[Gecko Bug 1686961] Don't cache ascent in CachedBAxisMeasurement. #29902
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CachedBAxisMeasurement::mAscent caches the ascent of a flex item after the measuring reflow, but the ascent may change after the final reflow if the item is stretched and does some vertical alignment internally. However, we don't cache the new ascent. Therefore, when we reflow the item incrementally, if the CachedBAxisMeasurement::Key is valid, we just skip the measuring reflow, and retrieve the wrong ascent from the cache. Instead of fixing this bug by updating the cached ascent or rejecting the ascent cache for a stretching flex item in block axis, this patch removes the cache and sets ReflowOutput's BlockStartAscent() to the flex item after the item's measuring reflow. (We've done the same after the item's final reflow.) If the ascent is ReflowOutput::ASK_FOR_BASELINE, we resolve in FlexItem::ResolvedAscent() anyway. Differential Revision: https://phabricator.services.mozilla.com/D121404 bugzilla-url: https://bugzilla.mozilla.org/show_bug.cgi?id=1686961 gecko-commit: 7ead777c03edcf446a3715886647fe015c8a3623 gecko-reviewers: dholbert
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CachedBAxisMeasurement::mAscent caches the ascent of a flex item after
the measuring reflow, but the ascent may change after the final reflow
if the item is stretched and does some vertical alignment internally.
However, we don't cache the new ascent. Therefore, when we reflow the
item incrementally, if the CachedBAxisMeasurement::Key is valid, we just
skip the measuring reflow, and retrieve the wrong ascent from the cache.
Instead of fixing this bug by updating the cached ascent or rejecting
the ascent cache for a stretching flex item in block axis, this patch
removes the cache and sets ReflowOutput's BlockStartAscent() to the flex
item after the item's measuring reflow. (We've done the same after the
item's final reflow.) If the ascent is ReflowOutput::ASK_FOR_BASELINE,
we resolve in FlexItem::ResolvedAscent() anyway.
Differential Revision: https://phabricator.services.mozilla.com/D121404
bugzilla-url: https://bugzilla.mozilla.org/show_bug.cgi?id=1686961
gecko-commit: 20e053eb704a67f75baa61342033128407797b01
gecko-reviewers: dholbert