Add Overlay component to gpui2

crates/gpui2/src/elements/overlay.rs

@@ -0,0 +1,203 @@
+use smallvec::SmallVec;
+
+use crate::{
+    point, AnyElement, BorrowWindow, Bounds, Element, LayoutId, ParentComponent, Pixels, Point,
+    Size, Style,
+};
+
+pub struct OverlayState {
+    child_layout_ids: SmallVec<[LayoutId; 4]>,
+}
+
+pub struct Overlay<V> {
+    children: SmallVec<[AnyElement<V>; 2]>,
+    anchor_corner: AnchorCorner,
+    fit_mode: OverlayFitMode,
+    // todo!();
+    // anchor_position: Option<Vector2F>,
+    // position_mode: OverlayPositionMode,
+}
+
+/// overlay gives you a floating element that will avoid overflowing the window bounds.
+/// Its children should have no margin to avoid measurement issues.
+pub fn overlay<V: 'static>() -> Overlay<V> {
+    Overlay {
+        children: SmallVec::new(),
+        anchor_corner: AnchorCorner::TopLeft,
+        fit_mode: OverlayFitMode::SwitchAnchor,
+    }
+}
+
+impl<V> Overlay<V> {
+    /// Sets which corner of the overlay should be anchored to the current position.
+    pub fn anchor(mut self, anchor: AnchorCorner) -> Self {
+        self.anchor_corner = anchor;
+        self
+    }
+
+    /// Snap to window edge instead of switching anchor corner when an overflow would occur.
+    pub fn snap_to_window(mut self) -> Self {
+        self.fit_mode = OverlayFitMode::SnapToWindow;
+        self
+    }
+}
+
+impl<V: 'static> ParentComponent<V> for Overlay<V> {
+    fn children_mut(&mut self) -> &mut SmallVec<[AnyElement<V>; 2]> {
+        &mut self.children
+    }
+}
+
+impl<V: 'static> Element<V> for Overlay<V> {
+    type ElementState = OverlayState;
+
+    fn element_id(&self) -> Option<crate::ElementId> {
+        None
+    }
+
+    fn layout(
+        &mut self,
+        view_state: &mut V,
+        _: Option<Self::ElementState>,
+        cx: &mut crate::ViewContext<V>,
+    ) -> (crate::LayoutId, Self::ElementState) {
+        let child_layout_ids = self
+            .children
+            .iter_mut()
+            .map(|child| child.layout(view_state, cx))
+            .collect::<SmallVec<_>>();
+        let layout_id = cx.request_layout(&Style::default(), child_layout_ids.iter().copied());
+
+        (layout_id, OverlayState { child_layout_ids })
+    }
+
+    fn paint(
+        &mut self,
+        bounds: crate::Bounds<crate::Pixels>,
+        view_state: &mut V,
+        element_state: &mut Self::ElementState,
+        cx: &mut crate::ViewContext<V>,
+    ) {
+        if element_state.child_layout_ids.is_empty() {
+            return;
+        }
+
+        let mut child_min = point(Pixels::MAX, Pixels::MAX);
+        let mut child_max = Point::default();
+        for child_layout_id in &element_state.child_layout_ids {
+            let child_bounds = cx.layout_bounds(*child_layout_id);
+            child_min = child_min.min(&child_bounds.origin);
+            child_max = child_max.max(&child_bounds.lower_right());
+        }
+        let size: Size<Pixels> = (child_max - child_min).into();
+        let origin = bounds.origin;
+
+        let mut desired = self.anchor_corner.get_bounds(origin, size);
+        let limits = Bounds {
+            origin: Point::zero(),
+            size: cx.viewport_size(),
+        };
+
+        match self.fit_mode {
+            OverlayFitMode::SnapToWindow => {
+                // Snap the horizontal edges of the overlay to the horizontal edges of the window if
+                // its horizontal bounds overflow
+                if desired.right() > limits.right() {
+                    desired.origin.x -= desired.right() - limits.right();
+                } else if desired.left() < limits.left() {
+                    desired.origin.x = limits.origin.x;
+                }
+
+                // Snap the vertical edges of the overlay to the vertical edges of the window if
+                // its vertical bounds overflow.
+                if desired.bottom() > limits.bottom() {
+                    desired.origin.y -= desired.bottom() - limits.bottom();
+                } else if desired.top() < limits.top() {
+                    desired.origin.y = limits.origin.y;
+                }
+            }
+            OverlayFitMode::SwitchAnchor => {
+                let mut anchor_corner = self.anchor_corner;
+
+                if desired.left() < limits.left() || desired.right() > limits.right() {
+                    anchor_corner = anchor_corner.switch_axis(Axis::Horizontal);
+                }
+
+                if bounds.top() < limits.top() || bounds.bottom() > limits.bottom() {
+                    anchor_corner = anchor_corner.switch_axis(Axis::Vertical);
+                }
+
+                // Update bounds if needed
+                if anchor_corner != self.anchor_corner {
+                    desired = anchor_corner.get_bounds(origin, size)
+                }
+            }
+            OverlayFitMode::None => {}
+        }
+
+        cx.with_element_offset(desired.origin - bounds.origin, |cx| {
+            for child in &mut self.children {
+                child.paint(view_state, cx);
+            }
+        })
+    }
+}
+
+enum Axis {
+    Horizontal,
+    Vertical,
+}
+
+#[derive(Copy, Clone)]
+pub enum OverlayFitMode {
+    SnapToWindow,
+    SwitchAnchor,
+    None,
+}
+
+#[derive(Clone, Copy, PartialEq, Eq)]
+pub enum AnchorCorner {
+    TopLeft,
+    TopRight,
+    BottomLeft,
+    BottomRight,
+}
+
+impl AnchorCorner {
+    fn get_bounds(&self, origin: Point<Pixels>, size: Size<Pixels>) -> Bounds<Pixels> {
+        let origin = match self {
+            Self::TopLeft => origin,
+            Self::TopRight => Point {
+                x: origin.x - size.width,
+                y: origin.y,
+            },
+            Self::BottomLeft => Point {
+                x: origin.x,
+                y: origin.y - size.height,
+            },
+            Self::BottomRight => Point {
+                x: origin.x - size.width,
+                y: origin.y - size.height,
+            },
+        };
+
+        Bounds { origin, size }
+    }
+
+    fn switch_axis(self, axis: Axis) -> Self {
+        match axis {
+            Axis::Vertical => match self {
+                AnchorCorner::TopLeft => AnchorCorner::BottomLeft,
+                AnchorCorner::TopRight => AnchorCorner::BottomRight,
+                AnchorCorner::BottomLeft => AnchorCorner::TopLeft,
+                AnchorCorner::BottomRight => AnchorCorner::TopRight,
+            },
+            Axis::Horizontal => match self {
+                AnchorCorner::TopLeft => AnchorCorner::TopRight,
+                AnchorCorner::TopRight => AnchorCorner::TopLeft,
+                AnchorCorner::BottomLeft => AnchorCorner::BottomRight,
+                AnchorCorner::BottomRight => AnchorCorner::BottomLeft,
+            },
+        }
+    }
+}