feat(ui): UI_ENTER_DOUBLE_BACK - double-click Enter goes back, off by default

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

docs/solo/developer/build-flags.md

@@ -56,6 +56,7 @@ existing `solo/<board>/platformio.ini` for what's already claimed).
 | `UI_HAS_JOYSTICK=1` + `UI_HAS_JOYSTICK_UPDOWN=1` (optional) + `JOYSTICK_UP` / `JOYSTICK_DOWN` / `JOYSTICK_LEFT` / `JOYSTICK_RIGHT` + `PIN_USER_BTN` + `PIN_BACK_BTN` | A wired joystick (four direction contacts + a press contact for Enter). Replaces single-button navigation entirely once enabled. See [External Keyboard & Joystick](../hardware.md#external-keyboard-and-joystick). |
 | `PIN_GPIO1` .. `PIN_GPIO4` | Up to four general-purpose pins, each independently switchable between Off / Input / Output (GPIO1/GPIO2 also get an Analog step, if wired to an ADC-capable pin) from Tools › GPIO, and via the `!gpio1`..`!gpio4` bot commands. Not restricted to any particular board — works anywhere the pins are actually free. See [Tools › GPIO](../tools.md#gpio). |
 | `PIN_HALL_SENSOR` + `HALL_ACTIVE_HIGH=1` (optional) | A Hall-effect or reed sensor for a magnetic flip cover: closing locks and blanks the screen instantly, opening unlocks and wakes it, no combo either way. `HALL_ACTIVE_HIGH` is only for a module wired to pull the pin high (rather than low) when the magnet is near. See [Screen lock › Magnetic cover](../lock.md#magnetic-cover). |
+| `UI_ENTER_DOUBLE_BACK=1` | Double-click Enter goes back, for a joystick whose Back button is hard to reach. Delays a single Enter by ~280 ms; in text entry a double is two Enters. Only the GAT562 30S target wires it up; off by default. |
 
 ---
 

examples/companion_radio/ui-new/UITask.cpp

@@ -1261,8 +1261,7 @@ void UITask::loop() {
 #if FEAT_DISPLAY_ROTATION_SETTING && defined(JOYSTICK_UPRIGHT_ROTATION)
   if (_node_prefs) joy_rot += (JOYSTICK_UPRIGHT_ROTATION - _node_prefs->display_rotation) & 3;
 #endif
-  int ev = user_btn.check();
-  if (ev == BUTTON_EVENT_CLICK) {
+  auto enterClick = [&]() {
     if (back_btn.isPressed() && !_unlock_kb) {
       // Enter clicked while Back is held — lock/unlock sequence
       if (_display && !_display->isOn()) {
@@ -1287,6 +1286,25 @@ void UITask::loop() {
       }
       enqueueKey(checkDisplayOn(KEY_ENTER));
     }
+  };
+  int ev = user_btn.check();
+#ifdef UI_ENTER_DOUBLE_BACK
+  // For a joystick without a reachable Back button: a double click on Enter goes
+  // back. Multi-click delays a single Enter by the click window. Where text is
+  // typed (on-screen keyboard, PIN pad) or the lock sequence is counting, a
+  // double is just two Enters, so a repeated letter still works.
+  if (ev == BUTTON_EVENT_DOUBLE_CLICK || ev == BUTTON_EVENT_TRIPLE_CLICK) {
+    int n = (ev == BUTTON_EVENT_DOUBLE_CLICK) ? 2 : 3;
+    if (_unlock_kb || _kb.isVisible() || back_btn.isPressed()) {
+      for (int i = 0; i < n; i++) enterClick();
+    } else {
+      enqueueKey(checkDisplayOn(KEY_CANCEL));
+    }
+    ev = BUTTON_EVENT_NONE;
+  }
+#endif
+  if (ev == BUTTON_EVENT_CLICK) {
+    enterClick();
   } else if (ev == BUTTON_EVENT_LONG_PRESS) {
     enqueueKey(handleLongPress(KEY_ENTER));  // REVISIT: could be mapped to different key code
   }

variants/gat562_30s_mesh_kit/target.cpp

@@ -11,7 +11,11 @@ GAT56230SMeshKitBoard board;
 
 #ifdef DISPLAY_CLASS
   DISPLAY_CLASS display;
-  MomentaryButton user_btn(PIN_USER_BTN, 1000, true, false, false);
+  #ifdef UI_ENTER_DOUBLE_BACK
+    MomentaryButton user_btn(PIN_USER_BTN, 1000, true, false, true);   // multi-click: double Enter = Back
+  #else
+    MomentaryButton user_btn(PIN_USER_BTN, 1000, true, false, false);
+  #endif
   MomentaryButton joystick_left(JOYSTICK_LEFT, 1000, true, false, false);
   MomentaryButton joystick_right(JOYSTICK_RIGHT, 1000, true, false, false);
   MomentaryButton back_btn(PIN_BACK_BTN, 1000, true, false, true);