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From Braden Shepherdson <bra...@chromium.org>
Subject Re: Cordova Screen Capture Plugin for Android
Date Wed, 13 Mar 2013 20:03:08 GMT
Jasmine does support asynchronous tests, and waiting an arbitrary period or
until some condition is true. Why does that not work for these tests?

Braden


On Wed, Mar 13, 2013 at 3:42 PM, Aaron Charbonneau <amcharbo@gmail.com>wrote:

> Quick follow up question for the return values stuff:
> Does it make sense to have my functions called from execute (capture() and
> captureAndCompare()) return an error string if one is encountered and pass
> that back in callbackContext.error, then have execute return true?
>
> Or is there a preferred way to get errors from sub functions back into
> Javascript?
>
> Thanks!
>
>
> On Wed, Mar 13, 2013 at 12:14 PM, Aaron Charbonneau <amcharbo@gmail.com
> >wrote:
>
> > Thanks Andrew these are great suggestions!
> >
> > About not needing the busy-wait in getScreenBits:
> > I'm not a fan of busy-waiting either.
> > Perhaps it's a side effect of Jasmine requiring tests to be run and
> > evaluated synchronously that I decided to use a busy-wait in
> getScreenBits.
> >  If the Runnable calls CallbackContext.success/error once the bits are
> > captured (but not written to file) on the UIThread, the Javascript side
> > will proceed to run before it has an image url/compare result, most
> likely
> > causing that test to fail.  As far as I know Jasmine doesn't allow for
> > kicking off a bunch of tests and then gather all the results at the end
> and
> > output pass/fails (each 'expect' function needs to be within an 'it'
> block,
> > essentially that means one test must be evaluated before the next can
> > begin).
> >
> > I can see the usefulness of allowing the capture, file io, and comparison
> > to be able to run asynchronously from the Javascript though. In the case
> > where you have your own test framework that CAN kick off a bunch of tests
> > and just gather the results as they come in and do a batch evaluation at
> > the end, or in the case where you don't want to do any evaluation in your
> > app and just want to get captures as fast as you can, asynchronous could
> > increase performance there.
> >
> > I could try to implement it this way too, if you think that's a worth
> > while use case, maybe just provide an 'asynchronous' flag in
> CaptureOptions?
> >
> > For doing the fileIO/compare using cordova.getThreadPool, is there a
> > benefit to doing that if I still plan having the operation block the
> > Javascript?  For asynchronous mode I see why that makes sense.
> >
> > For the return values, I'll make those changes right away!  Thanks again
> > for providing your insight, hopefully I understood it correctly.
> >
> > -Aaron
> >
> >
> > On Wed, Mar 13, 2013 at 8:04 AM, Andrew Grieve <agrieve@chromium.org
> >wrote:
> >
> >> Had a glance at your code. Things you may want to address:
> >>
> >> while(!mUIThreadDone) {}
> >>
> >> You shouldn't need to busy-wait. Pass the CallbackContext to the
> Runnable,
> >> and call success/error on it whenever you're done. No need to have the
> web
> >> thread wait for it. Even better would be to use a second Runnable to do
> >> the
> >> image compare / file IO on a background thread via
> cordova.getThreadPool()
> >>
> >> The return value to execute() should only be false if an invalid command
> >> was passed. It's not meant to indicate the success of the operation. You
> >> should be returning true for it.
> >>
> >> Instead of return "success"/"", it might simplify things a bit to
> return a
> >> boolean of true/false
> >>
> >>
> >> On Tue, Mar 12, 2013 at 4:51 PM, Lorin Beer <lorin.beer.dev@gmail.com
> >> >wrote:
> >>
> >> > all the same, very impressive and faster then I expected.
> >> >
> >> > - Lorin
> >> >
> >> >
> >> > On Tue, Mar 12, 2013 at 1:46 PM, Aaron Charbonneau <
> amcharbo@gmail.com
> >> > >wrote:
> >> >
> >> > > Thanks Lorin.
> >> > >
> >> > > I did a quick test for throughput on an animating canvas.  I was
> able
> >> to
> >> > > grab 30 frames within a 5 seconds which equates to around 166ms per
> >> > capture
> >> > > on a Galaxy Nexus.  Unfortunately not fast enough to automate
> >> something
> >> > > like video.  As with any kind of capturing system, often the
> overhead
> >> of
> >> > > copying bits around is enough to slow down the operation of the app.
> >> > >
> >> > > -Aaron
> >> > >
> >> > >
> >> > > On Tue, Mar 12, 2013 at 11:58 AM, Lorin Beer <
> >> lorin.beer.dev@gmail.com
> >> > > >wrote:
> >> > >
> >> > > > Hey Aaron,
> >> > > >
> >> > > > very cool stuff, looking forward to checking it out!
> >> > > >
> >> > > > Question: any performance hit on the app by using Capture? What's
> >> the
> >> > > > expected throughput on images taken in this way (given a
> particular
> >> > > device,
> >> > > > say Galaxy Nexus)?
> >> > > >
> >> > > > - Lorin
> >> > > >
> >> > > >
> >> > > > On Tue, Mar 12, 2013 at 11:30 AM, Aaron Charbonneau <
> >> > amcharbo@gmail.com
> >> > > > >wrote:
> >> > > >
> >> > > > > Glad you like it :)
> >> > > > > Yes in fact the actual capture makes use of
> View.capturePicture()
> >> > which
> >> > > > > actually grabs the entire document, then that can be clipped
> down
> >> to
> >> > > the
> >> > > > > size/location of a specific element.
> >> > > > >
> >> > > > > -Aaron
> >> > > > >
> >> > > > >
> >> > > > > On Tue, Mar 12, 2013 at 11:27 AM, Michal Mocny <
> >> mmocny@chromium.org>
> >> > > > > wrote:
> >> > > > >
> >> > > > > > Aaron,
> >> > > > > >
> >> > > > > > I haven't even begun looking at your implementation,
but I'm
> >> just
> >> > > going
> >> > > > > to
> >> > > > > > say it: this is awesome!
> >> > > > > >
> >> > > > > > First question: When Capturing a DOM element, can you
capture
> >> > 'body'
> >> > > to
> >> > > > > > grab it&children for a "full content screenshot",
or does it
> >> have
> >> > to
> >> > > > be a
> >> > > > > > specific single element?
> >> > > > > >
> >> > > > > > -Michal
> >> > > > > >
> >> > > > > >
> >> > > > > > On Tue, Mar 12, 2013 at 1:58 PM, Aaron Charbonneau
<
> >> > > amcharbo@gmail.com
> >> > > > > > >wrote:
> >> > > > > >
> >> > > > > > > Greetings!  My name is Aaron Charbonneau, happy
to be a new
> >> > member
> >> > > of
> >> > > > > the
> >> > > > > > > mailing list!
> >> > > > > > >
> >> > > > > > > I have been developing a sceenshot plugin for
Cordova to
> help
> >> > > > > facilitate
> >> > > > > > > automation testing and debugging of Cordova apps,
and I
> would
> >> > love
> >> > > > some
> >> > > > > > > feedback on it.  Currently Cordova provides a
bunch of
> native
> >> > > > functions
> >> > > > > > > that allow you to do some cool stuff, but not
much
> >> functionality
> >> > to
> >> > > > > test
> >> > > > > > > the apps that make use of them.  Being able to
take a
> capture
> >> of
> >> > > the
> >> > > > > > screen
> >> > > > > > > from within you app is a great way to automate
testing or
> get
> >> > > > > additional
> >> > > > > > > information for debugging an issue.  Since there
is no
> >> > > > > > > Javascript mechanism for taking screen captures
the solution
> >> > would
> >> > > > have
> >> > > > > > to
> >> > > > > > > be native, which fits nicely into the "gap" that
> >> Cordova/Phonegap
> >> > > > > > bridges.
> >> > > > > > >  Any medium to large scale app can benefit greatly
from
> >> > automation
> >> > > > > > testing
> >> > > > > > > and any app can benefit from an extra debugging
tool, and
> >> that is
> >> > > > what
> >> > > > > I
> >> > > > > > > hope this screenshot plugin can help achieve.
> >> > > > > > >
> >> > > > > > > Currently the plugin offers 2 functions:
> >> > > > > > >
> >> > > > > > > Capture():
> >> > > > > > > * Take a capture of the current view, write that
capture to
> a
> >> > .png
> >> > > > file
> >> > > > > > > with the specified file name and sub directory
of the sdcard
> >> > > > (fallback
> >> > > > > to
> >> > > > > > > emulated sdcard in the case there isn't an sdcard
mounted)
> >> > > > > > > * Able to create a sub-screenshot with a specified
rectangle
> >> in
> >> > > order
> >> > > > > to
> >> > > > > > > block out ui elements that may be variable, and
also save
> >> space.
> >> > > > > > > * Can take captures of images/dom elements (including
> canvas)
> >> > that
> >> > > > are
> >> > > > > > > lager than the actual screen size
> >> > > > > > >
> >> > > > > > > CaptureAndCompare():
> >> > > > > > > * All the functionality of Capture()
> >> > > > > > > * Perform a comparison between the captured image
and a
> >> baseline
> >> > > > image
> >> > > > > > > located at the specified location in either the
assets
> folder
> >> or
> >> > > the
> >> > > > > > > sdcard.
> >> > > > > > > * User can specify per color channel tolerances
as well as
> >> total
> >> > > > pixel
> >> > > > > > > tolerances to avoid false positives for the inevitable
> >> rendering
> >> > > > > > > differences across devices.
> >> > > > > > > * Optionally output a png file that contains the
differences
> >> > > between
> >> > > > > the
> >> > > > > > > actual and the baseline for debugging/triage purposes,
two
> >> modes:
> >> > > > > binary
> >> > > > > > > diff (all failing pixels appear as solid white)
or the true
> >> > > > differences
> >> > > > > > > between pixels.
> >> > > > > > >
> >> > > > > > > If you can spare some time, I would love it if
you could
> take
> >> a
> >> > > look
> >> > > > at
> >> > > > > > the
> >> > > > > > > api and parameters I have defined to make sure
they adhere
> to
> >> > > Cordova
> >> > > > > > > plugin best practices.  The most crucial part
would be in
> the
> >> > > plugin
> >> > > > > > itself
> >> > > > > > > at ScreenCapture.java:
> >> > > > > > >
> >> > > > > > >
> >> > > > > >
> >> > > > >
> >> > > >
> >> > >
> >> >
> >>
> https://github.com/Charbs09/Cordova-Mobile-Spec-ScreenCapture/blob/master/src/org/apache/cordova/plugin/ScreenCapture.java(capture()
> >> > > > > > > and captureAndCompare() are the two exposed functions)
> >> > > > > > >
> >> > > > > > > I'm also interested to know you thoughts on it's
usage.  I
> >> > started
> >> > > > with
> >> > > > > > the
> >> > > > > > > mobile-spec testing framework and put some quick
rendering
> >> tests
> >> > > into
> >> > > > > the
> >> > > > > > > Autotest section as a viable use case.  In order
to get the
> >> > WebView
> >> > > > > into
> >> > > > > > > the state I wanted to capture, I had to implement
a wait
> >> timer to
> >> > > > allow
> >> > > > > > the
> >> > > > > > > view to update before taking the capture.  Once
the wait
> >> function
> >> > > > > > > completes, the capture can be taken and everything
from
> there
> >> is
> >> > > > > callback
> >> > > > > > > based.  I use the Jasmine waitsFor()/runs() blocks
to make
> the
> >> > > tests
> >> > > > > run
> >> > > > > > > synchronously.  For some validation testing I
made a compare
> >> > > function
> >> > > > > in
> >> > > > > > > Javascript to run against the native compare.
 Turns out
> Java
> >> > runs
> >> > > > alot
> >> > > > > > > faster than Javascript (surprise!) thus the native
compare
> is
> >> > about
> >> > > > > 2-5x
> >> > > > > > > faster.  All in all the process is fairly quick,
the full
> >> > > > > > captureAndCompare
> >> > > > > > > with 3 file io's takes about 233ms on a Nexus
One, and
> ~100ms
> >> on
> >> > a
> >> > > > > Nexus
> >> > > > > > 10
> >> > > > > > > (256x256 image size).
> >> > > > > > >
> >> > > > > > > Anyways here is the usage:
> >> > > > > > >
> >> > > > > > >
> >> > > > > >
> >> > > > >
> >> > > >
> >> > >
> >> >
> >>
> https://github.com/Charbs09/Cordova-Mobile-Spec-ScreenCapture/blob/master/assets/www/autotest/tests/rendering.tests.js
> >> > > > > > >
> >> > > > > > > And here's the JS wrapper for the plugin calls:
> >> > > > > > >
> >> > > > > > >
> >> > > > > >
> >> > > > >
> >> > > >
> >> > >
> >> >
> >>
> https://github.com/Charbs09/Cordova-Mobile-Spec-ScreenCapture/blob/master/assets/www/screencapture.js
> >> > > > > > >
> >> > > > > > > Thanks for your time, and I look forward to ANY
feedback
> >> positive
> >> > > or
> >> > > > > > > negative.
> >> > > > > > >
> >> > > > > > > Thanks,
> >> > > > > > > Aaron
> >> > > > > > >
> >> > > > > >
> >> > > > >
> >> > > >
> >> > >
> >> >
> >>
> >
> >
>

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