[line-clamp] Always clamp immediately after a line box #48482
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In our initial implementation of `line-clamp: auto`, we allowed clamping after lineless boxes, in order to better match the behavior of `line-clamp` as it follows from the spec's `continue: discard` model, even though our implementation uses a different model which is not yet in the specification (see w3c/csswg-drafts#7708). However, in hallway conversations in TPAC 2024, we agreed that it would be better for this model to instead only allow clamping immediately after a line. If the first line does not fit, we calmp at the first line even if that overflows the clamp height. If there are no lines, we do not clamp. This patch implements this. Additionally, a previous patch (https://crrev.com/c/5868971) had increased the memory size of `LineClampData` from 8 to 20 bytes, causing a memory regression. This patch shrinks it to 12 bytes, since `LineClampData` no longer needs to keep track of how many block boxes there are between the last line and the clmap point, and now OOFs after the clamped line behave the same when clamping by a number of lines or by a height, so there is no need for a flag to distinguish these behaviors. This patch also adds a size assertion for `LineClampData`. This patch also changes or removes some WPT tests that were written assuming the previous behavior. Bug: 40336192, 368114054 Change-Id: I8c8afebb5dc566de92112cee2fcf24a2e60b42c8 Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5904459 Reviewed-by: Ian Kilpatrick <[email protected]> Commit-Queue: Andreu Botella <[email protected]> Cr-Commit-Position: refs/heads/main@{#1364495}
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In our initial implementation of
line-clamp: auto, we allowedclamping after lineless boxes, in order to better match the behavior
of
line-clampas it follows from the spec'scontinue: discardmodel, even though our implementation uses a different model which is
not yet in the specification (see
w3c/csswg-drafts#7708).
However, in hallway conversations in TPAC 2024, we agreed that it
would be better for this model to instead only allow clamping
immediately after a line. If the first line does not fit, we calmp at
the first line even if that overflows the clamp height. If there are
no lines, we do not clamp. This patch implements this.
Additionally, a previous patch (https://crrev.com/c/5868971) had
increased the memory size of
LineClampDatafrom 8 to 20 bytes,causing a memory regression. This patch shrinks it to 12 bytes, since
LineClampDatano longer needs to keep track of how many block boxesthere are between the last line and the clmap point, and now OOFs
after the clamped line behave the same when clamping by a number of
lines or by a height, so there is no need for a flag to distinguish
these behaviors. This patch also adds a size assertion for
LineClampData.This patch also changes or removes some WPT tests that were written
assuming the previous behavior.
Bug: 40336192, 368114054
Change-Id: I8c8afebb5dc566de92112cee2fcf24a2e60b42c8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5904459
Reviewed-by: Ian Kilpatrick <[email protected]>
Commit-Queue: Andreu Botella <[email protected]>
Cr-Commit-Position: refs/heads/main@{#1364495}