feat(native): add Tooltip widget

14 files changed, 381 insertions, 16 deletions

diff --git a/native/src/element.rs b/native/src/element.rs
index d6e9639a..5e906524 100644
--- a/native/src/element.rs
+++ b/native/src/element.rs
@@ -259,8 +259,11 @@ where
     pub fn overlay<'b>(
         &'b mut self,
         layout: Layout<'_>,
+        overlay_content_bounds: Option<Rectangle>,
+        cursor_position: Point,
     ) -> Option<overlay::Element<'b, Message, Renderer>> {
-        self.widget.overlay(layout)
+        self.widget
+            .overlay(layout, overlay_content_bounds, cursor_position)
     }
 }
 
@@ -352,11 +355,13 @@ where
     fn overlay(
         &mut self,
         layout: Layout<'_>,
+        overlay_content_bounds: Option<Rectangle>,
+        cursor_position: Point,
     ) -> Option<overlay::Element<'_, B, Renderer>> {
         let mapper = &self.mapper;
 
         self.widget
-            .overlay(layout)
+            .overlay(layout, overlay_content_bounds, cursor_position)
             .map(move |overlay| overlay.map(mapper))
     }
 }
@@ -440,7 +445,10 @@ where
     fn overlay(
         &mut self,
         layout: Layout<'_>,
+        overlay_content_bounds: Option<Rectangle>,
+        cursor_position: Point,
     ) -> Option<overlay::Element<'_, Message, Renderer>> {
-        self.element.overlay(layout)
+        self.element
+            .overlay(layout, overlay_content_bounds, cursor_position)
     }
 }
diff --git a/native/src/overlay.rs b/native/src/overlay.rs
index ea8bb384..20e3ee92 100644
--- a/native/src/overlay.rs
+++ b/native/src/overlay.rs
@@ -4,6 +4,7 @@ mod element;
 pub mod menu;
 
 pub use element::Element;
+use iced_core::Rectangle;
 pub use menu::Menu;
 
 use crate::event::{self, Event};
@@ -35,6 +36,7 @@ where
         defaults: &Renderer::Defaults,
         layout: Layout<'_>,
         cursor_position: Point,
+        viewport: &Rectangle,
     ) -> Renderer::Output;
 
     /// Computes the _layout_ hash of the [`Overlay`].
diff --git a/native/src/overlay/element.rs b/native/src/overlay/element.rs
index 0f44a781..fbe05d31 100644
--- a/native/src/overlay/element.rs
+++ b/native/src/overlay/element.rs
@@ -1,3 +1,5 @@
+use iced_core::Rectangle;
+
 pub use crate::Overlay;
 
 use crate::event::{self, Event};
@@ -74,9 +76,10 @@ where
         defaults: &Renderer::Defaults,
         layout: Layout<'_>,
         cursor_position: Point,
+        viewport: &Rectangle,
     ) -> Renderer::Output {
         self.overlay
-            .draw(renderer, defaults, layout, cursor_position)
+            .draw(renderer, defaults, layout, cursor_position, viewport)
     }
 
     /// Computes the _layout_ hash of the [`Element`].
@@ -145,9 +148,10 @@ where
         defaults: &Renderer::Defaults,
         layout: Layout<'_>,
         cursor_position: Point,
+        viewport: &Rectangle,
     ) -> Renderer::Output {
         self.content
-            .draw(renderer, defaults, layout, cursor_position)
+            .draw(renderer, defaults, layout, cursor_position, viewport)
     }
 
     fn hash_layout(&self, state: &mut Hasher, position: Point) {
diff --git a/native/src/overlay/menu.rs b/native/src/overlay/menu.rs
index 5ad1391f..c920e86e 100644
--- a/native/src/overlay/menu.rs
+++ b/native/src/overlay/menu.rs
@@ -239,6 +239,7 @@ where
         defaults: &Renderer::Defaults,
         layout: Layout<'_>,
         cursor_position: Point,
+        _viewport: &Rectangle,
     ) -> Renderer::Output {
         let primitives = self.container.draw(
             renderer,
diff --git a/native/src/user_interface.rs b/native/src/user_interface.rs
index 7a64ac59..996bdd30 100644
--- a/native/src/user_interface.rs
+++ b/native/src/user_interface.rs
@@ -198,8 +198,11 @@ where
         messages: &mut Vec<Message>,
     ) -> Vec<event::Status> {
         let (base_cursor, overlay_statuses) = if let Some(mut overlay) =
-            self.root.overlay(Layout::new(&self.base.layout))
-        {
+            self.root.overlay(
+                Layout::new(&self.base.layout),
+                self.overlay.as_ref().map(|l| l.layout.bounds()),
+                cursor_position,
+            ) {
             let layer = Self::overlay_layer(
                 self.overlay.take(),
                 self.bounds,
@@ -334,9 +337,11 @@ where
     ) -> Renderer::Output {
         let viewport = Rectangle::with_size(self.bounds);
 
-        let overlay = if let Some(mut overlay) =
-            self.root.overlay(Layout::new(&self.base.layout))
-        {
+        let overlay = if let Some(mut overlay) = self.root.overlay(
+            Layout::new(&self.base.layout),
+            self.overlay.as_ref().map(|l| l.layout.bounds()),
+            cursor_position,
+        ) {
             let layer = Self::overlay_layer(
                 self.overlay.take(),
                 self.bounds,
@@ -351,6 +356,7 @@ where
                 &Renderer::Defaults::default(),
                 Layout::new(&layer.layout),
                 cursor_position,
+                &viewport,
             );
 
             self.overlay = Some(layer);
diff --git a/native/src/widget.rs b/native/src/widget.rs
index 3677713a..1309d6af 100644
--- a/native/src/widget.rs
+++ b/native/src/widget.rs
@@ -36,6 +36,7 @@ pub mod space;
 pub mod svg;
 pub mod text;
 pub mod text_input;
+pub mod tooltip;
 
 #[doc(no_inline)]
 pub use button::Button;
@@ -71,6 +72,8 @@ pub use svg::Svg;
 pub use text::Text;
 #[doc(no_inline)]
 pub use text_input::TextInput;
+#[doc(no_inline)]
+pub use tooltip::Tooltip;
 
 use crate::event::{self, Event};
 use crate::layout;
@@ -172,6 +175,8 @@ where
     fn overlay(
         &mut self,
         _layout: Layout<'_>,
+        _overlay_content_bounds: Option<Rectangle>,
+        _cursor_position: Point,
     ) -> Option<overlay::Element<'_, Message, Renderer>> {
         None
     }
diff --git a/native/src/widget/column.rs b/native/src/widget/column.rs
index e0e88d31..9ee60627 100644
--- a/native/src/widget/column.rs
+++ b/native/src/widget/column.rs
@@ -198,11 +198,19 @@ where
     fn overlay(
         &mut self,
         layout: Layout<'_>,
+        overlay_content_bounds: Option<Rectangle>,
+        cursor_position: Point,
     ) -> Option<overlay::Element<'_, Message, Renderer>> {
         self.children
             .iter_mut()
             .zip(layout.children())
-            .filter_map(|(child, layout)| child.widget.overlay(layout))
+            .filter_map(|(child, layout)| {
+                child.widget.overlay(
+                    layout,
+                    overlay_content_bounds,
+                    cursor_position,
+                )
+            })
             .next()
     }
 }
diff --git a/native/src/widget/container.rs b/native/src/widget/container.rs
index 65764148..2fc6707e 100644
--- a/native/src/widget/container.rs
+++ b/native/src/widget/container.rs
@@ -200,8 +200,14 @@ where
     fn overlay(
         &mut self,
         layout: Layout<'_>,
+        overlay_content_bounds: Option<Rectangle>,
+        cursor_position: Point,
     ) -> Option<overlay::Element<'_, Message, Renderer>> {
-        self.content.overlay(layout.children().next().unwrap())
+        self.content.overlay(
+            layout.children().next().unwrap(),
+            overlay_content_bounds,
+            cursor_position,
+        )
     }
 }
 
diff --git a/native/src/widget/pane_grid.rs b/native/src/widget/pane_grid.rs
index c6fe4b60..0a7d818d 100644
--- a/native/src/widget/pane_grid.rs
+++ b/native/src/widget/pane_grid.rs
@@ -558,11 +558,15 @@ where
     fn overlay(
         &mut self,
         layout: Layout<'_>,
+        overlay_content_bounds: Option<Rectangle>,
+        cursor_position: Point,
     ) -> Option<overlay::Element<'_, Message, Renderer>> {
         self.elements
             .iter_mut()
             .zip(layout.children())
-            .filter_map(|((_, pane), layout)| pane.overlay(layout))
+            .filter_map(|((_, pane), layout)| {
+                pane.overlay(layout, overlay_content_bounds, cursor_position)
+            })
             .next()
     }
 }
diff --git a/native/src/widget/pane_grid/content.rs b/native/src/widget/pane_grid/content.rs
index 913cfe96..28515624 100644
--- a/native/src/widget/pane_grid/content.rs
+++ b/native/src/widget/pane_grid/content.rs
@@ -1,3 +1,5 @@
+use iced_core::Rectangle;
+
 use crate::container;
 use crate::event::{self, Event};
 use crate::layout;
@@ -189,6 +191,8 @@ where
     pub(crate) fn overlay(
         &mut self,
         layout: Layout<'_>,
+        overlay_content_bounds: Option<Rectangle>,
+        cursor_position: Point,
     ) -> Option<overlay::Element<'_, Message, Renderer>> {
         let body_layout = if self.title_bar.is_some() {
             let mut children = layout.children();
@@ -201,7 +205,8 @@ where
             layout
         };
 
-        self.body.overlay(body_layout)
+        self.body
+            .overlay(body_layout, overlay_content_bounds, cursor_position)
     }
 }
 
diff --git a/native/src/widget/pick_list.rs b/native/src/widget/pick_list.rs
index 74f4508e..6c424d28 100644
--- a/native/src/widget/pick_list.rs
+++ b/native/src/widget/pick_list.rs
@@ -274,6 +274,8 @@ where
     fn overlay(
         &mut self,
         layout: Layout<'_>,
+        _overlay_content_bounds: Option<Rectangle>,
+        _cursor_position: Point,
     ) -> Option<overlay::Element<'_, Message, Renderer>> {
         if *self.is_open {
             let bounds = layout.bounds();
diff --git a/native/src/widget/row.rs b/native/src/widget/row.rs
index b71663bd..c542aedc 100644
--- a/native/src/widget/row.rs
+++ b/native/src/widget/row.rs
@@ -197,11 +197,19 @@ where
     fn overlay(
         &mut self,
         layout: Layout<'_>,
+        overlay_content_bounds: Option<Rectangle>,
+        cursor_position: Point,
     ) -> Option<overlay::Element<'_, Message, Renderer>> {
         self.children
             .iter_mut()
             .zip(layout.children())
-            .filter_map(|(child, layout)| child.widget.overlay(layout))
+            .filter_map(|(child, layout)| {
+                child.widget.overlay(
+                    layout,
+                    overlay_content_bounds,
+                    cursor_position,
+                )
+            })
             .next()
     }
 }
diff --git a/native/src/widget/scrollable.rs b/native/src/widget/scrollable.rs
index 18cdf169..86a68f22 100644
--- a/native/src/widget/scrollable.rs
+++ b/native/src/widget/scrollable.rs
@@ -401,11 +401,17 @@ where
     fn overlay(
         &mut self,
         layout: Layout<'_>,
+        overlay_content_bounds: Option<Rectangle>,
+        cursor_position: Point,
     ) -> Option<overlay::Element<'_, Message, Renderer>> {
         let Self { content, state, .. } = self;
 
         content
-            .overlay(layout.children().next().unwrap())
+            .overlay(
+                layout.children().next().unwrap(),
+                overlay_content_bounds,
+                cursor_position,
+            )
             .map(|overlay| {
                 let bounds = layout.bounds();
                 let content_layout = layout.children().next().unwrap();
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)
+    }
+}