Implement XTPUSHSGR, XTPOPSGR

This change adds a new pair of methods to ITermDispatch:
PushGraphicsRendition and PopGraphicsRendition, and then plumbs the
change through AdaptDispatch, TerminalDispatch, ITerminalApi and
TerminalApi.

The stack logic is encapsulated in the SgrStack class, to allow it to be
reused between the two APIs (AdaptDispatch and TerminalDispatch).

Like xterm, only ten levels of nesting are supported.

The stack is implemented as a "ring stack": if you push when the stack
is full, the bottom of the stack will be dropped to make room.

src/buffer/out/TextAttribute.cpp

@@ -81,6 +81,32 @@ bool TextAttribute::IsLegacy() const noexcept
     return _foreground.IsLegacy() && _background.IsLegacy();
 }
 
+// Routine Description:
+// - Makes this TextAttribute's foreground color the same as the other one.
+// Arguments:
+// - The TextAttribute to copy the foreground color from
+// Return Value:
+// - <none>
+void TextAttribute::SetForegroundFrom(const TextAttribute& other) noexcept
+{
+    _foreground = other._foreground;
+    WI_ClearAllFlags(_wAttrLegacy, FG_ATTRS);
+    _wAttrLegacy |= (other._wAttrLegacy & FG_ATTRS);
+}
+
+// Routine Description:
+// - Makes this TextAttribute's background color the same as the other one.
+// Arguments:
+// - The TextAttribute to copy the background color from
+// Return Value:
+// - <none>
+void TextAttribute::SetBackgroundFrom(const TextAttribute& other) noexcept
+{
+    _background = other._background;
+    WI_ClearAllFlags(_wAttrLegacy, BG_ATTRS);
+    _wAttrLegacy |= (other._wAttrLegacy & BG_ATTRS);
+}
+
 // Routine Description:
 // - Calculates rgb colors based off of current color table and active modification attributes.
 // Arguments:

src/buffer/out/TextAttribute.hpp

@@ -72,6 +72,9 @@ class TextAttribute final
                                                      const bool reverseScreenMode = false,
                                                      const bool blinkingIsFaint = false) const noexcept;
 
+    void SetForegroundFrom(const TextAttribute& other) noexcept;
+    void SetBackgroundFrom(const TextAttribute& other) noexcept;
+
     bool IsLeadingByte() const noexcept;
     bool IsTrailingByte() const noexcept;
     bool IsTopHorizontalDisplayed() const noexcept;

src/cascadia/TerminalCore/ITerminalApi.hpp

@@ -70,6 +70,9 @@ namespace Microsoft::Terminal::Core
         virtual bool SetWorkingDirectory(std::wstring_view uri) noexcept = 0;
         virtual std::wstring_view GetWorkingDirectory() noexcept = 0;
 
+        virtual bool PushGraphicsRendition(const ::Microsoft::Console::VirtualTerminal::VTParameters options) noexcept = 0;
+        virtual bool PopGraphicsRendition() noexcept = 0;
+
     protected:
         ITerminalApi() = default;
     };

src/cascadia/TerminalCore/Terminal.hpp

@@ -6,6 +6,7 @@
 #include <conattrs.hpp>
 
 #include "../../buffer/out/textBuffer.hpp"
+#include "../../types/inc/sgrStack.hpp"
 #include "../../renderer/inc/BlinkingState.hpp"
 #include "../../terminal/parser/StateMachine.hpp"
 #include "../../terminal/input/terminalInput.hpp"
@@ -124,6 +125,10 @@ class Microsoft::Terminal::Core::Terminal final :
     bool SetTaskbarProgress(const size_t state, const size_t progress) noexcept override;
     bool SetWorkingDirectory(std::wstring_view uri) noexcept override;
     std::wstring_view GetWorkingDirectory() noexcept override;
+
+    bool PushGraphicsRendition(const ::Microsoft::Console::VirtualTerminal::VTParameters options) noexcept override;
+    bool PopGraphicsRendition() noexcept override;
+
 #pragma endregion
 
 #pragma region ITerminalInput
@@ -347,6 +352,8 @@ class Microsoft::Terminal::Core::Terminal final :
     COORD _ConvertToBufferCell(const COORD viewportPos) const;
 #pragma endregion
 
+    Microsoft::Console::VirtualTerminal::SgrStack _sgrStack;
+
 #ifdef UNIT_TESTING
     friend class TerminalCoreUnitTests::TerminalBufferTests;
     friend class TerminalCoreUnitTests::TerminalApiTest;

src/cascadia/TerminalCore/TerminalApi.cpp

@@ -640,3 +640,31 @@ std::wstring_view Terminal::GetWorkingDirectory() noexcept
 {
     return _workingDirectory;
 }
+
+// Method Description:
+// - Saves the current text attributes to an internal stack.
+// Arguments:
+// - options, cOptions: if present, specify which portions of the current text attributes
+//   should be saved. Only a small subset of GraphicsOptions are actually supported;
+//   others are ignored. If no options are specified, all attributes are stored.
+// Return Value:
+// - true
+bool Terminal::PushGraphicsRendition(const VTParameters options) noexcept
+{
+    _sgrStack.Push(_buffer->GetCurrentAttributes(), options);
+    return true;
+}
+
+// Method Description:
+// - Restores text attributes from the internal stack. If only portions of text attributes
+//   were saved, combines those with the current attributes.
+// Arguments:
+// - <none>
+// Return Value:
+// - true
+bool Terminal::PopGraphicsRendition() noexcept
+{
+    const TextAttribute current = _buffer->GetCurrentAttributes();
+    _buffer->SetCurrentAttributes(_sgrStack.Pop(current));
+    return true;
+}

src/cascadia/TerminalCore/TerminalDispatch.hpp

@@ -18,6 +18,9 @@ class TerminalDispatch : public Microsoft::Console::VirtualTerminal::TermDispatc
 
     bool SetGraphicsRendition(const ::Microsoft::Console::VirtualTerminal::VTParameters options) noexcept override;
 
+    bool PushGraphicsRendition(const ::Microsoft::Console::VirtualTerminal::VTParameters options) noexcept override;
+    bool PopGraphicsRendition() noexcept override;
+
     bool CursorPosition(const size_t line,
                         const size_t column) noexcept override; // CUP
 

src/cascadia/TerminalCore/TerminalDispatchGraphics.cpp

@@ -276,3 +276,13 @@ bool TerminalDispatch::SetGraphicsRendition(const VTParameters options) noexcept
     _terminalApi.SetTextAttributes(attr);
     return true;
 }
+
+bool TerminalDispatch::PushGraphicsRendition(const VTParameters options) noexcept
+{
+    return _terminalApi.PushGraphicsRendition(options);
+}
+
+bool TerminalDispatch::PopGraphicsRendition() noexcept
+{
+    return _terminalApi.PopGraphicsRendition();
+}

src/terminal/adapter/DispatchTypes.hpp

@@ -311,6 +311,40 @@ namespace Microsoft::Console::VirtualTerminal::DispatchTypes
         BrightBackgroundWhite = 107,
     };
 
+    // Many of these correspond directly to SGR parameters (the GraphicsOptions enum), but
+    // these are distinct (notably 10 and 11, which as SGR parameters would select fonts,
+    // are used here to indicate that the foreground/background colors should be saved).
+    // From xterm's ctlseqs doc for XTPUSHSGR:
+    //
+    //      Ps = 1    =>  Bold.
+    //      Ps = 2    =>  Faint.
+    //      Ps = 3    =>  Italicized.
+    //      Ps = 4    =>  Underlined.
+    //      Ps = 5    =>  Blink.
+    //      Ps = 7    =>  Inverse.
+    //      Ps = 8    =>  Invisible.
+    //      Ps = 9    =>  Crossed-out characters.
+    //      Ps = 2 1  =>  Doubly-underlined.
+    //      Ps = 3 0  =>  Foreground color.
+    //      Ps = 3 1  =>  Background color.
+    //
+    enum class SgrSaveRestoreStackOptions : size_t
+    {
+        All = 0,
+        Boldness = 1,
+        Faintness = 2,
+        Italics = 3,
+        Underline = 4,
+        Blink = 5,
+        Negative = 7,
+        Invisible = 8,
+        CrossedOut = 9,
+        DoublyUnderlined = 21,
+        SaveForegroundColor = 30,
+        SaveBackgroundColor = 31,
+        Max = SaveBackgroundColor
+    };
+
     enum class AnsiStatusType : size_t
     {
         OS_OperatingStatus = 5,

src/terminal/adapter/ITermDispatch.hpp

@@ -89,6 +89,9 @@ class Microsoft::Console::VirtualTerminal::ITermDispatch
 
     virtual bool SetGraphicsRendition(const VTParameters options) = 0; // SGR
 
+    virtual bool PushGraphicsRendition(const VTParameters options) = 0; // XTPUSHSGR
+    virtual bool PopGraphicsRendition() = 0; // XTPOPSGR
+
     virtual bool SetMode(const DispatchTypes::ModeParams param) = 0; // DECSET
 
     virtual bool ResetMode(const DispatchTypes::ModeParams param) = 0; // DECRST