v0.4.0 terminal over caller's backend

README.md

@@ -35,6 +35,11 @@ consoles with VT processing, and browsers via xterm.js (WASM builds).
 Shared code carries no build tags: cell diffing, ANSI generation, escape parsing.
 Platform specifics are isolated in the `Backend` implementations.
 
+`NewWithBackend(b, mode)` builds a Terminal over a `Backend` of the caller's
+own: a pipe, an in-process emulator or a test standing in for the tty. It
+behaves as `New`'s Terminal does, the writer goroutine included; `New` is
+`NewWithBackend` over the platform's backend and the detected color mode.
+
 ### Rendering pipeline
 
 The application owns a flat `[]Cell` buffer (row-major, `cells[y*width+x]`) and

terminal.go

@@ -156,6 +156,14 @@ func New(colorMode ...ColorMode) Terminal {
 		c = ColorModeNone
 	}
 
+	return NewWithBackend(b, c)
+}
+
+// NewWithBackend creates a Terminal over b in color mode c, for a pipe, an
+// in-process emulator or a test standing in for the tty. b must not be nil;
+// the Terminal calls its Init on Init and its Fini on Fini, and writes to it
+// on its own goroutine as New's does
+func NewWithBackend(b Backend, c ColorMode) Terminal {
 	return newTerm(b, c)
 }
 

terminal_test.go

@@ -376,3 +376,18 @@ func waitFor(t *testing.T, what string, ok func() bool) {
 		time.Sleep(time.Millisecond)
 	}
 }
+
+// A Terminal built over a caller's backend draws a flushed frame to it
+func TestNewWithBackendFlushesToTheBackend(t *testing.T) {
+	f := &fakeBackend{}
+	term := NewWithBackend(f, ColorMode256)
+	if err := term.Init(); err != nil {
+		t.Fatal(err)
+	}
+	defer term.Fini()
+	if term.ColorMode() != ColorMode256 {
+		t.Fatalf("color mode %v", term.ColorMode())
+	}
+	term.Flush([]Cell{{Rune: 'x'}}, 1, 1)
+	waitFor(t, "the frame to reach the backend", func() bool { return strings.Contains(f.written(), "x") })
+}