Implement easing curve in the runtime

api/sixtyfps-cpp/include/sixtyfps.h

@@ -28,6 +28,7 @@ using internal::ItemTreeNode;
 using ComponentRef = VRef<ComponentVTable>;
 using ItemVisitorRefMut = VRefMut<internal::ItemVisitorVTable>;
 using internal::WindowProperties;
+using internal::EasingCurve;
 
 struct ComponentWindow
 {

api/sixtyfps-node/native/lib.rs

@@ -166,6 +166,7 @@ fn to_js_value<'cx>(
         }
         Value::Color(c) => JsNumber::new(cx, c.as_argb_encoded()).as_value(cx),
         Value::PathElements(_) => todo!(),
+        Value::EasingCurve(_) => todo!(),
     })
 }
 

sixtyfps_compiler/generator/rust.rs

@@ -2,7 +2,7 @@
 */
 
 use crate::diagnostics::{BuildDiagnostics, CompilerDiagnostic, Spanned};
-use crate::expression_tree::{Expression, NamedReference, OperatorClass, Path};
+use crate::expression_tree::{EasingCurve, Expression, NamedReference, OperatorClass, Path};
 use crate::object_tree::{Component, ElementRc};
 use crate::typeregister::Type;
 use proc_macro2::TokenStream;
@@ -709,7 +709,12 @@ fn compile_expression(e: &Expression, component: &Rc<Component>) -> TokenStream
             let name = quote::format_ident!("{}", name);
             quote!(#name)
         }
-        Expression::EasingCurve(_) => quote!(todo!("EasingCurve not yet implemented in rust.rs")),
+        Expression::EasingCurve(EasingCurve::Linear) => {
+            quote!(sixtyfps::re_exports::EasingCurve::Linear)
+        }
+        Expression::EasingCurve(EasingCurve::CubicBezier(a, b, c, d)) => {
+            quote!(sixtyfps::re_exports::EasingCurve::CubicBezier([#a, #b, #c, #d]))
+        }
     }
 }
 

sixtyfps_runtime/corelib/abi/datastructures.rs

@@ -647,6 +647,23 @@ pub struct MouseEvent {
     pub what: MouseEventType,
 }
 
+/// The representation of an easing curve, for animations
+#[repr(C, u32)]
+#[derive(Debug, Clone, Copy, PartialEq)]
+pub enum EasingCurve {
+    /// The linear curve
+    Linear,
+    /// A Cubic bezier curve, with its 4 parameter
+    CubicBezier([f32; 4]),
+    //Custom(Box<dyn Fn(f32) -> f32>),
+}
+
+impl Default for EasingCurve {
+    fn default() -> Self {
+        Self::Linear
+    }
+}
+
 #[repr(C)]
 #[derive(Default)]
 /// WindowProperties is used to pass the references to properties of the instantiated

sixtyfps_runtime/corelib/abi/primitives.rs

@@ -365,4 +365,6 @@ pub struct PropertyAnimation {
     pub duration: i32,
     #[rtti_field]
     pub loop_count: i32,
+    #[rtti_field]
+    pub easing: crate::abi::datastructures::EasingCurve,
 }

sixtyfps_runtime/corelib/abi/properties.rs

@@ -622,7 +622,8 @@ impl<T: InterpolatedPropertyValue> PropertyValueAnimationData<T> {
         }
         let progress = time_progress as f32 / self.details.duration as f32;
         assert!(progress <= 1.);
-        let val = self.from_value.interpolate(self.to_value, progress);
+        let t = crate::animations::easing_curve(&self.details.easing, progress);
+        let val = self.from_value.interpolate(self.to_value, t);
         (val, false)
     }
 }
@@ -997,8 +998,10 @@ mod animation_tests {
     fn properties_test_animation_triggered_by_set() {
         let compo = Component::new_test_component();
 
-        let animation_details =
-            PropertyAnimation { duration: DURATION.as_millis() as _, loop_count: 0 };
+        let animation_details = PropertyAnimation {
+            duration: DURATION.as_millis() as _,
+            ..PropertyAnimation::default()
+        };
 
         compo.width.set(100);
         assert_eq!(get_prop_value(&compo.width), 100);
@@ -1036,8 +1039,10 @@ mod animation_tests {
         let start_time =
             crate::animations::CURRENT_ANIMATION_DRIVER.with(|driver| driver.current_tick());
 
-        let animation_details =
-            PropertyAnimation { duration: DURATION.as_millis() as _, loop_count: 0 };
+        let animation_details = PropertyAnimation {
+            duration: DURATION.as_millis() as _,
+            ..PropertyAnimation::default()
+        };
 
         let w = Rc::downgrade(&compo);
         compo.width.set_animated_binding(
@@ -1073,8 +1078,11 @@ mod animation_tests {
     fn test_loop() {
         let compo = Component::new_test_component();
 
-        let animation_details =
-            PropertyAnimation { duration: DURATION.as_millis() as _, loop_count: 2 };
+        let animation_details = PropertyAnimation {
+            duration: DURATION.as_millis() as _,
+            loop_count: 2,
+            ..PropertyAnimation::default()
+        };
 
         compo.width.set(100);
 
@@ -1116,8 +1124,11 @@ mod animation_tests {
     fn test_loop_overshoot() {
         let compo = Component::new_test_component();
 
-        let animation_details =
-            PropertyAnimation { duration: DURATION.as_millis() as _, loop_count: 2 };
+        let animation_details = PropertyAnimation {
+            duration: DURATION.as_millis() as _,
+            loop_count: 2,
+            ..PropertyAnimation::default()
+        };
 
         compo.width.set(100);
 

sixtyfps_runtime/corelib/animations.rs

@@ -1,5 +1,6 @@
 #![warn(missing_docs)]
 
+use crate::abi::datastructures::EasingCurve;
 use std::cell::Cell;
 
 /// The AnimationDriver
@@ -44,3 +45,27 @@ impl AnimationDriver {
 }
 
 thread_local!(pub(crate) static CURRENT_ANIMATION_DRIVER : AnimationDriver = AnimationDriver::default());
+
+/// map a value betwen 0 and 1 to another value between 0 and 1 according to the curve
+pub fn easing_curve(curve: &EasingCurve, value: f32) -> f32 {
+    match curve {
+        EasingCurve::Linear => value,
+        EasingCurve::CubicBezier([a, b, c, d]) => {
+            if !(0.0..=1.0).contains(a) && !(0.0..=1.0).contains(c) {
+                return value;
+            };
+            let curve = lyon::algorithms::geom::cubic_bezier::CubicBezierSegment {
+                from: (0., 0.).into(),
+                ctrl1: (*a, *b).into(),
+                ctrl2: (*c, *d).into(),
+                to: (1., 1.).into(),
+            };
+            let curve = curve.assume_monotonic();
+            curve.y(curve.solve_t_for_x(
+                value,
+                0.0..1.0,
+                lyon::tessellation::StrokeOptions::DEFAULT_TOLERANCE,
+            ))
+        }
+    }
+}

sixtyfps_runtime/corelib/build.rs

@@ -15,6 +15,7 @@ fn main() {
         "Slice",
         "ComponentWindowOpaque",
         "PropertyAnimation",
+        "EasingCurve",
     ]
     .iter()
     .map(|x| x.to_string())
@@ -142,6 +143,11 @@ fn main() {
         "CachedRenderingData".to_owned(),
         "    constexpr CachedRenderingData() : cache_index{}, cache_ok{} {}".to_owned(),
     );
+    config.export.body.insert(
+        "EasingCurve".to_owned(),
+        "    constexpr EasingCurve() : tag(Tag::Linear), cubic_bezier{{0,0,1,1}} {}
+    constexpr explicit EasingCurve(EasingCurve::Tag tag, float a, float b, float c, float d) : tag(tag), cubic_bezier{{a,b,c,d}} {}".into()
+    );
     cbindgen::Builder::new()
         .with_config(config)
         .with_src(crate_dir.join("abi/datastructures.rs"))

sixtyfps_runtime/corelib/rtti.rs

@@ -23,7 +23,8 @@ declare_ValueType![
     crate::SharedString,
     crate::Resource,
     crate::Color,
-    crate::PathData
+    crate::PathData,
+    crate::abi::datastructures::EasingCurve
 ];
 
 pub trait PropertyInfo<Item, Value> {

sixtyfps_runtime/interpreter/eval.rs

@@ -1,7 +1,8 @@
 use core::convert::{TryFrom, TryInto};
 use core::pin::Pin;
 use sixtyfps_compilerlib::expression_tree::{
-    Expression, ExpressionSpanned, NamedReference, Path as ExprPath, PathElement as ExprPathElement,
+    EasingCurve, Expression, ExpressionSpanned, NamedReference, Path as ExprPath,
+    PathElement as ExprPathElement,
 };
 use sixtyfps_compilerlib::{object_tree::ElementRc, typeregister::Type};
 use sixtyfps_corelib as corelib;
@@ -69,6 +70,8 @@ pub enum Value {
     Color(Color),
     /// The elements of a path
     PathElements(PathData),
+    /// An easing curve
+    EasingCurve(corelib::abi::datastructures::EasingCurve),
 }
 
 impl Default for Value {
@@ -114,6 +117,7 @@ declare_value_conversion!(Resource => [Resource] );
 declare_value_conversion!(Object => [HashMap<String, Value>] );
 declare_value_conversion!(Color => [Color] );
 declare_value_conversion!(PathElements => [PathData]);
+declare_value_conversion!(EasingCurve => [corelib::abi::datastructures::EasingCurve]);
 
 /// The local variable needed for binding evaluation
 #[derive(Default)]
@@ -348,7 +352,12 @@ pub fn eval_expression(
         Expression::ReadLocalVariable { name, .. } => {
             local_context.local_variables.get(name).unwrap().clone()
         }
-        Expression::EasingCurve(_) => todo!("EasingCurve not yet implemented"),
+        Expression::EasingCurve(curve) => Value::EasingCurve(match curve {
+            EasingCurve::Linear => corelib::abi::datastructures::EasingCurve::Linear,
+            EasingCurve::CubicBezier(a, b, c, d) => {
+                corelib::abi::datastructures::EasingCurve::CubicBezier([*a, *b, *c, *d])
+            }
+        }),
     }
 }
 

sixtyfps_widgets/sixtyfps_widgets.60

@@ -44,7 +44,7 @@ export CheckBox := Rectangle {
             y: 4lx;
             x: root.checked ? 4lx : indicator.width - bubble.width - 4lx;
             color: root.checked ? #aea : #eaa;
-            animate x, color { duration: 200ms; }
+            animate x, color { duration: 200ms; easing: ease;}
         }
     }