Nexus 7 Gen 2 takes 1600+ ms each page turn getting first and last visible CFI

[jdempcy]

This issue is a Bug

Expected Behaviour

Page turns should be faster.

Observed behaviour

In a very simple book (The Iliad, Feedbooks) it takes 1600 milliseconds just getting the first and last visible CFIs to turn pages in chapters with approximately 20 or more screens. Some smaller chapters take 800 milliseconds or longer. This is on top of other time spent turning the page.

I am testing with a 2014 Nexus 7 Gen 2.

Steps to reproduce

1. First, open The Iliad.
2. Then turn pages and notice that the larger chapters take multiple seconds for each page turn.
3. You may verify that it is fetching the first and last visible CFIs which adds over a second to each page turn.

Test file(s)

This occurs in all books but the one I am using for testing is:
http://www.feedbooks.com/book/2962/the-iliad-of-homer

Product

SDKLauncher-Android

[rkwright]

@jmgeffroy Does this ring any bells for you? Are you seeing this kind of performance hit in your Android device?

[jmgeffroy]

@rkwright As I said in a PM to @bluefirepatrick and @jdempcy, no, I tried again with the same book and it's very fast. But we are currently still using a pretty old version of the plugin
It could be interesting to look at the diffs that could explain this difference of behavior.
UPDATE Feb. 13, 2017: To be clear, I meant we don't have the issue in our own apps (based on an old version), but I do observe the issue with the latest Android launcher.

[jccr]

This sounds pretty bad.. I have a Nexus 7 Gen 2. @jdempcy Do you think I could reproduce this by pointing it to a cloud reader instance on the Chrome browser app? That's what I'll try first.

[jccr]

@jdempcy
I'm using http://readium.firebaseapp.com with Accessible EPUB.
The firstVisibleCFI call is taking 60-200ms on my Nexus 7 Gen 2*.

Edit: Typo.. I meant Gen 2.
Also I'm using the Chrome Browser

[jdempcy]

@jccr
I just tested http://readium.firebaseapp.com with Nexus 7 Gen 2 in Chrome Browser and it is blazing fast. However, I am not sure if page turns are calling firstVisibleCFI or not. Nor do I know how to open the JS console and execute the call manually to check.

I was thinking that perhaps SDKLauncher-Android is using the LauncherUI JavaScript Interface to make the calls to firstVisibleCFI within the webview.

Also, it is very fast on small spine items for me in SDKLauncher-Android. I'm seeing the 800+ms times when I navigate in spine items with 20 or 30 screens.

Thanks for checking! I can confirm that readium.firebaseapp.com does not seem to have the slow page turn issue.

If you want to let me know how to test calling firstVisibleCFI from a JS console in Android, I'll try that.

EDIT: I just realized I can click the link icon in the top nav to open the "Share reader bookmark…" dialog which will call firstVisibleCFI. It takes about half a second to do so in some spine items in Accessible EPUB 3 by my visual estimate. (However, I am not running console.time/console.timeEnd methods to confirm this.)

But, for instance, in the chapter "Conventions Used in This Book" from the TOC, clicking the link and opening "Share reader bookmark…" is very fast, like ~100ms.

EDIT 2: I just tried "A First Course in Linear Algebra" — navigate to the Archetype X chapter from the table of contents and try bookmarking that one. For me, in the Nexus 7 Gen 2 in Chrome it takes what seems like at least 800ms. (Again, just visually estimating.)

This isn't bad when it's just bookmarking, but multiply by two for first and last visible CFI on every page turn in SDKLauncher-Android and it feels quite slow. Again, this is only affecting the larger chapters on SDKLauncher-Android, so at least that is one saving grace. I shudder to think what would happen if someone tries opening an export from Google Drive, however, which makes ePubs consisting of a single spine item!

[rkwright]

Note that Linear Algebra is notoriously slow but still ...

[jmgeffroy]

If you want to let me know how to test calling firstVisibleCFI from a JS console in Android, I'll try that.

@jdempcy In the console, you can do:
ReadiumSDK.reader.getFirstVisibleCfi();

[jccr]

@jdempcy
Thanks for sharing your investigation.
Even with my own findings I can extrapolate that with 20-30 screens the performance can degrade to the levels that you are seeing.

I'll keep investigating this