Bug 23241 – Scroll will jerk at first then operate smooth until direction shifts 90 degrees

• Component: New Bugs
• Status: UNCONFIRMED

[Jim Oase]

There is a problem with scrolling using a super mouse with WebKit-SVN-r39790.

This problem occurred after the animation problem was fixed.
I am using a super mouse with a MacBook Pro 17"
After animation begins do a slow steady scroll using the scroll ball. The picture will not follow the scroll ball input at first.
Then the picture will jerk to the correct position and scroll correctly in that direction ie... west to east
When the direction changes to north/south the scroll will jerk at first then work as expected.

[Jim Oase]

Scroll is smooth until animation starts, then scroll becomes jerky.... small scrolled movement in the same direction will happen smooth as expected.  

After a about a half inch of movement scroll will stall and then jerk to the new position inches away.

Reversing direction will at first jerk then work smooth for about a half inch then jerk to new position about an inch away.

This characteristic  happens in any axis.

[Jim Oase]

Scrolling continues to be jerky with WebKit-SVN-r40288.  

Initial loading for most sites seems to have a stall period as well.  I am not sure if these are related issues.

Scrolling is really jerky, taking several seconds for reaction to the first scroll ball input.  Then scroll will be smooth for a half inch before scrolling becomes jerky again.....

Jim

[Jim Oase]

Scroll continues to be jerky with build WebKit-SVN-r40771

Scroll is quick and smooth as expected until animation begins, then there are long delays between input and reaction making scroll action very jerky.

Jim

[Jim Oase]

Created attachment 27638 [details]
Screen shot ... initial load results

[Jim Oase]

WebKit-SVN-r41017  fixed this problem
WebKit-SVN-r41018 broke it again

When this site loaded with r41017 there is several blue display over the map is use to be the case months ago and scrolling work smoothly as expected.

My first test with each build is this site.  Build r41018 loaded without the blue display over the map and when animation begin the scrolling became erratic and jerky again.

Jim

[Jim Oase]

Using WebKit build r41242 it takes 20 seconds for the animation feature to begin.  When animation begins
-  user inputs are delayed several seconds resulting in jerky scroll action from a super mouse,
-  keyboard inputs are seconds behind real time when inputs are in bursts, such as ordinary typing,
-  click action for access to menus is delayed seconds.

[Jim Oase]

http://nightly.webkit.org/start/trunk/41348   12...20 second delay between the time the page is loaded and animation begins.  

After animation begins reaction to user inputs from the mouse scroll ball or click or keyboard is delayed several seconds.  The scroll ball problem is most noticeable as extremely jerky screen movement.

The several second delay is the result of the recent "fix" for the animation problem.

JIm

[Jim Oase]

Mail also show the effects of a slow user input while and after viewing this site  http://radar.weather.gov/Conus/full_loop.php

Here is what I do to see this delayed input effect.   
Open    http://radar.weather.gov/Conus/full_loop.php
Wait 12...20 seconds for animation to begin
Then  using the scroll ball move the view point..... it will jerk around when moves are repeatedly made

Scheme two.... access Report Bugs to Apple
Type any input....  the characters will appear almost a second after the key is pressed

Scheme three... after using Safari to access  http://radar.weather.gov/Conus/full_loop.php
switch to Mail and create a new email
Enter a known address that you have not used recently..... the address will take seconds to appear.

Happy Easter

Jim

[Jim Oase]

When accessing this site CPU usage jumps to approximately 50% while typing and scroll ball input are delayed by about 1 second.

Lot of CPU being used for such poor performance.

[Jim Oase]

This problem seems to be associated with priorities.  WebKit is giving animation higher priority than user input.  As a result is trying, without success, to keep animation going during and at the expense of the scrolling process.  Instead of stopping animation during user input, doing the user command, smoothly scrolling the display, and then reinitiating the animation process.

This problem with WebKit has bugged me for years now so I downloaded FireFox to see what happens.  Smooth scrolling.  Then I noticed that animation is suspended during the scrolling process.  Makes sense and takes far less CPU resources which is another symptom.  CPU on this site is hovers around 50+% with WebKit and 5% with FireFox.

You can try both and see what you think.
http://radar.weather.gov/Conus/full_loop.php

[Jim Oase]

Version 4.0.3 (6531.9, r50006)

CPU usage is spikes between 30...98%
User input is delayed about a second
Load time takes 12...14 seconds, then animation begins after another 1 minute and 55 seconds

I have compared this performance with the current version of FireFox.  
Load time about 2..3 seconds
Animation begins immediately
CPU usage 3...7%
User input is instantaneous

This problem has existed for a couple years.  In that time there have been hundreds of updates, none have affected this problem.  I think this is a core design issue rather than a faulty routine.

This problem is still marked unconfirmed... Load this URL
http://radar.weather.gov/Conus/full_loop.php   confirmation will take another 2 minutes, realized while waiting for animation to begin.  30 seconds more to confirm the scrolling problem.