Allow exporting terminal buffer into file via tab context menu (#11062)

## Summary of the Pull Request
**Naive implementation** of exporting the text buffer of the current pane
into a text file triggered from the tab context menu.

**Disclaimer: this is not an export of the command  history,** 
but rather just a text buffer dumped into a file when asked explicitly.

## References
Should provide partial solution for #642.

## Detailed Description of the Pull Request / Additional comments
The logic is following:
* Open a file save picker
  * The location is Downloads folder (should be always accessible)
  * The suggest name of the file equals to the pane's title
  * The allowed file formats list contains .txt only
* If no file selected stop
* Lock terminal
* Read all lines till the cursor
* Format each line by removing trailing white-spaces and adding CRLF if not wrapped
* Asynchronously write to selected file
* Show confirmation

As the action is relatively fast didn't add a progress bar or any other UX.
As the buffer is relatively small, holding it entirely in the memory rather than
writing line by line to disk.

src/cascadia/TerminalApp/Resources/en-US/Resources.resw

@@ -685,4 +685,16 @@
   <data name="DropPathTabSplit.Text" xml:space="preserve">
     <value>Split the window and start in given directory</value>
   </data>
+  <data name="ExportTabText" xml:space="preserve">
+    <value>Export Text</value>
+  </data>
+  <data name="ExportFailure" xml:space="preserve">
+    <value>Failed to export terminal content</value>
+  </data>
+  <data name="ExportSuccess" xml:space="preserve">
+    <value>Successfully exported terminal content</value>
+  </data>
+  <data name="PlainText" xml:space="preserve">
+    <value>Plain Text</value>
+  </data>
 </root>

src/cascadia/TerminalApp/TabManagement.cpp

@@ -28,6 +28,9 @@ using namespace winrt::Windows::UI::Core;
 using namespace winrt::Windows::System;
 using namespace winrt::Windows::ApplicationModel::DataTransfer;
 using namespace winrt::Windows::UI::Text;
+using namespace winrt::Windows::Storage;
+using namespace winrt::Windows::Storage::Pickers;
+using namespace winrt::Windows::Storage::Provider;
 using namespace winrt::Microsoft::Terminal;
 using namespace winrt::Microsoft::Terminal::Control;
 using namespace winrt::Microsoft::Terminal::TerminalConnection;
@@ -171,6 +174,16 @@ namespace winrt::TerminalApp::implementation
             }
         });
 
+        newTabImpl->ExportTabRequested([weakTab, weakThis{ get_weak() }]() {
+            auto page{ weakThis.get() };
+            auto tab{ weakTab.get() };
+
+            if (page && tab)
+            {
+                page->_ExportTab(*tab);
+            }
+        });
+
         auto tabViewItem = newTabImpl->TabViewItem();
         _tabView.TabItems().Append(tabViewItem);
 
@@ -391,6 +404,45 @@ namespace winrt::TerminalApp::implementation
         CATCH_LOG();
     }
 
+    // Method Description:
+    // - Exports the content of the Terminal Buffer inside the tab
+    // Arguments:
+    // - tab: tab to export
+    winrt::fire_and_forget TerminalPage::_ExportTab(const TerminalTab& tab)
+    {
+        try
+        {
+            if (const auto control{ tab.GetActiveTerminalControl() })
+            {
+                const FileSavePicker savePicker;
+                savePicker.as<IInitializeWithWindow>()->Initialize(*_hostingHwnd);
+                savePicker.SuggestedStartLocation(PickerLocationId::Downloads);
+                const auto fileChoices = single_threaded_vector<hstring>({ L".txt" });
+                savePicker.FileTypeChoices().Insert(RS_(L"PlainText"), fileChoices);
+                savePicker.SuggestedFileName(control.Title());
+
+                const StorageFile file = co_await savePicker.PickSaveFileAsync();
+                if (file != nullptr)
+                {
+                    const auto buffer = control.ReadEntireBuffer();
+                    CachedFileManager::DeferUpdates(file);
+                    co_await FileIO::WriteTextAsync(file, buffer);
+                    const auto status = co_await CachedFileManager::CompleteUpdatesAsync(file);
+                    switch (status)
+                    {
+                    case FileUpdateStatus::Complete:
+                    case FileUpdateStatus::CompleteAndRenamed:
+                        _ShowControlNoticeDialog(RS_(L"NoticeInfo"), RS_(L"ExportSuccess"));
+                        break;
+                    default:
+                        _ShowControlNoticeDialog(RS_(L"NoticeError"), RS_(L"ExportFailure"));
+                    }
+                }
+            }
+        }
+        CATCH_LOG();
+    }
+
     // Method Description:
     // - Removes the tab (both TerminalControl and XAML) after prompting for approval
     // Arguments:

src/cascadia/TerminalApp/TerminalPage.h

@@ -220,6 +220,7 @@ namespace winrt::TerminalApp::implementation
         void _DuplicateTab(const TerminalTab& tab);
 
         void _SplitTab(TerminalTab& tab);
+        winrt::fire_and_forget _ExportTab(const TerminalTab& tab);
 
         winrt::Windows::Foundation::IAsyncAction _HandleCloseTabRequested(winrt::TerminalApp::TabBase tab);
         void _CloseTabAtIndex(uint32_t index);

src/cascadia/TerminalApp/TerminalTab.cpp

@@ -1211,6 +1211,23 @@ namespace winrt::TerminalApp::implementation
             splitTabMenuItem.Icon(splitTabSymbol);
         }
 
+        Controls::MenuFlyoutItem exportTabMenuItem;
+        {
+            // "Split Tab"
+            Controls::FontIcon exportTabSymbol;
+            exportTabSymbol.FontFamily(Media::FontFamily{ L"Segoe MDL2 Assets" });
+            exportTabSymbol.Glyph(L"\xE74E"); // Save
+
+            exportTabMenuItem.Click([weakThis](auto&&, auto&&) {
+                if (auto tab{ weakThis.get() })
+                {
+                    tab->_ExportTabRequestedHandlers();
+                }
+            });
+            exportTabMenuItem.Text(RS_(L"ExportTabText"));
+            exportTabMenuItem.Icon(exportTabSymbol);
+        }
+
         // Build the menu
         Controls::MenuFlyout contextMenuFlyout;
         Controls::MenuFlyoutSeparator menuSeparator;
@@ -1218,6 +1235,7 @@ namespace winrt::TerminalApp::implementation
         contextMenuFlyout.Items().Append(renameTabMenuItem);
         contextMenuFlyout.Items().Append(duplicateTabMenuItem);
         contextMenuFlyout.Items().Append(splitTabMenuItem);
+        contextMenuFlyout.Items().Append(exportTabMenuItem);
         contextMenuFlyout.Items().Append(menuSeparator);
 
         // GH#5750 - When the context menu is dismissed with ESC, toss the focus
@@ -1592,4 +1610,5 @@ namespace winrt::TerminalApp::implementation
     DEFINE_EVENT(TerminalTab, TabRaiseVisualBell, _TabRaiseVisualBellHandlers, winrt::delegate<>);
     DEFINE_EVENT(TerminalTab, DuplicateRequested, _DuplicateRequestedHandlers, winrt::delegate<>);
     DEFINE_EVENT(TerminalTab, SplitTabRequested, _SplitTabRequestedHandlers, winrt::delegate<>);
+    DEFINE_EVENT(TerminalTab, ExportTabRequested, _ExportTabRequestedHandlers, winrt::delegate<>);
 }

src/cascadia/TerminalApp/TerminalTab.h

@@ -103,6 +103,7 @@ namespace winrt::TerminalApp::implementation
         DECLARE_EVENT(TabRaiseVisualBell, _TabRaiseVisualBellHandlers, winrt::delegate<>);
         DECLARE_EVENT(DuplicateRequested, _DuplicateRequestedHandlers, winrt::delegate<>);
         DECLARE_EVENT(SplitTabRequested, _SplitTabRequestedHandlers, winrt::delegate<>);
+        DECLARE_EVENT(ExportTabRequested, _ExportTabRequestedHandlers, winrt::delegate<>);
         TYPED_EVENT(TaskbarProgressChanged, IInspectable, IInspectable);
 
     private:

src/cascadia/TerminalApp/pch.h

@@ -56,6 +56,9 @@
 #include <winrt/Microsoft.Terminal.TerminalConnection.h>
 #include <winrt/Microsoft.Terminal.Settings.Editor.h>
 #include <winrt/Microsoft.Terminal.Settings.Model.h>
+#include <winrt/Windows.Storage.h>
+#include <winrt/Windows.Storage.Provider.h>
+#include <winrt/Windows.Storage.Pickers.h>
 
 #include <windows.ui.xaml.media.dxinterop.h>
 

src/cascadia/TerminalControl/ControlCore.cpp

@@ -1499,4 +1499,32 @@ namespace winrt::Microsoft::Terminal::Control::implementation
         _updatePatternLocations->Run();
     }
 
+    hstring ControlCore::ReadEntireBuffer() const
+    {
+        auto terminalLock = _terminal->LockForWriting();
+
+        const auto& textBuffer = _terminal->GetTextBuffer();
+
+        std::wstringstream ss;
+        const auto lastRow = textBuffer.GetLastNonSpaceCharacter().Y;
+        for (auto rowIndex = 0; rowIndex <= lastRow; rowIndex++)
+        {
+            const auto& row = textBuffer.GetRowByOffset(rowIndex);
+            auto rowText = row.GetText();
+            const auto strEnd = rowText.find_last_not_of(UNICODE_SPACE);
+            if (strEnd != std::string::npos)
+            {
+                rowText.erase(strEnd + 1);
+                ss << rowText;
+            }
+
+            if (!row.WasWrapForced())
+            {
+                ss << UNICODE_CARRIAGERETURN << UNICODE_LINEFEED;
+            }
+        }
+
+        return hstring(ss.str());
+    }
+
 }

src/cascadia/TerminalControl/ControlCore.h

@@ -144,6 +144,8 @@ namespace winrt::Microsoft::Terminal::Control::implementation
         bool IsInReadOnlyMode() const;
         void ToggleReadOnlyMode();
 
+        hstring ReadEntireBuffer() const;
+
         // -------------------------------- WinRT Events ---------------------------------
         // clang-format off
         WINRT_CALLBACK(FontSizeChanged, Control::FontSizeChangedEventArgs);

src/cascadia/TerminalControl/ControlCore.idl

@@ -81,6 +81,8 @@ namespace Microsoft.Terminal.Control
         Boolean CursorOn;
         void EnablePainting();
 
+        String ReadEntireBuffer();
+
         event FontSizeChangedEventArgs FontSizeChanged;
 
         event Windows.Foundation.TypedEventHandler<Object, CopyToClipboardEventArgs> CopyToClipboard;

src/cascadia/TerminalControl/TermControl.cpp

@@ -2586,4 +2586,9 @@ namespace winrt::Microsoft::Terminal::Control::implementation
     {
         _playWarningBell->Run();
     }
+
+    hstring TermControl::ReadEntireBuffer() const
+    {
+        return _core.ReadEntireBuffer();
+    }
 }

src/cascadia/TerminalControl/TermControl.h

@@ -107,6 +107,8 @@ namespace winrt::Microsoft::Terminal::Control::implementation
         static unsigned int GetPointerUpdateKind(const winrt::Windows::UI::Input::PointerPoint point);
         static Windows::UI::Xaml::Thickness ParseThicknessFromPadding(const hstring padding);
 
+        hstring ReadEntireBuffer() const;
+
         // -------------------------------- WinRT Events ---------------------------------
         // clang-format off
         WINRT_CALLBACK(FontSizeChanged, Control::FontSizeChangedEventArgs);

src/cascadia/TerminalControl/TermControl.idl

@@ -67,5 +67,7 @@ namespace Microsoft.Terminal.Control
 
         Boolean ReadOnly { get; };
         void ToggleReadOnly();
+
+        String ReadEntireBuffer();
     }
 }