Render ::backdrop for replaced <object> elements

lilles · chromium-wpt-export-bot · commit fc4f94d9aff2 · 2025-08-07T07:14:21.000-07:00
The <object> element is blocked from rendering children if it is rendered as a replaced element. However, ::backdrop is rendered as a sibling in the top layer. This worked a lot of the time in Blink, because the first time we create the ::backdrop, we typically don't know yet what the <object> will render as, but doing mutations on the <object> while rendered in the top layer, including the anchor() style recalculations during layout, we would know what the layout object type is and incorrectly stop rendering the ::backdrop. Bug: 436811729 Change-Id: I94157ea2112dfd980ee25c83c7c284eaa857e3e2 Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6827402 Reviewed-by: Anders Hartvoll Ruud <andruud@chromium.org> Commit-Queue: Rune Lillesveen <futhark@chromium.org> Cr-Commit-Position: refs/heads/main@{#1498171}
diff --git a/css/css-position/replaced-object-backdrop.html b/css/css-position/replaced-object-backdrop.html
@@ -0,0 +1,13 @@
+<!DOCTYPE html>
+<title>CSS Position Test: Replaced &lt;object&gt; renders ::backdrop in top layer</title>
+<link rel="help" href="https://drafts.csswg.org/css-position-4/#backdrop">
+<link rel="match" href="/css/reference/green.html">
+<style>
+  object.green::backdrop { background-color: green; visibility: visible; }
+  object { visibility: hidden; }
+</style>
+<object id="pop" popover="auto"></object>
+<script>
+  pop.showPopover();
+  pop.className = "green";
+</script>
diff --git a/css/reference/green.html b/css/reference/green.html
@@ -0,0 +1,3 @@
+<!DOCTYPE html>
+<title>CSS Test Reference</title>
+<body style="background-color:green"></body>

Original file line number	Diff line number	Diff line change
`@@ -0,0 +1,3 @@`
	`1`	`+<!DOCTYPE html>`
	`2`	`+<title>CSS Test Reference</title>`
	`3`	`+<body style="background-color:green"></body>`