More work on the state binding for transition:

When there is a transition, turn the state property into a property of StateInfo

Not yet implemented for C++

api/sixtyfps-cpp/include/sixtyfps.h

@@ -64,6 +64,7 @@ using ItemVisitorRefMut = vtable::VRefMut<cbindgen_private::ItemVisitorVTable>;
 }
 using cbindgen_private::EasingCurve;
 using cbindgen_private::PropertyAnimation;
+using cbindgen_private::StateInfo;
 using cbindgen_private::Slice;
 using cbindgen_private::TextHorizontalAlignment;
 using cbindgen_private::TextVerticalAlignment;

api/sixtyfps-rs/lib.rs

@@ -159,6 +159,11 @@ pub use sixtyfps_corelib::string::SharedString;
 pub use sixtyfps_corelib::timers::{Timer, TimerMode};
 pub use sixtyfps_corelib::{ARGBColor, Color};
 
+// FIXME: this should not be in this namespace
+// but the name is `sixtyfps::StateInfo` in builtin.60
+#[doc(hidden)]
+pub use sixtyfps_corelib::properties::StateInfo;
+
 /// internal re_exports used by the macro generated
 #[doc(hidden)]
 pub mod re_exports {
@@ -187,7 +192,7 @@ pub mod re_exports {
     pub use sixtyfps_corelib::items::*;
     pub use sixtyfps_corelib::layout::*;
     pub use sixtyfps_corelib::model::*;
-    pub use sixtyfps_corelib::properties::{Property, PropertyTracker};
+    pub use sixtyfps_corelib::properties::{set_state_binding, Property, PropertyTracker};
     pub use sixtyfps_corelib::signals::Signal;
     pub use sixtyfps_corelib::slice::Slice;
     pub use sixtyfps_corelib::Color;

sixtyfps_compiler/builtins.60

@@ -203,6 +203,13 @@ export struct StandardListViewItem := {
     text: string
 }
 
+export struct StateInfo := {
+    //-name:sixtyfps::StateInfo
+    current_state: int,
+    previous_state: int,
+    //change_time: duration,
+}
+
 export NativeButton := _ {
     property <length> x;
     property <length> y;

sixtyfps_compiler/generator/rust.rs

@@ -144,7 +144,8 @@ fn handle_property_binding(
     init: &mut Vec<TokenStream>,
 ) {
     let rust_property = access_member(item_rc, prop_name, component, quote!(_self), false);
-    if matches!(item_rc.borrow().lookup_property(prop_name), Type::Signal{..}) {
+    let prop_type = item_rc.borrow().lookup_property(prop_name);
+    if matches!(prop_type, Type::Signal{..}) {
         let tokens_for_expression = compile_expression(binding_expression, &component);
         init.push(quote!(
             #rust_property.set_handler({
@@ -172,26 +173,30 @@ fn handle_property_binding(
         }
     } else {
         let tokens_for_expression = compile_expression(binding_expression, &component);
-        let setter = if binding_expression.is_constant() {
-            quote!(set((#tokens_for_expression) as _))
+        init.push(if binding_expression.is_constant() {
+            quote! { #rust_property.set((#tokens_for_expression) as _); }
         } else {
-            property_set_binding_tokens(
-                component,
-                &item_rc,
-                prop_name,
-                quote!({
+            let binding_tokens = quote!({
                 let self_weak = sixtyfps::re_exports::VRc::downgrade(&self_pinned);
                 move || {
                     let self_pinned = self_weak.upgrade().unwrap();
                     let _self = self_pinned.as_pin_ref();
                     (#tokens_for_expression) as _
                 }
-                }),
-            )
+            });
+
+            let is_state_info = match prop_type {
+                Type::Object { name: Some(name), .. } if name.ends_with("::StateInfo") => true,
+                _ => false,
             };
-        init.push(quote!(
-            #rust_property.#setter;
-        ));
+            if is_state_info {
+                quote! { sixtyfps::re_exports::set_state_binding(#rust_property, #binding_tokens); }
+            } else if let Some(anim) = property_animation_tokens(component, &item_rc, prop_name) {
+                quote! { #rust_property.set_animated_binding(#binding_tokens, #anim); }
+            } else {
+                quote! { #rust_property.set_binding(#binding_tokens); }
+            }
+        });
     }
 }
 
@@ -899,19 +904,6 @@ fn property_set_value_tokens(
     }
 }
 
-fn property_set_binding_tokens(
-    component: &Rc<Component>,
-    element: &ElementRc,
-    property_name: &str,
-    binding_tokens: TokenStream,
-) -> TokenStream {
-    if let Some(animation_tokens) = property_animation_tokens(component, element, property_name) {
-        quote!(set_animated_binding(#binding_tokens, #animation_tokens))
-    } else {
-        quote!(set_binding(#binding_tokens))
-    }
-}
-
 /// Returns the code that can access the given property or signal (but without the set or get)
 ///
 /// to be used like:

sixtyfps_compiler/lib.rs

@@ -156,7 +156,7 @@ pub async fn run_passes<'a>(
     passes::materialize_fake_properties::materialize_fake_properties(&doc.root_component);
     passes::collect_resources::collect_resources(&doc.root_component);
     doc.root_component.embed_file_resources.set(compiler_config.embed_resources);
-    passes::lower_states::lower_states(&doc.root_component, diag);
+    passes::lower_states::lower_states(&doc.root_component, &doc.local_registry, diag);
     passes::repeater_component::process_repeater_components(&doc.root_component);
     passes::lower_layout::lower_layouts(&doc.root_component, &mut type_loader, diag).await;
     passes::deduplicate_property_read::deduplicate_property_read(&doc.root_component);

sixtyfps_compiler/passes/lower_states.rs

@@ -15,19 +15,38 @@ use crate::langtype::Type;
 use crate::object_tree::*;
 use std::rc::Rc;
 
-pub fn lower_states(component: &Rc<Component>, diag: &mut BuildDiagnostics) {
-    recurse_elem(&component.root_element, &(), &mut |elem, _| lower_state_in_element(elem, diag));
+pub fn lower_states(
+    component: &Rc<Component>,
+    tr: &crate::typeregister::TypeRegister,
+    diag: &mut BuildDiagnostics,
+) {
+    let state_info_type = tr.lookup("StateInfo");
+    assert!(matches!(state_info_type, Type::Object{ name: Some(_), .. }));
+    recurse_elem(&component.root_element, &(), &mut |elem, _| {
+        lower_state_in_element(elem, &state_info_type, diag)
+    });
 }
 
-fn lower_state_in_element(root_element: &ElementRc, _diag: &mut BuildDiagnostics) {
+fn lower_state_in_element(
+    root_element: &ElementRc,
+    state_info_type: &Type,
+    _diag: &mut BuildDiagnostics,
+) {
     if root_element.borrow().states.is_empty() {
         return;
     }
+    let has_transitions = !root_element.borrow().transitions.is_empty();
     let state_property = compute_state_property_name(root_element);
-    let state_property_ref = Expression::PropertyReference(NamedReference {
+    let mut state_property_ref = Expression::PropertyReference(NamedReference {
         element: Rc::downgrade(root_element),
         name: state_property.clone(),
     });
+    if has_transitions {
+        state_property_ref = Expression::ObjectAccess {
+            base: Box::new(state_property_ref),
+            name: "current_state".into(),
+        };
+    }
     let mut state_value = Expression::NumberLiteral(0., Unit::None);
     let states = std::mem::take(&mut root_element.borrow_mut().states);
     for (idx, state) in states.into_iter().enumerate().rev() {
@@ -58,7 +77,10 @@ fn lower_state_in_element(root_element: &ElementRc, _diag: &mut BuildDiagnostics
     }
     root_element.borrow_mut().property_declarations.insert(
         state_property.clone(),
-        PropertyDeclaration { property_type: Type::Int32, ..PropertyDeclaration::default() },
+        PropertyDeclaration {
+            property_type: if has_transitions { state_info_type.clone() } else { Type::Int32 },
+            ..PropertyDeclaration::default()
+        },
     );
     root_element.borrow_mut().bindings.insert(state_property.clone(), state_value.into());
 }

sixtyfps_runtime/corelib/animations.rs

@@ -31,7 +31,7 @@ impl Default for EasingCurve {
 /// Represent an instant, in miliseconds since the AnimationDriver's initial_instant
 #[repr(transparent)]
 #[derive(Copy, Clone, Debug, Default, PartialEq, Ord, PartialOrd, Eq)]
-pub struct Instant(u64);
+pub struct Instant(pub u64);
 
 impl core::ops::Sub<Instant> for Instant {
     type Output = core::time::Duration;

sixtyfps_runtime/corelib/properties.rs

@@ -1175,11 +1175,11 @@ mod animation_tests {
 #[derive(Clone, Default, Debug, PartialEq)]
 pub struct StateInfo {
     /// The current state value
-    current_state: u32,
+    pub current_state: i32,
     /// The previous state
-    previous_state: u32,
+    pub previous_state: i32,
     /// The instant in which the state changed last
-    change_time: crate::animations::Instant,
+    pub change_time: crate::animations::Instant,
 }
 
 struct StateInfoBinding<F> {
@@ -1187,7 +1187,7 @@ struct StateInfoBinding<F> {
     binding: F,
 }
 
-impl<F: Fn() -> u32> crate::properties::BindingCallable for StateInfoBinding<F> {
+impl<F: Fn() -> i32> crate::properties::BindingCallable for StateInfoBinding<F> {
     unsafe fn evaluate(self: Pin<&Self>, value: *mut ()) -> BindingResult {
         // Safety: We should ony set this binding on a property of type StateInfo
         let value = &mut *(value as *mut StateInfo);
@@ -1196,6 +1196,7 @@ impl<F: Fn() -> u32> crate::properties::BindingCallable for StateInfoBinding<F>
         if new_state != value.current_state {
             value.previous_state = value.current_state;
             value.change_time = timestamp.unwrap_or_else(crate::animations::current_tick);
+            value.current_state = new_state;
         }
         BindingResult::KeepBinding
     }
@@ -1208,7 +1209,7 @@ impl<F: Fn() -> u32> crate::properties::BindingCallable for StateInfoBinding<F>
 }
 
 /// Sets a binding that returns a state to a StateInfo property
-pub fn set_state_binding(property: Pin<&Property<StateInfo>>, binding: impl Fn() -> u32 + 'static) {
+pub fn set_state_binding(property: Pin<&Property<StateInfo>>, binding: impl Fn() -> i32 + 'static) {
     let bind_callable = StateInfoBinding { dirty_time: Cell::new(None), binding };
     // Safety: The StateInfoBinding is a BindingCallable for type StateInfo
     unsafe { property.handle.set_binding(bind_callable) }

sixtyfps_runtime/interpreter/dynamic_component.rs

@@ -643,6 +643,9 @@ fn generate_component<'id>(
                     .insert(name.clone(), builder.add_field_type::<Signal<[eval::Value]>>());
                 continue;
             }
+            Type::Object { name: Some(name), .. } if name.ends_with("::StateInfo") => {
+                property_info::<sixtyfps_corelib::properties::StateInfo>()
+            }
             Type::Object { .. } => property_info::<eval::Value>(),
             Type::Array(_) => property_info::<eval::Value>(),
             Type::Percent => property_info::<f32>(),
@@ -888,6 +891,39 @@ pub fn instantiate<'id>(
                         offset, prop: prop_info, ..
                     }) = component_type.custom_properties.get(prop.as_str())
                     {
+                        let c = Pin::new_unchecked(vtable::VRef::from_raw(
+                            NonNull::from(&component_type.ct).cast(),
+                            component_box.instance.as_ptr().cast(),
+                        ));
+
+                        let is_state_info = match ty {
+                            Type::Object { name: Some(name), .. }
+                                if name.ends_with("::StateInfo") =>
+                            {
+                                true
+                            }
+                            _ => false,
+                        };
+                        if is_state_info {
+                            let prop = Pin::new_unchecked(
+                                &*(instance_ref.as_ptr().add(*offset)
+                                    as *const Property<sixtyfps_corelib::properties::StateInfo>),
+                            );
+                            let e = expr.expression.clone();
+                            sixtyfps_corelib::properties::set_state_binding(prop, move || {
+                                generativity::make_guard!(guard);
+                                eval::eval_expression(
+                                    &e,
+                                    &mut eval::EvalLocalContext::from_component_instance(
+                                        InstanceRef::from_pin_ref(c, guard),
+                                    ),
+                                )
+                                .try_into()
+                                .unwrap()
+                            });
+                            continue;
+                        }
+
                         let maybe_animation = animation_for_property(
                             instance_ref,
                             &component_type.original.root_element.borrow().property_animations,
@@ -912,12 +948,6 @@ pub fn instantiate<'id>(
                                 prop_info.set(item, v, None).unwrap();
                             } else {
                                 let e = e.clone();
-                                let component_type = component_type.clone();
-                                let instance = component_box.instance.as_ptr();
-                                let c = Pin::new_unchecked(vtable::VRef::from_raw(
-                                    NonNull::from(&component_type.ct).cast(),
-                                    instance.cast(),
-                                ));
                                 prop_info
                                     .set_binding(
                                         item,

sixtyfps_runtime/interpreter/eval.rs

@@ -159,27 +159,33 @@ declare_value_conversion!(Color => [Color] );
 declare_value_conversion!(PathElements => [PathData]);
 declare_value_conversion!(EasingCurve => [corelib::animations::EasingCurve]);
 
-impl TryFrom<corelib::model::StandardListViewItem> for Value {
+macro_rules! declare_value_struct_conversion {
+    (struct $name:path { $($field:ident),* $(,)? }) => {
+        impl TryFrom<$name> for Value {
             type Error = ();
-    fn try_from(
-        corelib::model::StandardListViewItem { text }: corelib::model::StandardListViewItem,
-    ) -> Result<Self, ()> {
+            fn try_from($name { $($field),* }: $name) -> Result<Self, ()> {
                 let mut hm = HashMap::new();
-        hm.insert("text".into(), text.try_into()?);
+                $(hm.insert(stringify!($field).into(), $field.try_into()?);)*
                 Ok(Value::Object(hm))
             }
         }
-impl TryInto<corelib::model::StandardListViewItem> for Value {
+        impl TryInto<$name> for Value {
             type Error = ();
-    fn try_into(self) -> Result<corelib::model::StandardListViewItem, ()> {
+            fn try_into(self) -> Result<$name, ()> {
                 match self {
-            Self::Object(x) => Ok(corelib::model::StandardListViewItem {
-                text: x.get("text").ok_or(())?.clone().try_into()?,
-            }),
+                    Self::Object(x) => {
+                        type Ty = $name;
+                        Ok(Ty { $($field: x.get(stringify!($field)).ok_or(())?.clone().try_into()?),* })
+                    }
                     _ => Err(()),
                 }
             }
         }
+    };
+}
+
+declare_value_struct_conversion!(struct corelib::model::StandardListViewItem { text });
+declare_value_struct_conversion!(struct corelib::properties::StateInfo { current_state, previous_state, change_time });
 
 macro_rules! declare_value_enum_conversion {
     ($ty:ty, $n:ident) => {
@@ -212,6 +218,22 @@ declare_value_enum_conversion!(corelib::items::TextHorizontalAlignment, TextHori
 declare_value_enum_conversion!(corelib::items::TextVerticalAlignment, TextVerticalAlignment);
 declare_value_enum_conversion!(corelib::layout::LayoutAlignment, LayoutAlignment);
 
+impl TryFrom<corelib::animations::Instant> for Value {
+    type Error = ();
+    fn try_from(value: corelib::animations::Instant) -> Result<Self, ()> {
+        Ok(Value::Number(value.0 as _))
+    }
+}
+impl TryInto<corelib::animations::Instant> for Value {
+    type Error = ();
+    fn try_into(self) -> Result<corelib::animations::Instant, ()> {
+        match self {
+            Value::Number(x) => Ok(corelib::animations::Instant(x as _)),
+            _ => Err(()),
+        }
+    }
+}
+
 #[derive(Copy, Clone)]
 enum ComponentInstance<'a, 'id> {
     InstanceRef(InstanceRef<'a, 'id>),

tests/driver_lib/cbindgen.rs

@@ -110,6 +110,11 @@ fn gen_corelib(include_dir: &Path) -> anyhow::Result<()> {
 
     let mut properties_config = config.clone();
     properties_config.export.exclude.clear();
+    properties_config.export.include.push("StateInfo".into());
+    properties_config
+        .export
+        .pre_body
+        .insert("StateInfo".to_owned(), "    using Instant = uint64_t;".into());
     cbindgen::Builder::new()
         .with_config(properties_config)
         .with_src(crate_dir.join("properties.rs"))