Add an auto-measure toggle with a cable length range, and console keys through the harness

input.go

@@ -160,11 +160,11 @@ func watchTouch(w, h int) (*touchState, error) {
 	return state, nil
 }
 
-// Delivers a value every time space is pressed. Puts the terminal in
-// non-canonical mode so the keypress arrives without waiting for a newline,
-// and returns a function that restores the original settings.
-func watchSpace() (<-chan struct{}, func()) {
-	ch := make(chan struct{}, 1)
+// Delivers each key as it is pressed. Puts the terminal in non-canonical mode
+// so keypresses arrive without waiting for a newline, and returns a function
+// that restores the original settings.
+func watchKeys() (<-chan byte, func()) {
+	ch := make(chan byte, 8)
 	restore := func() {}
 	fd := int(os.Stdin.Fd())
 
@@ -187,11 +187,8 @@ func watchSpace() (<-chan struct{}, func()) {
 				return
 			}
 			for _, b := range buf[:n] {
-				if b != ' ' {
-					continue
-				}
 				select {
-				case ch <- struct{}{}:
+				case ch <- b:
 				default:
 				}
 			}