Implement Marcin Bulandra's suggestion of only automatically updating the

port number in the GUI when the connection type is changed if the current
port number is the standard one for the current protocol.
It's not perfect, but it should make the common case of tabbing through the
Session panel easier when starting non-SSH connections on odd ports.

[originally from svn r7635]

config.c

@@ -90,7 +90,7 @@ struct hostport {
 void config_protocolbuttons_handler(union control *ctrl, void *dlg,
 				    void *data, int event)
 {
-    int button, defport;
+    int button;
     Config *cfg = (Config *)data;
     struct hostport *hp = (struct hostport *)ctrl->radio.context.p;
 
@@ -114,15 +114,20 @@ void config_protocolbuttons_handler(union control *ctrl, void *dlg,
 	assert(button >= 0 && button < ctrl->radio.nbuttons);
 	cfg->protocol = ctrl->radio.buttondata[button].i;
 	if (oldproto != cfg->protocol) {
-	    defport = -1;
-	    switch (cfg->protocol) {
-	      case PROT_SSH: defport = 22; break;
-	      case PROT_TELNET: defport = 23; break;
-	      case PROT_RLOGIN: defport = 513; break;
-	    }
-	    if (defport > 0 && cfg->port != defport) {
-		cfg->port = defport;
-	    }
+	    Backend *ob = backend_from_proto(oldproto);
+	    Backend *nb = backend_from_proto(cfg->protocol);
+	    assert(ob);
+	    assert(nb);
+	    /* Iff the user hasn't changed the port from the protocol
+	     * default (if any), update it with the new protocol's
+	     * default.
+	     * (XXX: this isn't perfect; a default can become permanent
+	     * by going via the serial backend. However, it helps with
+	     * the common case of tabbing through the controls in order
+	     * and setting a non-default port.) */
+	    if (cfg->port == ob->default_port &&
+		cfg->port > 0 && nb->default_port > 0)
+		cfg->port = nb->default_port;
 	}
 	dlg_refresh(hp->host, dlg);
 	dlg_refresh(hp->port, dlg);

raw.c

@@ -280,5 +280,5 @@ Backend raw_backend = {
     raw_cfg_info,
     "raw",
     PROT_RAW,
-    1
+    0
 };

rlogin.c

@@ -351,5 +351,5 @@ Backend rlogin_backend = {
     rlogin_cfg_info,
     "rlogin",
     PROT_RLOGIN,
-    1
+    513
 };

unix/uxpty.c

@@ -1087,5 +1087,5 @@ Backend pty_backend = {
     pty_cfg_info,
     "pty",
     -1,
-    1
+    0
 };

unix/uxser.c

@@ -538,5 +538,5 @@ Backend serial_backend = {
     serial_cfg_info,
     "serial",
     PROT_SERIAL,
-    1
+    0
 };

windows/winser.c

@@ -456,5 +456,5 @@ Backend serial_backend = {
     serial_cfg_info,
     "serial",
     PROT_SERIAL,
-    1
+    0
 };