diff kitten: Abort when run inside a terminal that does not support the kitty keyboard protocol

Fixes #8185

docs/changelog.rst

@@ -93,6 +93,8 @@ Detailed list of changes
 
 - ssh kitten: Fix kitten not being on PATH when SSHing into Debian systems (:iss:`7160`)
 
+- diff kitten: Abort when run inside a terminal that does not support the kitty keyboard protocol (:iss:`8185`)
+
 0.38.1 [2024-12-26]
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 

kittens/diff/main.go

@@ -146,9 +146,16 @@ func main(_ *cli.Command, opts_ *Options, args []string) (rc int, err error) {
 		lp.SetCursorShape(loop.BAR_CURSOR, true)
 		lp.AllowLineWrapping(false)
 		lp.SetWindowTitle(fmt.Sprintf("%s vs. %s", left, right))
+		lp.QueryCapabilities()
 		h.initialize()
 		return "", nil
 	}
+	lp.OnCapabilitiesReceived = func(tc loop.TerminalCapabilities) error {
+		if !tc.KeyboardProtocol {
+			return fmt.Errorf("This terminal does not support the kitty keyboard protocol, or you are running inside a terminal multiplexer that is blocking querying for kitty keyboard protocol support. The diff kitten cannot function without it.")
+		}
+		return nil
+	}
 	lp.OnWakeup = h.on_wakeup
 	lp.OnFinalize = func() string {
 		lp.SetCursorVisible(true)

tools/tui/loop/api.go

@@ -117,7 +117,7 @@ type Loop struct {
 	OnSIGTERM func() (bool, error)
 
 	// Called when capabilities response is received
-	OnCapabilitiesReceived func(TerminalCapabilities)
+	OnCapabilitiesReceived func(TerminalCapabilities) error
 }
 
 func New(options ...func(self *Loop)) (*Loop, error) {

tools/tui/loop/run.go

@@ -128,7 +128,9 @@ func (self *Loop) handle_csi(raw []byte) (err error) {
 		if strings.HasPrefix(csi, "?") && strings.HasSuffix(csi, "c") {
 			self.waiting_for_capabilities_response = false
 			if self.OnCapabilitiesReceived != nil {
-				self.OnCapabilitiesReceived(self.TerminalCapabilities)
+				if err = self.OnCapabilitiesReceived(self.TerminalCapabilities); err != nil {
+					return err
+				}
 			}
 		} else if strings.HasPrefix(csi, "?997;") && strings.HasSuffix(csi, "n") {
 			switch csi[len(csi)-2] {