1070512 - Slow panning / scrolling of pdfs on documentcloud.org

Status: RESOLVED INVALID

(Web Compatibility :: Site Reports, defect, P3)

Description

[bug.zilla]

User Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:34.0) Gecko/20100101 Firefox/34.0
Build ID: 20140920004004

Steps to reproduce:

Visited this:
http://www.documentcloud.org/documents/1184766-bicoin-pdf.html


Actual results:

Slow scrolling


Expected results:

Scrolling works fine in Chrome

Comment 1

[bug.zilla]

This is on a Samsung Galaxy S4 (4.4.4).
Can I provide anything else useful?

Comment 2

[u279076]

Scrolling is definitely a bit janky but I have the same experience in Fennec Aurora 35.0a2 as I do in Chrome 38. I tested this on a Moto G 2014 on Android 4.4.4.

Comment 3

[u279076]

Aaron, do you have a Galaxy S4 to test?

Comment 4

[Aaron Train [:aaronmt]]

Yes. Yes, it's janky. Maybe this will be resolved with bug 776030 (AZPC support on Fennec).

Comment 5

[Kartikaya Gupta (email:[e-mail])]

This site is implementing scrolling themselves, so there's nothing we can do here.

Comment 6

[Botond Ballo [:botond]]

Since the OP said scrolling works fine on Chrome, is it perhaps worth investigating why the performance of Firefox and Chrome are different? That might lead us to identifying an area of the platform where we can improve performance, or otherwise providing feedback to the site authors about what to avoid (i.e. Tech Evangelism).

Comment 7

[Kartikaya Gupta (email:[e-mail])]

I looked at the touch handlers in their code, and they're basically updating the scrollTop/scrollLeft properties on an element based on the pageX/pageY coordinates in the event. If they just didn't bother with any of their touch listeners we should end up using APZ for it which would be smoother. I guess we can move it to Tech Evangelism.

Comment 8

[Karl Dubost💡 :karlcow]

Pushing to needsdiagnosis.
The bug has been partially explained, but we should suggest which piece of code is not working and how to modify it, if possible. 
For example, if it's in a library, first we would need to resolve the issue in the library itself, and then ask them to upgrade.

Comment 9

[Mike Taylor [:miketaylr]]

In http://assets.documentcloud.org/viewer/viewer.js

What Kats is describing is in the touchStart, touchMove and touchEnd methods attached to the `DV.Schema.helpers` object. Basically, if they ditched touch listeners scrolling would be smoother. There aren't any libraries to update, this looks like their own code.

Comment 10

[Sergiu Logigan [:sergiu]]

The scroll behavior is the same as on Chrome.