LibWeb: Missing layout updates causes failed subtest in css-masking/animations/clip-interpolation

[shannonbooth]

To reproduce, add a very updatey call to update_layout() inthe HTMLElement attribute changed steps:

diff --git a/Libraries/LibWeb/HTML/HTMLElement.cpp b/Libraries/LibWeb/HTML/HTMLElement.cpp
index 7aaaf60f76c..892dc141f65 100644
--- a/Libraries/LibWeb/HTML/HTMLElement.cpp
+++ b/Libraries/LibWeb/HTML/HTMLElement.cpp
@@ -598,6 +598,8 @@ void HTMLElement::attribute_changed(FlyString const& name, Optional<String> cons
     Base::attribute_changed(name, old_value, value, namespace_);
     HTMLOrSVGElement::attribute_changed(name, old_value, value, namespace_);

+    document().update_layout();
+
     if (name == HTML::AttributeNames::contenteditable) {
         if (!value.has_value()) {
             // No value maps to the "inherit" state.

And observe that one extra test passes in:

--- Tests/LibWeb/Text/expected/./wpt-import/css/css-masking/animations/clip-interpolation.txt
+++ Tests/LibWeb/Text/expected/./wpt-import/css/css-masking/animations/clip-interpolation.txt
@@ -2,8 +2,8 @@

 Found 324 tests

-248 Pass
-76 Fail
+249 Pass
+75 Fail
 Fail   CSS Transitions: property <clip> from neutral to [rect(20px, 20px, 20px, 20px)] at (-1) should be [rect(-20px 180px -20px 180px)]
 Fail   CSS Transitions: property <clip> from neutral to [rect(20px, 20px, 20px, 20px)] at (0) should be [rect(0px 100px 0px 100px)]
 Fail   CSS Transitions: property <clip> from neutral to [rect(20px, 20px, 20px, 20px)] at (0.25) should be [rect(5px 80px 5px 80px)]
@@ -21,7 +21,7 @@
 Fail   CSS Animations: property <clip> from neutral to [rect(20px, 20px, 20px, 20px)] at (0.25) should be [rect(5px 80px 5px 80px)]
 Fail   CSS Animations: property <clip> from neutral to [rect(20px, 20px, 20px, 20px)] at (0.75) should be [rect(15px 40px 15px 40px)]
 Pass   CSS Animations: property <clip> from neutral to [rect(20px, 20px, 20px, 20px)] at (1) should be [rect(20px 20px 20px 20px)]
-Fail   CSS Animations: property <clip> from neutral to [rect(20px, 20px, 20px, 20px)] at (2) should be [rect(40px -60px 40px -60px)]
+Pass   CSS Animations: property <clip> from neutral to [rect(20px, 20px, 20px, 20px)] at (2) should be [rect(40px -60px 40px -60px)]
 Fail   Web Animations: property <clip> from neutral to [rect(20px, 20px, 20px, 20px)] at (-1) should be [rect(-20px 180px -20px 180px)]
 Fail   Web Animations: property <clip> from neutral to [rect(20px, 20px, 20px, 20px)] at (0) should be [rect(0px 100px 0px 100px)]
 Fail   Web Animations: property <clip> from neutral to [rect(20px, 20px, 20px, 20px)] at (0.25) should be [rect(5px 80px 5px 80px)]

[awesomekling]

Sounds like whichever API is producing the incorrect result needs to do a bit of update_layout(). Doing it on every attribute change is obviously excessive :)

[shannonbooth]

Yeah, that's why I reported the issue, I haven't spent the time digging into what is missing it 😆 I just happened to notice it from that.