From ab7f7b3754ed90470e2d3d68d0d4f3cc4d40408c Mon Sep 17 00:00:00 2001
From: Mikayla Maki <mikayla@zed.dev>
Date: Wed, 21 Sep 2022 22:23:07 -0700
Subject: [PATCH] Added on_scroll to mouse_event_handler and fixed the uniform
 list scroll implementation

---
 .../gpui/src/elements/mouse_event_handler.rs  | 11 ++++-
 crates/gpui/src/elements/uniform_list.rs      | 47 ++++++++++++-------
 2 files changed, 39 insertions(+), 19 deletions(-)

diff --git a/crates/gpui/src/elements/mouse_event_handler.rs b/crates/gpui/src/elements/mouse_event_handler.rs
index bb958ce99c..5b3b9b13f6 100644
--- a/crates/gpui/src/elements/mouse_event_handler.rs
+++ b/crates/gpui/src/elements/mouse_event_handler.rs
@@ -7,7 +7,8 @@ use crate::{
     platform::CursorStyle,
     scene::{
         ClickRegionEvent, CursorRegion, DownOutRegionEvent, DownRegionEvent, DragRegionEvent,
-        HandlerSet, HoverRegionEvent, MoveRegionEvent, UpOutRegionEvent, UpRegionEvent,
+        HandlerSet, HoverRegionEvent, MoveRegionEvent, ScrollWheelRegionEvent, UpOutRegionEvent,
+        UpRegionEvent,
     },
     DebugContext, Element, ElementBox, Event, EventContext, LayoutContext, MeasurementContext,
     MouseButton, MouseRegion, MouseState, PaintContext, RenderContext, SizeConstraint, View,
@@ -122,6 +123,14 @@ impl<Tag> MouseEventHandler<Tag> {
         self
     }
 
+    pub fn on_scroll(
+        mut self,
+        handler: impl Fn(ScrollWheelRegionEvent, &mut EventContext) + 'static,
+    ) -> Self {
+        self.handlers = self.handlers.on_scroll(handler);
+        self
+    }
+
     pub fn with_hoverable(mut self, is_hoverable: bool) -> Self {
         self.hoverable = is_hoverable;
         self
diff --git a/crates/gpui/src/elements/uniform_list.rs b/crates/gpui/src/elements/uniform_list.rs
index 103cb00d8c..718a9fe8a2 100644
--- a/crates/gpui/src/elements/uniform_list.rs
+++ b/crates/gpui/src/elements/uniform_list.rs
@@ -6,7 +6,8 @@ use crate::{
     },
     json::{self, json},
     presenter::MeasurementContext,
-    ElementBox, RenderContext, ScrollWheelEvent, View,
+    scene::ScrollWheelRegionEvent,
+    ElementBox, MouseRegion, RenderContext, ScrollWheelEvent, View,
 };
 use json::ToJson;
 use std::{cell::RefCell, cmp, ops::Range, rc::Rc};
@@ -50,6 +51,7 @@ pub struct UniformList {
     padding_top: f32,
     padding_bottom: f32,
     get_width_from_item: Option<usize>,
+    view_id: usize,
 }
 
 impl UniformList {
@@ -77,6 +79,7 @@ impl UniformList {
             padding_top: 0.,
             padding_bottom: 0.,
             get_width_from_item: None,
+            view_id: cx.handle().id(),
         }
     }
 
@@ -96,7 +99,7 @@ impl UniformList {
     }
 
     fn scroll(
-        &self,
+        state: UniformListState,
         _: Vector2F,
         mut delta: Vector2F,
         precise: bool,
@@ -107,7 +110,7 @@ impl UniformList {
             delta *= 20.;
         }
 
-        let mut state = self.state.0.borrow_mut();
+        let mut state = state.0.borrow_mut();
         state.scroll_top = (state.scroll_top - delta.y()).max(0.0).min(scroll_max);
         cx.notify();
 
@@ -283,6 +286,28 @@ impl Element for UniformList {
     ) -> Self::PaintState {
         cx.scene.push_layer(Some(bounds));
 
+        cx.scene.push_mouse_region(
+            MouseRegion::new::<Self>(self.view_id, 0, bounds).on_scroll({
+                let scroll_max = layout.scroll_max;
+                let state = self.state.clone();
+                move |ScrollWheelRegionEvent {
+                          platform_event:
+                              ScrollWheelEvent {
+                                  position,
+                                  delta,
+                                  precise,
+                                  ..
+                              },
+                          ..
+                      },
+                      cx| {
+                    if !Self::scroll(state.clone(), position, delta, precise, scroll_max, cx) {
+                        cx.propogate_event();
+                    }
+                }
+            }),
+        );
+
         let mut item_origin = bounds.origin()
             - vec2f(
                 0.,
@@ -300,7 +325,7 @@ impl Element for UniformList {
     fn dispatch_event(
         &mut self,
         event: &Event,
-        bounds: RectF,
+        _: RectF,
         _: RectF,
         layout: &mut Self::LayoutState,
         _: &mut Self::PaintState,
@@ -311,20 +336,6 @@ impl Element for UniformList {
             handled = item.dispatch_event(event, cx) || handled;
         }
 
-        if let Event::ScrollWheel(ScrollWheelEvent {
-            position,
-            delta,
-            precise,
-            ..
-        }) = event
-        {
-            if bounds.contains_point(*position)
-                && self.scroll(*position, *delta, *precise, layout.scroll_max, cx)
-            {
-                handled = true;
-            }
-        }
-
         handled
     }