Bug 155334 – REGRESSION(r195661): [GTK] very slow scrolling

• Component: WebKitGTK
• Status: RESOLVED FIXED

[Tomasz Majer]

Created attachment 273642 [details]
full speed scrolling in Epiphany 3.19.91

I have Gnome 3.19.91 installed on Arch Linux from unofficial repo. In Epiphany with 'smooth scrolling' enabled scrolling is now "kinetic" and very slow, almost unusable. 
Workaround: I downgraded webkit2gtk to 2.10.7 and it solves the problem.

[Tomasz Majer]

Also, is there any way to disable kinetic scrolling but with smooth scrolling still enabled? This is the most useless feature on desktop without touchscreen.

[Michael Catanzaro]

I have no clue what could cause this, maybe it thinks you have a touchscreen?

[Tomasz Majer]

But why?
Smooth scrolling in Epiphany 2.18 was excellent, but now it is unusable. For me it is huge regression, and I will change my default web browser because of it.

[Tomasz Majer]

Created attachment 273881 [details]
dmesg output

[Michael Catanzaro]

(In reply to comment #2)
> I have no clue what could cause this

If you could try a few different 2.11.x releases to pinpoint which release introduced the regression, that would be very helpful. Otherwise, since you seem to be the only one who is affected by this issue so far (no doubt we'll start to get more complaints in a few weeks), there's not much we can do. :/

[Carlos Garcia Campos]

The smooth scrolling implementation hasn't changed since 2.10.7. We just refactored the scroll animator classes and it's now in its own file, see http://trac.webkit.org/browser/trunk/Source/WebCore/platform/ScrollAnimatorSmooth.cpp

[Carlos Garcia Campos]

(In reply to comment #2)
> I have no clue what could cause this, maybe it thinks you have a touchscreen?

We don't have anything to detect if there's a touchscreen and do scrolling differently.

[Tomasz Majer]

(In reply to comment #7)
> (In reply to comment #2)
> > I have no clue what could cause this, maybe it thinks you have a touchscreen?
> 
> We don't have anything to detect if there's a touchscreen and do scrolling
> differently.

There is no touchscreen. I have Lenovo Z510 laptop with tachpad, but I mostly use mouse with wheel. I usually use mouse wheel to scroll web pages, and now with "smooth scrolling" enabled in dconf I have very slow kinetic scrolling , no matter if I use touchpad, or mouse wheel... scrolling takes "ages" now.

(In reply to comment #5)
>If you could try a few different 2.11.x releases to pinpoint which release >introduced the regression, that would be very helpful.

I had tried few releases... same problem with 2.11.90, 2.11.5.
With 2.11.4 everything is OK again. With "smooth scrollong" enabled, scrolling useing mouse wheel and touchpad is smooth but not kinetic, and with normal speed.
So it seems that 2.11.5 release introduced the regression.

My english is not very good, sorry.

[Carlos Garcia Campos]

So, it looks like the ScrollAnimator refactoring caused this problem then.

[Michael Catanzaro]

OK, I found the org.gnome.Epiphany enable-smooth-scrolling setting, and can reproduce now. Didn't realize this setting was hooked up to anything as it never worked when I tried it in the past, but it just needs a browser restart.

[Tomasz Majer]

(In reply to comment #10)
> OK, I found the org.gnome.Epiphany enable-smooth-scrolling setting, and can
> reproduce now. Didn't realize this setting was hooked up to anything as it
> never worked when I tried it in the past, but it just needs a browser
> restart.

I hope this bug is possible to fix. I like smooth scrolling, to be honest I have started useing this feature with epiphany last month, and in my opinion it is  much better than Chromium's smooth scrolling.

[Carlos Garcia Campos]

(In reply to comment #10)
> OK, I found the org.gnome.Epiphany enable-smooth-scrolling setting, and can
> reproduce now. Didn't realize this setting was hooked up to anything as it
> never worked when I tried it in the past, but it just needs a browser
> restart.

It used to require a restart, before the refactoring, now we correctly react to the setting change.

[Carlos Garcia Campos]

(In reply to comment #11)
> (In reply to comment #10)
> > OK, I found the org.gnome.Epiphany enable-smooth-scrolling setting, and can
> > reproduce now. Didn't realize this setting was hooked up to anything as it
> > never worked when I tried it in the past, but it just needs a browser
> > restart.
> 
> I hope this bug is possible to fix. I like smooth scrolling, to be honest I
> have started useing this feature with epiphany last month, and in my opinion
> it is  much better than Chromium's smooth scrolling.

Yes, of course it can be fixed, we just need to figure out what I did wrong in the refactoring to change the behavior.

[Carlos Garcia Campos]

Yes, I made a couple of mistakes in r195661

[Carlos Garcia Campos]

Created attachment 274184 [details]
Patch

This patch fixes the issues and restores the previous behavior.

[Carlos Garcia Campos]

Committed r198269: <http://trac.webkit.org/changeset/198269>

[Tomasz Majer]

I have installed webkit2gtk 2.11.92 and it is very weird. When I switch tabs, and try to scroll page by mouse wheel the behaviour change, from good to bad as before. I don't konw how to describe it. I will upload video but I doubt that it will be well visible.

[Carlos Garcia Campos]

(In reply to comment #17)
> I have installed webkit2gtk 2.11.92 and it is very weird. When I switch
> tabs, and try to scroll page by mouse wheel the behaviour change, from good
> to bad as before. I don't konw how to describe it. I will upload video but I
> doubt that it will be well visible.

I think it's because we are losing the visible length again when scrolling without animations in ScrollAnimationSmooth::setCurrentPosition(). I'll look at it.

[Tomasz Majer]

Created attachment 274273 [details]
Smooth scrolling in 2.11.92

[Tomasz Majer]

The behaviour change randomly when I reload the page.

[Carlos Garcia Campos]

Created attachment 274275 [details]
Patch

Could you try this patch on top of 2.11.92?

[WebKit Commit Bot]

Attachment 274275 [details] did not pass style-queue:


ERROR: Source/WebCore/platform/ScrollAnimationSmooth.cpp:43:  Extra space before ( in function call  [whitespace/parens] [4]
ERROR: Source/WebCore/platform/ScrollAnimationSmooth.h:46:  Extra space before ( in function call  [whitespace/parens] [4]
Total errors found: 2 in 5 files


If any of these errors are false positives, please file a bug against check-webkit-style.

[Tomasz Majer]

(In reply to comment #21)
> Created attachment 274275 [details]
> Patch
> 
> Could you try this patch on top of 2.11.92?

Yes, of course.
Could you tell me how to do this? I've never patched anything.
I have webkitgtk-2.11.92.tar.xz and wcore-smooth-scrolling.diff in the same directory. What now?

[Carlos Garcia Campos]

(In reply to comment #23)
> (In reply to comment #21)
> > Created attachment 274275 [details]
> > Patch
> > 
> > Could you try this patch on top of 2.11.92?
> 
> Yes, of course.
> Could you tell me how to do this? I've never patched anything.
> I have webkitgtk-2.11.92.tar.xz and wcore-smooth-scrolling.diff in the same
> directory. What now?

But you already built webkitgtk-2.11.92 from sources right?

$ cd webkitgtk-2.11.92
$ cat ../wcore-smooth-scrolling.diff | patch -p1

Don't worry about merge conflicts in ChangeLog if any. And then build again.

[Tomasz Majer]

I have built package useing 'makepkg -cs' in ArchLinux, so unfortunatelly all files have beed removed and I must build whole webkitgtk again :/
I will tell you in about 3 hours, if that patch works or not.

[Tomasz Majer]

It seems that everything is ok now.

[Carlos Garcia Campos]

Committed r198383: <http://trac.webkit.org/changeset/198383>

[Tomasz Majer]

I have tested it for a while and I have impression that scrolling now is a bit slower and less smooth compared to webkit 2.10. But I don't have any proof.