servo: Merge #11616 - Add support for navigating by a delta (from cbrewster:navigation_delta); r=asajeffrey

<!-- Please describe your changes on the following line: -->
This adds support for passing a delta with `NavigationDirection`. This will be used with `history.go`

r? @asajeffrey

---
<!-- Thank you for contributing to Servo! Please replace each `[ ]` by `[X]` when the step is complete, and replace `__` with appropriate data: -->
- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors
- [X] These changes do not require tests because I am unsure how to write a test for this

<!-- Pull requests that do not address these steps are welcome, but they will require additional verification as part of the review process. -->

Source-Repo: https://github.com/servo/servo
Source-Revision: a80767993b6b2b885dfac9666f16fb1e1649ac99

servo/components/compositing/compositor.rs

@@ -1803,8 +1803,8 @@ impl<Window: WindowMethods> IOCompositor<Window> {
 
     fn on_navigation_window_event(&self, direction: WindowNavigateMsg) {
         let direction = match direction {
-            windowing::WindowNavigateMsg::Forward => NavigationDirection::Forward,
-            windowing::WindowNavigateMsg::Back => NavigationDirection::Back,
+            windowing::WindowNavigateMsg::Forward => NavigationDirection::Forward(1),
+            windowing::WindowNavigateMsg::Back => NavigationDirection::Back(1),
         };
         let msg = ConstellationMsg::Navigate(None, direction);
         if let Err(e) = self.constellation_chan.send(msg) {

servo/components/constellation/constellation.rs

@@ -1278,34 +1278,35 @@ impl<Message, LTF, STF> Constellation<Message, LTF, STF>
         // Get the ids for the previous and next pipelines.
         let (prev_pipeline_id, next_pipeline_id) = match self.frames.get_mut(&frame_id) {
             Some(frame) => {
+                let prev = frame.current;
                 let next = match direction {
-                    NavigationDirection::Forward => {
-                        match frame.next.pop() {
-                            None => {
-                                warn!("no next page to navigate to");
-                                return;
-                            },
-                            Some(next) => {
-                                frame.prev.push(frame.current);
-                                next
-                            },
+                    NavigationDirection::Forward(delta) => {
+                        if delta > frame.next.len() && delta > 0 {
+                            return warn!("Invalid navigation delta");
                         }
+                        let new_next_len = frame.next.len() - (delta - 1);
+                        frame.prev.push(frame.current);
+                        frame.prev.extend(frame.next.drain(new_next_len..).rev());
+                        frame.current = match frame.next.pop() {
+                            Some(frame) => frame,
+                            None => return warn!("Could not get next frame for forward navigation"),
+                        };
+                        frame.current
                     }
-                    NavigationDirection::Back => {
-                        match frame.prev.pop() {
-                            None => {
-                                warn!("no previous page to navigate to");
-                                return;
-                            },
-                            Some(prev) => {
-                                frame.next.push(frame.current);
-                                prev
-                            },
+                    NavigationDirection::Back(delta) => {
+                        if delta > frame.prev.len() && delta > 0 {
+                            return warn!("Invalid navigation delta");
                         }
+                        let new_prev_len = frame.prev.len() - (delta - 1);
+                        frame.next.push(frame.current);
+                        frame.next.extend(frame.prev.drain(new_prev_len..).rev());
+                        frame.current = match frame.prev.pop() {
+                            Some(frame) => frame,
+                            None => return warn!("Could not get prev frame for back navigation"),
+                        };
+                        frame.current
                     }
                 };
-                let prev = frame.current;
-                frame.current = next;
                 (prev, next)
             },
             None => {

servo/components/msg/constellation_msg.rs

@@ -244,8 +244,8 @@ impl LoadData {
 
 #[derive(Clone, PartialEq, Eq, Copy, Hash, Debug, Deserialize, Serialize)]
 pub enum NavigationDirection {
-    Forward,
-    Back,
+    Forward(usize),
+    Back(usize),
 }
 
 #[derive(Clone, PartialEq, Eq, Copy, Hash, Debug, Deserialize, Serialize)]

servo/components/script/dom/htmliframeelement.rs

@@ -468,12 +468,12 @@ impl HTMLIFrameElementMethods for HTMLIFrameElement {
 
     // https://developer.mozilla.org/en-US/docs/Web/API/HTMLIFrameElement/goBack
     fn GoBack(&self) -> ErrorResult {
-        Navigate(self, NavigationDirection::Back)
+        Navigate(self, NavigationDirection::Back(1))
     }
 
     // https://developer.mozilla.org/en-US/docs/Web/API/HTMLIFrameElement/goForward
     fn GoForward(&self) -> ErrorResult {
-        Navigate(self, NavigationDirection::Forward)
+        Navigate(self, NavigationDirection::Forward(1))
     }
 
     // https://developer.mozilla.org/en-US/docs/Web/API/HTMLIFrameElement/reload

servo/components/webdriver_server/lib.rs

@@ -417,12 +417,12 @@ impl Handler {
     }
 
     fn handle_go_back(&self) -> WebDriverResult<WebDriverResponse> {
-        self.constellation_chan.send(ConstellationMsg::Navigate(None, NavigationDirection::Back)).unwrap();
+        self.constellation_chan.send(ConstellationMsg::Navigate(None, NavigationDirection::Back(1))).unwrap();
         Ok(WebDriverResponse::Void)
     }
 
     fn handle_go_forward(&self) -> WebDriverResult<WebDriverResponse> {
-        self.constellation_chan.send(ConstellationMsg::Navigate(None, NavigationDirection::Forward)).unwrap();
+        self.constellation_chan.send(ConstellationMsg::Navigate(None, NavigationDirection::Forward(1))).unwrap();
         Ok(WebDriverResponse::Void)
     }