68947 - we should set flags during reflow about containers

Status: NEW

(Core :: Layout, defect)

Description

[buster]

There is code in layout to walk up the parent list to find out if a child is in
a certain kind of container.  We should remove this code (in fact, it looks like
nsTableFrame::IsNested is unused dead code) and replace it with a bitfield in
nsHTMLReflowState where each bit corresponds to an interesting container type.
Three uses off the top of my head:
1. nsTableFrame would set it so all child content would know it was inside a
table (nsTableFrame::IsNested, or whatever replaced it)
2. nsTextControlFrame would set it so child content could optimize incremental
reflows (nsBlockFrame::IsIncrementalDamageConstrained).
3. combo boxes could probably have a similar optimization.

This could be used in conjunction with the ideas we have for propagating a bit
up in the nsHTMLReflowMetrics that told the parent whether anything had changed
or not.

Comment 1

[Boris Zbarsky [:bzbarsky]]

*** Bug 68967 has been marked as a duplicate of this bug. ***

Comment 2

[Marc Attinasi]

Accepting and moving to just past Mozilla 0.9 - I may be able to address sooner,
but not likely.

Comment 3

[Marc Attinasi]

Performance issue: moving off to Mozilla 1.0 to make room for stability issues

Comment 4

[Boris Zbarsky [:bzbarsky]]

.

Comment 5

[Boris Zbarsky [:bzbarsky]]

Note that nsBlockFrame::IsIncrementalDamageConstrained has been replaced by the
REFLOW_ROOT frame flag, looks like.

The IsNested() code in tables is alive and well, however.   Does that one use
justify these reflow flags?  Or are there other proposed uses?