buffer movement is now working as I would only wish it would. Needs layers implementation, will do in the future

client/src/state/app/state.rs

@@ -49,6 +49,7 @@ pub struct UiState {
     pub show_register: bool,
     pub focus_outside_canvas: bool,
     pub buffer_history: Vec<AppView>,
+    pub active_buffer_index: usize,
     pub dialog: DialogState,
 }
 
@@ -166,6 +167,7 @@ impl Default for UiState {
             show_buffer_list: false,
             focus_outside_canvas: false,
             buffer_history: vec![AppView::Intro],
+            active_buffer_index: 0,
             dialog: DialogState::default(),
         }
     }
@@ -186,10 +188,18 @@ impl Default for DialogState {
 }
 
 impl UiState {
-    /// Adds the given view to the history if it's different from the last one.
+    /// Updates the buffer history and active index.
     pub fn update_buffer_history(&mut self, view: AppView) {
-        if self.buffer_history.last() != Some(&view) {
-            self.buffer_history.push(view.clone());
+        let existing_pos = self.buffer_history.iter().position(|v| v == &view);
+
+        match existing_pos {
+            Some(pos) => {
+                self.active_buffer_index = pos;
+            }
+            None => {
+                self.buffer_history.push(view.clone());
+                self.active_buffer_index = self.buffer_history.len() - 1;
+            }
         }
     }
 }