Bug 157834 – [css-grid] Fix behavior of flexible track breadths

• Component: Layout and Rendering
• Status: RESOLVED FIXED

[Manuel Rego Casasnovas]

There have been some changes on the spec so we need to update the implementation.
This bug is about 2 changes that are interrelated.

1) First change [1] is from January 2015 [2]:
  "When appearing outside a minmax() notation,
   implies an automatic minimum (i.e. ''minmax(auto, <flex>)'')."

  Right now, we're considering that "1fr" is equivalent to "minmax(1fr, 1fr)".
  But it should be "minmax(auto, 1fr)".

2) Another change [3] from the spec  that we should implement.
  "fr" should be invalid if it's used in the min slot of minmax().

  The new syntax on the spec is [4]:
    <track-size> =
      <track-breadth> |
      minmax( <inflexible-breadth> , <track-breadth> )

    <inflexible-breadth> =
      <length> |
      <percentage> |
      min-content |
      max-content |
      auto

  This means that a declaration like "grid-column: minmax(1fr, 100px);"
  should be considered invalid.

As you can see both changes are very related. It would be strange that
we're rejecting "fr" explicitly on the min slot (e.g. "minmax(1fr, 100px)"),
but accepting it implicitly as "1fr" would behave like "minmax(1fr, 1fr)"
instead of "minmax(auto, 1fr)".

BTW, this has been already fixed in Blink:
https://codereview.chromium.org/1979603002/

[1] https://drafts.csswg.org/css-grid/#valdef-grid-template-columns-flex
[2] https://github.com/w3c/csswg-drafts/commit/129f2c1ad684e47ef85900f8e156efe07a3f13d6
[3] https://github.com/w3c/csswg-drafts/commit/4040ba7fa068905f7fe1c1bf35d665a2062acafa
[4] https://drafts.csswg.org/css-grid/#typedef-track-size

[Manuel Rego Casasnovas]

Created attachment 279473 [details]
Patch

[Sergio Villar Senin]

Comment on attachment 279473 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=279473&action=review

Awesome. Just some minor nits here and there.

> Source/WebCore/ChangeLog:10
> +        1) Flex sizes are invalid on the min slot of minmax().

Nit: "min track sizing function"

> Source/WebCore/ChangeLog:18
> +          adding a new type of restriction "InflexibleSizeOnly".

I prefer this to be inlined bellow in the changed files list.

> Source/WebCore/ChangeLog:28
> +          RenderGrid::gridTrackSize();

Ditto.

> Source/WebCore/rendering/RenderGrid.cpp:751
> +    // if the track had a flex size directly (e.g. "1fr"), the spec says that in this case it implies an automatic minimum.

" if the track had a flex size directly" sounds weird to me, could you rephrase it?

> LayoutTests/ChangeLog:8
> +        The patch includes new test cases checking specifically these 2 issues.

"checking specifically these 2 issues" note that you have not mentioned any issue in this ChangeLog, it only makes sense when reading the WebCore one, so perhaps it's better to add a description or completely wipe out that sentence (and adapting the following ones)

[Manuel Rego Casasnovas]

Created attachment 279636 [details]
Patch

[Manuel Rego Casasnovas]

Comment on attachment 279636 [details]
Patch

Thanks for the review. Applied suggested changes.

[WebKit Commit Bot]

Comment on attachment 279636 [details]
Patch

Clearing flags on attachment: 279636

Committed r201325: <http://trac.webkit.org/changeset/201325>

[WebKit Commit Bot]

All reviewed patches have been landed.  Closing bug.