Bug 225878

Summary:	Replace non-ownership transfer requiring uses of WTF::Function to use WTF::ScopeLambda to avoid allocation of WTF::Function
Product:	WebKit	Reporter:	Sam Weinig <sam>
Component:	Web Template Framework	Assignee:	Nobody <webkit-unassigned>
Status:	NEW ---
Severity:	Normal	CC:	darin, fpizlo, webkit-bug-importer
Priority:	P2	Keywords:	InRadar
Version:	Other
Hardware:	Unspecified
OS:	Unspecified

Description Sam Weinig 2021-05-17 10:28:13 PDT

Using WTF::Function (or std::function) in cases where are using a functor as an abstraction to allow scope customization, iteration or predicate functions is wasteful. We should instead be using the non-allocating WTF::ScopedLambda. 

Some examples in WebCore are:
- the traverseSubresources() functions on various classes.
- readURLsFromPasteboardAsString() in DataTransfer.cpp
- Document::forEachMediaElement()
- etc.

Comment 1 Darin Adler 2021-05-17 23:34:09 PDT

Grep for "const Function&" perhaps to find a lot of these?

Comment 2 Darin Adler 2021-05-17 23:34:31 PDT

Is there a reason this class needs to be named "lambda" and not "function"?

Comment 3 Sam Weinig 2021-05-18 16:23:09 PDT

(In reply to Darin Adler from comment #2)
> Is there a reason this class needs to be named "lambda" and not "function"?

The patch that added it doesn't give much justification: https://trac.webkit.org/changeset/191705/webkit

Phil, any reason you chose "lambda" over "function" here?

Comment 4 Radar WebKit Bug Importer 2021-05-24 10:29:20 PDT

<rdar://problem/78407384>