wezterm: ActivateTab now accepts negative numbers

This allows setting up shortcuts relative to the final tab in
a window, rather than always being relative to the first.

The default assignment for CTRL+SHIFT+9 is now `ActivateTab=-1`
as a convenient way to always reach the last tab.

refs: https://github.com/wez/wezterm/issues/228

docs/changelog.markdown

@@ -41,6 +41,9 @@ brief notes about them may accumulate here.
   to a similar degree as iTerm2
 * Fixed an issue where unmodified F5+ would use the CSI-u encoded-modifiers
   format, and confused eg: `htop`.
+* `ActivateTab` now accepts negative numbers as a way to reference the last
+  tab in the Window.  The default assignment for `CTRL+SHIFT+9` and `CMD+9`
+  is now `ActivateTab=-1`, which selects the last tab.
 
 ### 20200607-144723-74889cd4
 

docs/config/keys.markdown

@@ -40,7 +40,7 @@ The default key bindings are:
 | `SUPER`     | `6`      | `ActivateTab=5` |
 | `SUPER`     | `7`      | `ActivateTab=6` |
 | `SUPER`     | `8`      | `ActivateTab=7` |
-| `SUPER`     | `9`      | `ActivateTab=8` |
+| `SUPER`     | `9`      | `ActivateTab=-1` |
 | `CTRL+SHIFT`     | `w`      | `CloseCurrentTab` |
 | `CTRL+SHIFT`     | `1`      | `ActivateTab=0` |
 | `CTRL+SHIFT`     | `2`      | `ActivateTab=1` |
@@ -50,7 +50,7 @@ The default key bindings are:
 | `CTRL+SHIFT`     | `6`      | `ActivateTab=5` |
 | `CTRL+SHIFT`     | `7`      | `ActivateTab=6` |
 | `CTRL+SHIFT`     | `8`      | `ActivateTab=7` |
-| `CTRL+SHIFT`     | `9`      | `ActivateTab=8` |
+| `CTRL+SHIFT`     | `9`      | `ActivateTab=-1` |
 | `SUPER+SHIFT` | `[` | `ActivateTabRelative=-1` |
 | `SUPER+SHIFT` | `]` | `ActivateTabRelative=1` |
 | `CTRL+SHIFT`     | `PAGEUP`      | `MoveTabRelative=-1` |
@@ -340,6 +340,13 @@ return {
 Activate the tab specified by the argument value. eg: `0` activates the
 leftmost tab, while `1` activates the second tab from the left, and so on.
 
+*since: nightly*
+
+`ActivateTab` now accepts negative numbers; these wrap around from the start
+of the tabs to the end, so `-1` references the right-most tab, `-2` the tab
+to its left and so on.
+
+
 ```lua
 local wezterm = require 'wezterm';
 

src/frontend/gui/termwindow.rs

@@ -1202,13 +1202,20 @@ impl TermWindow {
         }
     }
 
-    fn activate_tab(&mut self, tab_idx: usize) -> anyhow::Result<()> {
+    fn activate_tab(&mut self, tab_idx: isize) -> anyhow::Result<()> {
         let mux = Mux::get().unwrap();
         let mut window = mux
             .get_window_mut(self.mux_window_id)
             .ok_or_else(|| anyhow!("no such window"))?;
 
         let max = window.len();
+
+        let tab_idx = if tab_idx < 0 {
+            max.saturating_sub(tab_idx.abs() as usize)
+        } else {
+            tab_idx as usize
+        };
+
         if tab_idx < max {
             window.set_active(tab_idx);
 
@@ -1232,7 +1239,7 @@ impl TermWindow {
         let tab = active + delta;
         let tab = if tab < 0 { max as isize + tab } else { tab };
         drop(window);
-        self.activate_tab(tab as usize % max)
+        self.activate_tab((tab as usize % max) as isize)
     }
 
     fn move_tab(&mut self, tab_idx: usize) -> anyhow::Result<()> {
@@ -2950,7 +2957,7 @@ impl TermWindow {
         match event.kind {
             WMEK::Press(MousePress::Left) => match self.tab_bar.hit_test(x) {
                 TabBarItem::Tab(tab_idx) => {
-                    self.activate_tab(tab_idx).ok();
+                    self.activate_tab(tab_idx as isize).ok();
                 }
                 TabBarItem::NewTabButton => {
                     self.spawn_tab(&SpawnTabDomain::CurrentTabDomain);

src/keyassignment.rs

@@ -82,7 +82,7 @@ pub enum KeyAssignment {
     IncreaseFontSize,
     DecreaseFontSize,
     ResetFontSize,
-    ActivateTab(usize),
+    ActivateTab(isize),
     SendString(String),
     Nop,
     DisableDefaultAssignment,
@@ -207,7 +207,7 @@ impl InputMap {
                 [KeyModifiers::SUPER, KeyCode::Char('6'), ActivateTab(5)],
                 [KeyModifiers::SUPER, KeyCode::Char('7'), ActivateTab(6)],
                 [KeyModifiers::SUPER, KeyCode::Char('8'), ActivateTab(7)],
-                [KeyModifiers::SUPER, KeyCode::Char('9'), ActivateTab(8)],
+                [KeyModifiers::SUPER, KeyCode::Char('9'), ActivateTab(-1)],
                 [KeyModifiers::SUPER, KeyCode::Char('w'), CloseCurrentTab],
                 [ctrl_shift, KeyCode::Char('1'), ActivateTab(0)],
                 [ctrl_shift, KeyCode::Char('2'), ActivateTab(1)],
@@ -217,7 +217,7 @@ impl InputMap {
                 [ctrl_shift, KeyCode::Char('6'), ActivateTab(5)],
                 [ctrl_shift, KeyCode::Char('7'), ActivateTab(6)],
                 [ctrl_shift, KeyCode::Char('8'), ActivateTab(7)],
-                [ctrl_shift, KeyCode::Char('9'), ActivateTab(8)],
+                [ctrl_shift, KeyCode::Char('9'), ActivateTab(-1)],
                 [ctrl_shift, KeyCode::Char('W'), CloseCurrentTab],
                 [
                     KeyModifiers::SUPER | KeyModifiers::SHIFT,