1822131 - Allow XUL to shrink by default

Status: RESOLVED FIXED

(Core :: XUL, task)

Description

[Emilio Cobos Álvarez (:emilio)]

Attachment: test-case courtesy of daniel

Bug 1821920 and bug 1821871 are instances of an interesting behavior change from bug 1820534.

The default flex-basis of old XUL was auto instead of max-content, so stuff that used to wrap now no longer does in an horizontal flex container:

This code prevents items from shrinking.

Per the comment, a few tests relied on this, but I believe it should generally be safe to shrink the items. This only causes to shrink if they have an explicit width but no explicit min-width.

Some tests like test_mousescroll.xhtml hit this, because they have explicit sizes but min-width: auto ends up being 0 effectively, but I believe we should tweak those tests instead.

Comment 1

[Emilio Cobos Álvarez (:emilio)]

Attachment: Bug 1822131 - Allow XUL elements to shrink-by-default. r=dholbert,Gijs,dao

Bug 1821920 and bug 1821871 are instances of an interesting behavior change
from bug 1820534.

The default flex-basis of old XUL was auto instead of max-content, because of this code:

https://searchfox.org/mozilla-central/rev/af78418c4b5f2c8721d1a06486cf4cf0b33e1e8d/layout/generic/nsFlexContainerFrame.cpp#1327

So stuff that used to wrap now no longer does, in an horizontal flex container,
since xul.css prevents XUL elements from shrinking.

Per the comment, a few tests relied on this, but I believe it should generally
be safe to shrink the items. This only causes to shrink if they have an
explicit width but no min-width (including min-width: auto).

Some tests like test_mousescroll.xhtml hit this, because they have explicit
sizes but min-width: auto ends up being 0 effectively, but I believe we should
tweak those tests instead.

Comment 2

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/e3fb28ffc489
Allow XUL elements to shrink-by-default. r=dholbert

Comment 3

[Norisz Fay [:noriszfay]]

Backed out for causing reftest failures on 540247-1.xhtml

Backout link

Push with failures

Failure log

There are also these TVs if you could take a look.

Comment 4

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/aa9a63adab87
Allow XUL elements to shrink-by-default. r=dholbert

Comment 5

[Natalia Csoregi [:nataliaCs]]

https://hg.mozilla.org/mozilla-central/rev/aa9a63adab87

Comment 6

[Alice0775 White]

If the browser is small in width, the Findbar buttons and result description will wrap.
See screencast: https://youtu.be/qjR3ViLsU3w .

Not that there is anything wrong with it, is this intentional change?

Comment 7

[Emilio Cobos Álvarez (:emilio)]

It's not intentional as "I was looking at the findbar when making this change", but it's not surprising and since it's a progression (before they overflowed) seems ok.