Bug 198324 – [GTK] Mouse wheel scroll doesn't update whole web view

• Component: WebKitGTK
• Status: NEW

[Milan Crha]

Created attachment 370831 [details]
test-wk2.c

I updated to Fedora 30, which has webkit2gtk3-2.24.2-1.fc30.x86_64 (I tried with 2.24.1 too, with the same result), and scrolling the web view with a mouse wheel doesn't update whole web view, only like 50 pixels at the top, eventually at the bottom (depending whether scrolling up or down), and the centre of the web view keeps the previous content. When I resize the window it fixes itself, till the next web view content (height?) change. I do not know whether it's anything with the video drivers or whatever. I can reproduce it on my main machine, but not in a virtual machine, where both use the same packages.

Attached is a test program, with which I can reproduce it in GNOME (both Wayland and on Xorg), Plasma and MATE. The first line of it contains a comment with a command to compile & run it.

Here is a video demonstrating the issue:
https://people.gnome.org/~mcrha/webview-scroll.webm

What I did there:
a) ran the test program
b) moved mouse above the web view and used the wheel to scroll it up and down.
   The scrollbar position changes, but the content doesn't update properly
c) resized the window and repeated the mouse wheel usage,
   the scrolling is updated properly now
d) click the Reload button, which changes content twice, once for a one-line
   text, then back to the long text, which allows scrolling
e) steps b) and c) are reproduced

Interestingly, the step d)+e) doesn't do it every time in GNOME, but in Plasma and MATE I've been able to reproduce this d)+e) reliably.

I also tried with WEBKIT_DISABLE_COMPOSITING_MODE=1, but it did not help.

[Milan Crha]

A little update, I had been composing a message in Evolution and the scrolling breaks in the editor more often, making editing a nightmare. Reproduced in `MiniBrowser -e" too, by writing enough lines to have scrolling required, then moving through the mail with arrow up/down.

[Milan Crha]

I tried to downgrade webkit2gtk3 on my machine and I've found out that
  webkit2gtk3-2.22.4-1.fc30
works properly, while
  webkit2gtk3-2.23.1-1.fc30
is broken. There's no other prebuilt package in koji between these versions:
https://koji.fedoraproject.org/koji/packageinfo?packageID=26162

[Tomas Popela]

(In reply to Milan Crha from comment #2)
> There's no other prebuilt package in koji between these versions:
> https://koji.fedoraproject.org/koji/packageinfo?packageID=26162

Because there was no release between them. But this should be pretty easy to bisect as you have a reproducer. I might look into it.

[Tomas Popela]

(In reply to Tomas Popela from comment #3)
> I might look into it.

I might not as the test case doesn't work for me (I don't have any problems). When you will come to the office, you can use the icecc to bisect it.

[Carlos Garcia Campos]

Is this still happening?

[Milan Crha]

(In reply to Carlos Garcia Campos from comment #5)
> Is this still happening?

I can give it a try. Which version this 'still' references, please?

[Carlos Garcia Campos]

Thanks, current trunk would be ideal, but 2.25.3 should be enough I guess.

[Milan Crha]

Right, stupid question, I'm sorry. I tried with git master at commit 82faa8a6360e54c75bc74f21287416cf7cefa44f, which references:
    git-svn-id: http://svn.webkit.org/repository/webkit/trunk@248099 268f45cc-cd09-0410-ab3c-d52691b4dbfc

and I can still reproduce it.

[Milan Crha]

This is still there when at git commit aec39837fb5478153424253f0a1871c5f2b2d7aa, aka git-svn-id: http://svn.webkit.org/repository/webkit/trunk@249376 268f45cc-cd09-0410-ab3c-d52691b4dbfc

[Milan Crha]

One more observation, trying with webkit2gtk3-2.25.4-1.fc31.x86_64. It's easily reproducible with GNOME on Xorg and then the test program is called as:

   $ GDK_SYNCHRONIZE=1 ./test-wk2

Without that GDK_SYNCHRONIZE exported the painting after mouse wheel scroll works fine. I wasn't able to reproduce this with gnome-shell 3.33.91-1.fc32 and gtk3-3.24.10-2.fc31 under Wayland, but it was easy using the X session. Just run the test program and use the mouse wheel to scroll it up and down.