Overlay scrolling with iframe-s broken

• Component: UI Events
• Status: RESOLVED FIXED

[Milan Crha]

Moving this from a downstream bug report:
https://bugzilla.redhat.com/show_bug.cgi?id=1395942

When gtk+ has set overlay scrollbars and the page contains at least one iframe, then the scrolling using the scrollbars with mouse left-click doesn't always work.

Observations:
a) mouse wheel works fine (when hovering mouse above the scroll bar)
b) when the vertical scrollbar is at the very bottom, then it works too
c) when I disable overlay scrollbars [1], then it works no matter what

[1] run the application as:
    $ GTK_OVERLAY_SCROLLING=0 test-wk2

[Milan Crha]

Created attachment 295395 [details]
/tmp/a.html

[Milan Crha]

Created attachment 295396 [details]
test-wk2.c

This is a reproducer.

Steps:
a) save the previous attachment as /tmp/a.html file
b) compile and run this test-wk2.c as written on the first line of the file

Make sure the overlay scrolling is not off when testing.

[Michael Catanzaro]

Note that this bug is highly-noticeable on Igalia's internal Etherpad site.

[Milan Crha]

Another downstream bug reports:
https://bugzilla.gnome.org/show_bug.cgi?id=775238
https://bugzilla.gnome.org/show_bug.cgi?id=777348

[Michael Catanzaro]

I noticed this recently in Evolution as well. It's very annoying and definitely WebKit's fault.

[Carlos Garcia Campos]

This is not specific to GTK+ it happens the same in Safari using overlay scrollbars, so it seems to be a general problem with overlay scrollbars.

[Tomas Popela]

(In reply to comment #6)
> This is not specific to GTK+ it happens the same in Safari using overlay
> scrollbars, so it seems to be a general problem with overlay scrollbars.

Yes it's not related to GTK+. I have a WIP patch, but I need to discuss it with someone. The thing is that the event is passed to the subframe even if the mouse pointer is on the scrollbar. Also that's the reason why even the cursors are wrong.

[Carlos Garcia Campos]

(In reply to comment #3)
> Note that this bug is highly-noticeable on Igalia's internal Etherpad site.

hmm, are you sure it's the same issue? This is because of frame flattening I think, but in the etherpads it happens even if frame flattening is disabled. What I tried in mac is the etherpad.

[Tomas Popela]

Created attachment 300221 [details]
wip patch

[Carlos Garcia Campos]

(In reply to comment #9)
> Created attachment 300221 [details]
> wip patch

Ok, definitely the same bug then because that patch makes etherpads work too.

[Carlos Garcia Campos]

Created attachment 300700 [details]
Patch

[Antonio Gomes]

Comment on attachment 300700 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=300700&action=review

r=me. Lets wait 'till Mac bots pass.

> Source/WebCore/page/EventHandler.cpp:1681
> +    updateLastScrollbarUnderMouse(scrollbar, true);

(I know it is not your code, ) can we name the boolean parameter or add a comment, now that we are touching it?

[Build Bot]

Comment on attachment 300700 [details]
Patch

Attachment 300700 [details] did not pass mac-ews (mac):
Output: http://webkit-queues.webkit.org/results/3012980

New failing tests:
fast/scrolling/scroll-animator-overlay-scrollbars-clicked.html

[Build Bot]

Created attachment 300706 [details]
Archive of layout-test-results from ews100 for mac-elcapitan

The attached test failures were seen while running run-webkit-tests on the mac-ews.
Bot: ews100  Port: mac-elcapitan  Platform: Mac OS X 10.11.6

[Build Bot]

Comment on attachment 300700 [details]
Patch

Attachment 300700 [details] did not pass mac-debug-ews (mac):
Output: http://webkit-queues.webkit.org/results/3012997

New failing tests:
fast/scrolling/scroll-animator-overlay-scrollbars-clicked.html

[Build Bot]

Created attachment 300707 [details]
Archive of layout-test-results from ews112 for mac-elcapitan

The attached test failures were seen while running run-webkit-tests on the mac-debug-ews.
Bot: ews112  Port: mac-elcapitan  Platform: Mac OS X 10.11.6

[Carlos Garcia Campos]

Created attachment 300710 [details]
Patch for landing

[Carlos Garcia Campos]

Committed r211775: <http://trac.webkit.org/changeset/211775>