221252 2021-02-02 04:46:55 -0800 Assertion failure in Debug build blocks webpage rendering 2021-02-09 04:47:54 -0800 1 1 1 Unclassified WebKit Layout and Rendering WebKit Local Build PC Linux NEW https://bugs.webkit.org/show_bug.cgi?id=191962 https://bugs.webkit.org/show_bug.cgi?id=166008 InRadar P2 Minor --- 1 estea webkit-unassigned bfulgham estea simon.fraser webkit-bug-importer zalan oldest_to_newest 1724618 0 estea 2021-02-02 04:46:55 -0800 Overview: Assertion failure from: ASSERT(willBeComposited == needsToBeComposited(layer, queryData)); in rendering/RenderLayerCompositor.cpp stops the rendering of some webpages in MiniBrowser in Debug builds. The reason seems to be that the layers are asynchronously updated since the time willBeComposited is set and needsToBeComposited is called, and so events like scrolling overflow can cause assertion failure. The assertion should be moved right after willBeComposited is set. Steps to reproduce: Build WPE/Webkit in Debug mode and run MiniBrowser with https://www.igalia.com. Results: An empty page will be displayed. Expected Result: The webpage to be displayed. Proposed Fix: If the assertion is moved right after: if (layer.needsPostLayoutCompositingUpdate() || compositingState.fullPaintOrderTraversalRequired || compositingState.descendantsRequireCompositingUpdate) { layer.setIndirectCompositingReason(IndirectCompositingReason::None); willBeComposited = needsToBeComposited(layer, queryData); } the page will appear fine in MiniBrowser. Additional Information: Bug was spotted on Linux/X11 using nested Weston and running MiniBrowser like this: ./run-wpe-x11 <path_to_minibrowser_installdir>MiniBrowser https://www.igalia.com 1724619 1 418983 estea 2021-02-02 05:03:54 -0800 Created attachment 418983 proposed patch Proposed patch: move the assertion before all other checks that might change the needsToBeComposited(layer, queryData) value. 1724717 2 418983 simon.fraser 2021-02-02 09:58:50 -0800 Comment on attachment 418983 proposed patch The whole point of this assertion is to check that willBeComposited has the correct value. 1724888 3 estea 2021-02-02 14:23:07 -0800 (In reply to Simon Fraser (smfr) from comment #2) > Comment on attachment 418983 [details] > proposed patch > > The whole point of this assertion is to check that willBeComposited has the > correct value. Thank you for your reply, What I tried to prevent by moving the assertion earlier was the case that needsToBeComposited() is different from willBeComposited value without that being a bug. I noticed that willBeComposited and needsToBeComposited have the same value at the beginning of the function but further down there are cases that change the value of the variable and so, the same check fails. I thought that the willBeComposited changes were correctly made and so I assumed that the problem is that the assertion failure takes place too late after the changes. My description was not so clear, sorry. What are your thoughts on this? Thanks in advance! 1724900 4 simon.fraser 2021-02-02 14:37:38 -0800 If this assertion fires, it means that some state changed that affected the answer to needsToBeComposited() inside this function, which implies there's some side-effect. If willBeComposited does not match needsToBeComposited() then the behavior is wrong. You should go looking for why needsToBeComposited() changes its answer unexpectedly. 1724910 5 estea 2021-02-02 15:05:34 -0800 (In reply to Simon Fraser (smfr) from comment #4) > If this assertion fires, it means that some state changed that affected the > answer to needsToBeComposited() inside this function, which implies there's > some side-effect. If willBeComposited does not match needsToBeComposited() > then the behavior is wrong. > > You should go looking for why needsToBeComposited() changes its answer > unexpectedly. Alright, thank you very much! needsToBeComposited() was true because compositing was required for overflow scrolling (although I saw the assertion failure in some other cases too). I hadn't realized this is unexpected, I will investigate it further. 1727005 6 webkit-bug-importer 2021-02-09 04:47:54 -0800 <rdar://problem/74138081> 418983 2021-02-02 05:03:54 -0800 2021-02-02 09:58:50 -0800 proposed patch 0001-rendering-Moved-assertion-that-was-blocking-the-rend.patch text/plain 2057 estea RnJvbSA4NDc0YTNiNThhZjgxYmU3YzMxNmQxNTBiODUyNGFjMTQ1MjQ3M2JhIE1vbiBTZXAgMTcg MDA6MDA6MDAgMjAwMQpGcm9tOiBFbGVuaSBNYXJpYSBTdGVhIDxlc3RlYUBpZ2FsaWEuY29tPgpE YXRlOiBUdWUsIDIgRmViIDIwMjEgMTM6MjU6MzYgKzAyMDAKU3ViamVjdDogW1BBVENIXSByZW5k ZXJpbmc6IE1vdmVkIGFzc2VydGlvbiB0aGF0IHdhcyBibG9ja2luZyB0aGUgcmVuZGVyaW5nIGlu CiBEZWJ1ZyBtb2RlCgp3aWxsQmVDb21wb3NpdGVkIGNhbiBtYXRjaCBuZWVkc1RvQmVDb21wb3Np dGVkIG9ubHkgcmlnaHQgYWZ0ZXIgaXMgc2V0LgpJZiB0aGUgY2hlY2sgaXMgcGVyZm9ybWVkIGxh dGVyIGFzeW5jaHJvbm91cyBldmVudHMgbGlrZSBzY3JvbGxpbmcKb3ZlcmZsb3cgbWlnaHQgaGF2 ZSBhbHRlciBuZWVkc1RvQmVDb21wb3NpdGVkIHJldHVybiB2YWx1ZS4KCkZpeDogaHR0cHM6Ly9i dWdzLndlYmtpdC5vcmcvc2hvd19idWcuY2dpP2lkPTIyMTI1MgoKUGxlYXNlIGVudGVyIHRoZSBj b21taXQgbWVzc2FnZSBmb3IgeW91ciBjaGFuZ2VzLiBMaW5lcyBzdGFydGluZwotLS0KIFNvdXJj ZS9XZWJDb3JlL3JlbmRlcmluZy9SZW5kZXJMYXllckNvbXBvc2l0b3IuY3BwIHwgNCArKy0tCiAx IGZpbGUgY2hhbmdlZCwgMiBpbnNlcnRpb25zKCspLCAyIGRlbGV0aW9ucygtKQoKZGlmZiAtLWdp dCBhL1NvdXJjZS9XZWJDb3JlL3JlbmRlcmluZy9SZW5kZXJMYXllckNvbXBvc2l0b3IuY3BwIGIv U291cmNlL1dlYkNvcmUvcmVuZGVyaW5nL1JlbmRlckxheWVyQ29tcG9zaXRvci5jcHAKaW5kZXgg OWM4MDk0Nzg4NDhjLi4wYTQzY2YxNGY3M2UgMTAwNjQ0Ci0tLSBhL1NvdXJjZS9XZWJDb3JlL3Jl bmRlcmluZy9SZW5kZXJMYXllckNvbXBvc2l0b3IuY3BwCisrKyBiL1NvdXJjZS9XZWJDb3JlL3Jl bmRlcmluZy9SZW5kZXJMYXllckNvbXBvc2l0b3IuY3BwCkBAIC05NTQsNiArOTU0LDggQEAgdm9p ZCBSZW5kZXJMYXllckNvbXBvc2l0b3I6OmNvbXB1dGVDb21wb3NpdGluZ1JlcXVpcmVtZW50cyhS ZW5kZXJMYXllciogYW5jZXN0b3IKICAgICAgICAgd2lsbEJlQ29tcG9zaXRlZCA9IG5lZWRzVG9C ZUNvbXBvc2l0ZWQobGF5ZXIsIHF1ZXJ5RGF0YSk7CiAgICAgfQogCisgICAgQVNTRVJUKHdpbGxC ZUNvbXBvc2l0ZWQgPT0gbmVlZHNUb0JlQ29tcG9zaXRlZChsYXllciwgcXVlcnlEYXRhKSk7CisK ICAgICBib29sIGxheWVyUGFpbnRzSW50b1Byb3ZpZGVkQmFja2luZyA9IGZhbHNlOwogICAgIGlm ICghd2lsbEJlQ29tcG9zaXRlZCAmJiBjb21wb3NpdGluZ1N0YXRlLnN1YnRyZWVJc0NvbXBvc2l0 aW5nICYmIGJhY2tpbmdTaGFyaW5nU3RhdGUuYmFja2luZ1Byb3ZpZGVyQ2FuZGlkYXRlKCkgJiYg Y2FuQmVDb21wb3NpdGVkKGxheWVyKSAmJiBiYWNraW5nUHJvdmlkZXJMYXllckNhbkluY2x1ZGVM YXllcigqYmFja2luZ1NoYXJpbmdTdGF0ZS5iYWNraW5nUHJvdmlkZXJDYW5kaWRhdGUoKSwgbGF5 ZXIpKSB7CiAgICAgICAgIGJhY2tpbmdTaGFyaW5nU3RhdGUuYXBwZW5kU2hhcmluZ0xheWVyKGxh eWVyKTsKQEAgLTExMjMsOCArMTEyNSw2IEBAIHZvaWQgUmVuZGVyTGF5ZXJDb21wb3NpdG9yOjpj b21wdXRlQ29tcG9zaXRpbmdSZXF1aXJlbWVudHMoUmVuZGVyTGF5ZXIqIGFuY2VzdG9yCiAjZW5k aWYKICAgICB9CiAKLSAgICBBU1NFUlQod2lsbEJlQ29tcG9zaXRlZCA9PSBuZWVkc1RvQmVDb21w b3NpdGVkKGxheWVyLCBxdWVyeURhdGEpKTsKLQogICAgIC8vIENyZWF0ZSBvciBkZXN0cm95IGJh Y2tpbmcgaGVyZS4gSG93ZXZlciwgd2UgY2FuJ3QgdXBkYXRlIGdlb21ldHJ5IGJlY2F1c2UgbGF5 ZXJzIGFib3ZlIHVzIG1heSBiZWNvbWUgY29tcG9zaXRlZAogICAgIC8vIGR1cmluZyBwb3N0LW9y ZGVyIHRyYXZlcnNhbCAoZS5nLiBmb3IgY2xpcHBpbmcpLgogICAgIGlmICh1cGRhdGVCYWNraW5n KGxheWVyLCBxdWVyeURhdGEsICZiYWNraW5nU2hhcmluZ1N0YXRlLCB3aWxsQmVDb21wb3NpdGVk ID8gQmFja2luZ1JlcXVpcmVkOjpZZXMgOiBCYWNraW5nUmVxdWlyZWQ6Ok5vKSkgewotLSAKMi4z MC4wCgo=