Add an Opacity element that does nothing

api/sixtyfps-cpp/include/sixtyfps.h

@@ -48,6 +48,7 @@ extern const cbindgen_private::ItemVTable TextInputVTable;
 extern const cbindgen_private::ItemVTable ClipVTable;
 extern const cbindgen_private::ItemVTable BoxShadowVTable;
 extern const cbindgen_private::ItemVTable RotateVTable;
+extern const cbindgen_private::ItemVTable OpacityVTable;
 
 extern const cbindgen_private::ItemVTable NativeButtonVTable;
 extern const cbindgen_private::ItemVTable NativeCheckBoxVTable;
@@ -153,6 +154,7 @@ using cbindgen_private::ClippedImage;
 using cbindgen_private::Flickable;
 using cbindgen_private::FocusScope;
 using cbindgen_private::Image;
+using cbindgen_private::Opacity;
 using cbindgen_private::Path;
 using cbindgen_private::Rectangle;
 using cbindgen_private::Rotate;

sixtyfps_compiler/builtins.60

@@ -200,6 +200,15 @@ export Clip := _ {
     //-default_size_binding:expands_to_parent_geometry
 }
 
+export Opacity := _ {
+    property <length> x;
+    property <length> y;
+    property <length> width;
+    property <length> height;
+    property <float> opacity;
+    //-default_size_binding:expands_to_parent_geometry
+}
+
 Row := _ {
     //-is_non_item_type
 }

sixtyfps_runtime/corelib/items.rs

@@ -16,7 +16,9 @@ When adding an item or a property, it needs to be kept in sync with different pl
  - It needs to be changed in this module
  - In the compiler: builtins.60
  - In the interpreter (new item only): dynamic_component.rs
- - For the C++ code (new item only): the cbindgen.rs to export the new item, and the `using` declaration in sixtyfps.h
+ - For the C++ code (new item only):
+   - the cbindgen.rs to export the new item
+   - the `using` declaration in sixtyfps.h for the item and its vtable
  - Don't forget to update the documentation
 */
 
@@ -630,6 +632,77 @@ ItemVTable_static! {
     pub static ClipVTable for Clip
 }
 
+#[repr(C)]
+#[derive(FieldOffsets, Default, SixtyFPSElement)]
+#[pin]
+/// The Opacity Item is not meant to be used directly by the .60 code, instead, the `opacity: xxx` or `visible: false` should be used
+pub struct Opacity {
+    // FIXME: this element shouldn't need these geometry property
+    pub x: Property<f32>,
+    pub y: Property<f32>,
+    pub width: Property<f32>,
+    pub height: Property<f32>,
+    pub opacity: Property<f32>,
+    pub cached_rendering_data: CachedRenderingData,
+}
+
+impl Item for Opacity {
+    fn init(self: Pin<&Self>, _window: &ComponentWindow) {}
+
+    fn geometry(self: Pin<&Self>) -> Rect {
+        euclid::rect(self.x(), self.y(), self.width(), self.height())
+    }
+
+    fn layouting_info(self: Pin<&Self>, _window: &ComponentWindow) -> LayoutInfo {
+        LayoutInfo { horizontal_stretch: 1., vertical_stretch: 1., ..LayoutInfo::default() }
+    }
+
+    fn implicit_size(self: Pin<&Self>, _window: &ComponentWindow) -> Size {
+        Default::default()
+    }
+
+    fn input_event_filter_before_children(
+        self: Pin<&Self>,
+        _: MouseEvent,
+        _window: &ComponentWindow,
+        _self_rc: &ItemRc,
+    ) -> InputEventFilterResult {
+        InputEventFilterResult::ForwardAndIgnore
+    }
+
+    fn input_event(
+        self: Pin<&Self>,
+        _: MouseEvent,
+        _window: &ComponentWindow,
+        _self_rc: &ItemRc,
+    ) -> InputEventResult {
+        InputEventResult::EventIgnored
+    }
+
+    fn key_event(self: Pin<&Self>, _: &KeyEvent, _window: &ComponentWindow) -> KeyEventResult {
+        KeyEventResult::EventIgnored
+    }
+
+    fn focus_event(self: Pin<&Self>, _: &FocusEvent, _window: &ComponentWindow) {}
+
+    fn render(self: Pin<&Self>, backend: &mut ItemRendererRef) {
+        // TODO
+    }
+}
+
+impl ItemConsts for Opacity {
+    const cached_rendering_data_offset: const_field_offset::FieldOffset<
+        Opacity,
+        CachedRenderingData,
+    > = Opacity::FIELD_OFFSETS.cached_rendering_data.as_unpinned_projection();
+}
+
+ItemVTable_static! {
+    /// The VTable for `Opacity`
+    #[no_mangle]
+    pub static OpacityVTable for Opacity
+}
+
 #[repr(C)]
 #[derive(FieldOffsets, Default, SixtyFPSElement)]
 #[pin]

sixtyfps_runtime/interpreter/dynamic_component.rs

@@ -623,6 +623,7 @@ fn generate_component<'id>(
                 rtti_for::<Clip>(),
                 rtti_for::<BoxShadow>(),
                 rtti_for::<Rotate>(),
+                rtti_for::<Opacity>(),
             ]
             .iter()
             .cloned(),

xtask/src/cbindgen.rs

@@ -72,6 +72,7 @@ fn gen_corelib(root_dir: &Path, include_dir: &Path) -> anyhow::Result<()> {
         "BoxShadow",
         "FillRule",
         "Rotate",
+        "Opacity",
     ]
     .iter()
     .map(|x| x.to_string())