Create module boundaries for `pane_grid` logic

5 files changed, 418 insertions, 0 deletions

diff --git a/native/src/widget/pane_grid/direction.rs b/native/src/widget/pane_grid/direction.rs
new file mode 100644
index 00000000..0ee90557
--- /dev/null
+++ b/native/src/widget/pane_grid/direction.rs
@@ -0,0 +1,7 @@
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum Direction {
+    Up,
+    Down,
+    Left,
+    Right,
+}
diff --git a/native/src/widget/pane_grid/node.rs b/native/src/widget/pane_grid/node.rs
new file mode 100644
index 00000000..a9aa7fdc
--- /dev/null
+++ b/native/src/widget/pane_grid/node.rs
@@ -0,0 +1,128 @@
+use crate::{
+    pane_grid::{Pane, Split},
+    Rectangle, Size,
+};
+
+use std::collections::HashMap;
+
+#[derive(Debug, Clone, Hash)]
+pub enum Node {
+    Split {
+        kind: Split,
+        ratio: u32,
+        a: Box<Node>,
+        b: Box<Node>,
+    },
+    Pane(Pane),
+}
+
+impl Node {
+    pub fn find(&mut self, pane: &Pane) -> Option<&mut Node> {
+        match self {
+            Node::Split { a, b, .. } => {
+                a.find(pane).or_else(move || b.find(pane))
+            }
+            Node::Pane(p) => {
+                if p == pane {
+                    Some(self)
+                } else {
+                    None
+                }
+            }
+        }
+    }
+
+    pub fn split(&mut self, kind: Split, new_pane: Pane) {
+        *self = Node::Split {
+            kind,
+            ratio: 500_000,
+            a: Box::new(self.clone()),
+            b: Box::new(Node::Pane(new_pane)),
+        };
+    }
+
+    pub fn update(&mut self, f: &impl Fn(&mut Node)) {
+        match self {
+            Node::Split { a, b, .. } => {
+                a.update(f);
+                b.update(f);
+            }
+            _ => {}
+        }
+
+        f(self);
+    }
+
+    pub fn remove(&mut self, pane: &Pane) -> Option<Pane> {
+        match self {
+            Node::Split { a, b, .. } => {
+                if a.pane() == Some(*pane) {
+                    *self = *b.clone();
+                    Some(self.first_pane())
+                } else if b.pane() == Some(*pane) {
+                    *self = *a.clone();
+                    Some(self.first_pane())
+                } else {
+                    a.remove(pane).or_else(|| b.remove(pane))
+                }
+            }
+            Node::Pane(_) => None,
+        }
+    }
+
+    pub fn regions(
+        &self,
+        spacing: f32,
+        size: Size,
+    ) -> HashMap<Pane, Rectangle> {
+        let mut regions = HashMap::new();
+
+        self.compute_regions(
+            spacing / 2.0,
+            &Rectangle {
+                x: 0.0,
+                y: 0.0,
+                width: size.width,
+                height: size.height,
+            },
+            &mut regions,
+        );
+
+        regions
+    }
+
+    pub fn pane(&self) -> Option<Pane> {
+        match self {
+            Node::Split { .. } => None,
+            Node::Pane(pane) => Some(*pane),
+        }
+    }
+
+    pub fn first_pane(&self) -> Pane {
+        match self {
+            Node::Split { a, .. } => a.first_pane(),
+            Node::Pane(pane) => *pane,
+        }
+    }
+
+    fn compute_regions(
+        &self,
+        halved_spacing: f32,
+        current: &Rectangle,
+        regions: &mut HashMap<Pane, Rectangle>,
+    ) {
+        match self {
+            Node::Split { kind, ratio, a, b } => {
+                let ratio = *ratio as f32 / 1_000_000.0;
+                let (region_a, region_b) =
+                    kind.apply(current, ratio, halved_spacing);
+
+                a.compute_regions(halved_spacing, &region_a, regions);
+                b.compute_regions(halved_spacing, &region_b, regions);
+            }
+            Node::Pane(pane) => {
+                let _ = regions.insert(*pane, *current);
+            }
+        }
+    }
+}
diff --git a/native/src/widget/pane_grid/pane.rs b/native/src/widget/pane_grid/pane.rs
new file mode 100644
index 00000000..cfca3b03
--- /dev/null
+++ b/native/src/widget/pane_grid/pane.rs
@@ -0,0 +1,2 @@
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub struct Pane(pub(super) usize);
diff --git a/native/src/widget/pane_grid/split.rs b/native/src/widget/pane_grid/split.rs
new file mode 100644
index 00000000..ca9ed5e1
--- /dev/null
+++ b/native/src/widget/pane_grid/split.rs
@@ -0,0 +1,54 @@
+use crate::Rectangle;
+
+#[derive(Debug, Clone, Copy, Hash, PartialEq, Eq)]
+pub enum Split {
+    Horizontal,
+    Vertical,
+}
+
+impl Split {
+    pub(super) fn apply(
+        &self,
+        rectangle: &Rectangle,
+        ratio: f32,
+        halved_spacing: f32,
+    ) -> (Rectangle, Rectangle) {
+        match self {
+            Split::Horizontal => {
+                let width_left =
+                    (rectangle.width * ratio).round() - halved_spacing;
+                let width_right = rectangle.width - width_left - halved_spacing;
+
+                (
+                    Rectangle {
+                        width: width_left,
+                        ..*rectangle
+                    },
+                    Rectangle {
+                        x: rectangle.x + width_left + halved_spacing,
+                        width: width_right,
+                        ..*rectangle
+                    },
+                )
+            }
+            Split::Vertical => {
+                let height_top =
+                    (rectangle.height * ratio).round() - halved_spacing;
+                let height_bottom =
+                    rectangle.height - height_top - halved_spacing;
+
+                (
+                    Rectangle {
+                        height: height_top,
+                        ..*rectangle
+                    },
+                    Rectangle {
+                        y: rectangle.y + height_top + halved_spacing,
+                        height: height_bottom,
+                        ..*rectangle
+                    },
+                )
+            }
+        }
+    }
+}
diff --git a/native/src/widget/pane_grid/state.rs b/native/src/widget/pane_grid/state.rs
new file mode 100644
index 00000000..130c7e34
--- /dev/null
+++ b/native/src/widget/pane_grid/state.rs
@@ -0,0 +1,227 @@
+use crate::{
+    input::keyboard,
+    pane_grid::{node::Node, Direction, Pane, Split},
+    Hasher, Point, Rectangle, Size,
+};
+
+use std::collections::HashMap;
+
+#[derive(Debug)]
+pub struct State<T> {
+    pub(super) panes: HashMap<Pane, T>,
+    pub(super) internal: Internal,
+    pub(super) modifiers: keyboard::ModifiersState,
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum Focus {
+    Idle,
+    Dragging,
+}
+
+impl<T> State<T> {
+    pub fn new(first_pane_state: T) -> (Self, Pane) {
+        let first_pane = Pane(0);
+
+        let mut panes = HashMap::new();
+        let _ = panes.insert(first_pane, first_pane_state);
+
+        (
+            State {
+                panes,
+                internal: Internal {
+                    layout: Node::Pane(first_pane),
+                    last_pane: 0,
+                    focused_pane: FocusedPane::None,
+                },
+                modifiers: keyboard::ModifiersState::default(),
+            },
+            first_pane,
+        )
+    }
+
+    pub fn len(&self) -> usize {
+        self.panes.len()
+    }
+
+    pub fn get_mut(&mut self, pane: &Pane) -> Option<&mut T> {
+        self.panes.get_mut(pane)
+    }
+
+    pub fn iter(&self) -> impl Iterator<Item = (&Pane, &T)> {
+        self.panes.iter()
+    }
+
+    pub fn iter_mut(&mut self) -> impl Iterator<Item = (&Pane, &mut T)> {
+        self.panes.iter_mut()
+    }
+
+    pub fn focused_pane(&self) -> Option<Pane> {
+        match self.internal.focused_pane {
+            FocusedPane::Some {
+                pane,
+                focus: Focus::Idle,
+            } => Some(pane),
+            FocusedPane::Some {
+                focus: Focus::Dragging,
+                ..
+            } => None,
+            FocusedPane::None => None,
+        }
+    }
+
+    pub fn adjacent_pane(
+        &self,
+        pane: &Pane,
+        direction: Direction,
+    ) -> Option<Pane> {
+        let regions =
+            self.internal.layout.regions(0.0, Size::new(4096.0, 4096.0));
+
+        let current_region = regions.get(pane)?;
+
+        let target = match direction {
+            Direction::Left => {
+                Point::new(current_region.x - 1.0, current_region.y + 1.0)
+            }
+            Direction::Right => Point::new(
+                current_region.x + current_region.width + 1.0,
+                current_region.y + 1.0,
+            ),
+            Direction::Up => {
+                Point::new(current_region.x + 1.0, current_region.y - 1.0)
+            }
+            Direction::Down => Point::new(
+                current_region.x + 1.0,
+                current_region.y + current_region.height + 1.0,
+            ),
+        };
+
+        let mut colliding_regions =
+            regions.iter().filter(|(_, region)| region.contains(target));
+
+        let (pane, _) = colliding_regions.next()?;
+
+        Some(*pane)
+    }
+
+    pub fn focus(&mut self, pane: &Pane) {
+        self.internal.focus(pane);
+    }
+
+    pub fn split_vertically(&mut self, pane: &Pane, state: T) -> Option<Pane> {
+        self.split(Split::Vertical, pane, state)
+    }
+
+    pub fn split_horizontally(
+        &mut self,
+        pane: &Pane,
+        state: T,
+    ) -> Option<Pane> {
+        self.split(Split::Horizontal, pane, state)
+    }
+
+    pub fn split(
+        &mut self,
+        kind: Split,
+        pane: &Pane,
+        state: T,
+    ) -> Option<Pane> {
+        let node = self.internal.layout.find(pane)?;
+
+        let new_pane = {
+            self.internal.last_pane = self.internal.last_pane.checked_add(1)?;
+
+            Pane(self.internal.last_pane)
+        };
+
+        node.split(kind, new_pane);
+
+        let _ = self.panes.insert(new_pane, state);
+        self.focus(&new_pane);
+
+        Some(new_pane)
+    }
+
+    pub fn swap(&mut self, a: &Pane, b: &Pane) {
+        self.internal.layout.update(&|node| match node {
+            Node::Split { .. } => {}
+            Node::Pane(pane) => {
+                if pane == a {
+                    *node = Node::Pane(*b);
+                } else if pane == b {
+                    *node = Node::Pane(*a);
+                }
+            }
+        });
+    }
+
+    pub fn close(&mut self, pane: &Pane) -> Option<T> {
+        if let Some(sibling) = self.internal.layout.remove(pane) {
+            self.focus(&sibling);
+            self.panes.remove(pane)
+        } else {
+            None
+        }
+    }
+}
+
+#[derive(Debug)]
+pub struct Internal {
+    layout: Node,
+    last_pane: usize,
+    focused_pane: FocusedPane,
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum FocusedPane {
+    None,
+    Some { pane: Pane, focus: Focus },
+}
+
+impl Internal {
+    pub fn focused(&self) -> FocusedPane {
+        self.focused_pane
+    }
+    pub fn dragged(&self) -> Option<Pane> {
+        match self.focused_pane {
+            FocusedPane::Some {
+                pane,
+                focus: Focus::Dragging,
+            } => Some(pane),
+            _ => None,
+        }
+    }
+
+    pub fn regions(
+        &self,
+        spacing: f32,
+        size: Size,
+    ) -> HashMap<Pane, Rectangle> {
+        self.layout.regions(spacing, size)
+    }
+
+    pub fn focus(&mut self, pane: &Pane) {
+        self.focused_pane = FocusedPane::Some {
+            pane: *pane,
+            focus: Focus::Idle,
+        };
+    }
+
+    pub fn drag(&mut self, pane: &Pane) {
+        self.focused_pane = FocusedPane::Some {
+            pane: *pane,
+            focus: Focus::Dragging,
+        };
+    }
+
+    pub fn unfocus(&mut self) {
+        self.focused_pane = FocusedPane::None;
+    }
+
+    pub fn hash_layout(&self, hasher: &mut Hasher) {
+        use std::hash::Hash;
+
+        self.layout.hash(hasher);
+    }
+}