New backend function to disable resizing.

Some protocols such as SUPDUP does not support resizing the terminal.

config.c

@@ -1472,6 +1472,7 @@ static void clipboard_control(struct controlset *s, const char *label,
 void setup_config_box(struct controlbox *b, bool midsession,
                       int protocol, int protcfginfo)
 {
+    const struct BackendVtable *backvt;
     struct controlset *s;
     struct sessionsaver_data *ssd;
     struct charclass_data *ccd;
@@ -1481,6 +1482,7 @@ void setup_config_box(struct controlbox *b, bool midsession,
     struct portfwd_data *pfd;
     struct manual_hostkey_data *mh;
     union control *c;
+    bool resize_forbidden = false;
     char *str;
 
     ssd = (struct sessionsaver_data *)
@@ -1864,17 +1866,23 @@ void setup_config_box(struct controlbox *b, bool midsession,
     ctrl_settitle(b, "Window", str);
     sfree(str);
 
-    s = ctrl_getset(b, "Window", "size", "Set the size of the window");
+    backvt = backend_vt_from_proto(protocol);
-    ctrl_columns(s, 2, 50, 50);
+    if (backvt)
-    c = ctrl_editbox(s, "Columns", 'm', 100,
+        resize_forbidden = (backvt->flags & BACKEND_RESIZE_FORBIDDEN);
-                     HELPCTX(window_size),
+
-                     conf_editbox_handler, I(CONF_width), I(-1));
+    if (!resize_forbidden || !midsession) {
-    c->generic.column = 0;
+        s = ctrl_getset(b, "Window", "size", "Set the size of the window");
-    c = ctrl_editbox(s, "Rows", 'r', 100,
+        ctrl_columns(s, 2, 50, 50);
-                     HELPCTX(window_size),
+        c = ctrl_editbox(s, "Columns", 'm', 100,
-                     conf_editbox_handler, I(CONF_height),I(-1));
+                         HELPCTX(window_size),
-    c->generic.column = 1;
+                         conf_editbox_handler, I(CONF_width), I(-1));
-    ctrl_columns(s, 1, 100);
+        c->generic.column = 0;
+        c = ctrl_editbox(s, "Rows", 'r', 100,
+                         HELPCTX(window_size),
+                         conf_editbox_handler, I(CONF_height),I(-1));
+        c->generic.column = 1;
+        ctrl_columns(s, 1, 100);
+    }
 
     s = ctrl_getset(b, "Window", "scrollback",
                     "Control the scrollback in the window");

putty.h

@@ -479,6 +479,10 @@ enum {
     ADDRTYPE_NAME      /* SockAddr storing an unresolved host name */
 };
 
+/* Backend flags */
+#define BACKEND_RESIZE_FORBIDDEN    0x01   /* Backend does not allow
+                                              resizing terminal */
+
 struct Backend {
     const BackendVtable *vt;
 };

unix/gtkwin.c

@@ -4445,6 +4445,7 @@ static void compute_geom_hints(GtkFrontend *inst, GdkGeometry *geom)
 
 void set_geom_hints(GtkFrontend *inst)
 {
+    const struct BackendVtable *vt;
     GdkGeometry geom;
     gint flags = GDK_HINT_MIN_SIZE | GDK_HINT_BASE_SIZE | GDK_HINT_RESIZE_INC;
     compute_geom_hints(inst, &geom);
@@ -4452,6 +4453,16 @@ void set_geom_hints(GtkFrontend *inst)
     if (inst->gotpos)
         flags |= GDK_HINT_USER_POS;
 #endif
+    vt = backend_vt_from_proto(conf_get_int(inst->conf, CONF_protocol));
+    if (vt && vt->flags & BACKEND_RESIZE_FORBIDDEN) {
+        /* Window resizing forbidden.  Set both minimum and maximum
+         * dimensions to be the initial size. */
+        geom.min_width = inst->width*inst->font_width + 2*inst->window_border;
+        geom.min_height = inst->height*inst->font_height + 2*inst->window_border;
+        geom.max_width = geom.min_width;
+        geom.max_height = geom.min_height;
+        flags |= GDK_HINT_MAX_SIZE;
+    }
     gtk_window_set_geometry_hints(GTK_WINDOW(inst->window),
                                   NULL, &geom, flags);
 }

windows/wincfg.c

@@ -43,6 +43,8 @@ static void variable_pitch_handler(union control *ctrl, dlgparam *dlg,
 void win_setup_config_box(struct controlbox *b, HWND *hwndp, bool has_help,
                           bool midsession, int protocol)
 {
+    const struct BackendVtable *backvt;
+    bool resize_forbidden = false;
     struct controlset *s;
     union control *c;
     char *str;
@@ -313,15 +315,21 @@ void win_setup_config_box(struct controlbox *b, HWND *hwndp, bool has_help,
     /*
      * Resize-by-changing-font is a Windows insanity.
      */
-    s = ctrl_getset(b, "Window", "size", "Set the size of the window");
+
-    ctrl_radiobuttons(s, "When window is resized:", 'z', 1,
+    backvt = backend_vt_from_proto(protocol);
-                      HELPCTX(window_resize),
+    if (backvt)
-                      conf_radiobutton_handler,
+        resize_forbidden = (backvt->flags & BACKEND_RESIZE_FORBIDDEN);
-                      I(CONF_resize_action),
+    if (!midsession || !resize_forbidden) {
-                      "Change the number of rows and columns", I(RESIZE_TERM),
+        s = ctrl_getset(b, "Window", "size", "Set the size of the window");
-                      "Change the size of the font", I(RESIZE_FONT),
+        ctrl_radiobuttons(s, "When window is resized:", 'z', 1,
-                      "Change font size only when maximised", I(RESIZE_EITHER),
+                          HELPCTX(window_resize),
-                      "Forbid resizing completely", I(RESIZE_DISABLED), NULL);
+                          conf_radiobutton_handler,
+                          I(CONF_resize_action),
+                          "Change the number of rows and columns", I(RESIZE_TERM),
+                          "Change the size of the font", I(RESIZE_FONT),
+                          "Change font size only when maximised", I(RESIZE_EITHER),
+                          "Forbid resizing completely", I(RESIZE_DISABLED), NULL);
+    }
 
     /*
      * Most of the Window/Behaviour stuff is there to mimic Windows

windows/window.c

@@ -732,10 +732,16 @@ int WINAPI WinMain(HINSTANCE inst, HINSTANCE prev, LPSTR cmdline, int show)
     {
         int winmode = WS_OVERLAPPEDWINDOW | WS_VSCROLL;
         int exwinmode = 0;
+        const struct BackendVtable *vt =
+            backend_vt_from_proto(be_default_protocol);
+        bool resize_forbidden = false;
+        if (vt && vt->flags & BACKEND_RESIZE_FORBIDDEN)
+            resize_forbidden = true;
         wchar_t *uappname = dup_mb_to_wc(DEFAULT_CODEPAGE, 0, appname);
         if (!conf_get_bool(conf, CONF_scrollbar))
             winmode &= ~(WS_VSCROLL);
-        if (conf_get_int(conf, CONF_resize_action) == RESIZE_DISABLED)
+        if (conf_get_int(conf, CONF_resize_action) == RESIZE_DISABLED ||
+            resize_forbidden)
             winmode &= ~(WS_THICKFRAME | WS_MAXIMIZEBOX);
         if (conf_get_bool(conf, CONF_alwaysontop))
             exwinmode |= WS_EX_TOPMOST;
@@ -1741,6 +1747,7 @@ static void deinit_fonts(void)
 
 static void wintw_request_resize(TermWin *tw, int w, int h)
 {
+    const struct BackendVtable *vt;
     int width, height;
 
     /* If the window is maximized suppress resizing attempts */
@@ -1750,6 +1757,9 @@ static void wintw_request_resize(TermWin *tw, int w, int h)
     }
 
     if (conf_get_int(conf, CONF_resize_action) == RESIZE_DISABLED) return;
+    vt = backend_vt_from_proto(be_default_protocol);
+    if (vt && vt->flags & BACKEND_RESIZE_FORBIDDEN)
+        return;
     if (h == term->rows && w == term->cols) return;
 
     /* Sanity checks ... */