slint/internal/core/items.rs

// Copyright © SixtyFPS GmbH <info@slint-ui.com>
// SPDX-License-Identifier: GPL-3.0-only OR LicenseRef-Slint-commercial

// cSpell: ignore nesw

/*!
This module contains the builtin items, either in this file or in sub-modules.

When adding an item or a property, it needs to be kept in sync with different place.
(This is less than ideal and maybe we can have some automation later)

 - It needs to be changed in this module
 - In the compiler: builtins.slint
 - In the interpreter (new item only): dynamic_component.rs
 - For the C++ code (new item only): the cbindgen.rs to export the new item
 - Don't forget to update the documentation
*/

#![allow(unsafe_code)]
#![allow(non_upper_case_globals)]
#![allow(missing_docs)] // because documenting each property of items is redundant

use crate::graphics::{Brush, Color, Point, Rect};
use crate::input::{
    FocusEvent, FocusEventResult, InputEventFilterResult, InputEventResult, KeyEvent,
    KeyEventResult, MouseEvent,
};
use crate::item_rendering::CachedRenderingData;
pub use crate::item_tree::ItemRc;
use crate::layout::{LayoutInfo, Orientation};
#[cfg(feature = "rtti")]
use crate::rtti::*;
use crate::window::WindowRc;
use crate::{Callback, Coord, Property, SharedString};
use const_field_offset::FieldOffsets;
use core::cell::Cell;
use core::pin::Pin;
use i_slint_core_macros::*;
use vtable::*;

mod flickable;
pub use flickable::*;
mod text;
pub use text::*;
mod image;
pub use self::image::*;
#[cfg(feature = "std")]
mod path;
#[cfg(feature = "std")]
pub use path::*;

/// Alias for `&mut dyn ItemRenderer`. Required so cbindgen generates the ItemVTable
/// despite the presence of trait object
type ItemRendererRef<'a> = &'a mut dyn crate::item_rendering::ItemRenderer;

/// Workarounds for cbindgen
pub type VoidArg = ();
pub type KeyEventArg = (KeyEvent,);
type PointerEventArg = (PointerEvent,);
type PointArg = (Point,);

#[cfg(all(feature = "ffi", windows))]
#[macro_export]
macro_rules! declare_item_vtable {
    (fn $getter:ident() -> $item_vtable_ty:ident for $item_ty:ty) => {
        ItemVTable_static! {
            #[no_mangle]
            pub static $item_vtable_ty for $item_ty
        }
        #[no_mangle]
        pub extern "C" fn $getter() -> *const ItemVTable {
            use vtable::HasStaticVTable;
            <$item_ty>::static_vtable()
        }
    };
}
#[cfg(not(all(feature = "ffi", windows)))]
#[macro_export]
macro_rules! declare_item_vtable {
    (fn $getter:ident() -> $item_vtable_ty:ident for $item_ty:ty) => {
        ItemVTable_static! {
            #[no_mangle]
            pub static $item_vtable_ty for $item_ty
        }
    };
}

/// Returned by the `render()` function on items to indicate whether the rendering of
/// children should be handled by the caller, of if the item took care of that (for example
/// through layer indirection)
#[repr(C)]
pub enum RenderingResult {
    ContinueRenderingChildren,
    ContinueRenderingWithoutChildren,
}

impl Default for RenderingResult {
    fn default() -> Self {
        Self::ContinueRenderingChildren
    }
}

/// Items are the nodes in the render tree.
#[vtable]
#[repr(C)]
pub struct ItemVTable {
    /// This function is called by the run-time after the memory for the item
    /// has been allocated and initialized. It will be called before any user specified
    /// bindings are set.
    pub init: extern "C" fn(core::pin::Pin<VRef<ItemVTable>>, window: &WindowRc),

    /// Returns the geometry of this item (relative to its parent item)
    pub geometry: extern "C" fn(core::pin::Pin<VRef<ItemVTable>>) -> Rect,

    /// offset in bytes from the *const ItemImpl.
    /// isize::MAX  means None
    #[allow(non_upper_case_globals)]
    #[field_offset(CachedRenderingData)]
    pub cached_rendering_data_offset: usize,

    /// We would need max/min/preferred size, and all layout info
    pub layout_info: extern "C" fn(
        core::pin::Pin<VRef<ItemVTable>>,
        orientation: Orientation,
        window: &WindowRc,
    ) -> LayoutInfo,

    /// Event handler for mouse and touch event. This function is called before being called on children.
    /// Then, depending on the return value, it is called for the children, and their children, then
    /// [`Self::input_event`] is called on the children, and finally [`Self::input_event`] is called
    /// on this item again.
    pub input_event_filter_before_children: extern "C" fn(
        core::pin::Pin<VRef<ItemVTable>>,
        MouseEvent,
        window: &WindowRc,
        self_rc: &ItemRc,
    ) -> InputEventFilterResult,

    /// Handle input event for mouse and touch event
    pub input_event: extern "C" fn(
        core::pin::Pin<VRef<ItemVTable>>,
        MouseEvent,
        window: &WindowRc,
        self_rc: &ItemRc,
    ) -> InputEventResult,

    pub focus_event: extern "C" fn(
        core::pin::Pin<VRef<ItemVTable>>,
        &FocusEvent,
        window: &WindowRc,
    ) -> FocusEventResult,

    pub key_event: extern "C" fn(
        core::pin::Pin<VRef<ItemVTable>>,
        &KeyEvent,
        window: &WindowRc,
    ) -> KeyEventResult,

    pub render: extern "C" fn(
        core::pin::Pin<VRef<ItemVTable>>,
        backend: &mut ItemRendererRef,
        self_rc: &ItemRc,
    ) -> RenderingResult,
}

/// Alias for `vtable::VRef<ItemVTable>` which represent a pointer to a `dyn Item` with
/// the associated vtable
pub type ItemRef<'a> = vtable::VRef<'a, ItemVTable>;

#[repr(C)]
#[derive(FieldOffsets, Default, SlintElement)]
#[pin]
/// The implementation of the `Rectangle` element
pub struct Rectangle {
    pub background: Property<Brush>,
    pub x: Property<Coord>,
    pub y: Property<Coord>,
    pub width: Property<Coord>,
    pub height: Property<Coord>,
    pub cached_rendering_data: CachedRenderingData,
}

impl Item for Rectangle {
    fn init(self: Pin<&Self>, _window: &WindowRc) {}

    fn geometry(self: Pin<&Self>) -> Rect {
        euclid::rect(self.x(), self.y(), self.width(), self.height())
    }

    fn layout_info(self: Pin<&Self>, _orientation: Orientation, _window: &WindowRc) -> LayoutInfo {
        LayoutInfo { stretch: 1., ..LayoutInfo::default() }
    }

    fn input_event_filter_before_children(
        self: Pin<&Self>,
        _: MouseEvent,
        _window: &WindowRc,
        _self_rc: &ItemRc,
    ) -> InputEventFilterResult {
        InputEventFilterResult::ForwardAndIgnore
    }

    fn input_event(
        self: Pin<&Self>,
        _: MouseEvent,
        _window: &WindowRc,
        _self_rc: &ItemRc,
    ) -> InputEventResult {
        InputEventResult::EventIgnored
    }

    fn key_event(self: Pin<&Self>, _: &KeyEvent, _window: &WindowRc) -> KeyEventResult {
        KeyEventResult::EventIgnored
    }

    fn focus_event(self: Pin<&Self>, _: &FocusEvent, _window: &WindowRc) -> FocusEventResult {
        FocusEventResult::FocusIgnored
    }

    fn render(
        self: Pin<&Self>,
        backend: &mut ItemRendererRef,
        _self_rc: &ItemRc,
    ) -> RenderingResult {
        (*backend).draw_rectangle(self);
        RenderingResult::ContinueRenderingChildren
    }
}

impl ItemConsts for Rectangle {
    const cached_rendering_data_offset: const_field_offset::FieldOffset<
        Rectangle,
        CachedRenderingData,
    > = Rectangle::FIELD_OFFSETS.cached_rendering_data.as_unpinned_projection();
}

declare_item_vtable! {
    fn slint_get_RectangleVTable() -> RectangleVTable for Rectangle
}

#[repr(C)]
#[derive(FieldOffsets, Default, SlintElement)]
#[pin]
/// The implementation of the `BorderRectangle` element
pub struct BorderRectangle {
    pub background: Property<Brush>,
    pub x: Property<Coord>,
    pub y: Property<Coord>,
    pub width: Property<Coord>,
    pub height: Property<Coord>,
    pub border_width: Property<Coord>,
    pub border_radius: Property<Coord>,
    pub border_color: Property<Brush>,
    pub cached_rendering_data: CachedRenderingData,
}

impl Item for BorderRectangle {
    fn init(self: Pin<&Self>, _window: &WindowRc) {}

    fn geometry(self: Pin<&Self>) -> Rect {
        euclid::rect(self.x(), self.y(), self.width(), self.height())
    }

    fn layout_info(self: Pin<&Self>, _orientation: Orientation, _window: &WindowRc) -> LayoutInfo {
        LayoutInfo { stretch: 1., ..LayoutInfo::default() }
    }

    fn input_event_filter_before_children(
        self: Pin<&Self>,
        _: MouseEvent,
        _window: &WindowRc,
        _self_rc: &ItemRc,
    ) -> InputEventFilterResult {
        InputEventFilterResult::ForwardAndIgnore
    }

    fn input_event(
        self: Pin<&Self>,
        _: MouseEvent,
        _window: &WindowRc,
        _self_rc: &ItemRc,
    ) -> InputEventResult {
        InputEventResult::EventIgnored
    }

    fn key_event(self: Pin<&Self>, _: &KeyEvent, _window: &WindowRc) -> KeyEventResult {
        KeyEventResult::EventIgnored
    }

    fn focus_event(self: Pin<&Self>, _: &FocusEvent, _window: &WindowRc) -> FocusEventResult {
        FocusEventResult::FocusIgnored
    }

    fn render(
        self: Pin<&Self>,
        backend: &mut ItemRendererRef,
        _self_rc: &ItemRc,
    ) -> RenderingResult {
        (*backend).draw_border_rectangle(self);
        RenderingResult::ContinueRenderingChildren
    }
}

impl ItemConsts for BorderRectangle {
    const cached_rendering_data_offset: const_field_offset::FieldOffset<
        BorderRectangle,
        CachedRenderingData,
    > = BorderRectangle::FIELD_OFFSETS.cached_rendering_data.as_unpinned_projection();
}

declare_item_vtable! {
    fn slint_get_BorderRectangleVTable() -> BorderRectangleVTable for BorderRectangle
}

/// The implementation of the `TouchArea` element
#[repr(C)]
#[derive(FieldOffsets, Default, SlintElement)]
#[pin]
pub struct TouchArea {
    pub x: Property<Coord>,
    pub y: Property<Coord>,
    pub width: Property<Coord>,
    pub height: Property<Coord>,
    pub enabled: Property<bool>,
    /// FIXME: We should annotate this as an "output" property.
    pub pressed: Property<bool>,
    pub has_hover: Property<bool>,
    /// FIXME: there should be just one property for the point instead of two.
    /// Could even be merged with pressed in a Property<Option<Point>> (of course, in the
    /// implementation item only, for the compiler it would stay separate properties)
    pub pressed_x: Property<Coord>,
    pub pressed_y: Property<Coord>,
    /// FIXME: should maybe be as parameter to the mouse event instead. Or at least just one property
    pub mouse_x: Property<Coord>,
    pub mouse_y: Property<Coord>,
    pub mouse_cursor: Property<MouseCursor>,
    pub clicked: Callback<VoidArg>,
    pub moved: Callback<VoidArg>,
    pub pointer_event: Callback<PointerEventArg>,
    /// FIXME: remove this
    pub cached_rendering_data: CachedRenderingData,
    /// true when we are currently grabbing the mouse
    grabbed: Cell<bool>,
}

impl Item for TouchArea {
    fn init(self: Pin<&Self>, _window: &WindowRc) {}

    fn geometry(self: Pin<&Self>) -> Rect {
        euclid::rect(self.x(), self.y(), self.width(), self.height())
    }

    fn layout_info(self: Pin<&Self>, _orientation: Orientation, _window: &WindowRc) -> LayoutInfo {
        LayoutInfo::default()
    }

    fn input_event_filter_before_children(
        self: Pin<&Self>,
        event: MouseEvent,
        window: &WindowRc,
        _self_rc: &ItemRc,
    ) -> InputEventFilterResult {
        if !self.enabled() {
            return InputEventFilterResult::ForwardAndIgnore;
        }
        if let Some(pos) = event.pos() {
            Self::FIELD_OFFSETS.mouse_x.apply_pin(self).set(pos.x);
            Self::FIELD_OFFSETS.mouse_y.apply_pin(self).set(pos.y);
        }
        let hovering = !matches!(event, MouseEvent::MouseExit);
        Self::FIELD_OFFSETS.has_hover.apply_pin(self).set(hovering);
        if hovering {
            window.set_mouse_cursor(self.mouse_cursor());
        }
        InputEventFilterResult::ForwardAndInterceptGrab
    }

    fn input_event(
        self: Pin<&Self>,
        event: MouseEvent,
        window: &WindowRc,
        _self_rc: &ItemRc,
    ) -> InputEventResult {
        if matches!(event, MouseEvent::MouseExit) {
            Self::FIELD_OFFSETS.has_hover.apply_pin(self).set(false);
            window.set_mouse_cursor(MouseCursor::default);
        }
        if !self.enabled() {
            return InputEventResult::EventIgnored;
        }
        let result = if let MouseEvent::MouseReleased { pos, button } = event {
            if button == PointerEventButton::left
                && euclid::rect(0 as Coord, 0 as Coord, self.width(), self.height()).contains(pos)
            {
                Self::FIELD_OFFSETS.clicked.apply_pin(self).call(&());
            }
            InputEventResult::EventAccepted
        } else {
            InputEventResult::GrabMouse
        };

        match event {
            MouseEvent::MousePressed { pos, button } => {
                self.grabbed.set(true);
                if button == PointerEventButton::left {
                    Self::FIELD_OFFSETS.pressed_x.apply_pin(self).set(pos.x);
                    Self::FIELD_OFFSETS.pressed_y.apply_pin(self).set(pos.y);
                    Self::FIELD_OFFSETS.pressed.apply_pin(self).set(true);
                }
                Self::FIELD_OFFSETS
                    .pointer_event
                    .apply_pin(self)
                    .call(&(PointerEvent { button, kind: PointerEventKind::down },));
            }
            MouseEvent::MouseExit => {
                Self::FIELD_OFFSETS.pressed.apply_pin(self).set(false);
                if self.grabbed.replace(false) {
                    Self::FIELD_OFFSETS.pointer_event.apply_pin(self).call(&(PointerEvent {
                        button: PointerEventButton::none,
                        kind: PointerEventKind::cancel,
                    },));
                }
            }
            MouseEvent::MouseReleased { button, .. } => {
                self.grabbed.set(false);
                if button == PointerEventButton::left {
                    Self::FIELD_OFFSETS.pressed.apply_pin(self).set(false);
                }
                Self::FIELD_OFFSETS
                    .pointer_event
                    .apply_pin(self)
                    .call(&(PointerEvent { button, kind: PointerEventKind::up },));
            }
            MouseEvent::MouseMoved { .. } => {
                return if self.grabbed.get() {
                    Self::FIELD_OFFSETS.moved.apply_pin(self).call(&());
                    InputEventResult::GrabMouse
                } else {
                    InputEventResult::EventAccepted
                }
            }
            MouseEvent::MouseWheel { .. } => {
                return if self.grabbed.get() {
                    InputEventResult::GrabMouse
                } else {
                    InputEventResult::EventAccepted
                }
            }
        };
        result
    }

    fn key_event(self: Pin<&Self>, _: &KeyEvent, _window: &WindowRc) -> KeyEventResult {
        KeyEventResult::EventIgnored
    }

    fn focus_event(self: Pin<&Self>, _: &FocusEvent, _window: &WindowRc) -> FocusEventResult {
        FocusEventResult::FocusIgnored
    }

    fn render(
        self: Pin<&Self>,
        _backend: &mut ItemRendererRef,
        _self_rc: &ItemRc,
    ) -> RenderingResult {
        RenderingResult::ContinueRenderingChildren
    }
}

impl ItemConsts for TouchArea {
    const cached_rendering_data_offset: const_field_offset::FieldOffset<
        TouchArea,
        CachedRenderingData,
    > = TouchArea::FIELD_OFFSETS.cached_rendering_data.as_unpinned_projection();
}

declare_item_vtable! {
    fn slint_get_TouchAreaVTable() -> TouchAreaVTable for TouchArea
}

/// A runtime item that exposes key
#[repr(C)]
#[derive(FieldOffsets, Default, SlintElement)]
#[pin]
pub struct FocusScope {
    pub x: Property<Coord>,
    pub y: Property<Coord>,
    pub width: Property<Coord>,
    pub height: Property<Coord>,
    pub enabled: Property<bool>,
    pub has_focus: Property<bool>,
    pub key_pressed: Callback<KeyEventArg, EventResult>,
    pub key_released: Callback<KeyEventArg, EventResult>,
    /// FIXME: remove this
    pub cached_rendering_data: CachedRenderingData,
}

impl Item for FocusScope {
    fn init(self: Pin<&Self>, _window: &WindowRc) {}

    fn geometry(self: Pin<&Self>) -> Rect {
        euclid::rect(self.x(), self.y(), self.width(), self.height())
    }

    fn layout_info(self: Pin<&Self>, _orientation: Orientation, _window: &WindowRc) -> LayoutInfo {
        LayoutInfo::default()
    }

    fn input_event_filter_before_children(
        self: Pin<&Self>,
        _: MouseEvent,
        _window: &WindowRc,
        _self_rc: &ItemRc,
    ) -> InputEventFilterResult {
        InputEventFilterResult::ForwardEvent
    }

    fn input_event(
        self: Pin<&Self>,
        event: MouseEvent,
        window: &WindowRc,
        self_rc: &ItemRc,
    ) -> InputEventResult {
        if self.enabled() && matches!(event, MouseEvent::MousePressed { .. }) && !self.has_focus() {
            window.clone().set_focus_item(self_rc);
        }
        InputEventResult::EventIgnored
    }

    fn key_event(self: Pin<&Self>, event: &KeyEvent, _window: &WindowRc) -> KeyEventResult {
        let r = match event.event_type {
            KeyEventType::KeyPressed => {
                Self::FIELD_OFFSETS.key_pressed.apply_pin(self).call(&(event.clone(),))
            }
            KeyEventType::KeyReleased => {
                Self::FIELD_OFFSETS.key_released.apply_pin(self).call(&(event.clone(),))
            }
        };
        match r {
            EventResult::accept => KeyEventResult::EventAccepted,
            EventResult::reject => KeyEventResult::EventIgnored,
        }
    }

    fn focus_event(self: Pin<&Self>, event: &FocusEvent, _window: &WindowRc) -> FocusEventResult {
        if !self.enabled() {
            return FocusEventResult::FocusIgnored;
        }

        match event {
            FocusEvent::FocusIn | FocusEvent::WindowReceivedFocus => {
                self.has_focus.set(true);
            }
            FocusEvent::FocusOut | FocusEvent::WindowLostFocus => {
                self.has_focus.set(false);
            }
        }
        FocusEventResult::FocusAccepted
    }

    fn render(
        self: Pin<&Self>,
        _backend: &mut ItemRendererRef,
        _self_rc: &ItemRc,
    ) -> RenderingResult {
        RenderingResult::ContinueRenderingChildren
    }
}

impl ItemConsts for FocusScope {
    const cached_rendering_data_offset: const_field_offset::FieldOffset<
        FocusScope,
        CachedRenderingData,
    > = FocusScope::FIELD_OFFSETS.cached_rendering_data.as_unpinned_projection();
}

declare_item_vtable! {
    fn slint_get_FocusScopeVTable() -> FocusScopeVTable for FocusScope
}

#[repr(C)]
#[derive(FieldOffsets, Default, SlintElement)]
#[pin]
/// The implementation of the `Clip` element
pub struct Clip {
    pub x: Property<Coord>,
    pub y: Property<Coord>,
    pub width: Property<Coord>,
    pub height: Property<Coord>,
    pub border_radius: Property<Coord>,
    pub border_width: Property<Coord>,
    pub cached_rendering_data: CachedRenderingData,
    pub clip: Property<bool>,
}

impl Item for Clip {
    fn init(self: Pin<&Self>, _window: &WindowRc) {}

    fn geometry(self: Pin<&Self>) -> Rect {
        euclid::rect(self.x(), self.y(), self.width(), self.height())
    }

    fn layout_info(self: Pin<&Self>, _orientation: Orientation, _window: &WindowRc) -> LayoutInfo {
        LayoutInfo { stretch: 1., ..LayoutInfo::default() }
    }

    fn input_event_filter_before_children(
        self: Pin<&Self>,
        event: MouseEvent,
        _window: &WindowRc,
        _self_rc: &ItemRc,
    ) -> InputEventFilterResult {
        if let Some(pos) = event.pos() {
            if self.clip()
                && (pos.x < 0 as Coord
                    || pos.y < 0 as Coord
                    || pos.x > self.width()
                    || pos.y > self.height())
            {
                return InputEventFilterResult::Intercept;
            }
        }
        InputEventFilterResult::ForwardAndIgnore
    }

    fn input_event(
        self: Pin<&Self>,
        _: MouseEvent,
        _window: &WindowRc,
        _self_rc: &ItemRc,
    ) -> InputEventResult {
        InputEventResult::EventIgnored
    }

    fn key_event(self: Pin<&Self>, _: &KeyEvent, _window: &WindowRc) -> KeyEventResult {
        KeyEventResult::EventIgnored
    }

    fn focus_event(self: Pin<&Self>, _: &FocusEvent, _window: &WindowRc) -> FocusEventResult {
        FocusEventResult::FocusIgnored
    }

    fn render(
        self: Pin<&Self>,
        backend: &mut ItemRendererRef,
        self_rc: &ItemRc,
    ) -> RenderingResult {
        (*backend).visit_clip(self, self_rc)
    }
}

impl ItemConsts for Clip {
    const cached_rendering_data_offset: const_field_offset::FieldOffset<Clip, CachedRenderingData> =
        Clip::FIELD_OFFSETS.cached_rendering_data.as_unpinned_projection();
}

declare_item_vtable! {
    fn slint_get_ClipVTable() -> ClipVTable for Clip
}

#[repr(C)]
#[derive(FieldOffsets, Default, SlintElement)]
#[pin]
/// The Opacity Item is not meant to be used directly by the .slint 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<Coord>,
    pub y: Property<Coord>,
    pub width: Property<Coord>,
    pub height: Property<Coord>,
    pub opacity: Property<f32>,
    pub cached_rendering_data: CachedRenderingData,
}

impl Item for Opacity {
    fn init(self: Pin<&Self>, _window: &WindowRc) {}

    fn geometry(self: Pin<&Self>) -> Rect {
        euclid::rect(self.x(), self.y(), self.width(), self.height())
    }

    fn layout_info(self: Pin<&Self>, _orientation: Orientation, _window: &WindowRc) -> LayoutInfo {
        LayoutInfo { stretch: 1., ..LayoutInfo::default() }
    }

    fn input_event_filter_before_children(
        self: Pin<&Self>,
        _: MouseEvent,
        _window: &WindowRc,
        _self_rc: &ItemRc,
    ) -> InputEventFilterResult {
        InputEventFilterResult::ForwardAndIgnore
    }

    fn input_event(
        self: Pin<&Self>,
        _: MouseEvent,
        _window: &WindowRc,
        _self_rc: &ItemRc,
    ) -> InputEventResult {
        InputEventResult::EventIgnored
    }

    fn key_event(self: Pin<&Self>, _: &KeyEvent, _window: &WindowRc) -> KeyEventResult {
        KeyEventResult::EventIgnored
    }

    fn focus_event(self: Pin<&Self>, _: &FocusEvent, _window: &WindowRc) -> FocusEventResult {
        FocusEventResult::FocusIgnored
    }

    fn render(
        self: Pin<&Self>,
        backend: &mut ItemRendererRef,
        self_rc: &ItemRc,
    ) -> RenderingResult {
        backend.visit_opacity(self, self_rc)
    }
}

impl Opacity {
    // This function determines the optimization opportunities for not having to render the
    // children of the Opacity element into a layer:
    //  *  The opacity item typically only one child (this is not guaranteed). If that item has
    //     no children, then we can skip the layer and apply the opacity directly. This is not perfect though,
    //     for example if the compiler inserts another synthetic element between the `Opacity` and the actual child,
    //     then this check will apply a layer even though it might not actually be necessary.
    //  * If the vale of the opacity is 1.0 then we don't need to do anything.
    pub fn need_layer(self_rc: &ItemRc, opacity: f32) -> bool {
        if opacity == 1.0 {
            return false;
        }

        let opacity_child = match self_rc.first_child() {
            Some(first_child) => first_child,
            None => return false, // No children? Don't need a layer then.
        };

        if opacity_child.next_sibling().is_some() {
            return true; // If the opacity item has more than one child, then we need a layer
        }

        // If the target of the opacity has any children then we need a layer
        opacity_child.first_child().is_some()
    }
}

impl ItemConsts for Opacity {
    const cached_rendering_data_offset: const_field_offset::FieldOffset<
        Opacity,
        CachedRenderingData,
    > = Opacity::FIELD_OFFSETS.cached_rendering_data.as_unpinned_projection();
}

declare_item_vtable! {
    fn slint_get_OpacityVTable() -> OpacityVTable for Opacity
}

#[repr(C)]
#[derive(FieldOffsets, Default, SlintElement)]
#[pin]
/// The Layer Item is not meant to be used directly by the .slint code, instead, the `layer: xxx` property should be used
pub struct Layer {
    // FIXME: this element shouldn't need these geometry property
    pub x: Property<Coord>,
    pub y: Property<Coord>,
    pub width: Property<Coord>,
    pub height: Property<Coord>,
    pub cache_rendering_hint: Property<bool>,
    pub cached_rendering_data: CachedRenderingData,
}

impl Item for Layer {
    fn init(self: Pin<&Self>, _window: &WindowRc) {}

    fn geometry(self: Pin<&Self>) -> Rect {
        euclid::rect(self.x(), self.y(), self.width(), self.height())
    }

    fn layout_info(self: Pin<&Self>, _orientation: Orientation, _window: &WindowRc) -> LayoutInfo {
        LayoutInfo { stretch: 1., ..LayoutInfo::default() }
    }

    fn input_event_filter_before_children(
        self: Pin<&Self>,
        _: MouseEvent,
        _window: &WindowRc,
        _self_rc: &ItemRc,
    ) -> InputEventFilterResult {
        InputEventFilterResult::ForwardAndIgnore
    }

    fn input_event(
        self: Pin<&Self>,
        _: MouseEvent,
        _window: &WindowRc,
        _self_rc: &ItemRc,
    ) -> InputEventResult {
        InputEventResult::EventIgnored
    }

    fn key_event(self: Pin<&Self>, _: &KeyEvent, _window: &WindowRc) -> KeyEventResult {
        KeyEventResult::EventIgnored
    }

    fn focus_event(self: Pin<&Self>, _: &FocusEvent, _window: &WindowRc) -> FocusEventResult {
        FocusEventResult::FocusIgnored
    }

    fn render(
        self: Pin<&Self>,
        backend: &mut ItemRendererRef,
        self_rc: &ItemRc,
    ) -> RenderingResult {
        backend.visit_layer(self, self_rc)
    }
}

impl ItemConsts for Layer {
    const cached_rendering_data_offset: const_field_offset::FieldOffset<
        Layer,
        CachedRenderingData,
    > = Layer::FIELD_OFFSETS.cached_rendering_data.as_unpinned_projection();
}

declare_item_vtable! {
    fn slint_get_LayerVTable() -> LayerVTable for Layer
}

#[repr(C)]
#[derive(FieldOffsets, Default, SlintElement)]
#[pin]
/// The implementation of the `Rotate` element
pub struct Rotate {
    pub angle: Property<f32>,
    pub origin_x: Property<Coord>,
    pub origin_y: Property<Coord>,
    pub width: Property<Coord>,
    pub height: Property<Coord>,
    pub cached_rendering_data: CachedRenderingData,
}

impl Item for Rotate {
    fn init(self: Pin<&Self>, _window: &WindowRc) {}

    fn geometry(self: Pin<&Self>) -> Rect {
        euclid::rect(0, 0, 0, 0).cast()
    }

    fn layout_info(self: Pin<&Self>, _orientation: Orientation, _window: &WindowRc) -> LayoutInfo {
        LayoutInfo { stretch: 1., ..LayoutInfo::default() }
    }

    fn input_event_filter_before_children(
        self: Pin<&Self>,
        _: MouseEvent,
        _window: &WindowRc,
        _self_rc: &ItemRc,
    ) -> InputEventFilterResult {
        InputEventFilterResult::ForwardAndIgnore
    }

    fn input_event(
        self: Pin<&Self>,
        _: MouseEvent,
        _window: &WindowRc,
        _self_rc: &ItemRc,
    ) -> InputEventResult {
        InputEventResult::EventIgnored
    }

    fn key_event(self: Pin<&Self>, _: &KeyEvent, _window: &WindowRc) -> KeyEventResult {
        KeyEventResult::EventIgnored
    }

    fn focus_event(self: Pin<&Self>, _: &FocusEvent, _window: &WindowRc) -> FocusEventResult {
        FocusEventResult::FocusIgnored
    }

    fn render(
        self: Pin<&Self>,
        backend: &mut ItemRendererRef,
        _self_rc: &ItemRc,
    ) -> RenderingResult {
        (*backend).translate(self.origin_x(), self.origin_y());
        (*backend).rotate(self.angle());
        (*backend).translate(-self.origin_x(), -self.origin_y());
        RenderingResult::ContinueRenderingChildren
    }
}

impl ItemConsts for Rotate {
    const cached_rendering_data_offset: const_field_offset::FieldOffset<
        Rotate,
        CachedRenderingData,
    > = Rotate::FIELD_OFFSETS.cached_rendering_data.as_unpinned_projection();
}

declare_item_vtable! {
    fn slint_get_RotateVTable() -> RotateVTable for Rotate
}

declare_item_vtable! {
    fn slint_get_FlickableVTable() -> FlickableVTable for Flickable
}

/// The implementation of the `PropertyAnimation` element
#[repr(C)]
#[derive(FieldOffsets, SlintElement, Clone, Debug)]
#[pin]
pub struct PropertyAnimation {
    #[rtti_field]
    pub delay: i32,
    #[rtti_field]
    pub duration: i32,
    #[rtti_field]
    pub iteration_count: f32,
    #[rtti_field]
    pub easing: crate::animations::EasingCurve,
}

impl Default for PropertyAnimation {
    fn default() -> Self {
        // Defaults for PropertyAnimation are defined here (for internal Rust code doing programmatic animations)
        // as well as in `builtins.slint` (for generated C++ and Rust code)
        Self { delay: 0, duration: 0, iteration_count: 1., easing: Default::default() }
    }
}

/// The implementation of the `Window` element
#[repr(C)]
#[derive(FieldOffsets, Default, SlintElement)]
#[pin]
pub struct WindowItem {
    pub width: Property<Coord>,
    pub height: Property<Coord>,
    pub background: Property<Color>,
    pub title: Property<SharedString>,
    pub no_frame: Property<bool>,
    pub icon: Property<crate::graphics::Image>,
    pub default_font_family: Property<SharedString>,
    pub default_font_size: Property<Coord>,
    pub default_font_weight: Property<i32>,
    pub cached_rendering_data: CachedRenderingData,
}

impl Item for WindowItem {
    fn init(self: Pin<&Self>, _window: &WindowRc) {}

    fn geometry(self: Pin<&Self>) -> Rect {
        euclid::rect(0 as _, 0 as _, self.width(), self.height())
    }

    fn layout_info(self: Pin<&Self>, _orientation: Orientation, _window: &WindowRc) -> LayoutInfo {
        LayoutInfo::default()
    }

    fn input_event_filter_before_children(
        self: Pin<&Self>,
        _: MouseEvent,
        _window: &WindowRc,
        _self_rc: &ItemRc,
    ) -> InputEventFilterResult {
        InputEventFilterResult::ForwardAndIgnore
    }

    fn input_event(
        self: Pin<&Self>,
        _event: MouseEvent,
        _window: &WindowRc,
        _self_rc: &ItemRc,
    ) -> InputEventResult {
        InputEventResult::EventIgnored
    }

    fn key_event(self: Pin<&Self>, _: &KeyEvent, _window: &WindowRc) -> KeyEventResult {
        KeyEventResult::EventIgnored
    }

    fn focus_event(self: Pin<&Self>, _: &FocusEvent, _window: &WindowRc) -> FocusEventResult {
        FocusEventResult::FocusIgnored
    }

    fn render(
        self: Pin<&Self>,
        _backend: &mut ItemRendererRef,
        _self_rc: &ItemRc,
    ) -> RenderingResult {
        RenderingResult::ContinueRenderingChildren
    }
}

impl WindowItem {
    /// Returns the font properties that can be used as defaults for child items
    pub fn default_font_properties(self: Pin<&Self>) -> crate::graphics::FontRequest {
        crate::graphics::FontRequest {
            family: {
                let maybe_family = self.default_font_family();
                if !maybe_family.is_empty() {
                    Some(maybe_family)
                } else {
                    None
                }
            },
            pixel_size: {
                let font_size = self.default_font_size();
                if font_size <= 0 as Coord {
                    None
                } else {
                    Some(font_size)
                }
            },
            weight: {
                let font_weight = self.default_font_weight();
                if font_weight == 0 {
                    None
                } else {
                    Some(font_weight)
                }
            },
            ..Default::default()
        }
    }
}

impl ItemConsts for WindowItem {
    const cached_rendering_data_offset: const_field_offset::FieldOffset<Self, CachedRenderingData> =
        Self::FIELD_OFFSETS.cached_rendering_data.as_unpinned_projection();
}

declare_item_vtable! {
    fn slint_get_WindowItemVTable() -> WindowItemVTable for WindowItem
}

/// The implementation of the `BoxShadow` element
#[repr(C)]
#[derive(FieldOffsets, Default, SlintElement)]
#[pin]
pub struct BoxShadow {
    // Rectangle properties
    pub x: Property<Coord>,
    pub y: Property<Coord>,
    pub width: Property<Coord>,
    pub height: Property<Coord>,
    pub border_radius: Property<Coord>,
    // Shadow specific properties
    pub offset_x: Property<Coord>,
    pub offset_y: Property<Coord>,
    pub color: Property<Color>,
    pub blur: Property<Coord>,
    pub cached_rendering_data: CachedRenderingData,
}

impl Item for BoxShadow {
    fn init(self: Pin<&Self>, _window: &WindowRc) {}

    fn geometry(self: Pin<&Self>) -> Rect {
        euclid::rect(self.x(), self.y(), self.width(), self.height())
    }

    fn layout_info(self: Pin<&Self>, _orientation: Orientation, _window: &WindowRc) -> LayoutInfo {
        LayoutInfo { stretch: 1., ..LayoutInfo::default() }
    }

    fn input_event_filter_before_children(
        self: Pin<&Self>,
        _: MouseEvent,
        _window: &WindowRc,
        _self_rc: &ItemRc,
    ) -> InputEventFilterResult {
        InputEventFilterResult::ForwardAndIgnore
    }

    fn input_event(
        self: Pin<&Self>,
        _event: MouseEvent,
        _window: &WindowRc,
        _self_rc: &ItemRc,
    ) -> InputEventResult {
        InputEventResult::EventIgnored
    }

    fn key_event(self: Pin<&Self>, _: &KeyEvent, _window: &WindowRc) -> KeyEventResult {
        KeyEventResult::EventIgnored
    }

    fn focus_event(self: Pin<&Self>, _: &FocusEvent, _window: &WindowRc) -> FocusEventResult {
        FocusEventResult::FocusIgnored
    }

    fn render(
        self: Pin<&Self>,
        backend: &mut ItemRendererRef,
        _self_rc: &ItemRc,
    ) -> RenderingResult {
        (*backend).draw_box_shadow(self);
        RenderingResult::ContinueRenderingChildren
    }
}

impl ItemConsts for BoxShadow {
    const cached_rendering_data_offset: const_field_offset::FieldOffset<Self, CachedRenderingData> =
        Self::FIELD_OFFSETS.cached_rendering_data.as_unpinned_projection();
}

declare_item_vtable! {
    fn slint_get_BoxShadowVTable() -> BoxShadowVTable for BoxShadow
}

declare_item_vtable! {
    fn slint_get_TextVTable() -> TextVTable for Text
}

declare_item_vtable! {
    fn slint_get_TextInputVTable() -> TextInputVTable for TextInput
}

declare_item_vtable! {
    fn slint_get_ImageItemVTable() -> ImageItemVTable for ImageItem
}

declare_item_vtable! {
    fn slint_get_ClippedImageVTable() -> ClippedImageVTable for ClippedImage
}

#[cfg(feature = "std")]
declare_item_vtable! {
    fn slint_get_PathVTable() -> PathVTable for Path
}

macro_rules! declare_enums {
    ($( $(#[$enum_doc:meta])* enum $Name:ident { $( $(#[$value_doc:meta])* $Value:ident,)* })*) => {
        $(
            #[derive(Copy, Clone, Debug, PartialEq, Eq, strum::EnumString, strum::Display, Hash)]
            #[repr(C)]
            #[allow(non_camel_case_types)]
            $(#[$enum_doc])*
            pub enum $Name {
                $( $(#[$value_doc])* $Value),*
            }

            impl Default for $Name {
                fn default() -> Self {
                    // Always return the first value
                    ($(Self::$Value,)*).0
                }
            }
        )*
    };
}

i_slint_common::for_each_enums!(declare_enums);

/// Represents a key event sent by the windowing system.
#[derive(Debug, Clone, PartialEq, Default)]
#[repr(C)]
pub struct PointerEvent {
    pub button: PointerEventButton,
    pub kind: PointerEventKind,
}