From 15d485cfb558f8ef64a865ec5f252aedb7835480 Mon Sep 17 00:00:00 2001
From: Garrett D'Amore <garrett@damore.org>
Date: Mon, 7 Jun 2021 12:58:03 -0700
Subject: [PATCH] Add a stdin version of Tty, and handle unset terminal sizes
 sanely.

---
 stdin_unix.go | 177 ++++++++++++++++++++++++++++++++++++++++++++++++++
 tty_unix.go   |  19 +++++-
 2 files changed, 195 insertions(+), 1 deletion(-)
 create mode 100644 stdin_unix.go

diff --git a/stdin_unix.go b/stdin_unix.go
new file mode 100644
index 0000000..e3d32e9
--- /dev/null
+++ b/stdin_unix.go
@@ -0,0 +1,177 @@
+// Copyright 2021 The TCell Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use file except in compliance with the License.
+// You may obtain a copy of the license at
+//
+//    http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// +build aix darwin dragonfly freebsd linux netbsd openbsd solaris zos
+
+package tcell
+
+import (
+	"errors"
+	"fmt"
+	"os"
+	"os/signal"
+	"strconv"
+	"sync"
+	"syscall"
+	"time"
+
+	"golang.org/x/term"
+)
+
+// stdIoTty is an implementation of the Tty API based upon stdin/stdout.
+type stdIoTty struct {
+	fd    int
+	in    *os.File
+	out   *os.File
+	saved *term.State
+	sig   chan os.Signal
+	cb    func()
+	stopQ chan struct{}
+	dev   string
+	wg    sync.WaitGroup
+	l     sync.Mutex
+}
+
+func (tty *stdIoTty) Read(b []byte) (int, error) {
+	return tty.in.Read(b)
+}
+
+func (tty *stdIoTty) Write(b []byte) (int, error) {
+	return tty.out.Write(b)
+}
+
+func (tty *stdIoTty) Close() error {
+	return nil
+}
+
+func (tty *stdIoTty) Start() error {
+	tty.l.Lock()
+	defer tty.l.Unlock()
+
+	// We open another copy of /dev/tty.  This is a workaround for unusual behavior
+	// observed in macOS, apparently caused when a subshell (for example) closes our
+	// own tty device (when it exits for example).  Getting a fresh new one seems to
+	// resolve the problem.  (We believe this is a bug in the macOS tty driver that
+	// fails to account for dup() references to the same file before applying close()
+	// related behaviors to the tty.)  We're also holding the original copy we opened
+	// since closing that might have deleterious effects as well.  The upshot is that
+	// we will have up to two separate file handles open on /dev/tty.  (Note that when
+	// using stdin/stdout instead of /dev/tty this problem is not observed.)
+	var err error
+	tty.in = os.Stdin
+	tty.out = os.Stdout
+	tty.fd = int(tty.in.Fd())
+
+	if !term.IsTerminal(tty.fd) {
+		return errors.New("device is not a terminal")
+	}
+
+	_ = tty.in.SetReadDeadline(time.Time{})
+	saved, err := term.MakeRaw(tty.fd) // also sets vMin and vTime
+	if err != nil {
+		return err
+	}
+	tty.saved = saved
+
+	tty.stopQ = make(chan struct{})
+	tty.wg.Add(1)
+	go func(stopQ chan struct{}) {
+		defer tty.wg.Done()
+		for {
+			select {
+			case <-tty.sig:
+				tty.l.Lock()
+				cb := tty.cb
+				tty.l.Unlock()
+				if cb != nil {
+					cb()
+				}
+			case <-stopQ:
+				return
+			}
+		}
+	}(tty.stopQ)
+
+	signal.Notify(tty.sig, syscall.SIGWINCH)
+	return nil
+}
+
+func (tty *stdIoTty) Drain() error {
+	_ = tty.in.SetReadDeadline(time.Now())
+	if err := tcSetBufParams(tty.fd, 0, 0); err != nil {
+		return err
+	}
+	return nil
+}
+
+func (tty *stdIoTty) Stop() error {
+	tty.l.Lock()
+	if err := term.Restore(tty.fd, tty.saved); err != nil {
+		tty.l.Unlock()
+		return err
+	}
+	_ = tty.in.SetReadDeadline(time.Now())
+
+	signal.Stop(tty.sig)
+	close(tty.stopQ)
+	tty.l.Unlock()
+
+	tty.wg.Wait()
+
+	return nil
+}
+
+func (tty *stdIoTty) WindowSize() (int, int, error) {
+	w, h, err := term.GetSize(tty.fd)
+	if err != nil {
+		return 0, 0, err
+	}
+	if w == 0 {
+		w, _ = strconv.Atoi(os.Getenv("COLUMNS"))
+	}
+	if w == 0 {
+		w = 80 // default
+	}
+	if h == 0 {
+		h, _ = strconv.Atoi(os.Getenv("LINES"))
+	}
+	if h == 0 {
+		h = 25 // default
+	}
+	return w, h, nil
+}
+
+func (tty *stdIoTty) NotifyResize(cb func()) {
+	tty.l.Lock()
+	tty.cb = cb
+	tty.l.Unlock()
+}
+
+// NewStdioTty opens a tty using standard input/output.
+func NewStdIoTty() (Tty, error) {
+	tty := &stdIoTty{
+		sig: make(chan os.Signal),
+		in: os.Stdin,
+		out: os.Stdout,
+	}
+	var err error
+	tty.fd = int(tty.in.Fd())
+	if !term.IsTerminal(tty.fd) {
+		return nil, errors.New("not a terminal")
+	}
+	if tty.saved, err = term.GetState(tty.fd); err != nil {
+		return nil, fmt.Errorf("failed to get state: %w", err)
+	}
+	return tty, nil
+}
diff --git a/tty_unix.go b/tty_unix.go
index a48b2e6..71b1e7a 100644
--- a/tty_unix.go
+++ b/tty_unix.go
@@ -21,6 +21,7 @@ import (
 	"fmt"
 	"os"
 	"os/signal"
+	"strconv"
 	"sync"
 	"syscall"
 	"time"
@@ -136,7 +137,23 @@ func (tty *devTty) Stop() error {
 }
 
 func (tty *devTty) WindowSize() (int, int, error) {
-	return term.GetSize(tty.fd)
+	w, h, err := term.GetSize(tty.fd)
+	if err != nil {
+		return 0, 0, err
+	}
+	if w == 0 {
+		w, _ = strconv.Atoi(os.Getenv("COLUMNS"))
+	}
+	if w == 0 {
+		w = 80 // default
+	}
+	if h == 0 {
+		h, _ = strconv.Atoi(os.Getenv("LINES"))
+	}
+	if h == 0 {
+		h = 25 // default
+	}
+	return w, h, nil
 }
 
 func (tty *devTty) NotifyResize(cb func()) {