feat(screen): add SetForegroundColor and SetBackgroundColor

screen.go

@@ -240,6 +240,20 @@ type Screen interface {
 	// the results may vary.  Use of unicode characters may not be supported.
 	SetTitle(string)
 
+	// SetForegroundColor sets the terminal's default foreground color, which
+	// text without a color of its own is drawn in. An invalid color, such as
+	// color.Default, restores the terminal's own. Tcell restores it when the
+	// screen is finalized or suspended, and sets it again on resume.
+	// Terminals may ignore this.
+	SetForegroundColor(color.Color)
+
+	// SetBackgroundColor sets the terminal's default background color, which
+	// cells without a color of their own are drawn in. An invalid color, such as
+	// color.Default, restores the terminal's own. Tcell restores it when the
+	// screen is finalized or suspended, and sets it again on resume.
+	// Terminals may ignore this.
+	SetBackgroundColor(color.Color)
+
 	// SetClipboard is used to post arbitrary data to the system clipboard.
 	// This need not be UTF-8 string data.  It's up to the recipient to decode the
 	// data meaningfully.  Terminals may prevent this for security reasons.
@@ -366,6 +380,8 @@ type screenImpl interface {
 	Resume() error
 	Beep() error
 	SetSize(int, int)
+	SetForegroundColor(color.Color)
+	SetBackgroundColor(color.Color)
 	SetTitle(string)
 	Tty() (Tty, bool)
 	SetClipboard([]byte)

tscreen.go

@@ -195,6 +195,10 @@ const (
 	exitKeypad        = "\x1b[?1l\x1b>"               // Also mode 1
 	requestWindowSize = "\x1b[18t"                    // For modern terminals
 	requestPixelSize  = "\x1b[14t"                    // Text area in pixels, for when the tty does not know it
+	setForeground     = "\x1b]10;#%02x%02x%02x\007"   // Set the terminal's default foreground
+	setBackground     = "\x1b]11;#%02x%02x%02x\007"   // Set the terminal's default background
+	resetForeground   = "\x1b]110\007"                // Restore the terminal's default foreground
+	resetBackground   = "\x1b]111\007"                // Restore the terminal's default background
 	requestPrimaryDA  = "\x1b[c"                      // Request primary device attributes
 	requestExtAttr    = "\x1b[>q"                     // Request extended attribute (emulator name and version)
 	setClipboard      = "\x1b]52;c;%s\x1b\\"          // Clipboard content is base64
@@ -293,6 +297,8 @@ type tScreen struct {
 	saveTitle          string
 	restoreTitle       string
 	title              string
+	foreground         color.Color // the terminal's default foreground, if valid
+	background         color.Color // the terminal's default background, if valid
 	setClipboard       string
 	notifyDesktop      string
 	termName           string
@@ -1800,6 +1806,8 @@ func (t *tScreen) engageLocked() error {
 	if t.title != "" && t.setTitle != "" {
 		t.Printf(t.setTitle, t.title)
 	}
+	t.printColor(setForeground, t.foreground)
+	t.printColor(setBackground, t.background)
 	if t.negotiate && !t.legacy && useVTWindowSizeQuery(runtime.GOOS) {
 		t.Print(requestWindowSize)
 	}
@@ -1836,6 +1844,13 @@ func (t *tScreen) disengageStart() bool {
 	}
 
 	t.running = false
+	// Reset the colors now, as setters stop writing them once we are not running.
+	if t.foreground.Valid() {
+		t.Print(resetForeground)
+	}
+	if t.background.Valid() {
+		t.Print(resetBackground)
+	}
 	if t.inlineResize {
 		t.Print(vt.PmResizeReports.Disable())
 	} else {
@@ -1925,6 +1940,41 @@ func (t *tScreen) GetCells() *CellBuffer {
 	return &t.cells
 }
 
+func (t *tScreen) SetForegroundColor(c color.Color) {
+	t.setColor(&t.foreground, c, setForeground, resetForeground)
+}
+
+func (t *tScreen) SetBackgroundColor(c color.Color) {
+	t.setColor(&t.background, c, setBackground, resetBackground)
+}
+
+// setColor stores c in dst, and sends it with set, or reset if it is invalid, while running.
+func (t *tScreen) setColor(dst *color.Color, c color.Color, set, reset string) {
+	t.Lock()
+	defer t.Unlock()
+	if t.fini {
+		return
+	}
+	old := *dst
+	*dst = c
+	if !t.running {
+		return
+	}
+	if c.Valid() {
+		t.printColor(set, c)
+	} else if old.Valid() {
+		t.Print(reset)
+	}
+}
+
+// printColor prints c with set, if it is valid.
+func (t *tScreen) printColor(set string, c color.Color) {
+	if c.Valid() {
+		r, g, b := c.RGB()
+		t.Printf(set, r, g, b)
+	}
+}
+
 func (t *tScreen) SetTitle(title string) {
 	t.Lock()
 	if t.fini {

tscreen_test.go

@@ -16,6 +16,7 @@ package tcell
 
 import (
 	"bytes"
+	"fmt"
 	"runtime"
 	"strings"
 	"sync"
@@ -1890,3 +1891,126 @@ func TestMouseDisabledPreventsNativeConsoleMouse(t *testing.T) {
 		t.Fatalf("native console mouse started despite TCELL_MOUSE=disable")
 	}
 }
+
+// TestDefaultColorSequences pins the xterm sequences the other default color tests use.
+func TestDefaultColorSequences(t *testing.T) {
+	for _, c := range []struct{ got, want string }{
+		{fmt.Sprintf(setForeground, 0xc0, 0xca, 0xf5), "\x1b]10;#c0caf5\x07"},
+		{fmt.Sprintf(setBackground, 0x1a, 0x1b, 0x26), "\x1b]11;#1a1b26\x07"},
+		{resetForeground, "\x1b]110\x07"},
+		{resetBackground, "\x1b]111\x07"},
+	} {
+		if c.got != c.want {
+			t.Errorf("got %q, want %q", c.got, c.want)
+		}
+	}
+}
+
+func TestDefaultColors(t *testing.T) {
+	tty := &spyTty{MockTerm: vt.NewMockTerm()}
+	scr, err := NewTerminfoScreenFromTty(tty)
+	if err != nil {
+		t.Fatalf("failed to get screen: %v", err)
+	}
+	if err := scr.Init(); err != nil {
+		t.Fatalf("failed to initialize screen: %v", err)
+	}
+
+	setFg := fmt.Sprintf(setForeground, 0xc0, 0xca, 0xf5)
+	setBg := fmt.Sprintf(setBackground, 0x1a, 0x1b, 0x26)
+	// written returns what step wrote to the terminal.
+	written := func(step func()) string {
+		before := len(tty.Output())
+		step()
+		return tty.Output()[before:]
+	}
+	expect := func(t *testing.T, got string, want ...string) {
+		t.Helper()
+		for _, w := range want {
+			if !strings.Contains(got, w) {
+				t.Fatalf("%q not written, got %q", w, got)
+			}
+		}
+	}
+
+	t.Run("set", func(t *testing.T) {
+		expect(t, written(func() {
+			scr.SetForegroundColor(NewHexColor(0xc0caf5))
+			scr.SetBackgroundColor(NewHexColor(0x1a1b26))
+		}), setFg, setBg)
+	})
+	t.Run("restored while suspended", func(t *testing.T) {
+		expect(t, written(func() { _ = scr.Suspend() }), resetForeground, resetBackground)
+		expect(t, written(func() { _ = scr.Resume() }), setFg, setBg)
+	})
+	t.Run("reset", func(t *testing.T) {
+		expect(t, written(func() { scr.SetForegroundColor(ColorDefault) }), resetForeground)
+		if got := written(scr.Fini); strings.Contains(got, resetForeground) || !strings.Contains(got, resetBackground) {
+			t.Fatalf("Fini wrote %q, want only the background restored", got)
+		}
+	})
+}
+
+// pausingTty blocks the first write that contains pause, once armed, until released.
+type pausingTty struct {
+	spyTty
+	mu      sync.Mutex
+	pause   string
+	paused  chan struct{}
+	release chan struct{}
+}
+
+func (t *pausingTty) Write(b []byte) (int, error) {
+	t.mu.Lock()
+	hit := t.pause != "" && strings.Contains(string(b), t.pause)
+	if hit {
+		t.pause = ""
+	}
+	t.mu.Unlock()
+	if hit {
+		close(t.paused)
+		<-t.release
+	}
+	return t.spyTty.Write(b)
+}
+
+func TestDefaultColorResetDuringSuspend(t *testing.T) {
+	tty := &pausingTty{
+		spyTty:  spyTty{MockTerm: vt.NewMockTerm()},
+		paused:  make(chan struct{}),
+		release: make(chan struct{}),
+	}
+	scr, err := NewTerminfoScreenFromTty(tty)
+	if err != nil {
+		t.Fatalf("failed to get screen: %v", err)
+	}
+	if err := scr.Init(); err != nil {
+		t.Fatalf("failed to initialize screen: %v", err)
+	}
+	defer scr.Fini()
+
+	scr.SetForegroundColor(NewHexColor(0xc0caf5))
+	before := len(tty.Output())
+
+	// Pause Suspend after it has stopped running, but before it restores the terminal.
+	tty.mu.Lock()
+	tty.pause = vt.PmShowCursor.Enable()
+	tty.mu.Unlock()
+	done := make(chan struct{})
+	go func() {
+		_ = scr.Suspend()
+		close(done)
+	}()
+	select {
+	case <-tty.paused:
+	case <-time.After(5 * time.Second):
+		t.Fatal("Suspend did not reach the terminal restore")
+	}
+	scr.SetForegroundColor(ColorDefault)
+	close(tty.release)
+	<-done
+
+	if got := tty.Output()[before:]; !strings.Contains(got, resetForeground) {
+		t.Fatalf("foreground was never restored, got %q", got)
+	}
+}