Fix jump_backwards behaviour when jumplist is at capacity

helix-view/src/view.rs

@@ -42,14 +42,16 @@ impl JumpList {
         self.jumps.truncate(self.current);
         // don't push duplicates
         if self.jumps.back() != Some(&jump) {
-            // If the jumplist is full, drop the oldest item.
+            // If the jumplist is full, drop the oldest items until we have space for another addition.
             while self.jumps.len() >= JUMP_LIST_CAPACITY {
-                self.jumps.pop_front();
+                if self.jumps.pop_front().is_some() {
+                    self.current = self.current.saturating_sub(1);
+                }
             }
 
             self.jumps.push_back(jump);
-            self.current = self.jumps.len();
         }
+        self.current = self.jumps.len();
     }
 
     pub fn forward(&mut self, count: usize) -> Option<&Jump> {
@@ -63,13 +65,21 @@ impl JumpList {
 
     // Taking view and doc to prevent unnecessary cloning when jump is not required.
     pub fn backward(&mut self, view_id: ViewId, doc: &mut Document, count: usize) -> Option<&Jump> {
-        if let Some(current) = self.current.checked_sub(count) {
+        if self.current.checked_sub(count).is_some() {
+            let cur_jump = (doc.id(), doc.selection(view_id).clone());
             if self.current == self.jumps.len() {
-                let jump = (doc.id(), doc.selection(view_id).clone());
-                self.push(jump);
+                self.push(cur_jump.clone());
             }
-            self.current = current;
-            self.jumps.get(self.current)
+            // We need to do this separately from checked_sub above as pushing to the jumplist might change the position of self.current
+            self.current = self.current.saturating_sub(count);
+            self.jumps.get(self.current).and_then(|next_jump| {
+                if next_jump == &cur_jump {
+                    self.current -= 1;
+                    self.jumps.get(self.current)
+                } else {
+                    Some(next_jump)
+                }
+            })
         } else {
             None
         }