1292930 - stylo: More proper handling of change hints, plus don't restyle display: none content.

Status: RESOLVED FIXED

(Core :: CSS Parsing and Computation, defect)

Description

[Emilio Cobos Álvarez (:emilio)]

Attachment: Servo PR

Before https://github.com/servo/servo/pull/12757, we had a hack in tree that effectively made us return nsChangeHint_ReconstructFrame always.

This explains why we didn't have to bother about quite a few things in the stylo side, but also means that we were always doing a vast amount of work (much more than what was needed in fact).

With that hack gone, this patches rework the handling of change hints, in order to fix all the uncovered bugs.

Comment 1

[Emilio Cobos Álvarez (:emilio)]

Attachment: Bug 1292930: Handle the case of having unresolved URIs in nsStyleDisplay::mBinding.

Review commit: https://reviewboard.mozilla.org/r/69830/diff/#index_header
See other reviews: https://reviewboard.mozilla.org/r/69830/

Comment 2

[Emilio Cobos Álvarez (:emilio)]

Attachment: Bug 1292930: Hoist ChangeHintToString to RestyleManagerBase

Review commit: https://reviewboard.mozilla.org/r/69832/diff/#index_header
See other reviews: https://reviewboard.mozilla.org/r/69832/

Comment 3

[Emilio Cobos Álvarez (:emilio)]

Attachment: Bug 1292930: stylo: Fix handling of eRestyle_LaterSiblings when not combined with other change hints.

Review commit: https://reviewboard.mozilla.org/r/69834/diff/#index_header
See other reviews: https://reviewboard.mozilla.org/r/69834/

Comment 4

[Emilio Cobos Álvarez (:emilio)]

Attachment: Bug 1292930: Allow comparing unresolved URLValueDatas.

This is used by the frame construction to know if it can skip recreating a frame
based on the -moz-binding value. Other approach would be doing string comparison
for each of the unresolved members or similar.

Review commit: https://reviewboard.mozilla.org/r/69836/diff/#index_header
See other reviews: https://reviewboard.mozilla.org/r/69836/

Comment 5

[Emilio Cobos Álvarez (:emilio)]

Attachment: Bug 1292930: stylo: Store the change hint generated by non-elements in their parent element.

Otherwise, the parent style context doesn't have some inherited structs in the
cache, so it avoids comparing them entirely.

For example, the following example:

<p>Hey</p>

p { color: blue }
p:hover { color: red }

Wouldn't work as intended, because when calculating the change hint the
nsStyleColor struct in the element hasn't been accessed by layout (only the
child text frame's has), so it will report a change hint of 0 when hovering over
the paragraph, and we would ignore the nsChangeHint_ReconstructFrame generated
by the text node.

Review commit: https://reviewboard.mozilla.org/r/69838/diff/#index_header
See other reviews: https://reviewboard.mozilla.org/r/69838/

Comment 6

[Emilio Cobos Álvarez (:emilio)]

Attachment: Bug 1292930: stylo: Remove expected warning.

This should actually have been a followup for bug 1290335.

Review commit: https://reviewboard.mozilla.org/r/69840/diff/#index_header
See other reviews: https://reviewboard.mozilla.org/r/69840/

Comment 7

[Emilio Cobos Álvarez (:emilio)]

Attachment: Bug 1292930: stylo: Make change hint processing more straight-forward.

Review commit: https://reviewboard.mozilla.org/r/69842/diff/#index_header
See other reviews: https://reviewboard.mozilla.org/r/69842/

Comment 8

[Cameron McCormack (:heycam)]

Comment on attachment 8778610 [details]
Bug 1292930: Handle the case of having unresolved URIs in nsStyleDisplay::mBinding.

https://reviewboard.mozilla.org/r/69830/#review67026

Comment 9

[Cameron McCormack (:heycam)]

Comment on attachment 8778611 [details]
Bug 1292930: Hoist ChangeHintToString to RestyleManagerBase

https://reviewboard.mozilla.org/r/69832/#review67028

Comment 10

[Cameron McCormack (:heycam)]

Comment on attachment 8778612 [details]
Bug 1292930: stylo: Fix handling of eRestyle_LaterSiblings when not combined with other change hints.

https://reviewboard.mozilla.org/r/69834/#review67030

Comment 11

[Cameron McCormack (:heycam)]

Comment on attachment 8778613 [details]
Bug 1292930: Allow comparing unresolved URLValueDatas.

https://reviewboard.mozilla.org/r/69836/#review67032

::: layout/style/nsCSSValue.cpp:2577
(Diff revision 1)
> -  MOZ_ASSERT(mURIResolved && aOther.mURIResolved,
> -             "How do you know the URIs aren't null?");
> +  if (MOZ_UNLIKELY(!mURIResolved || !aOther.mURIResolved)) {
> +    NS_WARNING("Comparing unresolved URIs");
> +    return false;
> +  }

Why do we trigger this assertion now?

Can we just resolve the URIs in here rather than return false?  Returning false seems OK for -moz-binding (it might result in us doing more work than necessary, although it's probably rare to change -moz-binding values between two different URLs) but I think I would prefer URIEquals to return an accurate result.

So how about we change this URIEquals to call GetURI() on both URLValueData objects, and do the comparison based on those, and then update the comment in the method body (it seems to be out of date already) and the comment above the declaration in nsCSSSValue.h.

Comment 12

[Cameron McCormack (:heycam)]

Comment on attachment 8778614 [details]
Bug 1292930: stylo: Store the change hint generated by non-elements in their parent element.

https://reviewboard.mozilla.org/r/69838/#review67044

::: layout/style/ServoBindings.cpp:232
(Diff revision 1)
>    MOZ_ASSERT(aNode->IsContent());
> +  MOZ_ASSERT(aNode->IsDirtyForServo(),
> +             "Change hint stored in a not-dirty node");
>  
> -  nsIContent* aContent = aNode->AsContent();
> -  nsIFrame* primaryFrame = aContent->GetPrimaryFrame();
> +  // For elements, we need to store the change hint in the proper style context.
> +  // For nodes, we want to store the change hint in the parent element, since

s/For nodes/For text nodes/

::: layout/style/ServoBindings.cpp:237
(Diff revision 1)
> +  // For Gecko this is not a problem, presumably because they access the
> +  // inherited structs from the parent style context to inherit them?

Yes, looks like that's the reason.  When an inherited struct is requested from the style context for a text node, since there are never any rules that match a text node, we fall into the case in nsRuleNode::WalkRuleTree where we decide we can just inherit the struct from the parent.  This is done by calling StyleData() on the parent, which causes it to cache that struct too.

Comment 13

[Cameron McCormack (:heycam)]

Comment on attachment 8778615 [details]
Bug 1292930: stylo: Remove expected warning.

https://reviewboard.mozilla.org/r/69840/#review67048

Comment 14

[Cameron McCormack (:heycam)]

Comment on attachment 8778616 [details]
Bug 1292930: stylo: Make change hint processing more straight-forward.

https://reviewboard.mozilla.org/r/69842/#review67050

::: layout/base/RestyleManagerBase.cpp
(Diff revision 1)
>    // option here would be a dedicated boolean to track whether we need
>    // to do so (set here and unset in ProcessPendingRestyles).
>    presShell->GetDocument()->SetNeedStyleFlush();
>  }
>  
> -

Nit: If you can be bothered, avoid adding this blank line in the first place in the earlier patch.

::: layout/base/ServoRestyleManager.cpp:94
(Diff revision 1)
> +      // Add the stored change hint if there's a frame. If there isn't a frame,
> +      // generate a ReconstructFrame change hint except if the new display value
> +      // (that we can look at in the content node) is not none.

Maybe reword that parenthetical to be a bit clearer -- does it mean "which we can get from the ComputedValues stored on the node"?

Also, s/except //?

Comment 15

[Emilio Cobos Álvarez (:emilio)]

Comment on attachment 8778613 [details]
Bug 1292930: Allow comparing unresolved URLValueDatas.

https://reviewboard.mozilla.org/r/69836/#review67230

::: layout/style/nsCSSValue.cpp:2577
(Diff revision 1)
> -  MOZ_ASSERT(mURIResolved && aOther.mURIResolved,
> -             "How do you know the URIs aren't null?");
> +  if (MOZ_UNLIKELY(!mURIResolved || !aOther.mURIResolved)) {
> +    NS_WARNING("Comparing unresolved URIs");
> +    return false;
> +  }

We don't trigger it on "normal" pages, I just noticed this when opening the build after a crash, in the about:sessionresore page.

I *think* I've only ever hit this in the frame constructor, but as far as I know, this also can get called from CalcStyleDifference, so it's possible for it to be called off main thread. That's why I didn't went the "resolve it" approach.

Comment 16

[Emilio Cobos Álvarez (:emilio)]

Comment on attachment 8778616 [details]
Bug 1292930: stylo: Make change hint processing more straight-forward.

https://reviewboard.mozilla.org/r/69842/#review67050

> Nit: If you can be bothered, avoid adding this blank line in the first place in the earlier patch.

Yeah, missed in the fixup commit, will fix it.

> Maybe reword that parenthetical to be a bit clearer -- does it mean "which we can get from the ComputedValues stored on the node"?
> 
> Also, s/except //?

Wow, I don't know how to English, I'll rephrase :P

Comment 17

[Cameron McCormack (:heycam)]

Comment on attachment 8778613 [details]
Bug 1292930: Allow comparing unresolved URLValueDatas.

https://reviewboard.mozilla.org/r/69836/#review67230

> We don't trigger it on "normal" pages, I just noticed this when opening the build after a crash, in the about:sessionresore page.
> 
> I *think* I've only ever hit this in the frame constructor, but as far as I know, this also can get called from CalcStyleDifference, so it's possible for it to be called off main thread. That's why I didn't went the "resolve it" approach.

OK.  I think we still shouldn't warn, if it is legitimate that we get in here from the frame constructor.  I wonder why we can get in here without having resolved the mBinding URL.  Maybe it is something to do with restyling display:none elements?

In any case, I think maybe your initial approach of considering unresolved URIs as unequal is OK, but let's do that check outside of URLValueData::URIEquals (and leave the assertion in there) so that we can catch legitimate problems with comparing unresolved URLs from e.g. CalcStyleDifference.  Either add an accessor for mIsResolved that we can check from the EqualURIs function in nsCSSFrameConstructor.cpp, or add a new method on URLValueData that return false if either is unresolved.  (And maybe rename the EqualURIs function since it will now operate a bit differently from the identically named one in nsStyleStruct.cpp.)

Comment 18

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/mozilla-inbound/rev/2d5a7f342256
stylo: Reuse RestyleManager::PostRestyleEventInternal. r=heycam
https://hg.mozilla.org/integration/mozilla-inbound/rev/294df63717f1
Hoist ChangeHintToString to RestyleManagerBase. r=heycam
https://hg.mozilla.org/integration/mozilla-inbound/rev/0890cda8c432
stylo: Fix handling of eRestyle_LaterSiblings when not combined with other change hints. r=heycam
https://hg.mozilla.org/integration/mozilla-inbound/rev/7be5dfc0e9c3
stylo: Store the change hint generated by non-elements in their parent element. r=heycam
https://hg.mozilla.org/integration/mozilla-inbound/rev/9c18533ec3fa
stylo: Remove expected warning. r=heycam
https://hg.mozilla.org/integration/mozilla-inbound/rev/c45412486f68
stylo: Make change hint processing more straight-forward. r=heycam

Comment 19

[Emilio Cobos Álvarez (:emilio)]

I pushed all the reviewed changes except the URL one, since the related changes in servo had already landed and this sort of blocks bobby.

Marking as leave-open

Comment 20

[Emilio Cobos Álvarez (:emilio)]

Comment on attachment 8778610 [details]
Bug 1292930: Handle the case of having unresolved URIs in nsStyleDisplay::mBinding.

Review request updated; see interdiff: https://reviewboard.mozilla.org/r/69830/diff/1-2/

Comment 21

[Wes Kocher (:KWierso) (Not reading bugmail; email directly if needed)]

https://hg.mozilla.org/mozilla-central/rev/2d5a7f342256
https://hg.mozilla.org/mozilla-central/rev/294df63717f1
https://hg.mozilla.org/mozilla-central/rev/0890cda8c432
https://hg.mozilla.org/mozilla-central/rev/7be5dfc0e9c3
https://hg.mozilla.org/mozilla-central/rev/9c18533ec3fa
https://hg.mozilla.org/mozilla-central/rev/c45412486f68

Comment 22

[Cameron McCormack (:heycam)]

Comment on attachment 8778610 [details]
Bug 1292930: Handle the case of having unresolved URIs in nsStyleDisplay::mBinding.

https://reviewboard.mozilla.org/r/69830/#review68988

(FYI: MozReview tells me I've reviewed this patch when I haven't.  Maybe you are re-using MozReview-Commit-IDs in the commit messages, so MozReview thinks this patch is logically a new version of a previous patch that I r+ed?  Also, working in a leave-open bug and pushing this new patch without the ones that already landed marked those as obsolete.)

::: layout/style/nsStyleStruct.cpp:63
(Diff revision 2)
>            NS_SUCCEEDED(aURI1->Equals(aURI2, &eq)) && // not equal on fail
>            eq);
>  }
>  
>  static bool
>  EqualURIs(mozilla::css::URLValue *aURI1, mozilla::css::URLValue *aURI2)

Let's rename this function since it's operating a bit differently from the other EqualURIs.

Why don't we need to do this in nsCSSFrameConstructor.cpp's comaprison of mBinding too?

Comment 23

[Cameron McCormack (:heycam)]

(Or it might not be re-used MozReview-Commit-IDs but just the fact we have a new patch in the same position in the patch queue, after the other ones were removed.)

Comment 24

[Bobby Holley (:bholley)]

(In reply to Cameron McCormack (:heycam) from comment #23)
> (Or it might not be re-used MozReview-Commit-IDs but just the fact we have a
> new patch in the same position in the patch queue, after the other ones were
> removed.)

I'm pretty sure that they use commit ids - that's the whole point of them, right?

Comment 25

[Emilio Cobos Álvarez (:emilio)]

Comment on attachment 8778610 [details]
Bug 1292930: Handle the case of having unresolved URIs in nsStyleDisplay::mBinding.

https://reviewboard.mozilla.org/r/69830/#review68988

> Let's rename this function since it's operating a bit differently from the other EqualURIs.
> 
> Why don't we need to do this in nsCSSFrameConstructor.cpp's comaprison of mBinding too?

I was not hitting that anymore, presumably because with this patch we don't generate ReconstructFrame hints that much.

Comment 26

[Cameron McCormack (:heycam)]

Comment on attachment 8778610 [details]
Bug 1292930: Handle the case of having unresolved URIs in nsStyleDisplay::mBinding.

https://reviewboard.mozilla.org/r/69830/#review69292

OK.  r=me with EqualsURI renamed.

Comment 27

[Cameron McCormack (:heycam)]

Comment on attachment 8778610 [details]
Bug 1292930: Handle the case of having unresolved URIs in nsStyleDisplay::mBinding.

https://reviewboard.mozilla.org/r/69830/#review69292

EqualURIs rather.

Comment 28

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/mozilla-inbound/rev/2d422399bc48
Handle the case of having unresolved URIs in nsStyleDisplay::mBinding. r=heycam

Comment 29

[Wes Kocher (:KWierso) (Not reading bugmail; email directly if needed)]

https://hg.mozilla.org/mozilla-central/rev/2d422399bc48