Implement mouse-based pane resizing for `PaneGrid`

1 files changed, 111 insertions, 5 deletions

diff --git a/native/src/widget/pane_grid.rs b/native/src/widget/pane_grid.rs
index 68f32bc0..5229962d 100644
--- a/native/src/widget/pane_grid.rs
+++ b/native/src/widget/pane_grid.rs
@@ -14,7 +14,7 @@ pub use state::{Focus, State};
 use crate::{
     input::{keyboard, mouse, ButtonState},
     layout, Clipboard, Element, Event, Hasher, Layout, Length, Point, Size,
-    Widget,
+    Vector, Widget,
 };
 
 #[allow(missing_debug_implementations)]
@@ -26,6 +26,7 @@ pub struct PaneGrid<'a, Message, Renderer> {
     height: Length,
     spacing: u16,
     on_drag: Option<Box<dyn Fn(DragEvent) -> Message>>,
+    on_resize: Option<Box<dyn Fn(ResizeEvent) -> Message>>,
 }
 
 impl<'a, Message, Renderer> PaneGrid<'a, Message, Renderer> {
@@ -67,6 +68,7 @@ impl<'a, Message, Renderer> PaneGrid<'a, Message, Renderer> {
             height: Length::Fill,
             spacing: 0,
             on_drag: None,
+            on_resize: None,
         }
     }
 
@@ -101,6 +103,14 @@ impl<'a, Message, Renderer> PaneGrid<'a, Message, Renderer> {
         self.on_drag = Some(Box::new(f));
         self
     }
+
+    pub fn on_resize(
+        mut self,
+        f: impl Fn(ResizeEvent) -> Message + 'static,
+    ) -> Self {
+        self.on_resize = Some(Box::new(f));
+        self
+    }
 }
 
 #[derive(Debug, Clone, Copy)]
@@ -110,6 +120,12 @@ pub enum DragEvent {
     Canceled { pane: Pane },
 }
 
+#[derive(Debug, Clone, Copy)]
+pub struct ResizeEvent {
+    pub split: Split,
+    pub ratio: f32,
+}
+
 impl<'a, Message, Renderer> Widget<Message, Renderer>
     for PaneGrid<'a, Message, Renderer>
 where
@@ -178,7 +194,7 @@ where
                     if let Some(((pane, _), _)) = clicked_region.next() {
                         match &self.on_drag {
                             Some(on_drag) if self.modifiers.alt => {
-                                self.state.drag(pane);
+                                self.state.pick_pane(pane);
 
                                 messages.push(on_drag(DragEvent::Picked {
                                     pane: *pane,
@@ -193,7 +209,7 @@ where
                     }
                 }
                 ButtonState::Released => {
-                    if let Some(pane) = self.state.dragged() {
+                    if let Some(pane) = self.state.picked_pane() {
                         self.state.focus(&pane);
 
                         if let Some(on_drag) = &self.on_drag {
@@ -220,13 +236,101 @@ where
                     }
                 }
             },
+            Event::Mouse(mouse::Event::Input {
+                button: mouse::Button::Right,
+                state,
+            }) if self.on_resize.is_some()
+                && self.state.picked_pane().is_none()
+                && self.modifiers.alt =>
+            {
+                match state {
+                    ButtonState::Pressed => {
+                        let bounds = layout.bounds();
+
+                        let splits = self.state.splits(
+                            f32::from(self.spacing),
+                            Size::new(bounds.width, bounds.height),
+                        );
+
+                        let mut sorted_splits: Vec<_> = splits.iter().collect();
+                        let offset = Vector::new(bounds.x, bounds.y);
+
+                        sorted_splits.sort_by_key(
+                            |(_, (axis, rectangle, ratio))| {
+                                let center = match axis {
+                                    Axis::Horizontal => Point::new(
+                                        rectangle.x + rectangle.width / 2.0,
+                                        rectangle.y + rectangle.height * ratio,
+                                    ),
+
+                                    Axis::Vertical => Point::new(
+                                        rectangle.x + rectangle.width * ratio,
+                                        rectangle.y + rectangle.height / 2.0,
+                                    ),
+                                };
+
+                                cursor_position
+                                    .distance(center + offset)
+                                    .round()
+                                    as u32
+                            },
+                        );
+
+                        if let Some((split, (axis, _, _))) =
+                            sorted_splits.first()
+                        {
+                            self.state.pick_split(split, *axis);
+                        }
+                    }
+                    ButtonState::Released => {
+                        self.state.drop_split();
+                    }
+                }
+            }
+            Event::Mouse(mouse::Event::CursorMoved { .. }) => {
+                if let Some(on_resize) = &self.on_resize {
+                    if let Some((split, _)) = self.state.picked_split() {
+                        let bounds = layout.bounds();
+
+                        let splits = self.state.splits(
+                            f32::from(self.spacing),
+                            Size::new(bounds.width, bounds.height),
+                        );
+
+                        if let Some((axis, rectangle, _)) = splits.get(&split) {
+                            let ratio = match axis {
+                                Axis::Horizontal => {
+                                    let position = cursor_position.x - bounds.x
+                                        + rectangle.x;
+
+                                    (position / (rectangle.x + rectangle.width))
+                                        .max(0.1)
+                                        .min(0.9)
+                                }
+                                Axis::Vertical => {
+                                    let position = cursor_position.y - bounds.y
+                                        + rectangle.y;
+
+                                    (position
+                                        / (rectangle.y + rectangle.height))
+                                        .max(0.1)
+                                        .min(0.9)
+                                }
+                            };
+
+                            messages
+                                .push(on_resize(ResizeEvent { split, ratio }));
+                        }
+                    }
+                }
+            }
             Event::Keyboard(keyboard::Event::Input { modifiers, .. }) => {
                 *self.modifiers = modifiers;
             }
             _ => {}
         }
 
-        if self.state.dragged().is_none() {
+        if self.state.picked_pane().is_none() {
             {
                 self.elements.iter_mut().zip(layout.children()).for_each(
                     |((_, pane), layout)| {
@@ -254,7 +358,8 @@ where
         renderer.draw(
             defaults,
             &self.elements,
-            self.state.dragged(),
+            self.state.picked_pane(),
+            self.state.picked_split().map(|(_, axis)| axis),
             layout,
             cursor_position,
         )
@@ -297,6 +402,7 @@ pub trait Renderer: crate::Renderer + Sized {
         defaults: &Self::Defaults,
         content: &[(Pane, Element<'_, Message, Self>)],
         dragging: Option<Pane>,
+        resizing: Option<Axis>,
         layout: Layout<'_>,
         cursor_position: Point,
     ) -> Self::Output;