Add moving tabs left and right with key shortcuts (#700)

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https://github.com/pop-os/cosmic-term/issues/441 This PR adds option to
move tabs with left and right with Ctrl+Shift+Left/Right Arrow or by
using buttons in view menu.

i18n/en/cosmic_term.ftl

@@ -132,6 +132,8 @@ zoom-reset = Default text size
 zoom-out = Smaller text
 next-tab = Next tab
 previous-tab = Previous tab
+move-tab-left = Move tab left
+move-tab-right = Move tab right
 split-horizontal = Split horizontal
 split-vertical = Split vertical
 pane-toggle-maximize = Maximize or restore pane

src/main.rs

@@ -8,7 +8,7 @@ use cosmic::iced::keyboard::key::Physical;
 use cosmic::widget::menu::action::MenuAction;
 use cosmic::widget::menu::key_bind::KeyBind;
 use cosmic::widget::pane_grid::Pane;
-use cosmic::widget::segmented_button::ReorderEvent;
+use cosmic::widget::segmented_button::{InsertPosition, ReorderEvent};
 use cosmic::{
     Application, ApplicationExt, Element, action,
     app::{Core, Settings, Task, context_drawer},
@@ -281,6 +281,8 @@ pub enum Action {
     TabNewNoProfile,
     TabNext,
     TabPrev,
+    TabMoveLeft,
+    TabMoveRight,
     ToggleFullscreen,
     WindowClose,
     WindowNew,
@@ -334,6 +336,8 @@ impl Action {
             Self::TabNewNoProfile => Message::TabNewNoProfile,
             Self::TabNext => Message::TabNext,
             Self::TabPrev => Message::TabPrev,
+            Self::TabMoveLeft => Message::TabMoveLeft,
+            Self::TabMoveRight => Message::TabMoveRight,
             Self::ToggleFullscreen => Message::ToggleFullscreen,
             Self::WindowClose => Message::WindowClose,
             Self::WindowNew => Message::WindowNew,
@@ -442,6 +446,8 @@ pub enum Message {
     TabNewNoProfile,
     TabNext,
     TabPrev,
+    TabMoveLeft,
+    TabMoveRight,
     TermEvent(pane_grid::Pane, segmented_button::Entity, TermEvent),
     TermEventTx(mpsc::UnboundedSender<(pane_grid::Pane, segmented_button::Entity, TermEvent)>),
     ToggleFullscreen,
@@ -2960,6 +2966,33 @@ impl Application for App {
                     }
                 }
             }
+            Message::TabMoveLeft => {
+                if let Some(tab_model) = self.pane_model.active_mut() {
+                    let pos: usize = tab_model
+                        .position(tab_model.active())
+                        .expect("at least one tab is always open")
+                        .into();
+                    if pos > 0 {
+                        let dragged = tab_model.iter().nth(pos).expect("tab unavailable");
+                        let target = tab_model.iter().nth(pos - 1).expect("previous tab missing");
+                        tab_model.reorder(dragged, target, InsertPosition::Before);
+                    }
+                }
+            }
+            Message::TabMoveRight => {
+                if let Some(tab_model) = self.pane_model.active_mut() {
+                    let len = tab_model.iter().count();
+                    let pos: usize = tab_model
+                        .position(tab_model.active())
+                        .expect("at least one tab is always open")
+                        .into();
+                    if pos < len - 1 && len > 1 {
+                        let dragged = tab_model.iter().nth(pos).expect("tab unavailable");
+                        let target = tab_model.iter().nth(pos + 1).expect("next tab missing");
+                        tab_model.reorder(dragged, target, InsertPosition::After);
+                    }
+                }
+            }
             Message::TermEvent(pane, entity, event) => {
                 match event {
                     TermEvent::Bell => {

src/menu.rs

@@ -195,6 +195,9 @@ pub fn menu_bar<'a>(
                         MenuItem::Button(fl!("next-tab"), None, Action::TabNext),
                         MenuItem::Button(fl!("previous-tab"), None, Action::TabPrev),
                         MenuItem::Divider,
+                        MenuItem::Button(fl!("move-tab-left"), None, Action::TabMoveLeft),
+                        MenuItem::Button(fl!("move-tab-right"), None, Action::TabMoveRight),
+                        MenuItem::Divider,
                         MenuItem::Button(
                             fl!("split-horizontal"),
                             None,

src/shortcuts.rs

@@ -87,6 +87,8 @@ pub enum KeyBindAction {
     TabNew,
     TabNext,
     TabPrev,
+    TabMoveLeft,
+    TabMoveRight,
     ToggleFullscreen,
     WindowClose,
     WindowNew,
@@ -127,6 +129,8 @@ impl KeyBindAction {
             Self::TabNew => Some(Action::TabNew),
             Self::TabNext => Some(Action::TabNext),
             Self::TabPrev => Some(Action::TabPrev),
+            Self::TabMoveLeft => Some(Action::TabMoveLeft),
+            Self::TabMoveRight => Some(Action::TabMoveRight),
             Self::ToggleFullscreen => Some(Action::ToggleFullscreen),
             Self::WindowClose => Some(Action::WindowClose),
             Self::WindowNew => Some(Action::WindowNew),
@@ -288,6 +292,8 @@ pub fn action_label(action: KeyBindAction) -> String {
         KeyBindAction::TabNew => fl!("new-tab"),
         KeyBindAction::TabNext => fl!("next-tab"),
         KeyBindAction::TabPrev => fl!("previous-tab"),
+        KeyBindAction::TabMoveLeft => fl!("move-tab-left"),
+        KeyBindAction::TabMoveRight => fl!("move-tab-right"),
         KeyBindAction::ToggleFullscreen => fl!("toggle-fullscreen"),
         KeyBindAction::WindowClose => fl!("close-window"),
         KeyBindAction::WindowNew => fl!("new-window"),
@@ -322,6 +328,8 @@ pub fn shortcut_groups() -> Vec<ShortcutGroup> {
             KeyBindAction::TabClose,
             KeyBindAction::TabNext,
             KeyBindAction::TabPrev,
+            KeyBindAction::TabMoveLeft,
+            KeyBindAction::TabMoveRight,
             KeyBindAction::TabActivate0,
             KeyBindAction::TabActivate1,
             KeyBindAction::TabActivate2,
@@ -470,6 +478,10 @@ fn fallback_shortcuts() -> Shortcuts {
     bind!([Ctrl], "Tab", TabNext);
     bind!([Ctrl, Shift], "Tab", TabPrev);
 
+    // Ctrl+Shift+PageUp/Down move tabs left and right
+    bind!([Ctrl, Shift], "PageUp", TabMoveLeft);
+    bind!([Ctrl, Shift], "PageDown", TabMoveRight);
+
     // Ctrl+Shift+# activates tabs by index
     bind!([Ctrl, Shift], "1", TabActivate0);
     bind!([Ctrl, Shift], "2", TabActivate1);