Add a proc macro for deriving override structs with optional fields

crates/gpui/playground/src/components.rs

@@ -1,6 +1,6 @@
 use crate::{
+    div,
     element::{Element, ElementMetadata},
-    frame,
     text::ArcCow,
     themes::rose_pine,
 };
@@ -82,8 +82,9 @@ pub fn button<V>() -> Button<V, ()> {
 impl<V: 'static, D: 'static> Button<V, D> {
     fn render(&mut self, view: &mut V, cx: &mut ViewContext<V>) -> impl Element<V> {
         // TODO: Drive theme from the context
-        let button = frame()
+        let button = div()
             .fill(rose_pine::dawn().error(0.5))
+            // .hover_fill(rose_pine::dawn().error(0.6))
             .h_4()
             .children(self.label.clone());
 

crates/gpui/playground/src/div.rs

@@ -1,8 +1,5 @@
-use crate::{
+use crate::element::{
-    element::{
+    AnyElement, Element, ElementMetadata, IntoElement, Layout, LayoutContext, NodeId, PaintContext,
-        AnyElement, Element, EventHandler, IntoElement, Layout, LayoutContext, NodeId, PaintContext,
-    },
-    style::ElementStyle,
 };
 use anyhow::{anyhow, Result};
 use gpui::LayoutNodeId;
@@ -10,29 +7,23 @@ use playground_macros::IntoElement;
 
 #[derive(IntoElement)]
 #[element_crate = "crate"]
-pub struct Frame<V: 'static> {
+pub struct Div<V: 'static> {
-    style: ElementStyle,
+    metadata: ElementMetadata<V>,
-    handlers: Vec<EventHandler<V>>,
     children: Vec<AnyElement<V>>,
 }
 
-pub fn frame<V>() -> Frame<V> {
+pub fn div<V>() -> Div<V> {
-    Frame {
+    Div {
-        style: ElementStyle::default(),
+        metadata: ElementMetadata::default(),
-        handlers: Vec::new(),
         children: Vec::new(),
     }
 }
 
-impl<V: 'static> Element<V> for Frame<V> {
+impl<V: 'static> Element<V> for Div<V> {
     type Layout = ();
 
-    fn style_mut(&mut self) -> &mut ElementStyle {
+    fn metadata(&mut self) -> &mut ElementMetadata<V> {
-        &mut self.style
+        &mut self.metadata
-    }
-
-    fn handlers_mut(&mut self) -> &mut Vec<EventHandler<V>> {
-        &mut self.handlers
     }
 
     fn layout(
@@ -50,7 +41,10 @@ impl<V: 'static> Element<V> for Frame<V> {
         let node_id = cx
             .layout_engine()
             .ok_or_else(|| anyhow!("no layout engine"))?
-            .add_node(self.style.to_taffy(rem_size), child_layout_node_ids)?;
+            .add_node(
+                self.metadata.style.to_taffy(rem_size),
+                child_layout_node_ids,
+            )?;
 
         Ok((node_id, ()))
     }
@@ -58,7 +52,7 @@ impl<V: 'static> Element<V> for Frame<V> {
     fn paint(&mut self, layout: Layout<()>, view: &mut V, cx: &mut PaintContext<V>) -> Result<()> {
         cx.scene.push_quad(gpui::scene::Quad {
             bounds: layout.from_engine.bounds,
-            background: self.style.fill.color().map(Into::into),
+            background: self.metadata.style.fill.color().map(Into::into),
             border: Default::default(),
             corner_radii: Default::default(),
         });
@@ -70,7 +64,7 @@ impl<V: 'static> Element<V> for Frame<V> {
     }
 }
 
-impl<V: 'static> Frame<V> {
+impl<V: 'static> Div<V> {
     pub fn child(mut self, child: impl IntoElement<V>) -> Self {
         self.children.push(child.into_any_element());
         self

crates/gpui/playground/src/element.rs

@@ -1,7 +1,7 @@
 use crate::{
     adapter::Adapter,
     color::Hsla,
-    style::{Display, ElementStyle, Fill, Overflow, Position},
+    style::{Display, ElementStyle, ElementStyleOverrides, Fill, Overflow, Position},
 };
 use anyhow::Result;
 pub use gpui::LayoutContext;
@@ -27,6 +27,7 @@ pub struct Layout<'a, E: ?Sized> {
 
 pub struct ElementMetadata<V> {
     pub style: ElementStyle,
+    pub hover_style: ElementStyleOverrides,
     pub handlers: Vec<EventHandler<V>>,
 }
 
@@ -50,6 +51,7 @@ impl<V> Default for ElementMetadata<V> {
     fn default() -> Self {
         Self {
             style: ElementStyle::default(),
+            hover_style: ElementStyleOverrides::default(),
             handlers: Vec::new(),
         }
     }
@@ -58,8 +60,7 @@ impl<V> Default for ElementMetadata<V> {
 pub trait Element<V: 'static>: 'static {
     type Layout: 'static;
 
-    fn style_mut(&mut self) -> &mut ElementStyle;
+    fn metadata(&mut self) -> &mut ElementMetadata<V>;
-    fn handlers_mut(&mut self) -> &mut Vec<EventHandler<V>>;
 
     fn layout(&mut self, view: &mut V, cx: &mut LayoutContext<V>)
         -> Result<(NodeId, Self::Layout)>;
@@ -126,7 +127,7 @@ pub trait Element<V: 'static>: 'static {
     where
         Self: Sized,
     {
-        self.handlers_mut().push(EventHandler {
+        self.metadata().handlers.push(EventHandler {
             handler: Rc::new(move |view, event, event_cx| {
                 let event = event.downcast_ref::<MouseButtonEvent>().unwrap();
                 if event.button == button && event.is_down {
@@ -147,7 +148,7 @@ pub trait Element<V: 'static>: 'static {
     where
         Self: Sized,
     {
-        self.handlers_mut().push(EventHandler {
+        self.metadata().handlers.push(EventHandler {
             handler: Rc::new(move |view, event, event_cx| {
                 let event = event.downcast_ref::<MouseButtonEvent>().unwrap();
                 if event.button == button && event.is_down {
@@ -168,7 +169,7 @@ pub trait Element<V: 'static>: 'static {
     where
         Self: Sized,
     {
-        self.handlers_mut().push(EventHandler {
+        self.metadata().handlers.push(EventHandler {
             handler: Rc::new(move |view, event, event_cx| {
                 let event = event.downcast_ref::<MouseButtonEvent>().unwrap();
                 if event.button == button && !event.is_down {
@@ -189,7 +190,7 @@ pub trait Element<V: 'static>: 'static {
     where
         Self: Sized,
     {
-        self.handlers_mut().push(EventHandler {
+        self.metadata().handlers.push(EventHandler {
             handler: Rc::new(move |view, event, event_cx| {
                 let event = event.downcast_ref::<MouseButtonEvent>().unwrap();
                 if event.button == button && !event.is_down {
@@ -208,7 +209,7 @@ pub trait Element<V: 'static>: 'static {
     where
         Self: Sized,
     {
-        self.style_mut().display = Display::Block;
+        self.metadata().style.display = Display::Block;
         self
     }
 
@@ -216,7 +217,7 @@ pub trait Element<V: 'static>: 'static {
     where
         Self: Sized,
     {
-        self.style_mut().display = Display::Flex;
+        self.metadata().style.display = Display::Flex;
         self
     }
 
@@ -224,7 +225,7 @@ pub trait Element<V: 'static>: 'static {
     where
         Self: Sized,
     {
-        self.style_mut().display = Display::Grid;
+        self.metadata().style.display = Display::Grid;
         self
     }
 
@@ -234,8 +235,8 @@ pub trait Element<V: 'static>: 'static {
     where
         Self: Sized,
     {
-        self.style_mut().overflow.x = Overflow::Visible;
+        self.metadata().style.overflow.x = Overflow::Visible;
-        self.style_mut().overflow.y = Overflow::Visible;
+        self.metadata().style.overflow.y = Overflow::Visible;
         self
     }
 
@@ -243,8 +244,8 @@ pub trait Element<V: 'static>: 'static {
     where
         Self: Sized,
     {
-        self.style_mut().overflow.x = Overflow::Hidden;
+        self.metadata().style.overflow.x = Overflow::Hidden;
-        self.style_mut().overflow.y = Overflow::Hidden;
+        self.metadata().style.overflow.y = Overflow::Hidden;
         self
     }
 
@@ -252,8 +253,8 @@ pub trait Element<V: 'static>: 'static {
     where
         Self: Sized,
     {
-        self.style_mut().overflow.x = Overflow::Scroll;
+        self.metadata().style.overflow.x = Overflow::Scroll;
-        self.style_mut().overflow.y = Overflow::Scroll;
+        self.metadata().style.overflow.y = Overflow::Scroll;
         self
     }
 
@@ -261,7 +262,7 @@ pub trait Element<V: 'static>: 'static {
     where
         Self: Sized,
     {
-        self.style_mut().overflow.x = Overflow::Visible;
+        self.metadata().style.overflow.x = Overflow::Visible;
         self
     }
 
@@ -269,7 +270,7 @@ pub trait Element<V: 'static>: 'static {
     where
         Self: Sized,
     {
-        self.style_mut().overflow.x = Overflow::Hidden;
+        self.metadata().style.overflow.x = Overflow::Hidden;
         self
     }
 
@@ -277,7 +278,7 @@ pub trait Element<V: 'static>: 'static {
     where
         Self: Sized,
     {
-        self.style_mut().overflow.x = Overflow::Scroll;
+        self.metadata().style.overflow.x = Overflow::Scroll;
         self
     }
 
@@ -285,7 +286,7 @@ pub trait Element<V: 'static>: 'static {
     where
         Self: Sized,
     {
-        self.style_mut().overflow.y = Overflow::Visible;
+        self.metadata().style.overflow.y = Overflow::Visible;
         self
     }
 
@@ -293,7 +294,7 @@ pub trait Element<V: 'static>: 'static {
     where
         Self: Sized,
     {
-        self.style_mut().overflow.y = Overflow::Hidden;
+        self.metadata().style.overflow.y = Overflow::Hidden;
         self
     }
 
@@ -301,7 +302,7 @@ pub trait Element<V: 'static>: 'static {
     where
         Self: Sized,
     {
-        self.style_mut().overflow.y = Overflow::Scroll;
+        self.metadata().style.overflow.y = Overflow::Scroll;
         self
     }
 
@@ -311,7 +312,7 @@ pub trait Element<V: 'static>: 'static {
     where
         Self: Sized,
     {
-        self.style_mut().position = Position::Relative;
+        self.metadata().style.position = Position::Relative;
         self
     }
 
@@ -319,7 +320,7 @@ pub trait Element<V: 'static>: 'static {
     where
         Self: Sized,
     {
-        self.style_mut().position = Position::Absolute;
+        self.metadata().style.position = Position::Absolute;
 
         self
     }
@@ -329,10 +330,10 @@ pub trait Element<V: 'static>: 'static {
     where
         Self: Sized,
     {
-        self.style_mut().inset.top = length;
+        self.metadata().style.inset.top = length;
-        self.style_mut().inset.right = length;
+        self.metadata().style.inset.right = length;
-        self.style_mut().inset.bottom = length;
+        self.metadata().style.inset.bottom = length;
-        self.style_mut().inset.left = length;
+        self.metadata().style.inset.left = length;
         self
     }
 
@@ -340,7 +341,7 @@ pub trait Element<V: 'static>: 'static {
     where
         Self: Sized,
     {
-        self.style_mut().size.width = width.into();
+        self.metadata().style.size.width = width.into();
         self
     }
 
@@ -348,7 +349,7 @@ pub trait Element<V: 'static>: 'static {
     where
         Self: Sized,
     {
-        self.style_mut().size.width = Length::Auto;
+        self.metadata().style.size.width = Length::Auto;
         self
     }
 
@@ -357,7 +358,7 @@ pub trait Element<V: 'static>: 'static {
     where
         Self: Sized,
     {
-        self.style_mut().size.width = length;
+        self.metadata().style.size.width = length;
         self
     }
 
@@ -366,7 +367,7 @@ pub trait Element<V: 'static>: 'static {
     where
         Self: Sized,
     {
-        self.style_mut().min_size.width = length;
+        self.metadata().style.min_size.width = length;
         self
     }
 
@@ -374,7 +375,7 @@ pub trait Element<V: 'static>: 'static {
     where
         Self: Sized,
     {
-        self.style_mut().size.height = height.into();
+        self.metadata().style.size.height = height.into();
         self
     }
 
@@ -382,7 +383,7 @@ pub trait Element<V: 'static>: 'static {
     where
         Self: Sized,
     {
-        self.style_mut().size.height = Length::Auto;
+        self.metadata().style.size.height = Length::Auto;
         self
     }
 
@@ -391,7 +392,7 @@ pub trait Element<V: 'static>: 'static {
     where
         Self: Sized,
     {
-        self.style_mut().size.height = height;
+        self.metadata().style.size.height = height;
         self
     }
 
@@ -400,7 +401,7 @@ pub trait Element<V: 'static>: 'static {
     where
         Self: Sized,
     {
-        self.style_mut().min_size.height = length;
+        self.metadata().style.min_size.height = length;
         self
     }
 
@@ -408,7 +409,7 @@ pub trait Element<V: 'static>: 'static {
     where
         Self: Sized,
     {
-        self.style_mut().fill = fill.into();
+        self.metadata().style.fill = fill.into();
         self
     }
 
@@ -416,15 +417,14 @@ pub trait Element<V: 'static>: 'static {
     where
         Self: Sized,
     {
-        self.style_mut().text_color = Some(color.into());
+        self.metadata().style.text_color = Some(color.into());
         self
     }
 }
 
 // Object-safe counterpart of Element used by AnyElement to store elements as trait objects.
 trait ElementObject<V> {
-    fn style_mut(&mut self) -> &mut ElementStyle;
+    fn metadata(&mut self) -> &mut ElementMetadata<V>;
-    fn handlers_mut(&mut self) -> &mut Vec<EventHandler<V>>;
     fn layout(&mut self, view: &mut V, cx: &mut LayoutContext<V>)
         -> Result<(NodeId, Box<dyn Any>)>;
     fn paint(
@@ -436,12 +436,8 @@ trait ElementObject<V> {
 }
 
 impl<V: 'static, E: Element<V>> ElementObject<V> for E {
-    fn style_mut(&mut self) -> &mut ElementStyle {
+    fn metadata(&mut self) -> &mut ElementMetadata<V> {
-        Element::style_mut(self)
+        Element::metadata(self)
-    }
-
-    fn handlers_mut(&mut self) -> &mut Vec<EventHandler<V>> {
-        Element::handlers_mut(self)
     }
 
     fn layout(
@@ -490,7 +486,7 @@ impl<V: 'static> AnyElement<V> {
     }
 
     pub fn push_text_style(&mut self, cx: &mut impl RenderContext) -> bool {
-        let text_style = self.element.style_mut().text_style();
+        let text_style = self.element.metadata().style.text_style();
         if let Some(text_style) = text_style {
             let mut current_text_style = cx.text_style();
             text_style.apply(&mut current_text_style);
@@ -516,7 +512,7 @@ impl<V: 'static> AnyElement<V> {
             from_element: element_layout.as_mut(),
         };
 
-        for event_handler in self.element.handlers_mut().iter().cloned() {
+        for event_handler in self.element.metadata().handlers.iter().cloned() {
             let EngineLayout { order, bounds } = layout.from_engine;
 
             let view_id = cx.view_id();
@@ -551,12 +547,8 @@ impl<V: 'static> AnyElement<V> {
 impl<V: 'static> Element<V> for AnyElement<V> {
     type Layout = ();
 
-    fn style_mut(&mut self) -> &mut ElementStyle {
+    fn metadata(&mut self) -> &mut ElementMetadata<V> {
-        self.element.style_mut()
+        self.element.metadata()
-    }
-
-    fn handlers_mut(&mut self) -> &mut Vec<EventHandler<V>> {
-        self.element.handlers_mut()
     }
 
     fn layout(

crates/gpui/playground/src/playground.rs

@@ -1,11 +1,11 @@
 #![allow(dead_code, unused_variables)]
 use color::black;
 use components::button;
+use div::div;
 use element::Element;
-use frame::frame;
 use gpui::{
     geometry::{rect::RectF, vector::vec2f},
-    platform::{MouseButton, WindowOptions},
+    platform::WindowOptions,
 };
 use log::LevelFilter;
 use simplelog::SimpleLogger;
@@ -16,8 +16,8 @@ use view::view;
 mod adapter;
 mod color;
 mod components;
+mod div;
 mod element;
-mod frame;
 mod paint_context;
 mod style;
 mod text;
@@ -44,7 +44,7 @@ fn main() {
 }
 
 fn playground<V: 'static>(theme: &ThemeColors) -> impl Element<V> {
-    frame()
+    div()
         .text_color(black())
         .h_full()
         .w_half()

crates/gpui/playground/src/style.rs

@@ -1,11 +1,20 @@
 use crate::color::Hsla;
 use gpui::geometry::{DefinedLength, Edges, Length, Point, Size};
+use playground_macros::Overrides;
 pub use taffy::style::{
     AlignContent, AlignItems, AlignSelf, Display, FlexDirection, FlexWrap, JustifyContent,
     Overflow, Position,
 };
 
-#[derive(Clone)]
+pub trait Overrides {
+    type Base;
+
+    fn is_some(&self) -> bool;
+    fn apply(&self, base: &mut Self::Base);
+}
+
+#[derive(Clone, Overrides)]
+#[overrides_crate = "crate"]
 pub struct ElementStyle {
     /// What layout strategy should be used?
     pub display: Display,

crates/gpui/playground/src/text.rs

@@ -1,4 +1,4 @@
-use crate::element::{Element, ElementMetadata, EventHandler, IntoElement};
+use crate::element::{Element, ElementMetadata, IntoElement};
 use gpui::{geometry::Size, text_layout::LineLayout, RenderContext};
 use parking_lot::Mutex;
 use std::sync::Arc;
@@ -22,8 +22,8 @@ pub struct Text<V> {
 impl<V: 'static> Element<V> for Text<V> {
     type Layout = Arc<Mutex<Option<TextLayout>>>;
 
-    fn style_mut(&mut self) -> &mut crate::style::ElementStyle {
+    fn metadata(&mut self) -> &mut crate::element::ElementMetadata<V> {
-        &mut self.metadata.style
+        &mut self.metadata
     }
 
     fn layout(
@@ -91,10 +91,6 @@ impl<V: 'static> Element<V> for Text<V> {
         );
         Ok(())
     }
-
-    fn handlers_mut(&mut self) -> &mut Vec<EventHandler<V>> {
-        &mut self.metadata.handlers
-    }
 }
 
 pub struct TextLayout {

crates/gpui/playground_macros/src/derive_element.rs

@@ -79,12 +79,8 @@ pub fn derive_element(input: TokenStream) -> TokenStream {
         {
             type Layout = #crate_name::element::AnyElement<V>;
 
-            fn style_mut(&mut self) -> &mut #crate_name::style::ElementStyle {
+            fn metadata(&mut self) -> &mut #crate_name::element::ElementMetadata<V> {
-                &mut self.metadata.style
+                &mut self.metadata
-            }
-
-            fn handlers_mut(&mut self) -> &mut Vec<#crate_name::element::EventHandler<V>> {
-                &mut self.metadata.handlers
             }
 
             fn layout(

crates/gpui/playground_macros/src/derive_overrides.rs

@@ -0,0 +1,119 @@
+extern crate proc_macro;
+use proc_macro::TokenStream;
+use quote::{format_ident, quote};
+use syn::{parse_macro_input, Data, DeriveInput, Fields, Lit, Meta};
+
+/// When deriving Overrides on a struct Foo, builds a new struct FooOverrides
+/// that implements the Overrides trait so it can be applied to Foo.
+pub fn derive_overrides(input: TokenStream) -> TokenStream {
+    let input = parse_macro_input!(input as DeriveInput);
+
+    let crate_name: String = input
+        .attrs
+        .iter()
+        .find_map(|attr| {
+            if attr.path.is_ident("overrides_crate") {
+                match attr.parse_meta() {
+                    Ok(Meta::NameValue(nv)) => {
+                        if let Lit::Str(s) = nv.lit {
+                            Some(s.value())
+                        } else {
+                            None
+                        }
+                    }
+                    _ => None,
+                }
+            } else {
+                None
+            }
+        })
+        .unwrap_or_else(|| String::from("playground"));
+    let crate_name = format_ident!("{}", crate_name);
+
+    let ident = input.ident;
+    let new_ident = syn::Ident::new(&format!("{}Overrides", ident), ident.span());
+    let data = match input.data {
+        Data::Struct(s) => s,
+        _ => panic!("Override can only be derived for structs"),
+    };
+
+    let fields = match data.fields {
+        Fields::Named(fields) => fields.named,
+        _ => panic!("Override can only be derived for structs with named fields"),
+    };
+
+    let new_fields = fields
+        .iter()
+        .map(|f| {
+            let name = &f.ident;
+            let ty = &f.ty;
+
+            if let syn::Type::Path(typepath) = ty {
+                if typepath.path.segments.last().unwrap().ident == "Option" {
+                    return quote! { #name: #ty };
+                }
+            }
+            quote! { #name: Option<#ty> }
+        })
+        .collect::<Vec<_>>();
+
+    let names = fields.iter().map(|f| &f.ident);
+    let is_some_implementation = names.clone().map(|name| {
+        quote! {
+            self.#name.is_some()
+        }
+    });
+
+    let apply_implementation = fields.iter().map(|f| {
+        let name = &f.ident;
+        let ty = &f.ty;
+
+        if let syn::Type::Path(typepath) = ty {
+            if typepath.path.segments.last().unwrap().ident == "Option" {
+                return quote! {
+                    base.#name = self.#name.clone();
+                };
+            }
+        }
+
+        quote! {
+            if let Some(value) = &self.#name {
+                base.#name = value.clone();
+            }
+        }
+    });
+
+    let default_implementation = names.map(|name| {
+        quote! {
+            #name: None,
+        }
+    });
+
+    let expanded = quote! {
+        pub struct #new_ident {
+            #(#new_fields,)*
+        }
+
+        impl #crate_name::style::Overrides for #new_ident {
+            type Base = #ident;
+
+            fn is_some(&self) -> bool {
+                #(#is_some_implementation)||*
+            }
+
+            fn apply(&self, base: &mut Self::Base) {
+                #(#apply_implementation)*
+            }
+        }
+
+        impl Default for #new_ident {
+            fn default() -> Self {
+                Self {
+                    #(#default_implementation)*
+                }
+            }
+        }
+    };
+
+    TokenStream::from(expanded)
+}

crates/gpui/playground_macros/src/playground_macros.rs

@@ -2,6 +2,7 @@ use proc_macro::TokenStream;
 
 mod derive_element;
 mod derive_into_element;
+mod derive_overrides;
 mod tailwind_lengths;
 
 #[proc_macro_derive(Element, attributes(element_crate))]
@@ -14,6 +15,11 @@ pub fn derive_into_element(input: TokenStream) -> TokenStream {
     derive_into_element::derive_into_element(input)
 }
 
+#[proc_macro_derive(Overrides, attributes(overrides_crate))]
+pub fn derive_overrides(input: TokenStream) -> TokenStream {
+    derive_overrides::derive_overrides(input)
+}
+
 #[proc_macro_attribute]
 pub fn tailwind_lengths(attr: TokenStream, item: TokenStream) -> TokenStream {
     tailwind_lengths::tailwind_lengths(attr, item)