Start on caching views

Co-Authored-By: Nathan Sobo <nathan@zed.dev>

crates/gpui/src/geometry.rs

@@ -2272,7 +2272,7 @@ impl From<f64> for GlobalPixels {
 /// For example, if the root element's font-size is `16px`, then `1rem` equals `16px`. A length of `2rems` would then be `32px`.
 ///
 /// [set_rem_size]: crate::WindowContext::set_rem_size
-#[derive(Clone, Copy, Default, Add, Sub, Mul, Div, Neg)]
+#[derive(Clone, Copy, Default, Add, Sub, Mul, Div, Neg, PartialEq)]
 pub struct Rems(pub f32);
 
 impl Mul<Pixels> for Rems {
@@ -2295,7 +2295,7 @@ impl Debug for Rems {
 /// affected by the current font size, or a number of rems, which is relative to the font size of
 /// the root element. It is used for specifying dimensions that are either independent of or
 /// related to the typographic scale.
-#[derive(Clone, Copy, Debug, Neg)]
+#[derive(Clone, Copy, Debug, Neg, PartialEq)]
 pub enum AbsoluteLength {
     /// A length in pixels.
     Pixels(Pixels),
@@ -2366,7 +2366,7 @@ impl Default for AbsoluteLength {
 /// This enum represents lengths that have a specific value, as opposed to lengths that are automatically
 /// determined by the context. It includes absolute lengths in pixels or rems, and relative lengths as a
 /// fraction of the parent's size.
-#[derive(Clone, Copy, Neg)]
+#[derive(Clone, Copy, Neg, PartialEq)]
 pub enum DefiniteLength {
     /// An absolute length specified in pixels or rems.
     Absolute(AbsoluteLength),

crates/gpui/src/style.rs

@@ -146,7 +146,7 @@ pub enum WhiteSpace {
     Nowrap,
 }
 
-#[derive(Refineable, Clone, Debug)]
+#[derive(Refineable, Clone, Debug, PartialEq)]
 #[refineable(Debug)]
 pub struct TextStyle {
     pub color: Hsla,

crates/gpui/src/taffy.rs

@@ -12,6 +12,7 @@ use taffy::{
 
 pub struct TaffyLayoutEngine {
     tree: TaffyTree,
+    styles: FxHashMap<LayoutId, Style>,
     absolute_layout_bounds: FxHashMap<LayoutId, Bounds<Pixels>>,
     computed_layouts: FxHashSet<LayoutId>,
     nodes_to_measure: FxHashMap<
@@ -32,6 +33,7 @@ impl TaffyLayoutEngine {
     pub fn new() -> Self {
         TaffyLayoutEngine {
             tree: TaffyTree::new(),
+            styles: FxHashMap::default(),
             absolute_layout_bounds: FxHashMap::default(),
             computed_layouts: FxHashSet::default(),
             nodes_to_measure: FxHashMap::default(),
@@ -43,6 +45,11 @@ impl TaffyLayoutEngine {
         self.absolute_layout_bounds.clear();
         self.computed_layouts.clear();
         self.nodes_to_measure.clear();
+        self.styles.clear();
+    }
+
+    pub fn requested_style(&self, layout_id: LayoutId) -> Option<&Style> {
+        self.styles.get(&layout_id)
     }
 
     pub fn request_layout(
@@ -51,16 +58,21 @@ impl TaffyLayoutEngine {
         rem_size: Pixels,
         children: &[LayoutId],
     ) -> LayoutId {
-        let style = style.to_taffy(rem_size);
+        let taffy_style = style.to_taffy(rem_size);
-        if children.is_empty() {
+        let layout_id = if children.is_empty() {
-            self.tree.new_leaf(style).expect(EXPECT_MESSAGE).into()
+            self.tree
+                .new_leaf(taffy_style)
+                .expect(EXPECT_MESSAGE)
+                .into()
         } else {
             self.tree
                 // This is safe because LayoutId is repr(transparent) to taffy::tree::NodeId.
-                .new_with_children(style, unsafe { std::mem::transmute(children) })
+                .new_with_children(taffy_style, unsafe { std::mem::transmute(children) })
                 .expect(EXPECT_MESSAGE)
                 .into()
-        }
+        };
+        self.styles.insert(layout_id, style.clone());
+        layout_id
     }
 
     pub fn request_measured_layout(
@@ -70,14 +82,16 @@ impl TaffyLayoutEngine {
         measure: impl FnMut(Size<Option<Pixels>>, Size<AvailableSpace>, &mut WindowContext) -> Size<Pixels>
             + 'static,
     ) -> LayoutId {
-        let style = style.to_taffy(rem_size);
+        let style = style.clone();
+        let taffy_style = style.to_taffy(rem_size);
 
         let layout_id = self
             .tree
-            .new_leaf_with_context(style, ())
+            .new_leaf_with_context(taffy_style, ())
             .expect(EXPECT_MESSAGE)
             .into();
         self.nodes_to_measure.insert(layout_id, Box::new(measure));
+        self.styles.insert(layout_id, style.clone());
         layout_id
     }
 

crates/gpui/src/view.rs

@@ -1,8 +1,8 @@
 use crate::{
     seal::Sealed, AnyElement, AnyModel, AnyWeakModel, AppContext, AvailableSpace, BorrowWindow,
-    Bounds, Element, ElementId, Entity, EntityId, Flatten, FocusHandle, FocusableView, IntoElement,
+    Bounds, ContentMask, Element, ElementId, Entity, EntityId, Flatten, FocusHandle, FocusableView,
-    LayoutId, Model, Pixels, Point, Render, Size, ViewContext, VisualContext, WeakModel,
+    IntoElement, LayoutId, Model, Pixels, Point, Render, Size, StackingOrder, Style, TextStyle,
-    WindowContext,
+    ViewContext, VisualContext, WeakModel, WindowContext,
 };
 use anyhow::{Context, Result};
 use std::{
@@ -17,6 +17,19 @@ pub struct View<V> {
 
 impl<V> Sealed for View<V> {}
 
+pub struct AnyViewState {
+    root_style: Style,
+    cache_key: Option<ViewCacheKey>,
+    element: Option<AnyElement>,
+}
+
+struct ViewCacheKey {
+    bounds: Bounds<Pixels>,
+    stacking_order: StackingOrder,
+    content_mask: ContentMask<Pixels>,
+    text_style: TextStyle,
+}
+
 impl<V: 'static> Entity<V> for View<V> {
     type Weak = WeakView<V>;
 
@@ -60,16 +73,6 @@ impl<V: 'static> View<V> {
         self.model.read(cx)
     }
 
-    // pub fn render_with<E>(&self, component: E) -> RenderViewWith<E, V>
-    // where
-    //     E: 'static + Element,
-    // {
-    //     RenderViewWith {
-    //         view: self.clone(),
-    //         element: Some(component),
-    //     }
-    // }
-
     pub fn focus_handle(&self, cx: &AppContext) -> FocusHandle
     where
         V: FocusableView,
@@ -183,16 +186,20 @@ impl<V> Eq for WeakView<V> {}
 #[derive(Clone, Debug)]
 pub struct AnyView {
     model: AnyModel,
-    layout: fn(&AnyView, &mut WindowContext) -> (LayoutId, AnyElement),
+    request_layout: fn(&AnyView, &mut WindowContext) -> (LayoutId, AnyElement),
-    paint: fn(&AnyView, &mut AnyElement, &mut WindowContext),
+    cache: bool,
 }
 
 impl AnyView {
+    pub fn cached(mut self) -> Self {
+        self.cache = true;
+        self
+    }
+
     pub fn downgrade(&self) -> AnyWeakView {
         AnyWeakView {
             model: self.model.downgrade(),
-            layout: self.layout,
+            layout: self.request_layout,
-            paint: self.paint,
         }
     }
 
@@ -201,8 +208,8 @@ impl AnyView {
             Ok(model) => Ok(View { model }),
             Err(model) => Err(Self {
                 model,
-                layout: self.layout,
+                request_layout: self.request_layout,
-                paint: self.paint,
+                cache: self.cache,
             }),
         }
     }
@@ -222,9 +229,9 @@ impl AnyView {
         cx: &mut WindowContext,
     ) {
         cx.with_absolute_element_offset(origin, |cx| {
-            let (layout_id, mut rendered_element) = (self.layout)(self, cx);
+            let (layout_id, mut rendered_element) = (self.request_layout)(self, cx);
             cx.compute_layout(layout_id, available_space);
-            (self.paint)(self, &mut rendered_element, cx);
+            rendered_element.paint(cx);
         })
     }
 }
@@ -233,30 +240,65 @@ impl<V: Render> From<View<V>> for AnyView {
     fn from(value: View<V>) -> Self {
         AnyView {
             model: value.model.into_any(),
-            layout: any_view::layout::<V>,
+            request_layout: any_view::request_layout::<V>,
-            paint: any_view::paint,
+            cache: false,
         }
     }
 }
 
 impl Element for AnyView {
-    type State = Option<AnyElement>;
+    type State = AnyViewState;
 
     fn request_layout(
         &mut self,
-        _state: Option<Self::State>,
+        state: Option<Self::State>,
         cx: &mut WindowContext,
     ) -> (LayoutId, Self::State) {
-        let (layout_id, state) = (self.layout)(self, cx);
+        if self.cache {
-        (layout_id, Some(state))
+            if let Some(state) = state {
+                let layout_id = cx.request_layout(&state.root_style, None);
+                return (layout_id, state);
+            }
         }
 
-    fn paint(&mut self, _: Bounds<Pixels>, state: &mut Self::State, cx: &mut WindowContext) {
+        let (layout_id, element) = (self.request_layout)(self, cx);
-        debug_assert!(
+        let root_style = cx.layout_style(layout_id).unwrap().clone();
-            state.is_some(),
+        let state = AnyViewState {
-            "state is None. Did you include an AnyView twice in the tree?"
+            root_style,
-        );
+            cache_key: None,
-        (self.paint)(self, state.as_mut().unwrap(), cx)
+            element: Some(element),
+        };
+        (layout_id, state)
+    }
+
+    fn paint(&mut self, bounds: Bounds<Pixels>, state: &mut Self::State, cx: &mut WindowContext) {
+        if !self.cache {
+            state.element.take().unwrap().paint(cx);
+            return;
+        }
+
+        if let Some(cache_key) = state.cache_key.as_mut() {
+            if cache_key.bounds == bounds
+                && cache_key.content_mask == cx.content_mask()
+                && cache_key.stacking_order == *cx.stacking_order()
+                && cache_key.text_style == cx.text_style()
+            {
+                println!("could reuse geometry for view {}", self.entity_id());
+            }
+        }
+
+        let mut element = state
+            .element
+            .take()
+            .unwrap_or_else(|| (self.request_layout)(self, cx).1);
+        element.draw(bounds.origin, bounds.size.into(), cx);
+
+        state.cache_key = Some(ViewCacheKey {
+            bounds,
+            stacking_order: cx.stacking_order().clone(),
+            content_mask: cx.content_mask(),
+            text_style: cx.text_style(),
+        });
     }
 }
 
@@ -287,7 +329,6 @@ impl IntoElement for AnyView {
 pub struct AnyWeakView {
     model: AnyWeakModel,
     layout: fn(&AnyView, &mut WindowContext) -> (LayoutId, AnyElement),
-    paint: fn(&AnyView, &mut AnyElement, &mut WindowContext),
 }
 
 impl AnyWeakView {
@@ -295,8 +336,8 @@ impl AnyWeakView {
         let model = self.model.upgrade()?;
         Some(AnyView {
             model,
-            layout: self.layout,
+            request_layout: self.layout,
-            paint: self.paint,
+            cache: false,
         })
     }
 }
@@ -305,8 +346,7 @@ impl<V: 'static + Render> From<WeakView<V>> for AnyWeakView {
     fn from(view: WeakView<V>) -> Self {
         Self {
             model: view.model.into(),
-            layout: any_view::layout::<V>,
+            layout: any_view::request_layout::<V>,
-            paint: any_view::paint,
         }
     }
 }
@@ -328,7 +368,7 @@ impl std::fmt::Debug for AnyWeakView {
 mod any_view {
     use crate::{AnyElement, AnyView, IntoElement, LayoutId, Render, WindowContext};
 
-    pub(crate) fn layout<V: 'static + Render>(
+    pub(crate) fn request_layout<V: 'static + Render>(
         view: &AnyView,
         cx: &mut WindowContext,
     ) -> (LayoutId, AnyElement) {
@@ -337,8 +377,4 @@ mod any_view {
         let layout_id = element.request_layout(cx);
         (layout_id, element)
     }
-
-    pub(crate) fn paint(_view: &AnyView, element: &mut AnyElement, cx: &mut WindowContext) {
-        element.paint(cx);
-    }
 }

crates/gpui/src/window.rs

@@ -754,6 +754,14 @@ impl<'a> WindowContext<'a> {
             .request_measured_layout(style, rem_size, measure)
     }
 
+    pub fn layout_style(&self, layout_id: LayoutId) -> Option<&Style> {
+        self.window
+            .layout_engine
+            .as_ref()
+            .unwrap()
+            .requested_style(layout_id)
+    }
+
     pub fn compute_layout(&mut self, layout_id: LayoutId, available_space: Size<AvailableSpace>) {
         let mut layout_engine = self.window.layout_engine.take().unwrap();
         layout_engine.compute_layout(layout_id, available_space, self);
@@ -1313,6 +1321,7 @@ impl<'a> WindowContext<'a> {
 
     /// Draw pixels to the display for this window based on the contents of its scene.
     pub(crate) fn draw(&mut self) -> Scene {
+        println!("=====================");
         self.window.dirty = false;
         self.window.drawing = true;
 

crates/workspace/src/dock.rs

@@ -601,7 +601,7 @@ impl Render for Dock {
                             Axis::Horizontal => this.min_w(size).h_full(),
                             Axis::Vertical => this.min_h(size).w_full(),
                         })
-                        .child(entry.panel.to_any()),
+                        .child(entry.panel.to_any().cached()),
                 )
                 .child(handle)
         } else {

crates/workspace/src/pane_group.rs

@@ -3,8 +3,8 @@ use anyhow::{anyhow, Result};
 use call::{ActiveCall, ParticipantLocation};
 use collections::HashMap;
 use gpui::{
-    point, size, AnyWeakView, Axis, Bounds, Entity as _, IntoElement, Model, Pixels, Point, View,
+    point, size, AnyView, AnyWeakView, Axis, Bounds, Entity as _, IntoElement, Model, Pixels,
-    ViewContext,
+    Point, View, ViewContext,
 };
 use parking_lot::Mutex;
 use project::Project;
@@ -244,7 +244,7 @@ impl Member {
                     .relative()
                     .flex_1()
                     .size_full()
-                    .child(pane.clone())
+                    .child(AnyView::from(pane.clone()).cached())
                     .when_some(leader_border, |this, color| {
                         this.child(
                             div()