Make hit tests against box shadows always fail.

Closes #9268.
servo · bors-servo · Jan 26, 2016 · Jan 26, 2016 · Jan 26, 2016 · 32a68a43ec52f248e955948210f6dfba9b34b0bf
commit 32a68a43ec52f248e955948210f6dfba9b34b0bf
diff --git a/components/gfx/display_list/mod.rs b/components/gfx/display_list/mod.rs
@@ -390,23 +390,30 @@ impl DisplayList {
                     return;
                 }
 
-                if let DisplayItem::BorderClass(ref border) = *item {
-                    // If the point is inside the border, it didn't hit the border!
-                    let interior_rect =
-                        Rect::new(
-                            Point2D::new(border.base.bounds.origin.x +
-                                         border.border_widths.left,
-                                         border.base.bounds.origin.y +
-                                         border.border_widths.top),
-                            Size2D::new(border.base.bounds.size.width -
-                                            (border.border_widths.left +
-                                             border.border_widths.right),
-                                        border.base.bounds.size.height -
-                                            (border.border_widths.top +
-                                             border.border_widths.bottom)));
-                    if interior_rect.contains(&point) {
-                        return;
+                match *item {
+                    DisplayItem::BorderClass(ref border) => {
+                        // If the point is inside the border, it didn't hit the border!
+                        let interior_rect =
+                            Rect::new(
+                                Point2D::new(border.base.bounds.origin.x +
+                                             border.border_widths.left,
+                                             border.base.bounds.origin.y +
+                                             border.border_widths.top),
+                                Size2D::new(border.base.bounds.size.width -
+                                                (border.border_widths.left +
+                                                 border.border_widths.right),
+                                            border.base.bounds.size.height -
+                                                (border.border_widths.top +
+                                                 border.border_widths.bottom)));
+                        if interior_rect.contains(&point) {
+                            return;
+                        }
                     }
+                    DisplayItem::BoxShadowClass(_) => {
+                        // Box shadows can never be hit.
+                        return
+                    }
+                    _ => {}
                 }
 
                 // We found a hit!

diff --git a/tests/html/shadow-hit-test.html b/tests/html/shadow-hit-test.html
@@ -0,0 +1,24 @@
+<!DOCTYPE html>
+<!-- Clicking under the shadow should still activate the green div. -->
+<style>
+  .green {
+    background: green;
+    position: absolute;
+    top: 45px;
+    left: 170px;
+    width: 100px;
+    height: 50px;
+  }
+  .red {
+    background: red;
+    position: absolute;
+    top: 20px;
+    left: 20px;
+    width: 100px;
+    height: 100px;
+    box-shadow: 100px 0 0 rgba(0,0,0,0.1);
+    transform: translateX(1px);
+  }
+</style>
+<div class="green" onclick="console.log('You clicked me!')"></div>
+<div class="red"></div>