Make 'current-fg' inherit from 'fg' to simplify configuration

If you do not want 'current-fg' to inherit attributes of 'fg', prefix it
with 'regular:' to reset them.

  # italic and underline
  fzf --color fg:italic,current-fg:underline

  # only underline
  fzf --color fg:italic,current-fg:regular:underline

src/tui/tcell.go

@@ -97,6 +97,7 @@ const (
 	AttrUndefined = Attr(0)
 	AttrRegular   = Attr(1 << 7)
 	AttrClear     = Attr(1 << 8)
+	BoldForce     = Attr(1 << 10)
 )
 
 func (r *FullscreenRenderer) PassThrough(str string) {
@@ -141,6 +142,11 @@ func (c Color) Style() tcell.Color {
 }
 
 func (a Attr) Merge(b Attr) Attr {
+	if b&AttrRegular > 0 {
+		// Only keep bold attribute set by the system
+		return b | (a & BoldForce)
+	}
+
 	return a | b
 }
 
@@ -556,13 +562,13 @@ func (r *FullscreenRenderer) NewWindow(top int, left int, width int, height int,
 	normal := ColBorder
 	switch windowType {
 	case WindowList:
-		normal = ColListBorder
+		normal = ColNormal
 	case WindowHeader:
-		normal = ColHeaderBorder
+		normal = ColHeader
 	case WindowInput:
-		normal = ColInputBorder
+		normal = ColInput
 	case WindowPreview:
-		normal = ColPreviewBorder
+		normal = ColPreview
 	}
 	w := &TcellWindow{
 		color:       r.theme.Colored,
@@ -694,7 +700,7 @@ func (w *TcellWindow) fillString(text string, pair ColorPair) FillReturn {
 	}
 	style = style.
 		Blink(a&Attr(tcell.AttrBlink) != 0).
-		Bold(a&Attr(tcell.AttrBold) != 0).
+		Bold(a&Attr(tcell.AttrBold) != 0 || a&BoldForce != 0).
 		Dim(a&Attr(tcell.AttrDim) != 0).
 		Reverse(a&Attr(tcell.AttrReverse) != 0).
 		Underline(a&Attr(tcell.AttrUnderline) != 0).