Add support for activating a pane by direction

Contributes: zed-industries/community#476
Contributes: zed-industries/community#478

crates/workspace/src/pane_group.rs

@@ -54,6 +54,20 @@ impl PaneGroup {
         }
     }
 
+    pub fn bounding_box_for_pane(&self, pane: &ViewHandle<Pane>) -> Option<RectF> {
+        match &self.root {
+            Member::Pane(_) => None,
+            Member::Axis(axis) => axis.bounding_box_for_pane(pane),
+        }
+    }
+
+    pub fn pane_at_pixel_position(&self, coordinate: Vector2F) -> Option<&ViewHandle<Pane>> {
+        match &self.root {
+            Member::Pane(pane) => Some(pane),
+            Member::Axis(axis) => axis.pane_at_pixel_position(coordinate),
+        }
+    }
+
     /// Returns:
     /// - Ok(true) if it found and removed a pane
     /// - Ok(false) if it found but did not remove the pane
@@ -309,15 +323,18 @@ pub(crate) struct PaneAxis {
     pub axis: Axis,
     pub members: Vec<Member>,
     pub flexes: Rc<RefCell<Vec<f32>>>,
+    pub bounding_boxes: Rc<RefCell<Vec<Option<RectF>>>>,
 }
 
 impl PaneAxis {
     pub fn new(axis: Axis, members: Vec<Member>) -> Self {
         let flexes = Rc::new(RefCell::new(vec![1.; members.len()]));
+        let bounding_boxes = Rc::new(RefCell::new(vec![None; members.len()]));
         Self {
             axis,
             members,
             flexes,
+            bounding_boxes,
         }
     }
 
@@ -326,10 +343,12 @@ impl PaneAxis {
         debug_assert!(members.len() == flexes.len());
 
         let flexes = Rc::new(RefCell::new(flexes));
+        let bounding_boxes = Rc::new(RefCell::new(vec![None; members.len()]));
         Self {
             axis,
             members,
             flexes,
+            bounding_boxes,
         }
     }
 
@@ -409,6 +428,40 @@ impl PaneAxis {
         }
     }
 
+    fn bounding_box_for_pane(&self, pane: &ViewHandle<Pane>) -> Option<RectF> {
+        for (idx, member) in self.members.iter().enumerate() {
+            match member {
+                Member::Pane(found) => {
+                    if pane == found {
+                        return self.bounding_boxes.borrow()[idx];
+                    }
+                }
+                Member::Axis(axis) => {
+                    if let Some(rect) = axis.bounding_box_for_pane(pane) {
+                        return Some(rect);
+                    }
+                }
+            }
+        }
+        None
+    }
+
+    fn pane_at_pixel_position(&self, coordinate: Vector2F) -> Option<&ViewHandle<Pane>> {
+        let bounding_boxes = self.bounding_boxes.borrow();
+
+        for (idx, member) in self.members.iter().enumerate() {
+            if let Some(coordinates) = bounding_boxes[idx] {
+                if coordinates.contains_point(coordinate) {
+                    return match member {
+                        Member::Pane(found) => Some(found),
+                        Member::Axis(axis) => axis.pane_at_pixel_position(coordinate),
+                    };
+                }
+            }
+        }
+        None
+    }
+
     fn render(
         &self,
         project: &ModelHandle<Project>,
@@ -423,7 +476,12 @@ impl PaneAxis {
     ) -> AnyElement<Workspace> {
         debug_assert!(self.members.len() == self.flexes.borrow().len());
 
-        let mut pane_axis = PaneAxisElement::new(self.axis, basis, self.flexes.clone());
+        let mut pane_axis = PaneAxisElement::new(
+            self.axis,
+            basis,
+            self.flexes.clone(),
+            self.bounding_boxes.clone(),
+        );
         let mut active_pane_ix = None;
 
         let mut members = self.members.iter().enumerate().peekable();
@@ -546,14 +604,21 @@ mod element {
         active_pane_ix: Option<usize>,
         flexes: Rc<RefCell<Vec<f32>>>,
         children: Vec<AnyElement<Workspace>>,
+        bounding_boxes: Rc<RefCell<Vec<Option<RectF>>>>,
     }
 
     impl PaneAxisElement {
-        pub fn new(axis: Axis, basis: usize, flexes: Rc<RefCell<Vec<f32>>>) -> Self {
+        pub fn new(
+            axis: Axis,
+            basis: usize,
+            flexes: Rc<RefCell<Vec<f32>>>,
+            bounding_boxes: Rc<RefCell<Vec<Option<RectF>>>>,
+        ) -> Self {
             Self {
                 axis,
                 basis,
                 flexes,
+                bounding_boxes,
                 active_pane_ix: None,
                 children: Default::default(),
             }
@@ -708,11 +773,16 @@ mod element {
 
             let mut child_origin = bounds.origin();
 
+            let mut bounding_boxes = self.bounding_boxes.borrow_mut();
+            bounding_boxes.clear();
+
             let mut children_iter = self.children.iter_mut().enumerate().peekable();
             while let Some((ix, child)) = children_iter.next() {
                 let child_start = child_origin.clone();
                 child.paint(scene, child_origin, visible_bounds, view, cx);
 
+                bounding_boxes.push(Some(RectF::new(child_origin, child.size())));
+
                 match self.axis {
                     Axis::Horizontal => child_origin += vec2f(child.size().x(), 0.0),
                     Axis::Vertical => child_origin += vec2f(0.0, child.size().y()),