Bug 250899 – Cocoa readPixels is slower in GPUP WebGL than in-process WebGL

• Component: WebGL
• Status: RESOLVED FIXED

[Kimmo Kinnunen]

GPUP WebGL readPixels is slower than in process
Should and could be improved

[Radar WebKit Bug Importer]

<rdar://problem/104475196>

[Kimmo Kinnunen]

Pull request: https://github.com/WebKit/WebKit/pull/9029

[EWS]

Committed 259550@main (4fbc3e1ca2be): <https://commits.webkit.org/259550@main>

Reviewed commits have been landed. Closing PR #9029 and removing active labels.

[Michael Catanzaro]

Hi, this won't work because the object is noncopyable on Unix:

/home/mcatanzaro/Projects/WebKit/Source/WebKit/Platform/SharedMemory.h:70:9: error: explicitly defaulted copy constructor is implicitly deleted [-Werror,-Wdefaulted-function-deleted]
        Handle(const Handle&) = default;
        ^
/home/mcatanzaro/Projects/WebKit/Source/WebKit/Platform/SharedMemory.h:98:36: note: copy constructor of 'Handle' is implicitly deleted because field 'm_handle' has a deleted copy constructor
        mutable UnixFileDescriptor m_handle;
                                   ^
/home/mcatanzaro/Projects/WebKit/WebKitBuild/gtk4/WTF/Headers/wtf/unix/UnixFileDescriptor.h:37:26: note: 'UnixFileDescriptor' has been explicitly marked deleted here
    WTF_MAKE_NONCOPYABLE(UnixFileDescriptor);

[Michael Catanzaro]

I'll try this:

diff --git a/Source/WebKit/Platform/SharedMemory.h b/Source/WebKit/Platform/SharedMemory.h
index 45a30661faa3..ff78942ba3d8 100644
--- a/Source/WebKit/Platform/SharedMemory.h
+++ b/Source/WebKit/Platform/SharedMemory.h
@@ -67,11 +67,14 @@ public:
     class Handle {
     public:
         Handle() = default;
-        Handle(const Handle&) = default;
         Handle(Handle&&) = default;
-        Handle& operator=(const Handle&) = default;
         Handle& operator=(Handle&&) = default;
 
+#if PLATFORM(COCOA)
+        Handle(const Handle&) = default;
+        Handle& operator=(const Handle&) = default;
+#endif
+
         bool isNull() const;
 
         size_t size() const { return m_size; }

and see if that works.

[Michael Catanzaro]

So that does seem to work. It doesn't feel great, though.

[Michael Catanzaro]

Zan has a better solution in https://github.com/WebKit/WebKit/pull/9310

[Michael Catanzaro]

(In reply to Michael Catanzaro from comment #7)
> Zan has a better solution in https://github.com/WebKit/WebKit/pull/9310

Well, I wound up leaving some negative feedback there.

Kimmo, any opinion on what to do here?