>>>> As a more concrete example, one can imagine a persistent Chromium
>>>> extension that floats above the edge of the page. A link may lie behind the
>>>> floating window.  That link would be inaccessible unless the page is allowed
>>>> to scroll beyond its edge.
>>>>
>>>> An experimental and incomplete implementation of this idea can be found
>>>> here: https://bugs.webkit.org/show_bug.cgi?id=68184
>>>>
>>>> After some additional consideration since this patch was posted, I don't
>>>> believe scroll padding should interact with
>>>> ScrollView::constrainsScrollingToContentEdge the way it does in the patch.
>>>> Instead, I feel that scroll padding should be ignored
>>>> if constrainsScrollingToContentEdge is false. That way rubber band scrolling
>>>> is not affected at all by this.
>>>>
>>>> What are your thoughts and suggestions? Is this feature sufficiently
>>>> general to be implemented in WebCore? What are your thoughts about its
>>>> interaction with ScrollView::constrainsScrollingToContentEdge?
>>>>
>>>> Thanks,
>>>> Fady
>>>> _______________________________________________
>>>> webkit-dev mailing list
>>>> webkit-dev at lists.webkit.org
>>>> http://lists.webkit.org/mailman/listinfo.cgi/webkit-dev
>>>>
>>>
>>>
>>
>>
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>
>
>
> --
> --Antonio Gomes
>
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