tweak ActivateLastTab and add a changelog entry for it

refs: #610

docs/changelog.md

@@ -35,6 +35,7 @@ brief notes about them may accumulate here.
 * Fixed: Windows: we now compile libssh2 against openssl on all platforms to improve overall key and crypto algorithm support
 * Fixed: spawning a new tab via the launcher menu failed because it used the pretty printed multiplexer domain label rather than the multiplexer domain name.
 * Fixed: macOS: middle mouse button wasn't recognized. Thanks to [@guswynn](https://github.com/guswynn)! [#599](https://github.com/wez/wezterm/pull/599)
+* New: added [ActivateLastTab](config/lua/keyassignment/ActivateLastTab.md) key assignment for jumping back to a previously active tab. Thanks to [@alexgartrell](https://github.com/alexgartrell) [#610](https://github.com/wez/wezterm/pull/610)
 
 ### 20210314-114017-04b7cedd
 

docs/config/lua/keyassignment/ActivateLastTab.md

@@ -1,11 +1,14 @@
 # ActivateLastTab
 
-Activate the last active tab. If there is none, it will do nothing.
+*Since: nightly builds only*
 
+Activate the last active tab. If there is none, it will do nothing.
 
 ```lua
 return {
+  leader = { key="a", mods="CTRL" },
   keys = {
+    -- CTRL-a, followed by CTRL-o will switch back to the last active tab
     {key="o", mods="LEADER|CTRL", action="ActivateLastTab"},
   }
 }

mux/src/window.rs

@@ -103,7 +103,7 @@ impl Window {
             self.tabs.remove(idx);
             let len = self.tabs.len();
             if len > 0 && self.active == idx && idx >= len {
-                self.set_active(len - 1);
+                self.set_active_without_saving(len - 1);
             }
             true
         } else {
@@ -139,7 +139,20 @@ impl Window {
         }
     }
 
-    pub fn set_active(&mut self, idx: usize) {
+    /// If `idx` is different from the current active tab,
+    /// save the current tabid and then make `idx` the active
+    /// tab position.
+    pub fn save_and_then_set_active(&mut self, idx: usize) {
+        if idx == self.get_active_idx() {
+            return;
+        }
+        self.save_last_active();
+        self.set_active_without_saving(idx);
+    }
+
+    /// Make `idx` the active tab position.
+    /// The saved tab id is not changed.
+    pub fn set_active_without_saving(&mut self, idx: usize) {
         assert!(idx < self.tabs.len());
         self.invalidated = true;
         self.active = idx;

wezterm-gui/src/overlay/tabnavigator.rs

@@ -80,7 +80,7 @@ pub fn tab_navigator(
                     .get_window_mut(mux_window_id)
                     .ok_or_else(|| anyhow!("no such window"))?;
 
-                window.set_active(idx);
+                window.save_and_then_set_active(idx);
                 anyhow::Result::<()>::Ok(())
             })
             .detach();

wezterm-gui/src/termwindow/mod.rs

@@ -1098,10 +1098,7 @@ impl TermWindow {
         };
 
         if tab_idx < max {
-            if tab_idx != window.get_active_idx() {
-                window.save_last_active();
-            }
-            window.set_active(tab_idx);
+            window.save_and_then_set_active(tab_idx);
 
             drop(window);
 
@@ -1160,7 +1157,7 @@ impl TermWindow {
 
         let tab_inst = window.remove_by_idx(active);
         window.insert(tab_idx, &tab_inst);
-        window.set_active(tab_idx);
+        window.set_active_without_saving(tab_idx);
 
         drop(window);
         self.update_title();

wezterm-gui/src/termwindow/spawn.rs

@@ -186,9 +186,8 @@ impl super::TermWindow {
                     let mut window = mux
                         .get_window_mut(target_window_id)
                         .ok_or_else(|| anyhow!("no such window!?"))?;
-                    window.save_last_active();
                     if let Some(idx) = window.idx_by_id(tab_id) {
-                        window.set_active(idx);
+                        window.save_and_then_set_active(idx);
                     }
                 }
             }