React when the client's window is smaller than the remote one

client.go

@@ -2,30 +2,44 @@ package main
 
 import (
 	"encoding/json"
+	"fmt"
 	"io"
 	"net/http"
 	"net/url"
 	"os"
-	"fmt"
+	"os/signal"
+	"sync"
+	"sync/atomic"
+	"syscall"
 
 	ttyServer "github.com/elisescu/tty-share/server"
 	"github.com/gorilla/websocket"
 	"github.com/moby/term"
 	log "github.com/sirupsen/logrus"
-	"golang.org/x/crypto/ssh/terminal"
 )
 
 type ttyShareClient struct {
-	url         string
-	connection  *websocket.Conn
+	url        string
+	connection *websocket.Conn
 	detachKeys string
+	wcChan     chan os.Signal
+	writeFlag  uint32 // used with atomic
+	winSizes   struct {
+		thisW   uint16
+		thisH   uint16
+		remoteW uint16
+		remoteH uint16
+	}
+	winSizesMutex sync.Mutex
 }
 
 func newTtyShareClient(url string, detachKeys string) *ttyShareClient {
 	return &ttyShareClient{
-		url:         url,
-		connection:  nil,
+		url:        url,
+		connection: nil,
 		detachKeys: detachKeys,
+		wcChan:     make(chan os.Signal, 1),
+		writeFlag:  1,
 	}
 }
 
@@ -37,7 +51,6 @@ type wsTextWriter struct {
 	conn *websocket.Conn
 }
 
-
 func (w *wsTextWriter) Write(data []byte) (n int, err error) {
 	err = w.conn.WriteMessage(websocket.TextMessage, data)
 	return len(data), err
@@ -55,6 +68,33 @@ func (kl *keyListener) Read(data []byte) (n int, err error) {
 	return
 }
 
+func (c *ttyShareClient) updateAndDecideStdoutMuted() {
+	log.Infof("This window: %dx%d. Remote window: %dx%d", c.winSizes.thisW, c.winSizes.thisH, c.winSizes.remoteW, c.winSizes.remoteH)
+
+	if c.winSizes.thisH < c.winSizes.remoteH || c.winSizes.thisW < c.winSizes.remoteW {
+		atomic.StoreUint32(&c.writeFlag, 0)
+		clearScreen()
+		fmt.Printf("\r\n\nYour terminal window has to be bigger than %dx%d\r\nDetach with <%s>, resize your window, and reconect.\r\n",
+			c.winSizes.remoteW, c.winSizes.remoteH, c.detachKeys)
+	} else {
+		if atomic.LoadUint32(&c.writeFlag) == 0 { // clear the screen when changing back to "write"
+			// TODO: notify the remote side to "refresh" the content.
+			clearScreen()
+		}
+		atomic.StoreUint32(&c.writeFlag, 1)
+	}
+}
+
+func (c *ttyShareClient) updateThisWinSize() {
+	size, err := term.GetWinsize(os.Stdin.Fd())
+	if err == nil {
+		c.winSizesMutex.Lock()
+		c.winSizes.thisW = size.Width
+		c.winSizes.thisH = size.Height
+		c.winSizesMutex.Unlock()
+	}
+}
+
 func (c *ttyShareClient) Run() (err error) {
 	log.Debugf("Connecting as a client to %s ..", c.url)
 
@@ -91,12 +131,26 @@ func (c *ttyShareClient) Run() (err error) {
 		return
 	}
 
-	state, err := terminal.MakeRaw(0)
-	defer terminal.Restore(0, state)
+	state, err := term.MakeRaw(os.Stdin.Fd())
+	defer term.RestoreTerminal(os.Stdin.Fd(), state)
 
 	c.connection = conn
-	// Clear the screen before processing any incoming data
+
 	clearScreen()
+	// start monitoring the size of the terminal
+	signal.Notify(c.wcChan, syscall.SIGWINCH)
+	defer signal.Stop(c.wcChan)
+
+	monitorWinChanges := func() {
+		for {
+			select {
+			case <-c.wcChan:
+				log.Debugf("Detected new win size")
+				c.updateThisWinSize()
+				c.updateAndDecideStdoutMuted()
+			}
+		}
+	}
 
 	readLoop := func() {
 		for {
@@ -120,15 +174,21 @@ func (c *ttyShareClient) Run() (err error) {
 					log.Errorf("Cannot read JSON: %s", err.Error())
 				}
 
-				os.Stdout.Write(msgWrite.Data)
+				if atomic.LoadUint32(&c.writeFlag) != 0 {
+					os.Stdout.Write(msgWrite.Data)
+				}
 			case ttyServer.MsgIDWinSize:
-				log.Infof("Remote window changed its size")
-				// We ignore the window size changes - can't do much about that for
-				// now.
-
-				// TODO: Maybe just clear the screen, and display an error message
-				// if the remote window gets bigger than this terminal window - when
-				// it does, it usually messes up the output
+				var msgRemoteWinSize ttyServer.MsgTTYWinSize
+				err := json.Unmarshal(msg.Data, &msgRemoteWinSize)
+				if err != nil {
+					continue
+				}
+				c.winSizesMutex.Lock()
+				c.winSizes.remoteW = uint16(msgRemoteWinSize.Cols)
+				c.winSizes.remoteH = uint16(msgRemoteWinSize.Rows)
+				c.winSizesMutex.Unlock()
+				c.updateThisWinSize()
+				c.updateAndDecideStdoutMuted()
 			}
 		}
 	}
@@ -148,8 +208,11 @@ func (c *ttyShareClient) Run() (err error) {
 			return
 		}
 	}
+
+	go monitorWinChanges()
 	go writeLoop()
 	readLoop()
+
 	clearScreen()
 	return
 }