Properly resize iframe root layers

When a layer containing an iframe changes, we also need to resize the root layer of the subpage. This ensures that content from the child layer tree is masked to the new size. Fixes #8301.
servo · bors-servo · Nov 4, 2015 · Nov 3, 2015 · Nov 3, 2015 · 261246ea25d8c937151e79d0ce1ad5f1bf1274af
commit 261246ea25d8c937151e79d0ce1ad5f1bf1274af
diff --git a/components/compositing/compositor.rs b/components/compositing/compositor.rs
@@ -791,8 +791,20 @@ impl<Window: WindowMethods> IOCompositor<Window> {
         self.pipeline_details.remove(&pipeline_id);
     }
 
-    fn update_layer_if_exists(&mut self, pipeline_id: PipelineId, properties: LayerProperties)
+    fn update_layer_if_exists(&mut self,
+                              pipeline_id: PipelineId,
+                              properties: LayerProperties)
                               -> bool {
+        if let Some(subpage_id) = properties.subpage_pipeline_id {
+            match self.find_layer_with_pipeline_and_layer_id(subpage_id, LayerId::null()) {
+                Some(layer) => {
+                    *layer.bounds.borrow_mut() = Rect::from_untyped(
+                        &Rect::new(Point2D::zero(), properties.rect.size));
+                }
+                None => warn!("Tried to update non-existent subpage root layer: {:?}", subpage_id),
+            }
+        }
+
         match self.find_layer_with_pipeline_and_layer_id(pipeline_id, properties.id) {
             Some(existing_layer) => {
                 existing_layer.update_layer(properties);

diff --git a/tests/wpt/mozilla/meta/MANIFEST.json b/tests/wpt/mozilla/meta/MANIFEST.json
@@ -4139,6 +4139,18 @@
             "url": "/_mozilla/mozilla/canvas/drawimage_html_image_9.html"
           }
         ],
+        "mozilla/iframe/resize_after_load.html": [
+          {
+            "path": "mozilla/iframe/resize_after_load.html",
+            "references": [
+              [
+                "/_mozilla/mozilla/iframe/resize_after_load_ref.html",
+                "=="
+              ]
+            ],
+            "url": "/_mozilla/mozilla/iframe/resize_after_load.html"
+          }
+        ],
         "mozilla/webgl/clearcolor.html": [
           {
             "path": "mozilla/webgl/clearcolor.html",
@@ -8928,6 +8940,18 @@
           "url": "/_mozilla/mozilla/canvas/drawimage_html_image_9.html"
         }
       ],
+      "mozilla/iframe/resize_after_load.html": [
+        {
+          "path": "mozilla/iframe/resize_after_load.html",
+          "references": [
+            [
+              "/_mozilla/mozilla/iframe/resize_after_load_ref.html",
+              "=="
+            ]
+          ],
+          "url": "/_mozilla/mozilla/iframe/resize_after_load.html"
+        }
+      ],
       "mozilla/webgl/clearcolor.html": [
         {
           "path": "mozilla/webgl/clearcolor.html",

diff --git a/tests/wpt/mozilla/tests/mozilla/iframe/resize_after_load.html b/tests/wpt/mozilla/tests/mozilla/iframe/resize_after_load.html
@@ -0,0 +1,24 @@
+<!doctype html>
+<html class="reftest-wait">
+    <head>
+        <meta charset=utf-8>
+        <title>Dynamically growing an iframe element</title>
+        <link rel=match href=/_mozilla/mozilla/iframe/resize_after_load_ref.html>
+    </head>
+
+    <body>
+        <iframe style="border: 0px; display: block; height: 100px; width: 50px" src="resources/green_inner_frame.html"></iframe>
+        <script>
+            var iframe = document.getElementsByTagName('iframe')[0];
+            iframe.onload = function() {
+                document.querySelector('iframe').style.width = "100px";
+
+                // We do this in a timeout, so that the compositor has a chance
+                // to update the layer tree.
+                setTimeout(function() {
+                    document.documentElement.classList.remove("reftest-wait");
+                }, 0);
+            }
+        </script>
+    </body>
+</html>
diff --git a/tests/wpt/mozilla/tests/mozilla/iframe/resize_after_load_ref.html b/tests/wpt/mozilla/tests/mozilla/iframe/resize_after_load_ref.html
@@ -0,0 +1,6 @@
+<!doctype html>
+<html>
+    <body>
+        <div style="height: 100px; width: 100px; background: green;"></div>
+    </body>
+</html>
diff --git a/tests/wpt/mozilla/tests/mozilla/iframe/resources/green_inner_frame.html b/tests/wpt/mozilla/tests/mozilla/iframe/resources/green_inner_frame.html
@@ -0,0 +1,5 @@
+<!DOCTYPE html>
+<html>
+    <body style="background: green;">
+    </body>
+</html>