1245979 - mfbt Function lacks functionality needed for interoperating with Skia

Status: RESOLVED FIXED

(Core :: MFBT, defect)

Description

[Lee Salzman [:lsalzman]]

When trying to shim mfbt Function in place of std::function inside Skia, I ran into the following deficiencies:

1) Skia copies std::function by value in several places, and we need a default copy constructor
2) Skia converts it to bool and we have no bool conversion operator
3) Skia initializes it with nullptr and we had no constructor for that

Comment 1

[Lee Salzman [:lsalzman]]

Attachment: make mfbt Function reference-counted so that it can be cheaply copied for compatibility with Skia

This patch addresses all the listed issues and makes Skia compile cleanly.

Comment 2

[Nathan Froyd [:froydnj]]

Comment on attachment 8716021 [details] [diff] [review]
make mfbt Function reference-counted so that it can be cheaply copied for compatibility with Skia

Review of attachment 8716021 [details] [diff] [review]:
-----------------------------------------------------------------

r=me  It's not great that we're making Function have higher overhead; OTOH, Function should be going away soonish and it's not widely used in the first place.

::: mfbt/Function.h
@@ +45,3 @@
>  {
>  public:
> +  MOZ_DECLARE_REFCOUNTED_VIRTUAL_TYPENAME(FunctionImplBase)

Does this need to be virtual?  I guess it doesn't matter that much for debug builds...

Comment 3

[Lee Salzman [:lsalzman]]

Try builds: https://treeherder.mozilla.org/#/jobs?repo=try&revision=0c70baa741c9

Comment 4

[Pulsebot]

https://hg.mozilla.org/integration/mozilla-inbound/rev/915eba505316

Comment 5

[Phil Ringnalda (:philor)]

https://hg.mozilla.org/mozilla-central/rev/915eba505316