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From Jesse <>
Subject Re: Wiping plugins on navigation
Date Wed, 05 Sep 2012 22:49:31 GMT
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
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

My 2 sense,

On Wed, Sep 5, 2012 at 3:30 PM, Bryce Curtis <> 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 <> 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 <> 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 <>
>>> wrote:
>>> > This is intended as a continuation of the discussion started in
>>> > .
>>> >
>>> > 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


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