Keep positioned pseudos out of inline sizing

crates/obscura-render/src/dom.rs

@@ -9435,6 +9435,38 @@ mod tests {
         assert_eq!(pseudo.line_height, host.line_height);
     }
 
+    #[test]
+    fn positioned_pseudo_does_not_wrap_shrink_to_fit_host_text() {
+        let tree = parse_html(
+            r#"<style>
+                html, body { margin:0 }
+                #host {
+                    position:absolute; width:max-content;
+                    padding:12px 24px; border:0;
+                    font-size:14px; font-weight:600; color:transparent;
+                }
+                #host::after {
+                    content:attr(text); position:absolute; inset:1px;
+                    display:flex; align-items:center; justify-content:center;
+                    color:black; background:white;
+                }
+            </style>
+            <button id="host" text="Learn more">Learn more</button>"#,
+        );
+        let laid = layout_dom(&tree, (500.0, 300.0));
+        let host = tree.get_element_by_id("host").unwrap();
+        let rect = laid.rects[&host];
+
+        assert!(
+            (120.0..=130.0).contains(&rect.width),
+            "max-content width must include the shaped inter-word advance: {rect:?}"
+        );
+        assert_eq!(
+            rect.height, 40.0,
+            "positioned generated content must not make the host label wrap"
+        );
+    }
+
     #[test]
     fn variable_font_properties_inherit_and_reset_through_elements_and_pseudos() {
         let tree = parse_html(

crates/obscura-render/src/inline.rs

@@ -1568,7 +1568,20 @@ fn is_pure_text_ifc(
     let Some(style) = styles.get(&id) else {
         return false;
     };
-    if style.before_pseudo.is_some() || style.after_pseudo.is_some() {
+    // Out-of-flow generated boxes neither contribute to nor interrupt the
+    // host's inline formatting context. Keeping a positioned decorative
+    // pseudo must not demote an otherwise text-only shrink-to-fit control to
+    // approximate per-word flex leaves: that path can disagree with shaped
+    // space advances and wrap text at its own max-content width.
+    let has_in_flow_pseudo = |pseudo: Option<&LayoutStyle>| {
+        pseudo.is_some_and(|pseudo| {
+            pseudo.display != Display::None
+                && !matches!(pseudo.position, Some(taffy::Position::Absolute))
+        })
+    };
+    if has_in_flow_pseudo(style.before_pseudo.as_deref())
+        || has_in_flow_pseudo(style.after_pseudo.as_deref())
+    {
         return false;
     }
     // Only containers that lay their children out in normal flow (block, or