add tcell's dim text style

cell/cell.go

@@ -31,6 +31,7 @@ type Options struct {
 	Strikethrough bool
 	Inverse       bool
 	Blink         bool
+	Dim           bool
 }
 
 // Set allows existing options to be passed as an option.
@@ -110,3 +111,10 @@ func Blink() Option {
 		co.Blink = true
 	})
 }
+
+// Dim makes the cell foreground color dim. Only works when using the tcell backend.
+func Dim() Option {
+	return option(func(co *Options) {
+		co.Dim = true
+	})
+}

cell/cell_test.go

@@ -82,6 +82,7 @@ func TestNewOptions(t *testing.T) {
 				Strikethrough(),
 				Inverse(),
 				Blink(),
+				Dim(),
 			},
 			want: &Options{
 				Bold:          true,
@@ -90,6 +91,7 @@ func TestNewOptions(t *testing.T) {
 				Strikethrough: true,
 				Inverse:       true,
 				Blink:         true,
+				Dim:           true,
 			},
 		},
 	}

terminal/tcell/cell_options.go

@@ -70,6 +70,7 @@ func cellOptsToStyle(opts *cell.Options, colorMode terminalapi.ColorMode) tcell.
 		Underline(opts.Underline).
 		StrikeThrough(opts.Strikethrough).
 		Reverse(opts.Inverse).
-		Blink(opts.Blink)
+		Blink(opts.Blink).
+		Dim(opts.Dim)
 	return st
 }

terminal/tcell/cell_options_test.go

@@ -325,6 +325,11 @@ func TestCellOptsToStyle(t *testing.T) {
 			opts:      cell.Options{Blink: true},
 			want:      tcell.StyleDefault.Blink(true),
 		},
+		{
+			colorMode: terminalapi.ColorModeNormal,
+			opts:      cell.Options{Dim: true},
+			want:      tcell.StyleDefault.Dim(true),
+		},
 	}
 
 	for _, tc := range tests {

terminal/termbox/cell_options.go

@@ -67,6 +67,11 @@ func cellOptsToFg(opts *cell.Options) (tbx.Attribute, error) {
 	if opts.Blink {
 		return 0, errors.New("Termbox: Unsupported attribute: Blink")
 	}
+
+	if opts.Dim {
+		return 0, errors.New("Termbox: Unsupported attribute: Dim")
+	}
+
 	return a, nil
 }
 

terminal/termbox/cell_options_test.go

@@ -62,6 +62,7 @@ func TestCellFontModifier(t *testing.T) {
 		{cell.Options{Strikethrough: true}, 0, true},
 		{cell.Options{Inverse: true}, tbx.AttrReverse, false},
 		{cell.Options{Blink: true}, 0, true},
+		{cell.Options{Dim: true}, 0, true},
 	}
 
 	for _, tc := range tests {