Add support for underline style and color in VT

src/buffer/out/TextAttribute.cpp

@@ -7,7 +7,7 @@
 
 // Keeping TextColor compact helps us keeping TextAttribute compact,
 // which in turn ensures that our buffer memory usage is low.
-static_assert(sizeof(TextAttribute) == 12);
+static_assert(sizeof(TextAttribute) == 18);
 static_assert(alignof(TextAttribute) == 2);
 // Ensure that we can memcpy() and memmove() the struct for performance.
 static_assert(std::is_trivially_copyable_v<TextAttribute>);
@@ -156,6 +156,16 @@ uint16_t TextAttribute::GetHyperlinkId() const noexcept
     return _hyperlinkId;
 }
 
+TextColor TextAttribute::GetUnderlineColor() const noexcept
+{
+    return _underlineColor;
+}
+
+UnderlineStyle TextAttribute::GetUnderlineStyle() const noexcept
+{
+    return _underlineStyle;
+}
+
 void TextAttribute::SetForeground(const TextColor foreground) noexcept
 {
     _foreground = foreground;
@@ -166,6 +176,11 @@ void TextAttribute::SetBackground(const TextColor background) noexcept
     _background = background;
 }
 
+void TextAttribute::SetUnderlineColor(const TextColor color) noexcept
+{
+    _underlineColor = color;
+}
+
 void TextAttribute::SetForeground(const COLORREF rgbForeground) noexcept
 {
     _foreground = TextColor(rgbForeground);
@@ -277,6 +292,9 @@ bool TextAttribute::IsCrossedOut() const noexcept
     return WI_IsFlagSet(_attrs, CharacterAttributes::CrossedOut);
 }
 
+// Method description:
+// - Returns true if the text is underlined with the any underline style,
+//   Eg. singly, doubly, curly, dotted, and dashed.
 bool TextAttribute::IsUnderlined() const noexcept
 {
     return WI_IsFlagSet(_attrs, CharacterAttributes::Underlined);
@@ -334,9 +352,43 @@ void TextAttribute::SetCrossedOut(bool isCrossedOut) noexcept
 
 void TextAttribute::SetUnderlined(bool isUnderlined) noexcept
 {
-    WI_UpdateFlag(_attrs, CharacterAttributes::Underlined, isUnderlined);
+    if (isUnderlined)
+    {
+        SetUnderlineStyle(UnderlineStyle::SinglyUnderlined);
+    }
+    else
+    {
+        SetUnderlineStyle(UnderlineStyle::NoUnderline);
+    }
+}
+
+void TextAttribute::SetUnderlineStyle(const UnderlineStyle underlineStyle) noexcept
+{
+    switch (underlineStyle)
+    {
+    case UnderlineStyle::NoUnderline:
+        WI_ClearFlag(_attrs, CharacterAttributes::Underlined);
+        _underlineStyle = underlineStyle;
+        break;
+    case UnderlineStyle::SinglyUnderlined:
+    case UnderlineStyle::DoublyUnderlined:
+    case UnderlineStyle::CurlyUnderlined:
+    case UnderlineStyle::DottedUnderlined:
+    case UnderlineStyle::DashedUnderlined:
+        WI_SetFlag(_attrs, CharacterAttributes::Underlined);
+        _underlineStyle = underlineStyle;
+        break;
+    default:
+        /* do nothing */
+        break;
+    }
 }
 
+// Method description:
+// - Sets doubly underlined in the attribute.
+// - This is used for SGR 21 sequences. (do not use with SGR 4:x)
+// Arguments:
+// - isDoublyUnderlined - whether to set doubly underlined or not.
 void TextAttribute::SetDoublyUnderlined(bool isDoublyUnderlined) noexcept
 {
     WI_UpdateFlag(_attrs, CharacterAttributes::DoublyUnderlined, isDoublyUnderlined);
@@ -374,12 +426,18 @@ void TextAttribute::SetDefaultBackground() noexcept
     _background = TextColor();
 }
 
+void TextAttribute::SetDefaultUnderlineColor() noexcept
+{
+    _underlineColor = TextColor{};
+}
+
 // Method description:
 // - Resets only the rendition character attributes, which includes everything
-//     except the Protected attribute.
+//     except the Protected attribute. Additionally, resets the underline style.
 void TextAttribute::SetDefaultRenditionAttributes() noexcept
 {
     _attrs &= ~CharacterAttributes::Rendition;
+    _underlineStyle = UnderlineStyle::NoUnderline;
 }
 
 // Method Description:
@@ -404,5 +462,6 @@ bool TextAttribute::BackgroundIsDefault() const noexcept
 void TextAttribute::SetStandardErase() noexcept
 {
     _attrs = CharacterAttributes::Normal;
+    _underlineStyle = UnderlineStyle::NoUnderline;
     _hyperlinkId = 0;
 }

src/buffer/out/TextAttribute.hpp

@@ -27,22 +27,38 @@ Revision History:
 #include "WexTestClass.h"
 #endif
 
+enum class UnderlineStyle : uint8_t
+{
+    NoUnderline = 0,
+    SinglyUnderlined = 1,
+    DoublyUnderlined = 2,
+    CurlyUnderlined = 3,
+    DottedUnderlined = 4,
+    DashedUnderlined = 5,
+};
+
 class TextAttribute final
 {
 public:
     constexpr TextAttribute() noexcept :
         _attrs{ CharacterAttributes::Normal },
         _foreground{},
         _background{},
-        _hyperlinkId{ 0 }
+        _hyperlinkId{ 0 },
+        _underlineColor{},
+        _underlineStyle{ UnderlineStyle::NoUnderline },
+        __unused{}
     {
     }
 
     explicit constexpr TextAttribute(const WORD wLegacyAttr) noexcept :
         _attrs{ gsl::narrow_cast<WORD>(wLegacyAttr & USED_META_ATTRS) },
         _foreground{ gsl::at(s_legacyForegroundColorMap, wLegacyAttr & FG_ATTRS) },
         _background{ gsl::at(s_legacyBackgroundColorMap, (wLegacyAttr & BG_ATTRS) >> 4) },
-        _hyperlinkId{ 0 }
+        _hyperlinkId{ 0 },
+        _underlineColor{},
+        _underlineStyle{ UnderlineStyle::NoUnderline },
+        __unused{}
     {
     }
 
@@ -51,7 +67,21 @@ class TextAttribute final
         _attrs{ CharacterAttributes::Normal },
         _foreground{ rgbForeground },
         _background{ rgbBackground },
-        _hyperlinkId{ 0 }
+        _hyperlinkId{ 0 },
+        _underlineColor{},
+        _underlineStyle{ UnderlineStyle::NoUnderline },
+        __unused{}
+    {
+    }
+
+    constexpr TextAttribute(const CharacterAttributes attrs, const TextColor foreground, const TextColor background, const uint16_t hyperlinkId, const TextColor underlineColor, const UnderlineStyle underlineStyle) noexcept :
+        _attrs{ attrs },
+        _foreground{ foreground },
+        _background{ background },
+        _hyperlinkId{ hyperlinkId },
+        _underlineColor{ underlineColor },
+        _underlineStyle{ underlineStyle },
+        __unused{}
     {
     }
 
@@ -99,6 +129,7 @@ class TextAttribute final
     void SetInvisible(bool isInvisible) noexcept;
     void SetCrossedOut(bool isCrossedOut) noexcept;
     void SetUnderlined(bool isUnderlined) noexcept;
+    void SetUnderlineStyle(const UnderlineStyle underlineStyle) noexcept;
     void SetDoublyUnderlined(bool isDoublyUnderlined) noexcept;
     void SetOverlined(bool isOverlined) noexcept;
     void SetReverseVideo(bool isReversed) noexcept;
@@ -118,8 +149,11 @@ class TextAttribute final
     TextColor GetForeground() const noexcept;
     TextColor GetBackground() const noexcept;
     uint16_t GetHyperlinkId() const noexcept;
+    TextColor GetUnderlineColor() const noexcept;
+    UnderlineStyle GetUnderlineStyle() const noexcept;
     void SetForeground(const TextColor foreground) noexcept;
     void SetBackground(const TextColor background) noexcept;
+    void SetUnderlineColor(const TextColor color) noexcept;
     void SetForeground(const COLORREF rgbForeground) noexcept;
     void SetBackground(const COLORREF rgbBackground) noexcept;
     void SetIndexedForeground(const BYTE fgIndex) noexcept;
@@ -131,6 +165,7 @@ class TextAttribute final
 
     void SetDefaultForeground() noexcept;
     void SetDefaultBackground() noexcept;
+    void SetDefaultUnderlineColor() noexcept;
     void SetDefaultRenditionAttributes() noexcept;
 
     bool BackgroundIsDefault() const noexcept;
@@ -175,6 +210,9 @@ class TextAttribute final
     uint16_t _hyperlinkId; // sizeof: 2, alignof: 2
     TextColor _foreground; // sizeof: 4, alignof: 1
     TextColor _background; // sizeof: 4, alignof: 1
+    TextColor _underlineColor; // sizeof: 4, alignof: 1
+    UnderlineStyle _underlineStyle; // sizeof: 1, alignof: 1
+    BYTE __unused; // sizeof: 1, alignof: 1 (avoids padding)
 
 #ifdef UNIT_TESTING
     friend class TextBufferTests;

src/cascadia/TerminalCore/Terminal.cpp

@@ -287,7 +287,7 @@ std::wstring_view Terminal::GetWorkingDirectory() noexcept
         // but after the resize, we'll want to make sure that the new buffer's
         // current attributes (the ones used for printing new text) match the
         // old buffer's.
-        const auto oldBufferAttributes = _mainBuffer->GetCurrentAttributes();
+        const auto& oldBufferAttributes = _mainBuffer->GetCurrentAttributes();
         newTextBuffer = std::make_unique<TextBuffer>(bufferSize,
                                                      TextAttribute{},
                                                      0, // temporarily set size to 0 so it won't render.

src/renderer/vt/VtSequences.cpp

@@ -241,6 +241,19 @@ using namespace Microsoft::Console::Render;
     return _WriteFormatted(FMT_COMPILE("\x1b[{}8;5;{}m"), fIsForeground ? '3' : '4', index);
 }
 
+// Method Description:
+// - Formats and writes a sequence to change the current underline color to an
+//   indexed color from the 256-color table.
+// - Uses sub parameters.
+// Arguments:
+// - index: color table index to emit as a VT sequence
+// Return Value:
+// - S_OK if we succeeded, else an appropriate HRESULT for failing to allocate or write.
+[[nodiscard]] HRESULT VtEngine::_SetGraphicsRenditionUnderline256Color(const BYTE index) noexcept
+{
+    return _WriteFormatted(FMT_COMPILE("\x1b[58:5:{}m"), index);
+}
+
 // Method Description:
 // - Formats and writes a sequence to change the current text attributes to an
 //      RGB color.
@@ -258,6 +271,22 @@ using namespace Microsoft::Console::Render;
     return _WriteFormatted(FMT_COMPILE("\x1b[{}8;2;{};{};{}m"), fIsForeground ? '3' : '4', r, g, b);
 }
 
+// Method Description:
+// - Formats and writes a sequence to change the current underline color to an
+//   RGB color.
+// - Uses sub parameters.
+// Arguments:
+// - color: The color to emit a VT sequence for.
+// Return Value:
+// - S_OK if we succeeded, else an appropriate HRESULT for failing to allocate or write.
+[[nodiscard]] HRESULT VtEngine::_SetGraphicsRenditionUnderlineRGBColor(const COLORREF color) noexcept
+{
+    const auto r = GetRValue(color);
+    const auto g = GetGValue(color);
+    const auto b = GetBValue(color);
+    return _WriteFormatted(FMT_COMPILE("\x1b[58:2::{}:{}:{}m"), r, g, b);
+}
+
 // Method Description:
 // - Formats and writes a sequence to change the current text attributes to the
 //      default foreground or background. Does not affect the intensity of text.
@@ -270,6 +299,16 @@ using namespace Microsoft::Console::Render;
     return _Write(fIsForeground ? ("\x1b[39m") : ("\x1b[49m"));
 }
 
+// Method Description:
+// - Formats and writes a sequence to change the current underline color to the
+//   default color.
+// Return Value:
+// - S_OK if we succeeded, else an appropriate HRESULT for failing to allocate or write.
+[[nodiscard]] HRESULT VtEngine::_SetGraphicsRenditionUnderlineDefaultColor() noexcept
+{
+    return _Write("\x1b[59m");
+}
+
 // Method Description:
 // - Formats and writes a sequence to change the terminal's window size.
 // Arguments:
@@ -332,6 +371,35 @@ using namespace Microsoft::Console::Render;
     return _Write(isFaint ? "\x1b[2m" : "\x1b[22m");
 }
 
+// Method Description:
+// - Formats and writes a sequence to change the extended underline styling of the following text.
+// - Uses backward compatible SGR 4 (without sub parameter) and SGR 21 for single and doubly underline.
+// Arguments:
+// - style: underline style to use.
+// Return Value:
+// - S_OK if we succeeded, else an appropriate HRESULT for failing to allocate or write.
+[[nodiscard]] HRESULT VtEngine::_SetUnderlineExtended(const UnderlineStyle style) noexcept
+{
+    switch (style)
+    {
+    // we don't expect style to be NoUnderline here, but we'll handle it anyway.
+    case UnderlineStyle::NoUnderline:
+        return _SetUnderlined(false);
+    case UnderlineStyle::SinglyUnderlined:
+        return _SetUnderlined(true);
+    case UnderlineStyle::DoublyUnderlined:
+        return _SetDoublyUnderlined(true);
+    case UnderlineStyle::CurlyUnderlined:
+        return _Write("\x1b[4:3m");
+    case UnderlineStyle::DottedUnderlined:
+        return _Write("\x1b[4:4m");
+    case UnderlineStyle::DashedUnderlined:
+        return _Write("\x1b[4:5m");
+    default:
+        return S_OK;
+    }
+}
+
 // Method Description:
 // - Formats and writes a sequence to change the underline of the following text.
 // Arguments:

src/renderer/vt/Xterm256Engine.cpp

@@ -100,8 +100,9 @@ Xterm256Engine::Xterm256Engine(_In_ wil::unique_hfile hPipe,
     // we can then check if either should be turned back on again.
     if (textAttributes.IsUnderlined() && !_lastTextAttributes.IsUnderlined())
     {
-        RETURN_IF_FAILED(_SetUnderlined(true));
-        _lastTextAttributes.SetUnderlined(true);
+        auto style = textAttributes.GetUnderlineStyle();
+        RETURN_IF_FAILED(_SetUnderlineExtended(style));
+        _lastTextAttributes.SetUnderlineStyle(style);
     }
     if (textAttributes.IsDoublyUnderlined() && !_lastTextAttributes.IsDoublyUnderlined())
     {

src/renderer/vt/paint.cpp

@@ -257,11 +257,13 @@ using namespace Microsoft::Console::Types;
 {
     const auto fg = textAttributes.GetForeground();
     const auto bg = textAttributes.GetBackground();
+    const auto ul = textAttributes.GetUnderlineColor();
     auto lastFg = _lastTextAttributes.GetForeground();
     auto lastBg = _lastTextAttributes.GetBackground();
+    auto lastUl = _lastTextAttributes.GetUnderlineColor();
 
-    // If both the FG and BG should be the defaults, emit a SGR reset.
-    if (fg.IsDefault() && bg.IsDefault() && !(lastFg.IsDefault() && lastBg.IsDefault()))
+    // If the FG, BG and UL should be the defaults, emit a SGR reset.
+    if (fg.IsDefault() && bg.IsDefault() && ul.IsDefault() && !(lastFg.IsDefault() && lastBg.IsDefault() && lastUl.IsDefault()))
     {
         // SGR Reset will clear all attributes (except hyperlink ID) - which means
         // we cannot reset _lastTextAttributes by simply doing
@@ -270,9 +272,11 @@ using namespace Microsoft::Console::Types;
         RETURN_IF_FAILED(_SetGraphicsDefault());
         _lastTextAttributes.SetDefaultBackground();
         _lastTextAttributes.SetDefaultForeground();
+        _lastTextAttributes.SetDefaultUnderlineColor();
         _lastTextAttributes.SetDefaultRenditionAttributes();
         lastFg = {};
         lastBg = {};
+        lastUl = {};
     }
 
     if (fg != lastFg)
@@ -317,6 +321,27 @@ using namespace Microsoft::Console::Types;
         _lastTextAttributes.SetBackground(bg);
     }
 
+    if (ul != lastUl)
+    {
+        if (ul.IsDefault())
+        {
+            RETURN_IF_FAILED(_SetGraphicsRenditionUnderlineDefaultColor());
+        }
+        else if (ul.IsIndex16()) // underline can't be 16 color
+        {
+            /* do nothing */
+        }
+        else if (ul.IsIndex256())
+        {
+            RETURN_IF_FAILED(_SetGraphicsRenditionUnderline256Color(ul.GetIndex()));
+        }
+        else if (ul.IsRgb())
+        {
+            RETURN_IF_FAILED(_SetGraphicsRenditionUnderlineRGBColor(ul.GetRGB()));
+        }
+        _lastTextAttributes.SetUnderlineColor(ul);
+    }
+
     return S_OK;
 }