The idea of these are not to penalize legit uses of scroll anchoring, and
catching pathological cases fast.
The current algorithm I thought of is just whether the average of all the
consecutive scroll anchoring adjustments is less than a given threshold.
If the average adjustment is close to zero and the user is not scrolling, it
means that we're not making much progress.
It is important that zero adjustments don't get counted, since those are common
during window resizes and don't have side-effects anyway.
Exact number may need tuning, let me know if you want it
nightly-and-early-beta-only for now or something.
Depends on D51038
Differential Revision: https://phabricator.services.mozilla.com/D51024
--HG--
extra : moz-landing-system : lando
This commit changes ScrollAnchorContainer to store the offset between the scroll anchoring
bounding rect start edge and the scroll-port start edge in the block axis of the scroll frame.
The logic to clamp the negative portions of scroll anchor bounding rect is also amended
to only clamp the portion that is beyond the border start edge in the block axis of the
scroll frame.
Differential Revision: https://phabricator.services.mozilla.com/D16757
--HG--
extra : rebase_source : 43b5bc4ece7f90cb38e3a7186a764d9cddac90f9
extra : source : f26d953d76fcfb02a5fa46cb62e389f852592fe9
This commit implements the first half of the heuristics to detect style changes
that could lead to feedback loops with scroll anchoring. [1]
When these style changes are made, a suppression flag is added to the anchor
container to ignore any adjustments that would be made at the next layout flush
and to invalidate the anchor at that time.
[1] https://drafts.csswg.org/css-scroll-anchoring/#suppression-triggers
Differential Revision: https://phabricator.services.mozilla.com/D13271
--HG--
extra : rebase_source : db0bf373e51325b7ef537c4c245ede4b4219d0d7
extra : source : d9445a5f3458b560fbdb7aee5faabb5a7a9327f3
This commit implements anchor offset adjustment. When the position of a frame
that is an anchor is changed during reflow, we notify the anchor container. The
anchor container will then post a reflow callback.
Then when reflow is completed, the anchor container will perform a scroll to
keep the anchor node in the same relative position.
Differential Revision: https://phabricator.services.mozilla.com/D13270
--HG--
extra : rebase_source : 9d40a5d5b73777d0da3799f162eeb85bb8e6d8f0
extra : source : d9052f7b34d9857863b66d64797f8b0b82504bec
This commit implements candidate selection for a scroll frame using a frame tree
traversal. It roughly tries to follow the algorithm given in the scroll
anchoring draft specification, adapted to operate on the frame tree [1].
Some details, such as not selecting an anchor if the user hasn't scrolled are
not currently in the specification but will be to match Blink's implementation.
Once a scroll anchor has been selected, we maintain a bit on it and its ancestor
frame's states. This is used in a later commit to detect changes to position
during a reflow so the scroll frame can perform an adjustment.
A scroll anchor will be invalidated when the user scrolls the frame or the
scroll anchor is destroyed. Later commits will add logic to drive selection and
invalidation appropriately.
[1] https://drafts.csswg.org/css-scroll-anchoring/#anchor-node-selection
Differential Revision: https://phabricator.services.mozilla.com/D13268
--HG--
extra : rebase_source : e05ba48662aafef5957322def33ddc5d93f3ca5a
extra : source : bdb766faa8679386bf4e9740781262ea4bb36544
This commit adds a barebones class called 'ScrollAnchorContainer' that will
contain most of the logic for scroll anchoring. It is owned as a member of
ScrollFrameHelper, and has the same lifetime.
Differential Revision: https://phabricator.services.mozilla.com/D13267
--HG--
extra : rebase_source : 41f6f7691af60401f18f98a89f1878cfad2e74d3
extra : source : 3033401ef320414ef5f489c53526d015c38a89d7
This commit implements the first half of the heuristics to detect style changes
that could lead to feedback loops with scroll anchoring. [1]
When these style changes are made, a suppression flag is added to the anchor
container to ignore any adjustments that would be made at the next layout flush
and to invalidate the anchor at that time.
[1] https://drafts.csswg.org/css-scroll-anchoring/#suppression-triggers
Differential Revision: https://phabricator.services.mozilla.com/D13271
--HG--
extra : rebase_source : 7919443bdad49ce3623e5b082decb4f5c4a54158
extra : histedit_source : a2283cc31060103ef0929ae11624b45f95113810
This commit implements anchor offset adjustment. When the position of a frame
that is an anchor is changed during reflow, we notify the anchor container. The
anchor container will then post a reflow callback.
Then when reflow is completed, the anchor container will perform a scroll to
keep the anchor node in the same relative position.
Differential Revision: https://phabricator.services.mozilla.com/D13270
--HG--
extra : rebase_source : 44797fcf6585d5912f83baea90a8e554f39618b5
extra : histedit_source : c4354ba8aac99e0d083f40b515369db6a95f997d
This commit implements candidate selection for a scroll frame using a frame tree
traversal. It roughly tries to follow the algorithm given in the scroll
anchoring draft specification, adapted to operate on the frame tree [1].
Some details, such as not selecting an anchor if the user hasn't scrolled are
not currently in the specification but will be to match Blink's implementation.
Once a scroll anchor has been selected, we maintain a bit on it and its ancestor
frame's states. This is used in a later commit to detect changes to position
during a reflow so the scroll frame can perform an adjustment.
A scroll anchor will be invalidated when the user scrolls the frame or the
scroll anchor is destroyed. Later commits will add logic to drive selection and
invalidation appropriately.
[1] https://drafts.csswg.org/css-scroll-anchoring/#anchor-node-selection
Differential Revision: https://phabricator.services.mozilla.com/D13268
--HG--
extra : rebase_source : 02ace6a966dd1c4bd42b7472501d05c412d6deb8
extra : histedit_source : 84bed6b2d13a308f4aea91c631b8792df293c76a
This commit adds a barebones class called 'ScrollAnchorContainer' that will
contain most of the logic for scroll anchoring. It is owned as a member of
ScrollFrameHelper, and has the same lifetime.
Differential Revision: https://phabricator.services.mozilla.com/D13267
--HG--
extra : rebase_source : 4d58b51aa6b893392d7c152d27750ebda059f784
extra : histedit_source : 9a2841931c47c4358e15d2fa6514ed347e3d0dad
Emilio Cobos Álvarez
Daniel Holbert
Ryan Hunt
Bogdan Tara