feat(native): add Tooltip widget

1 files changed, 300 insertions, 0 deletions

diff --git a/native/src/widget/tooltip.rs b/native/src/widget/tooltip.rs
new file mode 100644
index 00000000..cae38d46
--- /dev/null
+++ b/native/src/widget/tooltip.rs
@@ -0,0 +1,300 @@
+//! Display a widget over another.
+use std::hash::Hash;
+
+use iced_core::Rectangle;
+
+use crate::{
+    event, layout, overlay, Clipboard, Element, Event, Hasher, Layout, Length,
+    Point, Size, Vector, Widget,
+};
+
+/// An element to display a widget over another.
+#[allow(missing_debug_implementations)]
+pub struct Tooltip<'a, Message, Renderer: self::Renderer> {
+    content: Element<'a, Message, Renderer>,
+    tooltip: Element<'a, Message, Renderer>,
+    tooltip_position: TooltipPosition,
+}
+
+impl<'a, Message, Renderer> Tooltip<'a, Message, Renderer>
+where
+    Renderer: self::Renderer,
+{
+    /// Creates an empty [`Tooltip`].
+    ///
+    /// [`Tooltip`]: struct.Tooltip.html
+    pub fn new<T, H>(
+        content: T,
+        tooltip: H,
+        tooltip_position: TooltipPosition,
+    ) -> Self
+    where
+        T: Into<Element<'a, Message, Renderer>>,
+        H: Into<Element<'a, Message, Renderer>>,
+    {
+        Tooltip {
+            content: content.into(),
+            tooltip: tooltip.into(),
+            tooltip_position,
+        }
+    }
+}
+
+/// The position of the tooltip. Defaults to following the cursor.
+#[derive(Debug, PartialEq)]
+pub enum TooltipPosition {
+    /// The tooltip will follow the cursor.
+    FollowCursor,
+    /// The tooltip will appear on the top of the widget.
+    Top,
+    /// The tooltip will appear on the bottom of the widget.
+    Bottom,
+    /// The tooltip will appear on the left of the widget.
+    Left,
+    /// The tooltip will appear on the right of the widget.
+    Right,
+}
+
+impl Default for TooltipPosition {
+    fn default() -> Self {
+        TooltipPosition::FollowCursor
+    }
+}
+
+impl<'a, Message, Renderer> Widget<Message, Renderer>
+    for Tooltip<'a, Message, Renderer>
+where
+    Renderer: self::Renderer,
+{
+    fn width(&self) -> Length {
+        self.content.width()
+    }
+
+    fn height(&self) -> Length {
+        self.content.height()
+    }
+
+    fn layout(
+        &self,
+        renderer: &Renderer,
+        limits: &layout::Limits,
+    ) -> layout::Node {
+        self.content.layout(renderer, limits)
+    }
+
+    fn on_event(
+        &mut self,
+        event: Event,
+        layout: Layout<'_>,
+        cursor_position: Point,
+        messages: &mut Vec<Message>,
+        renderer: &Renderer,
+        clipboard: Option<&dyn Clipboard>,
+    ) -> event::Status {
+        self.content.widget.on_event(
+            event,
+            layout,
+            cursor_position,
+            messages,
+            renderer,
+            clipboard,
+        )
+    }
+
+    fn draw(
+        &self,
+        renderer: &mut Renderer,
+        defaults: &Renderer::Defaults,
+        layout: Layout<'_>,
+        cursor_position: Point,
+        viewport: &Rectangle,
+    ) -> Renderer::Output {
+        renderer.draw(
+            defaults,
+            cursor_position,
+            &self.content,
+            layout,
+            viewport,
+        )
+    }
+
+    fn hash_layout(&self, state: &mut Hasher) {
+        struct Marker;
+        std::any::TypeId::of::<Marker>().hash(state);
+
+        self.content.hash_layout(state);
+    }
+
+    fn overlay(
+        &mut self,
+        layout: Layout<'_>,
+        overlay_content_bounds: Option<Rectangle>,
+        cursor_position: Point,
+    ) -> Option<overlay::Element<'_, Message, Renderer>> {
+        let bounds = layout.bounds();
+
+        if bounds.contains(cursor_position) {
+            let mut position = cursor_position;
+
+            if let Some(content_bounds) = overlay_content_bounds {
+                if TooltipPosition::FollowCursor != self.tooltip_position {
+                    match self.tooltip_position {
+                        TooltipPosition::Top | TooltipPosition::Bottom => {
+                            let x = bounds.x + bounds.width * 0.5
+                                - content_bounds.width * 0.5;
+
+                            position = match self.tooltip_position {
+                                TooltipPosition::Top => Point::new(
+                                    x,
+                                    bounds.y - content_bounds.height,
+                                ),
+                                TooltipPosition::Bottom => Point::new(
+                                    x,
+                                    bounds.y
+                                        + bounds.height
+                                        + content_bounds.height,
+                                ),
+                                _ => unreachable!(),
+                            };
+                        }
+                        TooltipPosition::Left | TooltipPosition::Right => {
+                            let y =
+                                bounds.center_y() + content_bounds.height * 0.5;
+
+                            position = match self.tooltip_position {
+                                TooltipPosition::Left => Point::new(
+                                    bounds.x - content_bounds.width,
+                                    y,
+                                ),
+                                TooltipPosition::Right => {
+                                    Point::new(bounds.x + bounds.width, y)
+                                }
+                                _ => unreachable!(),
+                            };
+                        }
+                        _ => {}
+                    }
+                }
+            }
+
+            Some(overlay::Element::new(
+                position,
+                Box::new(Overlay::new(&self.tooltip)),
+            ))
+        } else {
+            None
+        }
+    }
+}
+
+struct Overlay<'a, Message, Renderer: self::Renderer> {
+    content: &'a Element<'a, Message, Renderer>,
+}
+
+impl<'a, Message, Renderer: self::Renderer> Overlay<'a, Message, Renderer>
+where
+    Message: 'a,
+    Renderer: 'a,
+{
+    pub fn new(content: &'a Element<'a, Message, Renderer>) -> Self {
+        Self { content }
+    }
+}
+
+impl<'a, Message, Renderer> crate::Overlay<Message, Renderer>
+    for Overlay<'a, Message, Renderer>
+where
+    Renderer: self::Renderer,
+{
+    fn layout(
+        &self,
+        renderer: &Renderer,
+        bounds: Size,
+        position: Point,
+    ) -> layout::Node {
+        let space_below = bounds.height - position.y;
+        let space_above = position.y;
+
+        let limits = layout::Limits::new(
+            Size::ZERO,
+            Size::new(
+                bounds.width - position.x,
+                if space_below > space_above {
+                    space_below
+                } else {
+                    space_above
+                },
+            ),
+        )
+        .width(self.content.width());
+
+        let mut node = self.content.layout(renderer, &limits);
+
+        node.move_to(position - Vector::new(0.0, node.size().height));
+
+        node
+    }
+
+    fn hash_layout(&self, state: &mut Hasher, position: Point) {
+        struct Marker;
+        std::any::TypeId::of::<Marker>().hash(state);
+
+        (position.x as u32).hash(state);
+        (position.y as u32).hash(state);
+        self.content.hash_layout(state);
+    }
+
+    fn draw(
+        &self,
+        renderer: &mut Renderer,
+        defaults: &Renderer::Defaults,
+        layout: Layout<'_>,
+        cursor_position: Point,
+        viewport: &Rectangle,
+    ) -> Renderer::Output {
+        renderer.draw(
+            defaults,
+            cursor_position,
+            &self.content,
+            layout,
+            viewport,
+        )
+    }
+}
+
+/// The renderer of a [`Tooltip`].
+///
+/// Your [renderer] will need to implement this trait before being
+/// able to use a [`Tooltip`] in your user interface.
+///
+/// [`Tooltip`]: struct.Tooltip.html
+/// [renderer]: ../../renderer/index.html
+pub trait Renderer: crate::Renderer {
+    /// The style supported by this renderer.
+    type Style: Default;
+
+    /// Draws a [`Tooltip`].
+    ///
+    /// [`Tooltip`]: struct.Tooltip.html
+    fn draw<Message>(
+        &mut self,
+        defaults: &Self::Defaults,
+        cursor_position: Point,
+        content: &Element<'_, Message, Self>,
+        content_layout: Layout<'_>,
+        viewport: &Rectangle,
+    ) -> Self::Output;
+}
+
+impl<'a, Message, Renderer> From<Tooltip<'a, Message, Renderer>>
+    for Element<'a, Message, Renderer>
+where
+    Renderer: 'a + self::Renderer,
+    Message: 'a,
+{
+    fn from(
+        column: Tooltip<'a, Message, Renderer>,
+    ) -> Element<'a, Message, Renderer> {
+        Element::new(column)
+    }
+}