162122 - stop paint suppression when vertical scrollbar appears

Status: NEW

(Core :: Layout, defect, P3)

Description

[Jesse Ruderman]

Mozilla should draw what it has immediately when a vertical scrollbar appears. 
It currently seems to wait 1.2 seconds from when the page starts to load unless
the page finishes loading during the first 1.2 seconds.

Rationale: if the vertical scrollbar appears, the page layout should be stable.
 The appearance of the vertical scrollbar may have changed the layout, but
loading the rest of the page is not likely to change it more.  Additionally,
starting to paint now won't slow down loading the rest of the page much, because
the rest of the page is below the edge of the content area.

Comment 1

[Jesse Ruderman]

Attachment: testcase

Comment 2

[Kevin McCluskey (gone)]

Not going to be able to get to this for a while.

nsbeta1-.

Comment 3

[Jo Hermans]

See bug 180241 : since dec 26th, we're experimenting with a default delay of
250 msec, instead of 1200. The final value might change though (500 ?)

Comment 4

[Kevin McCluskey (gone)]

This is appears to be rational solution. If one page of content has been loaded
display the content. Otherwise, if painting has not occurred within the
specified timeout display the content. 

Note: The scrollbar appearing is driven by frames being constructed which means
the content notification interval may need to be smaller than what it is
currently so frame construction will happen more frequently. Other mechanism's
which affect the initial painting of the page including The
PAINT_STARVATION_LIMIT in plevent.c and the paint suppression delay would need
to be taken into account as well.  


  

Comment 5

[Kevin McCluskey (gone)]

nsbeta1-

Comment 6

[Robert O'Callahan (:roc) (email my personal email if necessary)]

This sounds like a great idea to me. We should do this soon.

Comment 7

[Markus Hübner]

Is this still something to address soon?

Comment 8

[Robert O'Callahan (:roc) (email my personal email if necessary)]

I'm not sure if this is still a problem.

Comment 9

[Jesse Ruderman]

This is more of an idea for an optimization than a problem.  Are you saying this optimization is no longer needed?

Comment 10

[Robert O'Callahan (:roc) (email my personal email if necessary)]

Now that the Firefox suppression timeout is only 250ms, I'm not sure if this is worth doing. Especially because it could hurt in non-unusual cases. For example, lots of pages have a sidebar that gets laid out first, which triggers a vertical scrollbar before the main content has come in.

Comment 11

[Sylvestre Ledru [:Sylvestre]]

Moving to p3 because no activity for at least 1 year(s).
See https://github.com/mozilla/bug-handling/blob/master/policy/triage-bugzilla.md#how-do-you-triage for more information