incubator-callback-dev mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Andrew Grieve <agri...@chromium.org>
Subject Re: Wiping plugins on navigation
Date Thu, 06 Sep 2012 01:33:53 GMT
Plugins could probably use static fields if they wanted to maintain some
state between page changes. I think it should be extremely rare to do so
though. e.g. For the platforms that implement their plugins in JS, is it
even possible to maintain state between page changes?

One nice outcome of this is that it will make our mobile-spec pages less
likely to affect each other.


On Wed, Sep 5, 2012 at 6:59 PM, Brian LeRoux <b@brian.io> wrote:

> Yes I do not refuting Cordova needs to work for both single page and
> multipage apps. Just saying there is a solution to this problem. ;P
>
>
> On Wed, Sep 5, 2012 at 3:49 PM, Jesse <purplecabbage@gmail.com> wrote:
> > Whether it is an edge case, or a common case, multi-page apps are a
> > reality, so we definitely need to notify plugins when the page is
> > changing.
> > I don't necessarily agree that the plugin should be destroyed and
> > recreated though, I can think of several cases where persistence would
> > be nice to have.
> >
> > I also do not see this as a security issue.  Security is already
> > governed by the white-list, so non-trusted pages cannot access device
> > functions.  If a plugin needs additional security, then it should be
> > built into the plugin, and not the responsibility of the framework.
> > ... Thinking of a SuperCookie plugin which uses the domain of the
> > currently loaded page before deciding what to return, or something
> > similar.
> >
> > My 2 sense,
> >   Jesse
> >
> >
> > On Wed, Sep 5, 2012 at 3:30 PM, Bryce Curtis <curtis.bryce@gmail.com>
> wrote:
> >> Sometimes multi-page apps are needed or you navigate from your app to
> >> another page.  One bug we ran into was that callback ids are reused
> >> when loading a new page.  So, a plugin trying to send data back to the
> >> original page could be calling a recycled plugin with erroneous data.
> >> In addition to the bugs, there is also a security issue with a
> >> subsequent page being able to access a plugin that was used in a
> >> previous page.
> >>
> >> The app/page lifecycle events are propagated to the plugins, and the
> >> plugins are destroyed when loading a new page.  However, looking at
> >> the code, it appears this may be broken now.  (At least for Android).
> >>
> >> On Wed, Sep 5, 2012 at 3:40 PM, Braden Shepherdson <braden@chromium.org>
> wrote:
> >>> Sure, and I'm a fan of single-page apps (I do work for Google, after
> >>> all...), but this causes very chaotic, hard-to-track bugs, so it makes
> >>> sense to be robust over a refresh/navigation.
> >>>
> >>>
> >>> On Wed, Sep 5, 2012 at 5:25 PM, Brian LeRoux <b@brian.io> wrote:
> >>>
> >>>> One thing to note, we tend to advise ppl author single page web apps
> >>>> which makes state visibility change an app logic concern (and avoid
> >>>> this issue from manifesting). Generally, we can say a page refresh is
> >>>> not a great user experience in apps.
> >>>>
> >>>> On Wed, Sep 5, 2012 at 1:15 PM, Braden Shepherdson <
> braden@chromium.org>
> >>>> wrote:
> >>>> > This is intended as a continuation of the discussion started in
> >>>> > https://issues.apache.org/jira/browse/CB-1318 .
> >>>> >
> >>>> > The bug in question is one where one page starts a long native
side
> >>>> action
> >>>> > such as a network call. Then the user navigates the app to another
> page.
> >>>> > When the long action completes, the call returns and the appropriate
> >>>> > Javascript callback is looked up and called.
> >>>> >
> >>>> > However when the page is navigated, the counter that provides
> supposedly
> >>>> > unique names for callbacks is reset, allowing a callback on the
new
> page
> >>>> to
> >>>> > have the same name as the callback from the old page. It then gets
> called
> >>>> > incorrectly, potentially introducing weird and transient bugs.
> >>>> >
> >>>> > The proposed solution is to do the following on navigation:
> >>>> > - Call a destroy() call on all plugins, which by default does
> nothing.
> >>>> This
> >>>> > allows the plugins a chance to cancel any outstanding network
> requests or
> >>>> > do any other cleanup work.
> >>>> > - Delete the plugin instance and recreate it.
> >>>> >
> >>>> > In the bug I also said one step would be to wipe the callback table
> in
> >>>> the
> >>>> > Javascript, but that isn't necessary since it would have been wiped
> by
> >>>> the
> >>>> > navigation anyway.
> >>>> >
> >>>> > This issue is cross-platform-ish. It (probably) doesn't apply to
> >>>> web-based
> >>>> > platforms like WebOS or Bada, because the plugins are Javascript
> shims
> >>>> > rather than native code, and are wiped on navigation like any other
> >>>> > Javascript. However this issue does exist on at least Android and
> iOS,
> >>>> and
> >>>> > probably a few others as well.
> >>>> >
> >>>> > I'm proposing to implement the solution outlined above on Android
> and
> >>>> iOS.
> >>>> > I don't have the devices or environment to do any other platforms,
> nor
> >>>> am I
> >>>> > sure which are necessary. The maintainers of other platforms will
> have to
> >>>> > consider this problem for their platform. I would also update the
> core
> >>>> > plugins to define a destroy() method if they have relevant cleanups
> to
> >>>> make.
> >>>> >
> >>>> > Thoughts on the approach, things I'm missing?
> >>>> >
> >>>> > Braden
> >>>>
> >
> >
> >
> > --
> > @purplecabbage
> > risingj.com
>

Mime
  • Unnamed multipart/alternative (inline, None, 0 bytes)
View raw message