servo: Merge #4934 - Fixes background-color calculation for iframes. Fixes #1248 (from glennw:fix-1248); r=pcwalton

Source-Repo: https://github.com/servo/servo
Source-Revision: 6d2e840bf49f7d9d8022ab2566cfb641dd578a44

servo/components/layout/layout_task.rs

@@ -666,7 +666,17 @@ impl LayoutTask {
 
             // FIXME(pcwalton): This is really ugly and can't handle overflow: scroll. Refactor
             // it with extreme prejudice.
-            let mut color = color::white();
+
+            // The default computed value for background-color is transparent (see
+            // http://dev.w3.org/csswg/css-backgrounds/#background-color). However, we
+            // need to propagate the background color from the root HTML/Body
+            // element (http://dev.w3.org/csswg/css-backgrounds/#special-backgrounds) if
+            // it is non-transparent. The phrase in the spec "If the canvas background
+            // is not opaque, what shows through is UA-dependent." is handled by rust-layers
+            // clearing the frame buffer to white. This ensures that setting a background
+            // color on an iframe element, while the iframe content itself has a default
+            // transparent background color is handled correctly.
+            let mut color = color::transparent_black();
             for child in node.traverse_preorder() {
                 if child.type_id() == Some(NodeTypeId::Element(ElementTypeId::HTMLElement(HTMLElementTypeId::HTMLHtmlElement))) ||
                         child.type_id() == Some(NodeTypeId::Element(ElementTypeId::HTMLElement(HTMLElementTypeId::HTMLBodyElement))) {

servo/components/servo/Cargo.lock

@@ -458,7 +458,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 [[package]]
 name = "layers"
 version = "0.1.0"
-source = "git+https://github.com/servo/rust-layers#1ef45363e38cb4257d99a4de6a43bf99c1a6f807"
+source = "git+https://github.com/servo/rust-layers#7f0ab52e147b778c79b9378fe3ddd4d13055df84"
 dependencies = [
  "azure 0.1.0 (git+https://github.com/servo/rust-azure)",
  "cgl 0.0.1 (git+https://github.com/servo/rust-cgl)",

servo/ports/cef/Cargo.lock

@@ -460,7 +460,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 [[package]]
 name = "layers"
 version = "0.1.0"
-source = "git+https://github.com/servo/rust-layers#1ef45363e38cb4257d99a4de6a43bf99c1a6f807"
+source = "git+https://github.com/servo/rust-layers#7f0ab52e147b778c79b9378fe3ddd4d13055df84"
 dependencies = [
  "azure 0.1.0 (git+https://github.com/servo/rust-azure)",
  "cgl 0.0.1 (git+https://github.com/servo/rust-cgl)",

servo/ports/gonk/Cargo.lock

@@ -378,7 +378,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 [[package]]
 name = "layers"
 version = "0.1.0"
-source = "git+https://github.com/servo/rust-layers#1ef45363e38cb4257d99a4de6a43bf99c1a6f807"
+source = "git+https://github.com/servo/rust-layers#7f0ab52e147b778c79b9378fe3ddd4d13055df84"
 dependencies = [
  "azure 0.1.0 (git+https://github.com/servo/rust-azure)",
  "cgl 0.0.1 (git+https://github.com/servo/rust-cgl)",