291217 2025-04-07 12:19:02 -0700 REGRESSION(292977@main): [Win] nested tasks are not dispatched 2025-04-07 23:23:18 -0700 1 1 1 Unclassified WebKit Platform WebKit Nightly Build PC Windows 11 RESOLVED FIXED https://bugs.webkit.org/show_bug.cgi?id=284823 InRadar P2 Normal --- 1 yurys webkit-unassigned dpino fujii ian.grunert webkit-bug-importer ysuzuki oldest_to_newest 2109490 0 yurys 2025-04-07 12:19:02 -0700 After https://commits.webkit.org/292977@main nested tasks on main thread are not dispatched. Try inserting the following code somewhere in the UI process, e.g. in `WebPageInspectorController` constructor. `step 2 callback` is printed, but `step 3 callback` is not. ``` fprintf(stderr, "step 1\n"); RunLoop::main().dispatch([] { fprintf(stderr, "step 2 callback\n"); RunLoop::main().dispatchAfter(Seconds(0.1), [] { fprintf(stderr, "step 3 callback\n"); }); }); ``` It broke Playwright screencast and video recording functionality. 2109525 1 fujii 2025-04-07 14:19:06 -0700 The run loop of UI process main thread is run by the application, not by WTF::RunLoop::run. https://github.com/WebKit/WebKit/blob/2bebfdc1ea6d02362f3b549004940f2ef8ea28e2/Tools/MiniBrowser/win/WinMain.cpp#L81-L91 I think we should revert 292977@main. 2109526 2 474861 fujii 2025-04-07 14:19:51 -0700 Created attachment 474861 test patch for MiniBrowser 2109531 3 ian.grunert 2025-04-07 14:33:01 -0700 Yeah, this used to work because the main thread's run loop and the WTF run loop both processed the WM_TIMER messages. Agree we should revert for now. We might be able to do something similar to PlayStation's MiniBrowser and use the WTF run loop in MiniBrowser, but I'd rather revert and we can land that later. 2109547 4 fujii 2025-04-07 14:47:06 -0700 (In reply to Ian Grunert from comment #3) > Agree we should revert for now. We might be able to do something similar to > PlayStation's MiniBrowser and use the WTF run loop in MiniBrowser, but I'd > rather revert and we can land that later. The run loop is a bit customized. https://github.com/WebKit/WebKit/blob/2bebfdc1ea6d02362f3b549004940f2ef8ea28e2/Tools/MiniBrowser/win/WinMain.cpp#L85-L86 Another customize is needed if we add a modeless dialog. https://learn.microsoft.com/en-us/windows/win32/dlgbox/using-dialog-boxes#creating-a-modeless-dialog-box 2109548 5 fujii 2025-04-07 14:47:16 -0700 293380@main reverted 292977@main. 2109549 6 webkit-bug-importer 2025-04-07 14:48:15 -0700 <rdar://problem/148773454> 474861 2025-04-07 14:19:51 -0700 2025-04-07 14:19:51 -0700 test patch for MiniBrowser t.patch text/plain 734 fujii ZGlmZiAtLWdpdCBhL1NvdXJjZS9XZWJLaXQvVUlQcm9jZXNzL3dpbi9XZWJWaWV3LmNwcCBiL1Nv dXJjZS9XZWJLaXQvVUlQcm9jZXNzL3dpbi9XZWJWaWV3LmNwcA0KaW5kZXggNTE4MGRhM2VjMjJk Li41ZjgwYTJiYzk4NWYgMTAwNjQ0DQotLS0gYS9Tb3VyY2UvV2ViS2l0L1VJUHJvY2Vzcy93aW4v V2ViVmlldy5jcHANCisrKyBiL1NvdXJjZS9XZWJLaXQvVUlQcm9jZXNzL3dpbi9XZWJWaWV3LmNw cA0KQEAgLTM4Niw2ICszODYsMTQgQEAgTFJFU1VMVCBXZWJWaWV3OjpvbldoZWVsRXZlbnQoSFdO RCBoV25kLCBVSU5UIG1lc3NhZ2UsIFdQQVJBTSB3UGFyYW0sIExQQVJBTSBsUGENCiANCiAgICAg bV9wYWdlLT5oYW5kbGVOYXRpdmVXaGVlbEV2ZW50KHdoZWVsRXZlbnQpOw0KIA0KKyAgICBBTFdB WVNfTE9HX1dJVEhfU1RSRUFNKHN0cmVhbSA8PCAic3RlcCAxIik7DQorICAgIFJ1bkxvb3A6Om1h aW4oKS5kaXNwYXRjaChbXSB7DQorICAgICAgICBBTFdBWVNfTE9HX1dJVEhfU1RSRUFNKHN0cmVh bSA8PCAic3RlcCAyIGNhbGxiYWNrIik7DQorICAgICAgICBSdW5Mb29wOjptYWluKCkuZGlzcGF0 Y2hBZnRlcihTZWNvbmRzKDAuMSksIFtdIHsNCisgICAgICAgICAgICBBTFdBWVNfTE9HX1dJVEhf U1RSRUFNKHN0cmVhbSA8PCAic3RlcCAzIGNhbGxiYWNrIik7DQorICAgICAgICB9KTsNCisgICAg fSk7DQorDQogICAgIGhhbmRsZWQgPSB0cnVlOw0KICAgICByZXR1cm4gMDsNCiB9DQo=