From c9ab75b013b8a0e3679ce01cf4f0f7bd6a89cfc5 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Emilio=20Cobos=20=C3=81lvarez?= <emilio@crisal.io>
Date: Mon, 8 May 2017 11:04:44 +0200
Subject: [PATCH] layout: Fix radius percentage resolution.

By resolving against the corresponding dimension of the border box, instead of
against the width.

Fixes #16764
---
 components/layout/display_list_builder.rs | 10 +++++-----
 components/layout/model.rs                | 18 +++++++++++++++---
 2 files changed, 20 insertions(+), 8 deletions(-)

diff --git a/components/layout/display_list_builder.rs b/components/layout/display_list_builder.rs
index ac1735b7a16..b48bb607ac7 100644
--- a/components/layout/display_list_builder.rs
+++ b/components/layout/display_list_builder.rs
@@ -564,13 +564,13 @@ fn build_border_radius(abs_bounds: &Rect<Au>,
 
     handle_overlapping_radii(&abs_bounds.size, &BorderRadii {
         top_left:     model::specified_border_radius(border_style.border_top_left_radius,
-                                                     abs_bounds.size.width),
+                                                     abs_bounds.size),
         top_right:    model::specified_border_radius(border_style.border_top_right_radius,
-                                                     abs_bounds.size.width),
+                                                     abs_bounds.size),
         bottom_right: model::specified_border_radius(border_style.border_bottom_right_radius,
-                                                     abs_bounds.size.width),
+                                                     abs_bounds.size),
         bottom_left:  model::specified_border_radius(border_style.border_bottom_left_radius,
-                                                     abs_bounds.size.width),
+                                                     abs_bounds.size),
     })
 }
 
@@ -1278,7 +1278,7 @@ impl FragmentDisplayListBuilding for Fragment {
                 spread_radius: box_shadow.spread_radius,
                 border_radius: model::specified_border_radius(style.get_border()
                                                                    .border_top_left_radius,
-                                                              absolute_bounds.size.width).width,
+                                                              absolute_bounds.size).width,
                 clip_mode: if box_shadow.inset {
                     BoxShadowClipMode::Inset
                 } else {
diff --git a/components/layout/model.rs b/components/layout/model.rs
index 27f0b2ce7a7..531d37038d7 100644
--- a/components/layout/model.rs
+++ b/components/layout/model.rs
@@ -478,10 +478,22 @@ pub fn specified(length: LengthOrPercentage, containing_length: Au) -> Au {
     }
 }
 
-pub fn specified_border_radius(radius: BorderRadiusSize, containing_length: Au) -> Size2D<Au> {
+/// Computes a border radius size against the containing size.
+///
+/// Note that percentages in `border-radius` are resolved against the relevant
+/// box dimension instead of only against the width per [1]:
+///
+/// > Percentages: Refer to corresponding dimension of the border box.
+///
+/// [1]: https://drafts.csswg.org/css-backgrounds-3/#border-radius
+pub fn specified_border_radius(
+    radius: BorderRadiusSize,
+    containing_size: Size2D<Au>)
+    -> Size2D<Au>
+{
     let generics::BorderRadiusSize(size) = radius;
-    let w = specified(size.width, containing_length);
-    let h = specified(size.height, containing_length);
+    let w = specified(size.width, containing_size.width);
+    let h = specified(size.height, containing_size.height);
     Size2D::new(w, h)
 }