From 317acbf1d72ad94e835b105e4aea1ce96f5dd8e6 Mon Sep 17 00:00:00 2001
From: Marshall Bowers <elliott.codes@gmail.com>
Date: Tue, 24 Oct 2023 14:55:23 +0200
Subject: [PATCH] WIP: Trampoline

---
 crates/gpui2/src/elements.rs                  |  2 +
 crates/gpui2/src/elements/trampoline.rs       | 65 +++++++++++++++++++
 .../src/derive_into_any_element.rs            | 64 +++++++++++++++++-
 crates/ui2/src/components/assistant_panel.rs  | 10 +--
 4 files changed, 132 insertions(+), 9 deletions(-)
 create mode 100644 crates/gpui2/src/elements/trampoline.rs

diff --git a/crates/gpui2/src/elements.rs b/crates/gpui2/src/elements.rs
index 83c27b8a3b..a1a54a2c87 100644
--- a/crates/gpui2/src/elements.rs
+++ b/crates/gpui2/src/elements.rs
@@ -2,8 +2,10 @@ mod div;
 mod img;
 mod svg;
 mod text;
+mod trampoline;
 
 pub use div::*;
 pub use img::*;
 pub use svg::*;
 pub use text::*;
+pub use trampoline::*;
diff --git a/crates/gpui2/src/elements/trampoline.rs b/crates/gpui2/src/elements/trampoline.rs
new file mode 100644
index 0000000000..5946e5eb7b
--- /dev/null
+++ b/crates/gpui2/src/elements/trampoline.rs
@@ -0,0 +1,65 @@
+use crate::{Element, ViewContext, AnyElement, IntoAnyElement};
+
+pub trait TemporaryRenderTraitDontWorryAboutIt<S> {
+    fn render(self, cx: &mut ViewContext<S>) -> AnyElement<S>;
+}
+
+
+struct IntoAnyElementTrampolineName<S, E: TemporaryRenderTraitDontWorryAboutIt<S>> {
+    contents: Option<E>,
+    phantom: std::marker::PhantomData<S>,
+}
+
+impl<S, E: TemporaryRenderTraitDontWorryAboutIt<S>> IntoAnyElementTrampolineName<S, E> {
+    fn new(contents: E) -> Self {
+        IntoAnyElementTrampolineName {
+            contents: Some(contents),
+            phantom: std::marker::PhantomData,
+
+        }
+    }
+}
+
+impl<S, E: TemporaryRenderTraitDontWorryAboutIt<S>> Element for IntoAnyElementTrampolineName<S, E> {
+    type ViewState = S;
+
+    type ElementState = AnyElement<S>;
+
+    fn id(&self) -> Option<crate::ElementId> {
+        None
+    }
+
+    fn initialize(
+        &mut self,
+        view_state: &mut Self::ViewState,
+        element_state: Option<Self::ElementState>,
+        cx: &mut ViewContext<Self::ViewState>,
+    ) -> Self::ElementState {
+        self.contents.take().unwrap().render(cx)
+    }
+
+    fn layout(
+        &mut self,
+        view_state: &mut Self::ViewState,
+        element_state: &mut Self::ElementState,
+        cx: &mut ViewContext<Self::ViewState>,
+    ) -> crate::LayoutId {
+        element_state.layout(view_state, cx)
+    }
+
+    fn paint(
+        &mut self,
+        bounds: crate::Bounds<crate::Pixels>,
+        view_state: &mut Self::ViewState,
+        element_state: &mut Self::ElementState,
+        cx: &mut ViewContext<Self::ViewState>,
+    ) {
+        element_state.paint(view_state, cx);
+    }
+}
+
+impl<S, E: TemporaryRenderTraitDontWorryAboutIt<S>> IntoAnyElement<S> for IntoAnyElementTrampolineName<S, E> {
+    fn into_any(self) -> AnyElement<S> {
+        AnyElement::new(self)
+    }
+}
diff --git a/crates/gpui2_macros/src/derive_into_any_element.rs b/crates/gpui2_macros/src/derive_into_any_element.rs
index 4c6d9e3d7f..7f0c9ae2c0 100644
--- a/crates/gpui2_macros/src/derive_into_any_element.rs
+++ b/crates/gpui2_macros/src/derive_into_any_element.rs
@@ -11,7 +11,7 @@
 
 // Defining a derive macro
 use proc_macro::TokenStream;
-use quote::quote;
+use quote::{quote, format_ident};
 use syn::{parse_macro_input, DeriveInput};
 
 pub fn derive_into_any_element(input: TokenStream) -> TokenStream {
@@ -57,12 +57,72 @@ pub fn derive_into_any_element(input: TokenStream) -> TokenStream {
         let (_, ty_generics, _) = generics.split_for_impl();
         let (impl_generics, _, where_clause) = trait_generics.split_for_impl();
 
+        let trampoline_name = format_ident!("{}{}", name, "Trampoline");
+
         quote! {
+            struct #trampoline_name<S, E> {
+                contents: Option<E>,
+                phantom: std::marker::PhantomData<S>,
+            }
+
+            impl<S, E> #trampoline_name<S, E> {
+                fn new(contents: E) -> Self {
+                    IntoAnyElementTrampolineName {
+                        contents: Some(contents),
+                        phantom: std::marker::PhantomData,
+                    }
+                }
+            }
+
+            impl<S, E> Element for #trampoline_name<S, E> {
+                type ViewState = S;
+
+                type ElementState = AnyElement<S>;
+
+                fn id(&self) -> Option<crate::ElementId> {
+                    None
+                }
+
+                fn initialize(
+                    &mut self,
+                    view_state: &mut Self::ViewState,
+                    element_state: Option<Self::ElementState>,
+                    cx: &mut ViewContext<Self::ViewState>,
+                ) -> Self::ElementState {
+                    self.contents.take().unwrap().render(cx)
+                }
+
+                fn layout(
+                    &mut self,
+                    view_state: &mut Self::ViewState,
+                    element_state: &mut Self::ElementState,
+                    cx: &mut ViewContext<Self::ViewState>,
+                ) -> crate::LayoutId {
+                    element_state.layout(view_state, cx)
+                }
+
+                fn paint(
+                    &mut self,
+                    bounds: crate::Bounds<crate::Pixels>,
+                    view_state: &mut Self::ViewState,
+                    element_state: &mut Self::ElementState,
+                    cx: &mut ViewContext<Self::ViewState>,
+                ) {
+                    element_state.paint(view_state, cx);
+                }
+            }
+
+            impl<S, E> IntoAnyElement<S> for IntoAnyElementTrampolineName<S, E> {
+                fn into_any(self) -> AnyElement<S> {
+                    AnyElement::new(self)
+                }
+            }
+
             impl #impl_generics gpui2::IntoAnyElement<ViewState> for #name #ty_generics
             #where_clause
             {
                 fn into_any(self) -> gpui2::AnyElement<ViewState> {
-                    Self::render(self).into_any()
+                    #trampoline_name(self).into_any()
                 }
             }
         }
diff --git a/crates/ui2/src/components/assistant_panel.rs b/crates/ui2/src/components/assistant_panel.rs
index 0f7aa8d75a..50046735d4 100644
--- a/crates/ui2/src/components/assistant_panel.rs
+++ b/crates/ui2/src/components/assistant_panel.rs
@@ -86,14 +86,10 @@ mod stories {
     use super::*;
 
     #[derive(IntoAnyElement)]
-    pub struct AssistantPanelStory<'a>(&'a AppContext);
+    pub struct AssistantPanelStory;
 
-    impl<'a> AssistantPanelStory<'a> {
-        pub fn new() -> Self {
-            Self
-        }
-
-        fn render<V>(self) -> impl IntoAnyElement<V> {
+    impl AssistantPanelStory {
+        fn render<V>(self, cx: &mut ViewContext<V>) -> impl IntoAnyElement<V> {
             Story::container(self.0)
                 .child(Story::title_for::<_, AssistantPanel>(self.0))
                 .child(Story::label(self.cx, "Default"))