Auto merge of #9708 - danlrobertson:i8623, r=KiChjang

Implement GetElementRect webdriver command: #8623

Implement the webdriver Get Element Rect command. Originally I wrote out the algorithm for [Step 7](https://w3c.github.io/webdriver/webdriver-spec.html#dfn-calculate-the-absolute-position) and then I found `GetBoundingClientRect`, and i thought it was probably best to use it instead.

As always, feedback is very welcomed!

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components/msg/webdriver_msg.rs

@@ -3,6 +3,7 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use constellation_msg::{PipelineId, WindowSizeData};
+use euclid::rect::Rect;
 use ipc_channel::ipc::IpcSender;
 use rustc_serialize::json::{Json, ToJson};
 use url::Url;
@@ -17,6 +18,7 @@ pub enum WebDriverScriptCommand {
     GetActiveElement(IpcSender<Option<String>>),
     GetElementAttribute(String, String, IpcSender<Result<Option<String>, ()>>),
     GetElementCSS(String, String, IpcSender<Result<String, ()>>),
+    GetElementRect(String, IpcSender<Result<Rect<f64>, ()>>),
     GetElementTagName(String, IpcSender<Result<String, ()>>),
     GetElementText(String, IpcSender<Result<String, ()>>),
     GetFrameId(WebDriverFrameId, IpcSender<Result<Option<PipelineId>, ()>>),

components/script/script_thread.rs

@@ -1246,6 +1246,8 @@ impl ScriptThread {
                 webdriver_handlers::handle_get_attribute(&page, pipeline_id, node_id, name, reply),
             WebDriverScriptCommand::GetElementCSS(node_id, name, reply) =>
                 webdriver_handlers::handle_get_css(&page, pipeline_id, node_id, name, reply),
+            WebDriverScriptCommand::GetElementRect(node_id, reply) =>
+                webdriver_handlers::handle_get_rect(&page, pipeline_id, node_id, reply),
             WebDriverScriptCommand::GetElementText(node_id, reply) =>
                 webdriver_handlers::handle_get_text(&page, pipeline_id, node_id, reply),
             WebDriverScriptCommand::GetFrameId(frame_id, reply) =>

components/script/webdriver_handlers.rs

@@ -22,6 +22,9 @@ use dom::htmlinputelement::HTMLInputElement;
 use dom::htmloptionelement::HTMLOptionElement;
 use dom::node::Node;
 use dom::window::ScriptHelpers;
+use euclid::point::Point2D;
+use euclid::rect::Rect;
+use euclid::size::Size2D;
 use ipc_channel::ipc::IpcSender;
 use js::jsapi::JSContext;
 use js::jsapi::{HandleValue, RootedValue};
@@ -37,15 +40,7 @@ use util::str::DOMString;
 fn find_node_by_unique_id(page: &Rc<Page>, pipeline: PipelineId, node_id: String) -> Option<Root<Node>> {
     let page = get_page(&*page, pipeline);
     let document = page.document();
-    let node = document.upcast::<Node>();
+    document.upcast::<Node>().traverse_preorder().find(|candidate| candidate.get_unique_id() == node_id)
-
-    for candidate in node.traverse_preorder() {
-        if candidate.get_unique_id() == node_id {
-            return Some(candidate);
-        }
-    }
-
-    None
 }
 
 #[allow(unsafe_code)]
@@ -185,6 +180,44 @@ pub fn handle_get_title(page: &Rc<Page>, _pipeline: PipelineId, reply: IpcSender
     reply.send(String::from(page.document().Title())).unwrap();
 }
 
+pub fn handle_get_rect(page: &Rc<Page>,
+                       pipeline: PipelineId,
+                       element_id: String,
+                       reply: IpcSender<Result<Rect<f64>, ()>>) {
+    reply.send(match find_node_by_unique_id(&*page, pipeline, element_id) {
+        Some(elem) => {
+            // https://w3c.github.io/webdriver/webdriver-spec.html#dfn-calculate-the-absolute-position
+            match elem.downcast::<HTMLElement>() {
+                Some(html_elem) => {
+                    // Step 1
+                    let mut x = 0;
+                    let mut y = 0;
+
+                    let mut offset_parent = html_elem.GetOffsetParent();
+
+                    // Step 2
+                    while let Some(element) = offset_parent {
+                        offset_parent = match element.downcast::<HTMLElement>() {
+                            Some(elem) => {
+                                x += elem.OffsetLeft();
+                                y += elem.OffsetTop();
+                                elem.GetOffsetParent()
+                            },
+                            None => None
+                        };
+                    }
+                    // Step 3
+                    Ok(Rect::new(Point2D::new(x as f64, y as f64),
+                                 Size2D::new(html_elem.OffsetWidth() as f64,
+                                             html_elem.OffsetHeight() as f64)))
+                },
+                None => Err(())
+            }
+        },
+        None => Err(())
+    }).unwrap();
+}
+
 pub fn handle_get_text(page: &Rc<Page>,
                        pipeline: PipelineId,
                        node_id: String,

components/webdriver_server/lib.rs

@@ -51,7 +51,8 @@ use webdriver::command::{WebDriverCommand, WebDriverExtensionCommand, WebDriverM
 use webdriver::common::{LocatorStrategy, WebElement};
 use webdriver::error::{ErrorStatus, WebDriverError, WebDriverResult};
 use webdriver::httpapi::{WebDriverExtensionRoute};
-use webdriver::response::{NewSessionResponse, ValueResponse, WebDriverResponse, WindowSizeResponse};
+use webdriver::response::{ElementRectResponse, NewSessionResponse, ValueResponse};
+use webdriver::response::{WebDriverResponse, WindowSizeResponse};
 use webdriver::server::{self, Session, WebDriverHandler};
 
 fn extension_routes() -> Vec<(Method, &'static str, ServoExtensionRoute)> {
@@ -540,6 +541,25 @@ impl Handler {
         }
     }
 
+    // https://w3c.github.io/webdriver/webdriver-spec.html#get-element-rect
+    fn handle_element_rect(&self, element: &WebElement) -> WebDriverResult<WebDriverResponse> {
+        let pipeline_id = try!(self.frame_pipeline());
+
+        let (sender, receiver) = ipc::channel().unwrap();
+        let cmd = WebDriverScriptCommand::GetElementRect(element.id.clone(), sender);
+        let cmd_msg = WebDriverCommandMsg::ScriptCommand(pipeline_id, cmd);
+        self.constellation_chan.send(ConstellationMsg::WebDriverCommand(cmd_msg)).unwrap();
+        match receiver.recv().unwrap() {
+            Ok(rect) => {
+                let response = ElementRectResponse::new(rect.origin.x, rect.origin.y,
+                                                        rect.size.width, rect.size.height);
+                Ok(WebDriverResponse::ElementRect(response))
+            },
+            Err(_) => Err(WebDriverError::new(ErrorStatus::StaleElementReference,
+                                              "Unable to find element in document"))
+        }
+    }
+
     fn handle_element_text(&self, element: &WebElement) -> WebDriverResult<WebDriverResponse> {
         let pipeline_id = try!(self.frame_pipeline());
 
@@ -798,6 +818,7 @@ impl WebDriverHandler<ServoExtensionRoute> for Handler {
             WebDriverCommand::FindElement(ref parameters) => self.handle_find_element(parameters),
             WebDriverCommand::FindElements(ref parameters) => self.handle_find_elements(parameters),
             WebDriverCommand::GetActiveElement => self.handle_active_element(),
+            WebDriverCommand::GetElementRect(ref element) => self.handle_element_rect(element),
             WebDriverCommand::GetElementText(ref element) => self.handle_element_text(element),
             WebDriverCommand::GetElementTagName(ref element) => self.handle_element_tag_name(element),
             WebDriverCommand::GetElementAttribute(ref element, ref name) =>