Take a RenderContext in ListState's build item callback

Co-Authored-By: Max Brunsfeld <maxbrunsfeld@gmail.com>

crates/chat_panel/src/chat_panel.rs

@@ -75,9 +75,9 @@ impl ChatPanel {
             })
         });
 
-        let mut message_list = ListState::new(0, Orientation::Bottom, 1000., {
+        let mut message_list = ListState::new(0, Orientation::Bottom, 1000., cx, {
             let this = cx.weak_handle();
-            move |ix, cx| {
+            move |_, ix, cx| {
                 let this = this.upgrade(cx).unwrap().read(cx);
                 let message = this.active_channel.as_ref().unwrap().0.read(cx).message(ix);
                 this.render_message(message, cx)

crates/contacts_panel/src/contacts_panel.rs

@@ -12,8 +12,8 @@ use gpui::{
     geometry::{rect::RectF, vector::vec2f},
     impl_actions, impl_internal_actions,
     platform::CursorStyle,
-    AppContext, ClipboardItem, Element, ElementBox, Entity, LayoutContext, ModelHandle,
-    MutableAppContext, RenderContext, Subscription, View, ViewContext, ViewHandle, WeakViewHandle,
+    AppContext, ClipboardItem, Element, ElementBox, Entity, ModelHandle, MutableAppContext,
+    RenderContext, Subscription, View, ViewContext, ViewHandle, WeakViewHandle,
 };
 use join_project_notification::JoinProjectNotification;
 use serde::Deserialize;
@@ -184,11 +184,8 @@ impl ContactsPanel {
         .detach();
 
         let mut this = Self {
-            list_state: ListState::new(0, Orientation::Top, 1000., {
-                let this = cx.weak_handle();
-                move |ix, cx| {
-                    let this = this.upgrade(cx).unwrap();
-                    let this = this.read(cx);
+            list_state: ListState::new(0, Orientation::Top, 1000., cx, {
+                move |this, ix, cx| {
                     let theme = cx.global::<Settings>().theme.clone();
                     let theme = &theme.contacts_panel;
                     let current_user_id =
@@ -258,7 +255,7 @@ impl ContactsPanel {
         theme: &theme::ContactsPanel,
         is_selected: bool,
         is_collapsed: bool,
-        cx: &mut LayoutContext,
+        cx: &mut RenderContext<Self>,
     ) -> ElementBox {
         enum Header {}
 
@@ -349,7 +346,7 @@ impl ContactsPanel {
         theme: &theme::ContactsPanel,
         is_last_project: bool,
         is_selected: bool,
-        cx: &mut LayoutContext,
+        cx: &mut RenderContext<Self>,
     ) -> ElementBox {
         let project = &contact.projects[project_index];
         let project_id = project.id;
@@ -462,7 +459,7 @@ impl ContactsPanel {
         theme: &theme::ContactsPanel,
         is_incoming: bool,
         is_selected: bool,
-        cx: &mut LayoutContext,
+        cx: &mut RenderContext<ContactsPanel>,
     ) -> ElementBox {
         enum Decline {}
         enum Accept {}

crates/gpui/src/elements/list.rs

@@ -5,7 +5,7 @@ use crate::{
     },
     json::json,
     DebugContext, Element, ElementBox, ElementRc, Event, EventContext, LayoutContext, PaintContext,
-    SizeConstraint,
+    RenderContext, SizeConstraint, View, ViewContext,
 };
 use std::{cell::RefCell, collections::VecDeque, ops::Range, rc::Rc};
 use sum_tree::{Bias, SumTree};
@@ -26,7 +26,7 @@ pub enum Orientation {
 
 struct StateInner {
     last_layout_width: Option<f32>,
-    render_item: Box<dyn FnMut(usize, &mut LayoutContext) -> ElementBox>,
+    render_item: Box<dyn FnMut(usize, &mut LayoutContext) -> Option<ElementBox>>,
     rendered_range: Range<usize>,
     items: SumTree<ListItem>,
     logical_scroll_top: Option<ListOffset>,
@@ -135,9 +135,12 @@ impl Element for List {
                 break;
             }
 
-            let element = state.render_item(scroll_top.item_ix + ix, item, item_constraint, cx);
-            rendered_height += element.size().y();
-            rendered_items.push_back(ListItem::Rendered(element));
+            if let Some(element) =
+                state.render_item(scroll_top.item_ix + ix, item, item_constraint, cx)
+            {
+                rendered_height += element.size().y();
+                rendered_items.push_back(ListItem::Rendered(element));
+            }
         }
 
         // Prepare to start walking upward from the item at the scroll top.
@@ -149,9 +152,12 @@ impl Element for List {
             while rendered_height < size.y() {
                 cursor.prev(&());
                 if let Some(item) = cursor.item() {
-                    let element = state.render_item(cursor.start().0, item, item_constraint, cx);
-                    rendered_height += element.size().y();
-                    rendered_items.push_front(ListItem::Rendered(element));
+                    if let Some(element) =
+                        state.render_item(cursor.start().0, item, item_constraint, cx)
+                    {
+                        rendered_height += element.size().y();
+                        rendered_items.push_front(ListItem::Rendered(element));
+                    }
                 } else {
                     break;
                 }
@@ -182,9 +188,12 @@ impl Element for List {
         while leading_overdraw < state.overdraw {
             cursor.prev(&());
             if let Some(item) = cursor.item() {
-                let element = state.render_item(cursor.start().0, item, item_constraint, cx);
-                leading_overdraw += element.size().y();
-                rendered_items.push_front(ListItem::Rendered(element));
+                if let Some(element) =
+                    state.render_item(cursor.start().0, item, item_constraint, cx)
+                {
+                    leading_overdraw += element.size().y();
+                    rendered_items.push_front(ListItem::Rendered(element));
+                }
             } else {
                 break;
             }
@@ -330,20 +339,25 @@ impl Element for List {
 }
 
 impl ListState {
-    pub fn new<F>(
+    pub fn new<F, V>(
         element_count: usize,
         orientation: Orientation,
         overdraw: f32,
-        render_item: F,
+        cx: &mut ViewContext<V>,
+        mut render_item: F,
     ) -> Self
     where
-        F: 'static + FnMut(usize, &mut LayoutContext) -> ElementBox,
+        V: View,
+        F: 'static + FnMut(&mut V, usize, &mut RenderContext<V>) -> ElementBox,
     {
         let mut items = SumTree::new();
         items.extend((0..element_count).map(|_| ListItem::Unrendered), &());
+        let handle = cx.handle();
         Self(Rc::new(RefCell::new(StateInner {
             last_layout_width: None,
-            render_item: Box::new(render_item),
+            render_item: Box::new(move |ix, cx| {
+                Some(cx.render(&handle, |view, cx| render_item(view, ix, cx)))
+            }),
             rendered_range: 0..0,
             items,
             logical_scroll_top: None,
@@ -414,13 +428,13 @@ impl StateInner {
         existing_item: &ListItem,
         constraint: SizeConstraint,
         cx: &mut LayoutContext,
-    ) -> ElementRc {
+    ) -> Option<ElementRc> {
         if let ListItem::Rendered(element) = existing_item {
-            element.clone()
+            Some(element.clone())
         } else {
-            let mut element = (self.render_item)(ix, cx);
+            let mut element = (self.render_item)(ix, cx)?;
             element.layout(constraint, cx);
-            element.into()
+            Some(element.into())
         }
     }
 
@@ -593,22 +607,26 @@ impl<'a> sum_tree::SeekTarget<'a, ListItemSummary, ListItemSummary> for Height {
 #[cfg(test)]
 mod tests {
     use super::*;
-    use crate::geometry::vector::vec2f;
+    use crate::{elements::Empty, geometry::vector::vec2f, Entity};
     use rand::prelude::*;
     use std::env;
 
     #[crate::test(self)]
     fn test_layout(cx: &mut crate::MutableAppContext) {
         let mut presenter = cx.build_presenter(0, 0.);
+        let (_, view) = cx.add_window(Default::default(), |_| TestView);
         let constraint = SizeConstraint::new(vec2f(0., 0.), vec2f(100., 40.));
 
         let elements = Rc::new(RefCell::new(vec![(0, 20.), (1, 30.), (2, 100.)]));
-        let state = ListState::new(elements.borrow().len(), Orientation::Top, 1000.0, {
-            let elements = elements.clone();
-            move |ix, _| {
-                let (id, height) = elements.borrow()[ix];
-                TestElement::new(id, height).boxed()
-            }
+
+        let state = view.update(cx, |_, cx| {
+            ListState::new(elements.borrow().len(), Orientation::Top, 1000.0, cx, {
+                let elements = elements.clone();
+                move |_, ix, _| {
+                    let (id, height) = elements.borrow()[ix];
+                    TestElement::new(id, height).boxed()
+                }
+            })
         });
 
         let mut list = List::new(state.clone());
@@ -687,6 +705,7 @@ mod tests {
             .map(|i| i.parse().expect("invalid `OPERATIONS` variable"))
             .unwrap_or(10);
 
+        let (_, view) = cx.add_window(Default::default(), |_| TestView);
         let mut presenter = cx.build_presenter(0, 0.);
         let mut next_id = 0;
         let elements = Rc::new(RefCell::new(
@@ -702,12 +721,15 @@ mod tests {
             .choose(&mut rng)
             .unwrap();
         let overdraw = rng.gen_range(1..=100) as f32;
-        let state = ListState::new(elements.borrow().len(), orientation, overdraw, {
-            let elements = elements.clone();
-            move |ix, _| {
-                let (id, height) = elements.borrow()[ix];
-                TestElement::new(id, height).boxed()
-            }
+
+        let state = view.update(cx, |_, cx| {
+            ListState::new(elements.borrow().len(), orientation, overdraw, cx, {
+                let elements = elements.clone();
+                move |_, ix, _| {
+                    let (id, height) = elements.borrow()[ix];
+                    TestElement::new(id, height).boxed()
+                }
+            })
         });
 
         let mut width = rng.gen_range(0..=2000) as f32 / 2.;
@@ -843,6 +865,22 @@ mod tests {
         }
     }
 
+    struct TestView;
+
+    impl Entity for TestView {
+        type Event = ();
+    }
+
+    impl View for TestView {
+        fn ui_name() -> &'static str {
+            "TestView"
+        }
+
+        fn render(&mut self, _: &mut RenderContext<'_, Self>) -> ElementBox {
+            Empty::new().boxed()
+        }
+    }
+
     struct TestElement {
         id: usize,
         size: Vector2F,

crates/project_panel/src/project_panel.rs

@@ -10,7 +10,7 @@ use gpui::{
     impl_internal_actions, keymap,
     platform::CursorStyle,
     AppContext, Element, ElementBox, Entity, ModelHandle, MutableAppContext, PromptLevel,
-    RenderContext, Task, View, ViewContext, ViewHandle, WeakViewHandle,
+    RenderContext, Task, View, ViewContext, ViewHandle,
 };
 use project::{Entry, EntryKind, Project, ProjectEntryId, ProjectPath, Worktree, WorktreeId};
 use settings::Settings;
@@ -36,7 +36,6 @@ pub struct ProjectPanel {
     selection: Option<Selection>,
     edit_state: Option<EditState>,
     filename_editor: ViewHandle<Editor>,
-    handle: WeakViewHandle<Self>,
 }
 
 #[derive(Copy, Clone)]
@@ -156,7 +155,6 @@ impl ProjectPanel {
                 selection: None,
                 edit_state: None,
                 filename_editor,
-                handle: cx.weak_handle(),
             };
             this.update_visible_entries(None, cx);
             this