Properly handle scroll offsets in hit testing

Scroll roots are no longer nested containers holding items, so instead
we need to track the offsets of each, carefully handling fixed position
items and stacking contexts that create new reference frames.
Additionally, we remove the complexity of the pre-computed page scroll
offset, instead opting to send script scrolls to the layout task in
order to more quickly have a ScrollState there that matches the
script's idea of the scroll world.

Fixes #16405.

1 files changed, 11 insertions, 12 deletions

diff --git a/components/script/dom/window.rs b/components/script/dom/window.rs
index 4317d2890b7..65d1a591adc 100644
--- a/components/script/dom/window.rs
+++ b/components/script/dom/window.rs
@@ -75,11 +75,11 @@ use script_layout_interface::rpc::{ContentBoxResponse, ContentBoxesResponse, Lay
 use script_layout_interface::rpc::{MarginStyleResponse, NodeScrollRootIdResponse};
 use script_layout_interface::rpc::{ResolvedStyleResponse, TextIndexResponse};
 use script_runtime::{CommonScriptMsg, ScriptChan, ScriptPort, ScriptThreadEventCategory};
-use script_thread::{MainThreadScriptChan, MainThreadScriptMsg, Runnable, RunnableWrapper};
-use script_thread::{SendableMainThreadScriptChan, ImageCacheMsg, ScriptThread};
-use script_traits::{ConstellationControlMsg, LoadData, MozBrowserEvent, UntrustedNodeAddress};
-use script_traits::{DocumentState, TimerEvent, TimerEventId};
-use script_traits::{ScriptMsg as ConstellationMsg, TimerSchedulerMsg, WindowSizeData, WindowSizeType};
+use script_thread::{ImageCacheMsg, MainThreadScriptChan, MainThreadScriptMsg, Runnable};
+use script_thread::{RunnableWrapper, ScriptThread, SendableMainThreadScriptChan};
+use script_traits::{ConstellationControlMsg, DocumentState, LoadData, MozBrowserEvent};
+use script_traits::{ScriptMsg as ConstellationMsg, ScrollState, TimerEvent, TimerEventId};
+use script_traits::{TimerSchedulerMsg, UntrustedNodeAddress, WindowSizeData, WindowSizeType};
 use script_traits::webdriver_msg::{WebDriverJSError, WebDriverJSResult};
 use servo_atoms::Atom;
 use servo_config::opts;
@@ -1111,6 +1111,11 @@ impl Window {
             ScrollBehavior::Smooth => true
         };
 
+        self.layout_chan.send(Msg::UpdateScrollStateFromScript(ScrollState {
+            scroll_root_id: scroll_root_id,
+            scroll_offset: Point2D::new(-x, -y),
+        })).unwrap();
+
         // TODO (farodin91): Raise an event to stop the current_viewport
         self.update_viewport_for_scroll(x, y);
 
@@ -1372,14 +1377,8 @@ impl Window {
                           client_point: Point2D<f32>,
                           update_cursor: bool)
                           -> Option<UntrustedNodeAddress> {
-        let translated_point =
-            Point2D::new(client_point.x + self.PageXOffset() as f32,
-                         client_point.y + self.PageYOffset() as f32);
-
         if !self.reflow(ReflowGoal::ForScriptQuery,
-                        ReflowQueryType::HitTestQuery(translated_point,
-                                                      client_point,
-                                                      update_cursor),
+                        ReflowQueryType::HitTestQuery(client_point, update_cursor),
                         ReflowReason::Query) {
             return None
         }