LibWeb: Update layout in HTMLElement.offset{Width,Height}

If we don't do this, we may be returning stale values.

1 files changed, 22 insertions, 6 deletions

diff --git a/Userland/Libraries/LibWeb/HTML/HTMLElement.cpp b/Userland/Libraries/LibWeb/HTML/HTMLElement.cpp
index 73de1cd369..ed1efe27c2 100644
--- a/Userland/Libraries/LibWeb/HTML/HTMLElement.cpp
+++ b/Userland/Libraries/LibWeb/HTML/HTMLElement.cpp
@@ -149,17 +149,33 @@ int HTMLElement::offset_left() const
 // https://drafts.csswg.org/cssom-view/#dom-htmlelement-offsetwidth
 int HTMLElement::offset_width() const
 {
-    if (auto* paint_box = this->paint_box())
-        return paint_box->border_box_width();
-    return 0;
+    // NOTE: Ensure that layout is up-to-date before looking at metrics.
+    const_cast<DOM::Document&>(document()).update_layout();
+
+    // 1. If the element does not have any associated CSS layout box return zero and terminate this algorithm.
+    if (!paint_box())
+        return 0;
+
+    // 2. Return the width of the axis-aligned bounding box of the border boxes of all fragments generated by the element’s principal box,
+    //    ignoring any transforms that apply to the element and its ancestors.
+    // FIXME: Account for inline boxes.
+    return paint_box()->border_box_width();
 }
 
 // https://drafts.csswg.org/cssom-view/#dom-htmlelement-offsetheight
 int HTMLElement::offset_height() const
 {
-    if (auto* paint_box = this->paint_box())
-        return paint_box->border_box_height();
-    return 0;
+    // NOTE: Ensure that layout is up-to-date before looking at metrics.
+    const_cast<DOM::Document&>(document()).update_layout();
+
+    // 1. If the element does not have any associated CSS layout box return zero and terminate this algorithm.
+    if (!paint_box())
+        return 0;
+
+    // 2. Return the height of the axis-aligned bounding box of the border boxes of all fragments generated by the element’s principal box,
+    //    ignoring any transforms that apply to the element and its ancestors.
+    // FIXME: Account for inline boxes.
+    return paint_box()->border_box_height();
 }
 
 bool HTMLElement::cannot_navigate() const