Support rendering of underline style and color

src/renderer/gdi/gdirenderer.hpp

@@ -121,7 +121,7 @@ namespace Microsoft::Console::Render
             int underlineWidth;
             int strikethroughOffset;
             int strikethroughWidth;
-            int curlylineHeight;
+            int curlylinePeakHeight;
         };
 
         LineMetrics _lineMetrics;

src/renderer/gdi/paint.cpp

@@ -525,6 +525,7 @@ bool GdiEngine::FontHasWesternScript(HDC hdc)
     wil::unique_hbrush hbr(CreateSolidBrush(gridlineColor));
     RETURN_HR_IF_NULL(E_FAIL, hbr.get());
 
+    // TODO: hbrPrev shouldn't be managed.
     wil::unique_hbrush hbrPrev(SelectBrush(_hdcMemoryContext, hbr.get()));
     RETURN_HR_IF_NULL(E_FAIL, hbrPrev.get());
     hbr.release(); // If SelectBrush was successful, GDI owns the brush. Release for now.
@@ -560,8 +561,8 @@ bool GdiEngine::FontHasWesternScript(HDC hdc)
     };
     const auto DrawCurlyLine = [&](const auto x, const auto y, const auto cCurlyLines) {
         const auto curlyLineWidth = fontWidth;
-        const auto curlyLineHalfWidth = gsl::narrow_cast<long>(std::floor(curlyLineWidth / 2));
-        const auto controlPointHeight = gsl::narrow_cast<long>(std::floor(3.5f * _lineMetrics.curlylineHeight));
+        const auto curlyLineHalfWidth = lrintf(curlyLineWidth / 2.0f);
+        const auto controlPointHeight = gsl::narrow_cast<long>(std::floor(3.5f * _lineMetrics.curlylinePeakHeight));
         // Each curlyLine requires 3 `POINT`s
         const auto cPoints = gsl::narrow<DWORD>(3 * cCurlyLines);
         std::vector<POINT> points;
@@ -626,28 +627,28 @@ bool GdiEngine::FontHasWesternScript(HDC hdc)
     hpen.release();
     const auto restorePenOnExit = wil::scope_exit([&] { hpen.reset(SelectPen(_hdcMemoryContext, prevPen)); });
 
-    const auto underlineY = std::lround(ptTarget.y + _lineMetrics.underlineOffset + _lineMetrics.underlineWidth / 2.0f);
+    const auto underlineMidY = std::lround(ptTarget.y + _lineMetrics.underlineOffset + _lineMetrics.underlineWidth / 2.0f);
     if (lines.test(GridLines::Underline))
     {
-        return DrawStrokedLine(ptTarget.x, underlineY, widthOfAllCells);
+        return DrawStrokedLine(ptTarget.x, underlineMidY, widthOfAllCells);
     }
     else if (lines.test(GridLines::DoubleUnderline))
     {
-        const auto doubleUnderlineBottomLineY = std::lround(ptTarget.y + _lineMetrics.underlineOffset2 + _lineMetrics.underlineWidth / 2.0f);
-        RETURN_IF_FAILED(DrawStrokedLine(ptTarget.x, underlineY, widthOfAllCells));
-        return DrawStrokedLine(ptTarget.x, doubleUnderlineBottomLineY, widthOfAllCells);
+        const auto doubleUnderlineBottomLineMidY = std::lround(ptTarget.y + _lineMetrics.underlineOffset2 + _lineMetrics.underlineWidth / 2.0f);
+        RETURN_IF_FAILED(DrawStrokedLine(ptTarget.x, underlineMidY, widthOfAllCells));
+        return DrawStrokedLine(ptTarget.x, doubleUnderlineBottomLineMidY, widthOfAllCells);
     }
     else if (lines.test(GridLines::CurlyUnderline))
     {
-        return DrawCurlyLine(ptTarget.x, underlineY, cchLine);
+        return DrawCurlyLine(ptTarget.x, underlineMidY, cchLine);
     }
     else if (lines.test(GridLines::DottedUnderline))
     {
-        return DrawStrokedLine(ptTarget.x, underlineY, widthOfAllCells);
+        return DrawStrokedLine(ptTarget.x, underlineMidY, widthOfAllCells);
     }
     else if (lines.test(GridLines::DashedUnderline))
     {
-        return DrawStrokedLine(ptTarget.x, underlineY, widthOfAllCells);
+        return DrawStrokedLine(ptTarget.x, underlineMidY, widthOfAllCells);
     }
 
     return S_OK;

src/renderer/gdi/state.cpp

@@ -11,6 +11,15 @@
 
 using namespace Microsoft::Console::Render;
 
+namespace
+{
+    // The max height of Curly line peak in `em` units.
+    constexpr auto MaxCurlyLinePeakHeightEm = 0.075f;
+
+    // The min height of Curly line peak.
+    constexpr auto MinCurlyLinePeakHeight = 2.0f;
+}
+
 // Routine Description:
 // - Creates a new GDI-based rendering engine
 // - NOTE: Will throw if initialization failure. Caller must catch.
@@ -397,18 +406,29 @@ GdiEngine::~GdiEngine()
         _lineMetrics.underlineOffset2 = _lineMetrics.underlineOffset - _lineMetrics.gridlineWidth;
     }
 
-    _lineMetrics.curlylineHeight = gsl::narrow_cast<int>(std::lround(fontSize * 0.07f));
-    // We need to lower the curly line height incase the gap between the underline
-    // and cell bottom isn't enough. Curly-line is a stroked line so we account
-    // for that as well.
-    const auto maxCurlyLineHeight = gsl::narrow_cast<int>(std::floor(Font.GetSize().height - (_lineMetrics.underlineOffset + _lineMetrics.underlineWidth)));
-    if (maxCurlyLineHeight <= 1) // too small to be curly, make it a straight line instead.
+    // Curly line doesn't render properly below 1px stroke width. Make it a straight line.
+    if (_lineMetrics.underlineWidth < 1)
     {
-        _lineMetrics.curlylineHeight = 0;
+        _lineMetrics.curlylinePeakHeight = 0;
     }
     else
     {
-        _lineMetrics.curlylineHeight = std::min(maxCurlyLineHeight, _lineMetrics.curlylineHeight);
+        // Curlyline uses the gap between cell bottom and singly underline
+        // position as the height of the wave's peak. The baseline for curly
+        // line is at the middle of singly underline. The gap could be too big,
+        // so we also apply a limit on the peak height.
+        const auto strokeHalfWidth = _lineMetrics.underlineWidth / 2.0f;
+        const auto underlineMidY = _lineMetrics.underlineOffset + strokeHalfWidth;
+        const auto cellBottomGap = Font.GetSize().height - underlineMidY - strokeHalfWidth;
+        const auto maxCurlyLinePeakHeight = MaxCurlyLinePeakHeightEm * fontSize;
+        auto curlyLinePeakHeight = std::min(cellBottomGap, maxCurlyLinePeakHeight);
+
+        // When it's too small to be curly, make it a straight line.
+        if (curlyLinePeakHeight < MinCurlyLinePeakHeight)
+        {
+            curlyLinePeakHeight = 0.0f;
+        }
+        _lineMetrics.curlylinePeakHeight = gsl::narrow_cast<int>(std::floor(curlyLinePeakHeight));
     }
 
     // Now find the size of a 0 in this current font and save it for conversions done later.