Bug 25313 – Missing scrollbars in GMail

• Component: Platform
• Status: RESOLVED FIXED

[Dimitri Glazkov (Google)]

This bug manifested itself most drastically in Chromium ToT, where GMail would never gain scrollbars. The condition occurs because the html element in the GMail canvas frame is given "overflow-y: scroll" dynamically (and repeatedly). Because of the "never one scrollbar at a time" check, even though it's already set to ScrollbarAlwaysOn, the vertical scrollbar may be occasionally disabled.

I am still trying to figure out how to write a layout test for this :).

[Dimitri Glazkov (Google)]

Created attachment 29663 [details]
GMail scroll bars missing, v1

 WebCore/ChangeLog               |   11 +++++++++++
 WebCore/platform/ScrollView.cpp |   22 +++++++++++-----------
 2 files changed, 22 insertions(+), 11 deletions(-)

[Dimitri Glazkov (Google)]

Comment on attachment 29663 [details]
GMail scroll bars missing, v1

Oops. Some extra changes snuck in.

[Dimitri Glazkov (Google)]

Created attachment 29665 [details]
GMail scroll bars missing, v1.1

 WebCore/ChangeLog               |   11 +++++++++++
 WebCore/platform/ScrollView.cpp |   20 ++++++++++----------
 2 files changed, 21 insertions(+), 10 deletions(-)

[Dimitri Glazkov (Google)]

Created attachment 29667 [details]
GMail scroll bars missing, v2.

 WebCore/ChangeLog                             |   11 +++++++++++
 WebCore/platform/ScrollView.cpp               |   17 +++++++++--------
 WebKit/mac/ChangeLog                          |   11 +++++++++++
 WebKit/mac/WebView/WebDynamicScrollBarsView.m |   19 ++++++++++---------
 4 files changed, 41 insertions(+), 17 deletions(-)

[Darin Adler]

Is there a way to make a regression test for this? I don't want it to break again.

[Dimitri Glazkov (Google)]

Created attachment 29669 [details]
Deficient layout test attempt

I haven't yet been able to come up with a good layout test. This is how far I've gotten, but I can only trigger failure on Safari/Win and Chromium. I'll think on this some more. Obviously, appreciate any ideas.

[Dimitri Glazkov (Google)]

Comment on attachment 29667 [details]
GMail scroll bars missing, v2.

Better patch coming up.

[Dimitri Glazkov (Google)]

Created attachment 29694 [details]
GMail scroll bars missing, v3.

 LayoutTests/ChangeLog                              |    9 +++++
 .../fast/overflow/overflow-y-scroll-expected.txt   |    3 ++
 LayoutTests/fast/overflow/overflow-y-scroll.html   |   39 ++++++++++++++++++++
 WebCore/ChangeLog                                  |   13 +++++++
 WebCore/platform/ScrollView.cpp                    |   17 +++++----
 WebKit/mac/ChangeLog                               |   11 ++++++
 WebKit/mac/WebView/WebDynamicScrollBarsView.m      |   19 +++++-----
 7 files changed, 94 insertions(+), 17 deletions(-)

[Darin Adler]

Comment on attachment 29694 [details]
GMail scroll bars missing, v3.

r=me

Hyatt should probably look at this too.

[Dimitri Glazkov (Google)]

Hyatt says fine.

[Dimitri Glazkov (Google)]

Landed as http://trac.webkit.org/changeset/42791.