Advanced Tab Switcher (#6732)

![TabSwitchingv2](https://user-images.githubusercontent.com/57155886/88237962-5505d500-cc35-11ea-8384-d91699155067.gif)

## Summary of the Pull Request
This PR adds the Advanced Tab Switcher (ATS) to Terminal. It'll work
similarly to VSCode's tab switcher. Because this implementation rides
off a lot of the Command Palette's XAML code, it'll look just like the
Command Palette, and also have support for tab title search.

## References
#3753 - ATS Spec

Closes #1502

doc/cascadia/profiles.schema.json

@@ -67,6 +67,7 @@
         "wt",
         "closeOtherTabs",
         "closeTabsAfter",
+        "tabSwitcher",
         "unbound"
       ],
       "type": "string"
@@ -88,6 +89,14 @@
       ],
       "type": "string"
     },
+    "AnchorKey": {
+      "enum": [
+        "ctrl",
+        "alt",
+        "shift"
+      ],
+      "type": "string"
+    },
     "NewTerminalArgs": {
       "properties": {
         "commandline": {
@@ -352,6 +361,22 @@
       ],
       "required": [ "index" ]
     },
+    "TabSwitcherAction": {
+      "description": "Arguments corresponding to a Tab Switcher Action",
+      "allOf": [
+        { "$ref": "#/definitions/ShortcutAction" },
+        {
+          "properties": {
+            "action": { "type": "string", "pattern": "tabSwitcher" },
+            "anchorKey": {
+              "$ref": "#/definitions/AnchorKey",
+              "default": null,
+              "description": "If provided, the tab switcher will stay open as long as the anchor key is held down. The anchor key should be part of the keybinding that opens the switcher."
+            }
+          }
+        }
+      ]
+    },
     "Keybinding": {
       "additionalProperties": false,
       "properties": {
@@ -372,6 +397,7 @@
               { "$ref": "#/definitions/WtAction" },
               { "$ref": "#/definitions/CloseOtherTabsAction" },
               { "$ref": "#/definitions/CloseTabsAfterAction" },
+              { "$ref": "#/definitions/TabSwitcherAction" },
               { "type": "null" }
             ]
         },

src/cascadia/TerminalApp/ActionAndArgs.cpp

@@ -44,6 +44,7 @@ static constexpr std::string_view ExecuteCommandlineKey{ "wt" };
 static constexpr std::string_view ToggleCommandPaletteKey{ "commandPalette" };
 static constexpr std::string_view CloseOtherTabsKey{ "closeOtherTabs" };
 static constexpr std::string_view CloseTabsAfterKey{ "closeTabsAfter" };
+static constexpr std::string_view ToggleTabSwitcherKey{ "tabSwitcher" };
 
 static constexpr std::string_view ActionKey{ "action" };
 
@@ -100,6 +101,7 @@ namespace winrt::TerminalApp::implementation
         { ToggleCommandPaletteKey, ShortcutAction::ToggleCommandPalette },
         { CloseOtherTabsKey, ShortcutAction::CloseOtherTabs },
         { CloseTabsAfterKey, ShortcutAction::CloseTabsAfter },
+        { ToggleTabSwitcherKey, ShortcutAction::ToggleTabSwitcher },
     };
 
     using ParseResult = std::tuple<IActionArgs, std::vector<::TerminalApp::SettingsLoadWarnings>>;
@@ -139,6 +141,8 @@ namespace winrt::TerminalApp::implementation
 
         { ShortcutAction::CloseTabsAfter, winrt::TerminalApp::implementation::CloseTabsAfterArgs::FromJson },
 
+        { ShortcutAction::ToggleTabSwitcher, winrt::TerminalApp::implementation::ToggleTabSwitcherArgs::FromJson },
+
         { ShortcutAction::Invalid, nullptr },
     };
 

src/cascadia/TerminalApp/ActionArgs.cpp

@@ -19,6 +19,7 @@
 #include "SetTabColorArgs.g.cpp"
 #include "RenameTabArgs.g.cpp"
 #include "ExecuteCommandlineArgs.g.cpp"
+#include "ToggleTabSwitcherArgs.g.h"
 
 #include <LibraryResources.h>
 
@@ -303,4 +304,22 @@ namespace winrt::TerminalApp::implementation
                         _Index)
         };
     }
+
+    winrt::hstring ToggleTabSwitcherArgs::GenerateName() const
+    {
+        // If there's an anchor key set, don't generate a name so that
+        // it won't show up in the command palette. Only an unanchored
+        // tab switcher should be able to be toggled from the palette.
+        // TODO: GH#7179 - once this goes in, make sure to hide the
+        // anchor mode command that was given a name in settings.
+        if (_AnchorKey != Windows::System::VirtualKey::None)
+        {
+            return L"";
+        }
+        else
+        {
+            return RS_(L"ToggleTabSwitcherCommandKey");
+        }
+    }
+
 }

src/cascadia/TerminalApp/ActionArgs.h

@@ -21,6 +21,7 @@
 #include "ExecuteCommandlineArgs.g.h"
 #include "CloseOtherTabsArgs.g.h"
 #include "CloseTabsAfterArgs.g.h"
+#include "ToggleTabSwitcherArgs.g.h"
 
 #include "../../cascadia/inc/cppwinrt_utils.h"
 #include "Utils.h"
@@ -512,6 +513,33 @@ namespace winrt::TerminalApp::implementation
         }
     };
 
+    struct ToggleTabSwitcherArgs : public ToggleTabSwitcherArgsT<ToggleTabSwitcherArgs>
+    {
+        ToggleTabSwitcherArgs() = default;
+        GETSET_PROPERTY(Windows::System::VirtualKey, AnchorKey, Windows::System::VirtualKey::None);
+
+        static constexpr std::string_view AnchorJsonKey{ "anchorKey" };
+
+    public:
+        hstring GenerateName() const;
+
+        bool Equals(const IActionArgs& other)
+        {
+            auto otherAsUs = other.try_as<ToggleTabSwitcherArgs>();
+            if (otherAsUs)
+            {
+                return otherAsUs->_AnchorKey == _AnchorKey;
+            }
+            return false;
+        };
+        static FromJsonResult FromJson(const Json::Value& json)
+        {
+            // LOAD BEARING: Not using make_self here _will_ break you in the future!
+            auto args = winrt::make_self<ToggleTabSwitcherArgs>();
+            JsonUtils::GetValueForKey(json, AnchorJsonKey, args->_AnchorKey);
+            return { *args, {} };
+        }
+    };
 }
 
 namespace winrt::TerminalApp::factory_implementation

src/cascadia/TerminalApp/ActionArgs.idl

@@ -135,4 +135,9 @@ namespace TerminalApp
     {
         UInt32 Index { get; };
     };
+
+    [default_interface] runtimeclass ToggleTabSwitcherArgs : IActionArgs
+    {
+        Windows.System.VirtualKey AnchorKey { get; };
+    };
 }

src/cascadia/TerminalApp/AppActionHandlers.cpp

@@ -285,6 +285,7 @@ namespace winrt::TerminalApp::implementation
     {
         // TODO GH#6677: When we add support for commandline mode, first set the
         // mode that the command palette should be in, before making it visible.
+        CommandPalette().EnableCommandPaletteMode();
         CommandPalette().Visibility(CommandPalette().Visibility() == Visibility::Visible ?
                                         Visibility::Collapsed :
                                         Visibility::Visible);
@@ -414,6 +415,7 @@ namespace winrt::TerminalApp::implementation
             actionArgs.Handled(true);
         }
     }
+
     void TerminalPage::_HandleCloseTabsAfter(const IInspectable& /*sender*/,
                                              const TerminalApp::ActionEventArgs& actionArgs)
     {
@@ -436,4 +438,28 @@ namespace winrt::TerminalApp::implementation
             actionArgs.Handled(true);
         }
     }
+
+    void TerminalPage::_HandleToggleTabSwitcher(const IInspectable& /*sender*/,
+                                                const TerminalApp::ActionEventArgs& args)
+    {
+        if (const auto& realArgs = args.ActionArgs().try_as<TerminalApp::ToggleTabSwitcherArgs>())
+        {
+            auto anchorKey = realArgs.AnchorKey();
+
+            auto opt = _GetFocusedTabIndex();
+            uint32_t startIdx = opt ? *opt : 0;
+
+            if (anchorKey != VirtualKey::None)
+            {
+                // TODO: GH#7178 - delta should also have the option of being -1, in the case when
+                // a user decides to open the tab switcher going to the prev tab.
+                int delta = 1;
+                startIdx = (startIdx + _tabs.Size() + delta) % _tabs.Size();
+            }
+
+            CommandPalette().EnableTabSwitcherMode(anchorKey, startIdx);
+            CommandPalette().Visibility(Visibility::Visible);
+        }
+        args.Handled(true);
+    }
 }

src/cascadia/TerminalApp/Command.h

@@ -32,10 +32,13 @@ namespace winrt::TerminalApp::implementation
         static std::vector<::TerminalApp::SettingsLoadWarnings> LayerJson(std::unordered_map<winrt::hstring, winrt::TerminalApp::Command>& commands,
                                                                           const Json::Value& json);
 
+        winrt::Windows::UI::Xaml::Data::INotifyPropertyChanged::PropertyChanged_revoker propertyChangedRevoker;
+
         WINRT_CALLBACK(PropertyChanged, Windows::UI::Xaml::Data::PropertyChangedEventHandler);
         OBSERVABLE_GETSET_PROPERTY(winrt::hstring, Name, _PropertyChangedHandlers);
         OBSERVABLE_GETSET_PROPERTY(winrt::TerminalApp::ActionAndArgs, Action, _PropertyChangedHandlers);
         OBSERVABLE_GETSET_PROPERTY(winrt::hstring, KeyChordText, _PropertyChangedHandlers);
+        OBSERVABLE_GETSET_PROPERTY(winrt::Windows::UI::Xaml::Controls::IconSource, IconSource, _PropertyChangedHandlers, nullptr);
     };
 }
 

src/cascadia/TerminalApp/Command.idl

@@ -12,5 +12,7 @@ namespace TerminalApp
         String Name;
         ActionAndArgs Action;
         String KeyChordText;
+
+        Windows.UI.Xaml.Controls.IconSource IconSource;
     }
 }