[WIP] Handle nondeterministic paint worklet registration #20269
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When different global paint worklet scopes register document paint definitions of the same name with different parameters, the registration should be marked invalid [1]. Currently, Servo unconditionally overwrites any prior registrations when a new definition is received. To implement this check, this commit passes the parameters from the paint worklet global scope through to the layout thread. In the absence of support for parsing input arguments, the length of the input argument vector is passed as a placeholder. There's still a hole left in this implementation. When the act of registering a paint class in the first place is non-deterministic, a paint worklet global scope may attempt to invoke a paint callback for a class it has not registered. When this happens, the spec states that the document paint definition should be invalidated and an invalid image should be output [2]. Currently, only the latter happens. [1] https://drafts.css-houdini.org/css-paint-api/#registering-custom-paint [2] https://drafts.css-houdini.org/css-paint-api/#invoke-a-paint-callback
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Thanks for the pull request, and welcome! The Servo team is excited to review your changes, and you should hear from @mbrubeck (or someone else) soon. |
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Heads up! This PR modifies the following files:
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When a custom paint is not always registered when its module is run, a paint worklet global scope may receive a request to invoke a paint callback for a paint it does not have registered. When this happens, the document's paint definition should be invalidated.
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☔ The latest upstream changes (presumably #20900) made this pull request unmergeable. Please resolve the merge conflicts. |
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When different global paint worklet scopes register document paint definitions of the same name with different parameters, the registration should be marked invalid [1]. Currently, Servo unconditionally overwrites any prior registrations when a new definition is received.
This commit passes the parameters from the paint worklet global scope through to the layout thread so that they can be tracked there. In the absence of support for parsing input arguments, I'm passing the length of the input argument vector as a placeholder.
TODO:
When the act of registering a paint class in the first place is non-deterministic, a paint worklet global scope may attempt to invoke a paint callback for a class it has not registered. When this happens, the spec states that the document paint definition should be invalidated and an invalid image should be output [2]. Currently, only the latter happens.
No tests yet. It's pretty easy to generate conflicting registrations manually, but I don't think it's possible to make this fully deterministic without a stateful server component or something.
[1] https://drafts.css-houdini.org/css-paint-api/#registering-custom-paint
[2] https://drafts.css-houdini.org/css-paint-api/#invoke-a-paint-callback
./mach build -ddoes not report any errors./mach test-tidydoes not report any errorsThis change is