From 9a9762fc957af9e393159174d2783e9dbd15f96e Mon Sep 17 00:00:00 2001
From: Patrick Walton <pcwalton@mimiga.net>
Date: Tue, 31 May 2016 23:23:47 -0700
Subject: [PATCH] compositing: Don't translate points to layer space when using
 WebRender.

This makes mouse events take the same code path, regardless of whether
WebRender is in use or not. This approach enables accurate
display-list-based hit testing when WebRender is in use.

Closes #11108.
---
 components/compositing/compositor.rs | 48 ++++++++++++----------------
 1 file changed, 21 insertions(+), 27 deletions(-)

diff --git a/components/compositing/compositor.rs b/components/compositing/compositor.rs
index f00cb496eb1..fb471ab90f9 100644
--- a/components/compositing/compositor.rs
+++ b/components/compositing/compositor.rs
@@ -1387,31 +1387,27 @@ impl<Window: WindowMethods> IOCompositor<Window> {
             MouseWindowEvent::MouseUp(_, p) => p,
         };
 
-        if let Some(ref webrender_api) = self.webrender_api {
+        if self.webrender_api.is_some() {
             let root_pipeline_id = match self.get_root_pipeline_id() {
                 Some(root_pipeline_id) => root_pipeline_id,
                 None => return,
             };
-            if self.pipeline(root_pipeline_id).is_none() {
-                return;
-            }
 
-            let (translated_point, translated_pipeline_id) =
-                webrender_api.translate_point_to_layer_space(&point.to_untyped());
-            let event_to_send = match mouse_window_event {
-                MouseWindowEvent::Click(button, _) => {
-                    MouseButtonEvent(MouseEventType::Click, button, translated_point)
-                }
-                MouseWindowEvent::MouseDown(button, _) => {
-                    MouseButtonEvent(MouseEventType::MouseDown, button, translated_point)
-                }
-                MouseWindowEvent::MouseUp(button, _) => {
-                    MouseButtonEvent(MouseEventType::MouseUp, button, translated_point)
-                }
-            };
-            let translated_pipeline_id = translated_pipeline_id.from_webrender();
-            let msg = ConstellationControlMsg::SendEvent(translated_pipeline_id, event_to_send);
-            if let Some(pipeline) = self.pipeline(translated_pipeline_id) {
+            if let Some(pipeline) = self.pipeline(root_pipeline_id) {
+                let dppx = self.page_zoom * self.device_pixels_per_screen_px();
+                let translated_point = (point / dppx).to_untyped();
+                let event_to_send = match mouse_window_event {
+                    MouseWindowEvent::Click(button, _) => {
+                        MouseButtonEvent(MouseEventType::Click, button, translated_point)
+                    }
+                    MouseWindowEvent::MouseDown(button, _) => {
+                        MouseButtonEvent(MouseEventType::MouseDown, button, translated_point)
+                    }
+                    MouseWindowEvent::MouseUp(button, _) => {
+                        MouseButtonEvent(MouseEventType::MouseUp, button, translated_point)
+                    }
+                };
+                let msg = ConstellationControlMsg::SendEvent(root_pipeline_id, event_to_send);
                 if let Err(e) = pipeline.script_chan.send(msg) {
                     warn!("Sending control event to script failed ({}).", e);
                 }
@@ -1431,7 +1427,7 @@ impl<Window: WindowMethods> IOCompositor<Window> {
             return
         }
 
-        if let Some(ref webrender_api) = self.webrender_api {
+        if self.webrender_api.is_some() {
             let root_pipeline_id = match self.get_root_pipeline_id() {
                 Some(root_pipeline_id) => root_pipeline_id,
                 None => return,
@@ -1440,12 +1436,10 @@ impl<Window: WindowMethods> IOCompositor<Window> {
                 return;
             }
 
-            let (translated_point, translated_pipeline_id) =
-                webrender_api.translate_point_to_layer_space(&cursor.to_untyped());
-            let translated_pipeline_id = translated_pipeline_id.from_webrender();
-            let event_to_send = MouseMoveEvent(Some(translated_point));
-            let msg = ConstellationControlMsg::SendEvent(translated_pipeline_id, event_to_send);
-            if let Some(pipeline) = self.pipeline(translated_pipeline_id) {
+            let dppx = self.page_zoom * self.device_pixels_per_screen_px();
+            let event_to_send = MouseMoveEvent(Some((cursor / dppx).to_untyped()));
+            let msg = ConstellationControlMsg::SendEvent(root_pipeline_id, event_to_send);
+            if let Some(pipeline) = self.pipeline(root_pipeline_id) {
                 if let Err(e) = pipeline.script_chan.send(msg) {
                     warn!("Sending mouse control event to script failed ({}).", e);
                 }