1610044 - Investigate alignment padding in flex container and other helper classes

Status: RESOLVED FIXED

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

Description

[Ting-Yu Lin [:TYLin] (PST, UTC-8)]

Per mats' review in https://phabricator.services.mozilla.com/D59048#1835927, we could investigate the alignment padding issue to make the classes more compact.

Currently, FlexItem, FlexLine and other position trackers exist only in reflow, but once we consider fragmenting flex containers in bug 939897, we might need to store some information on the first continuation in order to share with later continuations. Memory usage could go up.

Comment 1

[Ting-Yu Lin [:TYLin] (PST, UTC-8)]

Searchfox has a handy feature to list the layout of a class. For example, https://searchfox.org/mozilla-central/query/default?q=field-layout%3A%27nsFlexContainerFrame%27

I've taken a look at nsFlexContainerFrame and other helper classes such as FlexItem, FlexboxAxisTracker, etc. They are all fairly compact. FlexLine can be improved slightly.

Comment 2

[Ting-Yu Lin [:TYLin] (PST, UTC-8)]

Attachment: Bug 1610044 - Fill the hole in FlexLine by reordering members. r?dholbert

On Android, there is a 4 byte hole between mTotalItemMBP and
mTotalOuterHypotheticalMainSize. See
https://searchfox.org/mozilla-central/query/default?q=field-layout%3A%27nsFlexContainerFrame%3A%3AFlexLine%27

By moving mTotalOuterHypotheticalMainSize to the beginning of the class, we
can make FlexLine more compact on Android. The size remains the same on other
platforms, with or without this change.

Comment 3

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/f3cf5ce3bd2f
Fill the hole in FlexLine by reordering members. r=dholbert

Comment 4

[Sandor Molnar[:smolnar]]

https://hg.mozilla.org/mozilla-central/rev/f3cf5ce3bd2f