Add an Easing namespace (#9179)

The definition of an Easing namespace allows to name an easing curve
outside an expression of type easing like, for instance, a struct field.

Closes #3943.

ChangeLog: Added an `Easing` namespace to reference easing curve outside of `easing` properties.

Author: gustavo-hms

docs/astro/src/content/docs/reference/primitive-types.mdx

@@ -229,8 +229,9 @@ See also the <Link type="Image" label="Image element"/>.
 ## Animation
 ### easing
 <SlintProperty propName="easing" typeName="easing" defaultValue='linear'>
-Property animation allow specifying an easing curve.
-`easing`: can be any of the following. See [`easings.net`](https://easings.net/) for a visual reference:
+The `easing` type allows defining an easing curve for animations.
+
+To specify an easing curve, use the values from the `Easing` namespace. For example you can use `Easing.ease-out` or `Easing.ease-in-quad`. The namespace consists of the following names (see [`easings.net`](https://easings.net/) for a visual reference):
 
     -   `linear`
     -   `ease-in-quad`
@@ -265,6 +266,26 @@ Property animation allow specifying an easing curve.
     -   `ease-out-bounce`
     -   `ease-in-out-bounce`
     -   `cubic-bezier(a, b, c, d)` as in CSS
+
+Additionally, in expressions of type `easing`, those names are available directly.
+
+```slint
+struct AnimationData {
+    curve: easing,
+}
+
+component Custom inherits Rectangle {
+    property<AnimationData> animation: {
+        // Using the Easing namespace.
+        curve: Easing.ease-in-circ,
+    };
+
+	animate x {
+    	// In easing expressions the names are available via global scope.
+    	easing: ease-out-bounce;
+	}
+}
+```
 </SlintProperty>
 
 

internal/compiler/generator/rust.rs

@@ -83,6 +83,7 @@ pub fn rust_primitive_type(ty: &Type) -> Option<proc_macro2::TokenStream> {
         Type::Float32 => Some(quote!(f32)),
         Type::String => Some(quote!(sp::SharedString)),
         Type::Color => Some(quote!(sp::Color)),
+        Type::Easing => Some(quote!(sp::EasingCurve)),
         Type::ComponentFactory => Some(quote!(slint::ComponentFactory)),
         Type::Duration => Some(quote!(i64)),
         Type::Angle => Some(quote!(f32)),

internal/compiler/lookup.rs

@@ -118,6 +118,7 @@ pub enum LookupResultCallable {
 #[derive(Debug, derive_more::Display)]
 pub enum BuiltinNamespace {
     Colors,
+    Easing,
     Math,
     Key,
     SlintInternal,
@@ -196,6 +197,9 @@ impl LookupObject for LookupResult {
             LookupResult::Namespace(BuiltinNamespace::Colors) => {
                 (ColorSpecific, ColorFunctions).for_each_entry(ctx, f)
             }
+            LookupResult::Namespace(BuiltinNamespace::Easing) => {
+                EasingSpecific.for_each_entry(ctx, f)
+            }
             LookupResult::Namespace(BuiltinNamespace::Math) => MathFunctions.for_each_entry(ctx, f),
             LookupResult::Namespace(BuiltinNamespace::Key) => KeysLookup.for_each_entry(ctx, f),
             LookupResult::Namespace(BuiltinNamespace::SlintInternal) => {
@@ -212,6 +216,7 @@ impl LookupObject for LookupResult {
             LookupResult::Namespace(BuiltinNamespace::Colors) => {
                 (ColorSpecific, ColorFunctions).lookup(ctx, name)
             }
+            LookupResult::Namespace(BuiltinNamespace::Easing) => EasingSpecific.lookup(ctx, name),
             LookupResult::Namespace(BuiltinNamespace::Math) => MathFunctions.lookup(ctx, name),
             LookupResult::Namespace(BuiltinNamespace::Key) => KeysLookup.lookup(ctx, name),
             LookupResult::Namespace(BuiltinNamespace::SlintInternal) => {
@@ -842,6 +847,7 @@ impl LookupObject for BuiltinNamespaceLookup {
     ) -> Option<R> {
         let mut f = |s, res| f(&SmolStr::new_static(s), res);
         None.or_else(|| f("Colors", LookupResult::Namespace(BuiltinNamespace::Colors)))
+            .or_else(|| f("Easing", LookupResult::Namespace(BuiltinNamespace::Easing)))
             .or_else(|| f("Math", LookupResult::Namespace(BuiltinNamespace::Math)))
             .or_else(|| f("Key", LookupResult::Namespace(BuiltinNamespace::Key)))
             .or_else(|| {

internal/compiler/tests/syntax/lookup/easing.slint

@@ -0,0 +1,31 @@
+// Copyright © SixtyFPS GmbH <[email protected]>
+// SPDX-License-Identifier: GPL-3.0-only OR LicenseRef-Slint-Royalty-free-2.0 OR LicenseRef-Slint-Software-3.0
+
+struct Animation {
+    easing: easing,
+}
+
+export component Test inherits Rectangle {
+    property <Animation> animation1: {
+        easing: Easing.linear,
+    };
+
+    property <Animation> animation2: {
+        easing: Easing.some-curve,
+//                     ^error{'some-curve' is not a member of the namespace Easing}
+    };
+
+    property <Animation> animation3: {
+        easing: Easing,
+//              ^error{Cannot take reference to a namespace}
+    };
+
+    property <Animation> animation4: {
+        easing: Easing.cubic-bezier(0.05, 07, 0.1, 1.0)
+    };
+
+    property <Animation> animation5: {
+        easing: Easing.cubic-bezier(0.05, 07)
+//                     ^error{Not enough arguments}
+    };
+}