Merge remote-tracking branch 'tarkah/image-pane' into image-pane

2 files changed, 503 insertions, 0 deletions

diff --git a/native/src/widget/image.rs b/native/src/widget/image.rs
index 51d7ba26..4d8e0a3f 100644
--- a/native/src/widget/image.rs
+++ b/native/src/widget/image.rs
@@ -1,4 +1,7 @@
 //! Display images in your user interface.
+pub mod viewer;
+pub use viewer::Viewer;
+
 use crate::layout;
 use crate::{Element, Hasher, Layout, Length, Point, Rectangle, Size, Widget};
 
diff --git a/native/src/widget/image/viewer.rs b/native/src/widget/image/viewer.rs
new file mode 100644
index 00000000..9544beab
--- /dev/null
+++ b/native/src/widget/image/viewer.rs
@@ -0,0 +1,500 @@
+//! Zoom and pan on an image.
+use crate::event::{self, Event};
+use crate::image;
+use crate::layout;
+use crate::mouse;
+use crate::{
+    Clipboard, Element, Hasher, Layout, Length, Point, Rectangle, Size, Vector,
+    Widget,
+};
+
+use std::{f32, hash::Hash, u32};
+
+/// A frame that displays an image with the ability to zoom in/out and pan.
+#[allow(missing_debug_implementations)]
+pub struct Viewer<'a> {
+    state: &'a mut State,
+    padding: u16,
+    width: Length,
+    height: Length,
+    max_width: u32,
+    max_height: u32,
+    min_scale: f32,
+    max_scale: f32,
+    scale_pct: f32,
+    handle: image::Handle,
+}
+
+impl<'a> Viewer<'a> {
+    /// Creates a new [`Viewer`] with the given [`State`] and [`Handle`].
+    ///
+    /// [`Viewer`]: struct.Viewer.html
+    /// [`State`]: struct.State.html
+    /// [`Handle`]: ../../image/struct.Handle.html
+    pub fn new(state: &'a mut State, handle: image::Handle) -> Self {
+        Viewer {
+            state,
+            padding: 0,
+            width: Length::Shrink,
+            height: Length::Shrink,
+            max_width: u32::MAX,
+            max_height: u32::MAX,
+            min_scale: 0.25,
+            max_scale: 10.0,
+            scale_pct: 0.10,
+            handle,
+        }
+    }
+
+    /// Sets the padding of the [`Viewer`].
+    ///
+    /// [`Viewer`]: struct.Viewer.html
+    pub fn padding(mut self, units: u16) -> Self {
+        self.padding = units;
+        self
+    }
+
+    /// Sets the width of the [`Viewer`].
+    ///
+    /// [`Viewer`]: struct.Viewer.html
+    pub fn width(mut self, width: Length) -> Self {
+        self.width = width;
+        self
+    }
+
+    /// Sets the height of the [`Viewer`].
+    ///
+    /// [`Viewer`]: struct.Viewer.html
+    pub fn height(mut self, height: Length) -> Self {
+        self.height = height;
+        self
+    }
+
+    /// Sets the max width of the [`Viewer`].
+    ///
+    /// [`Viewer`]: struct.Viewer.html
+    pub fn max_width(mut self, max_width: u32) -> Self {
+        self.max_width = max_width;
+        self
+    }
+
+    /// Sets the max height of the [`Viewer`].
+    ///
+    /// [`Viewer`]: struct.Viewer.html
+    pub fn max_height(mut self, max_height: u32) -> Self {
+        self.max_height = max_height;
+        self
+    }
+
+    /// Sets the max scale applied to the image of the [`Viewer`].
+    ///
+    /// Default is `10.0`
+    ///
+    /// [`Viewer`]: struct.Viewer.html
+    pub fn max_scale(mut self, max_scale: f32) -> Self {
+        self.max_scale = max_scale;
+        self
+    }
+
+    /// Sets the min scale applied to the image of the [`Viewer`].
+    ///
+    /// Default is `0.25`
+    ///
+    /// [`Viewer`]: struct.Viewer.html
+    pub fn min_scale(mut self, min_scale: f32) -> Self {
+        self.min_scale = min_scale;
+        self
+    }
+
+    /// Sets the percentage the image of the [`Viewer`] will be scaled by
+    /// when zoomed in / out.
+    ///
+    /// Default is `0.10`
+    ///
+    /// [`Viewer`]: struct.Viewer.html
+    pub fn scale_pct(mut self, scale_pct: f32) -> Self {
+        self.scale_pct = scale_pct;
+        self
+    }
+
+    /// Returns the bounds of the underlying image, given the bounds of
+    /// the [`Viewer`]. Scaling will be applied and original aspect ratio
+    /// will be respected.
+    ///
+    /// [`Viewer`]: struct.Viewer.html
+    fn image_bounds<Renderer>(
+        &self,
+        renderer: &Renderer,
+        bounds: Rectangle,
+    ) -> Rectangle
+    where
+        Renderer: self::Renderer + image::Renderer,
+    {
+        let (width, height) = renderer.dimensions(&self.handle);
+
+        let dimensions = {
+            let dimensions = (width as f32, height as f32);
+
+            let width_ratio = bounds.width / dimensions.0;
+            let height_ratio = bounds.height / dimensions.1;
+
+            let ratio = width_ratio.min(height_ratio);
+
+            let scale = self.state.scale.unwrap_or(1.0);
+
+            if ratio < 1.0 {
+                (dimensions.0 * ratio * scale, dimensions.1 * ratio * scale)
+            } else {
+                (dimensions.0 * scale, dimensions.1 * scale)
+            }
+        };
+
+        Rectangle {
+            x: bounds.x,
+            y: bounds.y,
+            width: dimensions.0,
+            height: dimensions.1,
+        }
+    }
+
+    /// Cursor position relative to the [`Viewer`] bounds.
+    ///
+    /// [`Viewer`]: struct.Viewer.html
+    fn relative_cursor_position(
+        &self,
+        mut absolute_position: Point,
+        bounds: Rectangle,
+    ) -> Point {
+        absolute_position.x -= bounds.x;
+        absolute_position.y -= bounds.y;
+        absolute_position
+    }
+
+    /// Center point relative to the [`Viewer`] bounds.
+    ///
+    /// [`Viewer`]: struct.Viewer.html
+    fn relative_center(&self, bounds: Rectangle) -> Point {
+        let mut center = bounds.center();
+        center.x -= bounds.x;
+        center.y -= bounds.y;
+        center
+    }
+}
+
+impl<'a, Message, Renderer> Widget<Message, Renderer> for Viewer<'a>
+where
+    Renderer: self::Renderer + image::Renderer,
+{
+    fn width(&self) -> Length {
+        self.width
+    }
+
+    fn height(&self) -> Length {
+        self.height
+    }
+
+    fn layout(
+        &self,
+        _renderer: &Renderer,
+        limits: &layout::Limits,
+    ) -> layout::Node {
+        let padding = f32::from(self.padding);
+
+        let limits = limits
+            .max_width(self.max_width)
+            .max_height(self.max_height)
+            .width(self.width)
+            .height(self.height)
+            .pad(padding);
+
+        let size = limits.resolve(Size::INFINITY);
+
+        layout::Node::new(size)
+    }
+
+    fn on_event(
+        &mut self,
+        event: Event,
+        layout: Layout<'_>,
+        cursor_position: Point,
+        _messages: &mut Vec<Message>,
+        renderer: &Renderer,
+        _clipboard: Option<&dyn Clipboard>,
+    ) -> event::Status {
+        let bounds = layout.bounds();
+        let is_mouse_over = bounds.contains(cursor_position);
+
+        if is_mouse_over {
+            match event {
+                Event::Mouse(mouse::Event::WheelScrolled { delta }) => {
+                    match delta {
+                        mouse::ScrollDelta::Lines { y, .. }
+                        | mouse::ScrollDelta::Pixels { y, .. } => {
+                            let previous_scale =
+                                self.state.scale.unwrap_or(1.0);
+
+                            if y < 0.0 && previous_scale > self.min_scale
+                                || y > 0.0 && previous_scale < self.max_scale
+                            {
+                                self.state.scale = Some(
+                                    (if y > 0.0 {
+                                        self.state.scale.unwrap_or(1.0)
+                                            * (1.0 + self.scale_pct)
+                                    } else {
+                                        self.state.scale.unwrap_or(1.0)
+                                            / (1.0 + self.scale_pct)
+                                    })
+                                    .max(self.min_scale)
+                                    .min(self.max_scale),
+                                );
+
+                                let image_bounds =
+                                    self.image_bounds(renderer, bounds);
+
+                                let factor = self.state.scale.unwrap()
+                                    / previous_scale
+                                    - 1.0;
+
+                                let cursor_to_center =
+                                    self.relative_cursor_position(
+                                        cursor_position,
+                                        bounds,
+                                    ) - self.relative_center(bounds);
+
+                                let adjustment = cursor_to_center * factor
+                                    + self.state.current_offset * factor;
+
+                                self.state.current_offset = Vector::new(
+                                    if image_bounds.width > bounds.width {
+                                        self.state.current_offset.x
+                                            + adjustment.x
+                                    } else {
+                                        0.0
+                                    },
+                                    if image_bounds.height > bounds.height {
+                                        self.state.current_offset.y
+                                            + adjustment.y
+                                    } else {
+                                        0.0
+                                    },
+                                );
+                            }
+                        }
+                    }
+                }
+                Event::Mouse(mouse::Event::ButtonPressed(button)) => {
+                    if button == mouse::Button::Left {
+                        self.state.starting_cursor_pos = Some(cursor_position);
+
+                        self.state.starting_offset = self.state.current_offset;
+                    }
+                }
+                Event::Mouse(mouse::Event::ButtonReleased(button)) => {
+                    if button == mouse::Button::Left {
+                        self.state.starting_cursor_pos = None
+                    }
+                }
+                Event::Mouse(mouse::Event::CursorMoved { position }) => {
+                    if self.state.is_cursor_clicked() {
+                        let image_bounds = self.image_bounds(renderer, bounds);
+
+                        self.state.pan(
+                            position.x,
+                            position.y,
+                            bounds,
+                            image_bounds,
+                        );
+                    }
+                }
+                _ => {}
+            }
+        } else if let Event::Mouse(mouse::Event::ButtonReleased(button)) = event
+        {
+            if button == mouse::Button::Left {
+                self.state.starting_cursor_pos = None;
+            }
+        }
+
+        event::Status::Ignored
+    }
+
+    fn draw(
+        &self,
+        renderer: &mut Renderer,
+        _defaults: &Renderer::Defaults,
+        layout: Layout<'_>,
+        cursor_position: Point,
+        _viewport: &Rectangle,
+    ) -> Renderer::Output {
+        let bounds = layout.bounds();
+
+        let image_bounds = self.image_bounds(renderer, bounds);
+
+        let translation = {
+            let image_top_left = Vector::new(
+                bounds.width / 2.0 - image_bounds.width / 2.0,
+                bounds.height / 2.0 - image_bounds.height / 2.0,
+            );
+
+            image_top_left - self.state.offset(bounds, image_bounds)
+        };
+
+        let is_mouse_over = bounds.contains(cursor_position);
+
+        self::Renderer::draw(
+            renderer,
+            &self.state,
+            bounds,
+            image_bounds,
+            translation,
+            self.handle.clone(),
+            is_mouse_over,
+        )
+    }
+
+    fn hash_layout(&self, state: &mut Hasher) {
+        struct Marker;
+        std::any::TypeId::of::<Marker>().hash(state);
+
+        self.width.hash(state);
+        self.height.hash(state);
+        self.max_width.hash(state);
+        self.max_height.hash(state);
+        self.padding.hash(state);
+
+        self.handle.hash(state);
+    }
+}
+
+/// The local state of a [`Viewer`].
+///
+/// [`Viewer`]: struct.Viewer.html
+#[derive(Debug, Clone, Copy, Default)]
+pub struct State {
+    scale: Option<f32>,
+    starting_offset: Vector,
+    current_offset: Vector,
+    starting_cursor_pos: Option<Point>,
+}
+
+impl State {
+    /// Creates a new [`State`].
+    ///
+    /// [`State`]: struct.State.html
+    pub fn new() -> Self {
+        State::default()
+    }
+
+    /// Apply a panning offset to the current [`State`], given the bounds of
+    /// the [`Viewer`] and its image.
+    ///
+    /// [`Viewer`]: struct.Viewer.html
+    /// [`State`]: struct.State.html
+    fn pan(
+        &mut self,
+        x: f32,
+        y: f32,
+        bounds: Rectangle,
+        image_bounds: Rectangle,
+    ) {
+        let hidden_width = ((image_bounds.width - bounds.width) as f32 / 2.0)
+            .max(0.0)
+            .round();
+        let hidden_height = ((image_bounds.height - bounds.height) as f32
+            / 2.0)
+            .max(0.0)
+            .round();
+
+        let delta_x = x - self.starting_cursor_pos.unwrap().x;
+        let delta_y = y - self.starting_cursor_pos.unwrap().y;
+
+        if bounds.width < image_bounds.width {
+            self.current_offset.x = (self.starting_offset.x - delta_x)
+                .min(hidden_width)
+                .max(-1.0 * hidden_width);
+        }
+
+        if bounds.height < image_bounds.height {
+            self.current_offset.y = (self.starting_offset.y - delta_y)
+                .min(hidden_height)
+                .max(-1.0 * hidden_height);
+        }
+    }
+
+    /// Returns the current offset of the [`State`], given the bounds
+    /// of the [`Viewer`] and its image.
+    ///
+    /// [`Viewer`]: struct.Viewer.html
+    /// [`State`]: struct.State.html
+    fn offset(&self, bounds: Rectangle, image_bounds: Rectangle) -> Vector {
+        let hidden_width = ((image_bounds.width - bounds.width) as f32 / 2.0)
+            .max(0.0)
+            .round();
+        let hidden_height = ((image_bounds.height - bounds.height) as f32
+            / 2.0)
+            .max(0.0)
+            .round();
+
+        Vector::new(
+            self.current_offset
+                .x
+                .min(hidden_width)
+                .max(-1.0 * hidden_width),
+            self.current_offset
+                .y
+                .min(hidden_height)
+                .max(-1.0 * hidden_height),
+        )
+    }
+
+    /// Returns if the left mouse button is still held down since clicking inside
+    /// the [`Viewer`].
+    ///
+    /// [`Viewer`]: struct.Viewer.html
+    /// [`State`]: struct.State.html
+    pub fn is_cursor_clicked(&self) -> bool {
+        self.starting_cursor_pos.is_some()
+    }
+}
+
+/// The renderer of an [`Viewer`].
+///
+/// Your [renderer] will need to implement this trait before being
+/// able to use a [`Viewer`] in your user interface.
+///
+/// [`Viewer`]: struct.Viewer.html
+/// [renderer]: ../../../renderer/index.html
+pub trait Renderer: crate::Renderer + Sized {
+    /// Draws the [`Viewer`].
+    ///
+    /// It receives:
+    /// - the [`State`] of the [`Viewer`]
+    /// - the bounds of the [`Viewer`] widget
+    /// - the bounds of the scaled [`Viewer`] image
+    /// - the translation of the clipped image
+    /// - the [`Handle`] to the underlying image
+    /// - whether the mouse is over the [`Viewer`] or not
+    ///
+    /// [`Viewer`]: struct.Viewer.html
+    /// [`State`]: struct.State.html
+    /// [`Handle`]: ../../image/struct.Handle.html
+    fn draw(
+        &mut self,
+        state: &State,
+        bounds: Rectangle,
+        image_bounds: Rectangle,
+        translation: Vector,
+        handle: image::Handle,
+        is_mouse_over: bool,
+    ) -> Self::Output;
+}
+
+impl<'a, Message, Renderer> From<Viewer<'a>> for Element<'a, Message, Renderer>
+where
+    Renderer: 'a + self::Renderer + image::Renderer,
+    Message: 'a,
+{
+    fn from(viewer: Viewer<'a>) -> Element<'a, Message, Renderer> {
+        Element::new(viewer)
+    }
+}