script: Only register one image callback per CSS image in use.#36612
Merged
jdm merged 1 commit intoservo:mainfrom Apr 19, 2025
Merged
script: Only register one image callback per CSS image in use.#36612jdm merged 1 commit intoservo:mainfrom
jdm merged 1 commit intoservo:mainfrom
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Signed-off-by: Josh Matthews <[email protected]>
mrobinson
approved these changes
Apr 19, 2025
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When layout encounters a CSS image, the script thread is responsible for fetching the image from the image cache. When the image is not yet available, the script thread creates image cache listeners to perform actions in response to future updates from the image cache.
In the current implementation, a cache listener would iterate over all nodes using a particular image and mark them as dirty. However, we mistakenly added one cache listener per node, leading to n^2 runtime while performing lots of redundant work. For cases like #36480 with over 1000 elements using the same image, this led to a completely unresponsive script thread.
Testing: Manual testing on the provided testcase, and a new WPT test that times out without this PR's changes.
Fixes: #36480