Reference C++ conversion experiment PoC

meson.build

@@ -75,12 +75,15 @@ openrtx_inc = ['openrtx/include', 'platform']
 ## OpenRTX UI sources
 ##
 
-ui_src_default = ['openrtx/src/ui/default/ui.c',
+ui_src_common = ['openrtx/src/ui/common/ui_events.cpp',
+                 'openrtx/src/ui/common/ui_nav.cpp',
+                 'openrtx/src/ui/default/ui_strings.c']
+
+ui_src_default = ui_src_common + ['openrtx/src/ui/default/ui.cpp',
                   'openrtx/src/ui/default/ui_main.c',
-                  'openrtx/src/ui/default/ui_menu.c',
-                  'openrtx/src/ui/default/ui_strings.c']
+                  'openrtx/src/ui/default/ui_menu.c']
 
-ui_src_module17 = ['openrtx/src/ui/module17/ui.c',
+ui_src_module17 = ui_src_common + ['openrtx/src/ui/module17/ui.cpp',
                    'openrtx/src/ui/module17/ui_main.c',
                    'openrtx/src/ui/module17/ui_menu.c']
 

openrtx/include/core/battery.h

@@ -9,11 +9,19 @@
 
 #include <stdint.h>
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 /**
  * This function computes the battery's state of charge given its current voltage.
  * @param vbat: battery voltage in millivolt.
  * @return state of charge percentage, from 0% to 100%.
  */
 uint8_t battery_getCharge(uint16_t vbat);
 
+#ifdef __cplusplus
+} // extern "C"
+#endif
+
 #endif /* BATTERY_H */

openrtx/include/core/beeps.h

@@ -6,6 +6,10 @@
 
 #ifndef BEEPS_H_INCLUDED
 #define BEEPS_H_INCLUDED
+
+#ifdef __cplusplus
+extern "C" {
+#endif
 // Duration in tenths of a second.
 #define SHORT_BEEP 3
 #define LONG_BEEP 7
@@ -18,4 +22,8 @@
 #define BEEP_KEY_GENERIC 750
 extern const uint16_t BOOT_MELODY[];
 
+#ifdef __cplusplus
+} // extern "C"
+#endif
+
 #endif // BEEPS_H_INCLUDED

openrtx/include/core/input.h

@@ -11,6 +11,10 @@
 #include <inttypes.h>
 #include <stdbool.h>
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 /**
  * Time interval in milliseconds after which a keypress is considered a long-press
  */
@@ -82,4 +86,8 @@ uint8_t input_getPressedNumber(kbd_msg_t msg);
  */
 uint8_t input_getPressedChar(kbd_msg_t msg);
 
+#ifdef __cplusplus
+} // extern "C"
+#endif
+
 #endif /* INPUT_H */

openrtx/include/core/state.h

@@ -14,6 +14,10 @@
 #include "core/cps.h"
 #include "core/gps.h"
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 /**
  * Part of this structure has been commented because the corresponding
  * functionality is not yet implemented.
@@ -103,4 +107,8 @@ void state_task();
  */
 void state_resetSettingsAndVfo();
 
+#ifdef __cplusplus
+} // extern "C"
+#endif
+
 #endif /* STATE_H */

openrtx/include/core/ui.h

@@ -10,6 +10,10 @@
 #include <stdbool.h>
 #include <stdint.h>
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 /**
  * This function initialises the User Interface, starting the
  * Finite State Machine describing the user interaction.
@@ -58,4 +62,8 @@ bool ui_pushEvent(const uint8_t type, const uint32_t data);
  */
 void ui_terminate();
 
+#ifdef __cplusplus
+}
+#endif
+
 #endif /* UI_H */

openrtx/include/core/voicePromptUtils.h

@@ -11,6 +11,10 @@
 #include "ui/ui_strings.h"
 #include "core/voicePrompts.h"
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 /*
 Please Note!
 
@@ -225,4 +229,8 @@ void vp_announceSplashScreen();
  */
 void vp_announceTimeZone(const int8_t timeZone, const vpQueueFlags_t flags);
 
+#ifdef __cplusplus
+} // extern "C"
+#endif
+
 #endif  // VOICE_PROMPT_UTILS_H

openrtx/include/core/voicePrompts.h

@@ -10,6 +10,10 @@
 #include "core/datatypes.h"
 #include <stdbool.h>
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 /**
  * List of voice prompts for spoken words or phrases which are not in the UI
  * string table. The voice prompt data file stores these first, then after the
@@ -328,4 +332,8 @@ void vp_beep(uint16_t freq, uint16_t duration);
  */
 void vp_beepSeries(const uint16_t* beepSeries);
 
+#ifdef __cplusplus
+} // extern "C"
+#endif
+
 #endif

openrtx/include/ui/Screen.hpp

@@ -0,0 +1,27 @@
+/*
+ * SPDX-FileCopyrightText: Copyright 2020-2026 OpenRTX Contributors
+ *
+ * SPDX-License-Identifier: GPL-3.0-or-later
+ */
+
+#pragma once
+
+#include "core/event.h"
+
+/**
+ * Abstract base class for UI screens.
+ *
+ * Mirrors the OpMode hierarchy used in rtx/: concrete screens are
+ * stack-allocated static instances; dispatch goes through a Screen* pointer.
+ * No RTTI, no exceptions, no dynamic_cast — consistent with the rest of the
+ * embedded codebase.
+ */
+class Screen
+{
+public:
+    virtual void enter() {}
+    virtual void exit()  {}
+    virtual bool handleInput(event_t ev) = 0;
+    virtual void render() = 0;
+    virtual ~Screen() = default;
+};

openrtx/include/ui/ui_common.h

@@ -0,0 +1,48 @@
+/*
+ * SPDX-FileCopyrightText: Copyright 2020-2026 OpenRTX Contributors
+ *
+ * SPDX-License-Identifier: GPL-3.0-or-later
+ */
+
+#ifndef UI_COMMON_H
+#define UI_COMMON_H
+
+#include "core/graphics.h"
+#include <stdbool.h>
+#include <stdint.h>
+
+// Maximum menu entry length
+#define MAX_ENTRY_LEN 21
+// Frequency digits
+#define FREQ_DIGITS 7
+// Time & Date digits
+#define TIMEDATE_DIGITS 10
+// Max number of UI events
+#define MAX_NUM_EVENTS 16
+
+enum SetRxTx
+{
+    SET_RX = 0,
+    SET_TX
+};
+
+enum backupRestoreItems
+{
+    BR_BACKUP = 0,
+    BR_RESTORE
+};
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+extern const color_t color_black;
+extern const color_t color_grey;
+extern const color_t color_white;
+extern const color_t yellow_fab413;
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* UI_COMMON_H */

openrtx/include/ui/ui_default.h

@@ -7,24 +7,13 @@
 #ifndef UI_DEFAULT_H
 #define UI_DEFAULT_H
 
-#include <stdbool.h>
+#include "ui/ui_common.h"
 #include "core/state.h"
-#include "core/graphics.h"
 #include "interfaces/keyboard.h"
-#include <stdint.h>
 #include "core/event.h"
 #include "hwconfig.h"
 #include "core/ui.h"
 
-// Maximum menu entry length
-#define MAX_ENTRY_LEN 21
-// Frequency digits
-#define FREQ_DIGITS 7
-// Time & Date digits
-#define TIMEDATE_DIGITS 10
-// Max number of UI events
-#define MAX_NUM_EVENTS 16
-
 enum uiScreen
 {
     MAIN_VFO = 0,
@@ -55,12 +44,6 @@ enum uiScreen
     LOW_BAT
 };
 
-enum SetRxTx
-{
-    SET_RX = 0,
-    SET_TX
-};
-
 // This enum is needed to have item numbers that match
 // menu elements even if some elements may be missing (GPS)
 enum menuItems
@@ -94,12 +77,6 @@ enum settingsItems
     S_RESET2DEFAULTS,
 };
 
-enum backupRestoreItems
-{
-    BR_BACKUP = 0,
-    BR_RESTORE
-};
-
 enum displayItems
 {
 #ifdef CONFIG_SCREEN_BRIGHTNESS
@@ -237,7 +214,7 @@ typedef struct ui_state_t
 }
 ui_state_t;
 
-extern layout_t layout;
+extern const layout_t layout;
 extern state_t last_state;
 extern bool    macro_latched;
 extern const char *menu_items[];
@@ -262,9 +239,4 @@ extern const uint8_t settings_accessibility_num;
 extern const uint8_t backup_restore_num;
 extern const uint8_t info_num;
 extern const uint8_t author_num;
-extern const color_t color_black;
-extern const color_t color_grey;
-extern const color_t color_white;
-extern const color_t yellow_fab413;
-
 #endif /* UI_DEFAULT_H */

openrtx/include/ui/ui_draw.h

@@ -0,0 +1,61 @@
+/*
+ * SPDX-FileCopyrightText: Copyright 2020-2026 OpenRTX Contributors
+ *
+ * SPDX-License-Identifier: GPL-3.0-or-later
+ */
+
+#ifndef UI_DRAW_H
+#define UI_DRAW_H
+
+/*
+ * Forward declarations for all _ui_draw* functions implemented in ui_main.c
+ * and ui_menu.c.  These are C functions called from C++ translation units, so
+ * the extern "C" linkage specification is mandatory.
+ *
+ * Each variant (default, module17) includes this header and declares only its
+ * variant-specific draw functions in its own extern "C" block.
+ */
+
+// ui_state_t is defined in the variant header (ui_default.h or ui_mod17.h).
+// A forward declaration is sufficient here since all parameters are pointers.
+struct ui_state_t;
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/* ---- ui_main.c ---- */
+void _ui_drawMainBackground();
+void _ui_drawVFOMiddle();
+void _ui_drawMEMMiddle();
+void _ui_drawVFOBottom();
+void _ui_drawMEMBottom();
+void _ui_drawMainVFO(ui_state_t *ui_state);
+void _ui_drawMainVFOInput(ui_state_t *ui_state);
+void _ui_drawMainMEM(ui_state_t *ui_state);
+
+/* ---- ui_menu.c ---- */
+void _ui_drawMenuTop(ui_state_t *ui_state);
+void _ui_drawMenuSettings(ui_state_t *ui_state);
+void _ui_drawMenuInfo(ui_state_t *ui_state);
+void _ui_drawMenuAbout(ui_state_t *ui_state);
+void _ui_drawSettingsDisplay(ui_state_t *ui_state);
+void _ui_drawSettingsM17(ui_state_t *ui_state);
+void _ui_drawSettingsReset2Defaults(ui_state_t *ui_state);
+bool _ui_drawMacroMenu(ui_state_t *ui_state);
+
+#ifdef CONFIG_GPS
+void _ui_drawMenuGPS();
+void _ui_drawSettingsGPS(ui_state_t *ui_state);
+#endif
+
+#ifdef CONFIG_RTC
+void _ui_drawSettingsTimeDate();
+void _ui_drawSettingsTimeDateSet(ui_state_t *ui_state);
+#endif
+
+#ifdef __cplusplus
+} // extern "C"
+#endif
+
+#endif /* UI_DRAW_H */