diff --git a/src/components/main/layout/block.rs b/src/components/main/layout/block.rs
index d6b54596e4d..a7064df92d8 100644
--- a/src/components/main/layout/block.rs
+++ b/src/components/main/layout/block.rs
@@ -323,6 +323,10 @@ impl BlockFlow {
let mut height = if self.is_root {
+ // FIXME(pcwalton): The max is taken here so that you can scroll the page, but this is
+ // not correct behavior according to CSS 2.1 § 10.5. Instead I think we should treat
+ // the root element as having `overflow: scroll` and use the layers-based scrolling
+ // infrastructure to make it scrollable.
Au::max(ctx.screen_size.size.height, cur_y)
} else {
cur_y - top_offset - collapsing
@@ -330,7 +334,11 @@ impl BlockFlow {
for &box in self.box.iter() {
let style = box.style();
- height = match MaybeAuto::from_style(style.Box.height, Au::new(0)) {
+
+ // At this point, `height` is the height of the containing block, so passing `height`
+ // as the second argument here effectively makes percentages relative to the containing
+ // block per CSS 2.1 § 10.5.
+ height = match MaybeAuto::from_style(style.Box.height, height) {
Auto => height,
Specified(value) => value
};
diff --git a/src/test/ref/basic.list b/src/test/ref/basic.list
index 5b8bb85e9a8..f628a80aec2 100644
--- a/src/test/ref/basic.list
+++ b/src/test/ref/basic.list
@@ -13,3 +13,4 @@
== last_of_type_pseudo_a.html last_of_type_pseudo_b.html
== only_of_type_pseudo_a.html only_of_type_pseudo_b.html
== visibility_hidden.html visibility_hidden_ref.html
+== root_height_a.html root_height_b.html
diff --git a/src/test/ref/root_height_a.html b/src/test/ref/root_height_a.html
new file mode 100644
index 00000000000..5e302588a20
--- /dev/null
+++ b/src/test/ref/root_height_a.html
@@ -0,0 +1,14 @@
+
+
+Aliens was a really good movie. But Alien 3 sucked.
+
+
+
+
+
+
diff --git a/src/test/ref/root_height_b.html b/src/test/ref/root_height_b.html
new file mode 100644
index 00000000000..b0f3d86a16c
--- /dev/null
+++ b/src/test/ref/root_height_b.html
@@ -0,0 +1,13 @@
+
+
+Aliens was a really good movie. But Alien 3 sucked.
+
+
+
+
+
+