86950 - make floats not require state recovery

Status: NEW

(Core :: Layout: Floats, task, P3)

Description

[David Baron :dbaron:]

Right now we create and destroy space managers during each reflow (for every
frame that could possibly need a space manager).  This leads to O(N^2) state
recovery for an incremental reflow.  This seems complicated to fix, but some
thoughts on how it could be done are:
 * store the frame that would have the space manager in the reflow state rather
than (or in addition to) the space manager itself, and store the space manager
for the lifetime of the frame tree as a property of the frame, but only for
frames that actually contain floats.
 * (the hard part, perhaps) Keep the space manager updated when things change
between reflows

Comment 1

[David Baron :dbaron:]

Note that the float damage stored by the space manager (see bug 86947) must be
cleared each reflow, or perhaps maintained separately from the space manager.

Comment 2

[Markus Hübner]

This one has a huge impact on performance (just see the dependency-tree).

Comment 3

[David Baron :dbaron:]

Why do you say it's huge?  My memory is that it's one of the smaller of the
remaining O(N^2) issues with loading long pages incrementally.

Comment 4

[Markus Hübner]

Well, you know this best. Which are the big killers (bugs) you'd say?

Comment 5

[Samir Gehani]

adt: nsbeta1-

Comment 6

[Sylvestre Ledru [:Sylvestre]]

Moving to p3 because no activity for at least 2 years.
See https://github.com/mozilla/bug-handling/blob/master/policy/triage-bugzilla.md#how-do-you-triage for more information