feat(include): add system volume following support

Implement configurable system volume following and replace JSON IPC with binary struct.

- New Feature: Introduce `system_volume_following` CLI and runtime option.
- Enhancement: Extend CLI options, reload, and user‑config APIs to propagate the new flag.
- Enhancement: Add `VbxEvent` binary IPC struct and logging macros for better performance.
- Enhancement: Add helper to persist system volume following state.
- Bug Fix: Remove stale `parse_keyboard_event` prototype.

include/app/cli.h

@@ -15,6 +15,7 @@ typedef struct {
   int mouse_mute;    // -1 unchanged, 0 unmute, 1 mute
   int keyboard_enabled; // -1 unchanged, 0 disabled, 1 enabled
   int mouse_enabled;    // -1 unchanged, 0 disabled, 1 enabled
+  int system_volume_following; // -1 unchanged, 0 disabled, 1 enabled
 } CliOptions;
 
 void print_usage(const char *program_name);

include/app/process.h

@@ -17,7 +17,8 @@ void stop_children(void);
 int start_children(const char *sound_dir, const char *config_path, int volume,
                    int verbose, int mute, const char *mouse_sound_dir,
                    const char *mouse_config_path, int mouse_volume,
-                   int keyboard_mute, int mouse_mute, int keyboard_enabled, int mouse_enabled);
+                   int keyboard_mute, int mouse_mute, int keyboard_enabled,
+                   int mouse_enabled, int system_volume_following);
 void handle_sighup(int sig);
 
 #endif // VBX_PROCESS_H

include/app/reload.h

@@ -7,8 +7,9 @@ int handle_reload(const char *user_cfg_path,
                   char *current_config_path, char *current_sound_dir,
                   char *current_mouse_config_path, char *current_mouse_sound_dir,
                   int current_mute, int current_verbose,
-                  int current_mouse_volume_arg, int current_keyboard_mute,
-                  int current_mouse_mute, int *current_keyboard_enabled, int *current_mouse_enabled);
+                  int current_keyboard_mute, int current_mouse_mute,
+                  int *current_keyboard_enabled, int *current_mouse_enabled,
+                  int *current_system_volume_following);
 
 #endif // VBX_RELOAD_H
 

include/audio/playback.h

@@ -2,7 +2,6 @@
 #define VBX_AUDIO_PLAYBACK_H
 
 int init_audio(void);
-int parse_keyboard_event(const char *json_line, int *key_code, int *is_pressed);
 void play_sound_segment(int key_code, int is_pressed);
 
 #endif // VBX_AUDIO_PLAYBACK_H

include/audio/types.h

@@ -41,5 +41,7 @@ extern int g_keyboard_mute;
 extern int g_mouse_mute;
 extern int g_keyboard_enabled;
 extern int g_mouse_enabled;
+extern int g_system_volume_following;
+extern float g_system_volume_multiplier;
 
 #endif // VBX_AUDIO_TYPES_H

include/common/ipc.h

@@ -0,0 +1,13 @@
+#ifndef VBX_IPC_H
+#define VBX_IPC_H
+
+#include <stdint.h>
+
+// Lightweight binary structure for IPC between vbx-input and vbx-audio
+// Replaces the heavy JSON parsing
+typedef struct {
+    uint32_t key_code;
+    uint8_t  is_pressed;
+} VbxEvent;
+
+#endif // VBX_IPC_H

include/common/log.h

@@ -0,0 +1,29 @@
+#ifndef VBX_LOG_H
+#define VBX_LOG_H
+
+#include <stdio.h>
+#include <time.h>
+
+// Assuming g_verbose is defined globally or we pass it
+extern int g_verbose;
+extern int is_daemon;
+
+#define LOG_LEVEL_DEBUG 0
+#define LOG_LEVEL_INFO  1
+#define LOG_LEVEL_WARN  2
+#define LOG_LEVEL_ERROR 3
+
+#define LOG_MACRO(level, prefix, out_stream, ...) do { \
+    if (level == LOG_LEVEL_DEBUG && !g_verbose) break; \
+    fprintf(out_stream, "[VBX-%s] ", prefix); \
+    fprintf(out_stream, __VA_ARGS__); \
+    fprintf(out_stream, "\n"); \
+    fflush(out_stream); \
+} while(0)
+
+#define LOG_DEBUG(...) LOG_MACRO(LOG_LEVEL_DEBUG, "DEBUG", stdout, __VA_ARGS__)
+#define LOG_INFO(...)  LOG_MACRO(LOG_LEVEL_INFO,  "INFO",  stdout, __VA_ARGS__)
+#define LOG_WARN(...)  LOG_MACRO(LOG_LEVEL_WARN,  "WARN",  stderr, __VA_ARGS__)
+#define LOG_ERROR(...) LOG_MACRO(LOG_LEVEL_ERROR, "ERROR", stderr, __VA_ARGS__)
+
+#endif // VBX_LOG_H

include/common/utils.h

@@ -29,6 +29,9 @@ void write_runtime_mouse_mute_file(int mute);
 int write_runtime_keyboard_enabled_file(int enabled);
 int write_runtime_mouse_enabled_file(int enabled);
 
+// System volume following helper
+int write_runtime_system_volume_following_file(int enabled);
+
 // Helper functions
 void int_to_str(char *buffer, size_t size, int value);
 char *xstrdup(const char *s);

include/user_config.h

@@ -8,11 +8,13 @@ char *get_user_config_path(char *buffer, size_t buflen);
 // Write ~/.vbx.json in new format
 int write_user_config(const char *path, const char *keyboard_sound,
                       const char *mouse_sound, int keyboard_volume,
-                      int mouse_volume, int keyboard_enabled, int mouse_enabled);
+                      int mouse_volume, int keyboard_enabled, int mouse_enabled,
+                      int system_volume_following);
 
 // Read ~/.vbx.json supporting new and legacy formats
 int read_user_config(const char *path, char **out_keyboard_sound,
                      char **out_mouse_sound, int *out_keyboard_volume,
-                     int *out_mouse_volume, int *out_keyboard_enabled, int *out_mouse_enabled);
+                     int *out_mouse_volume, int *out_keyboard_enabled, int *out_mouse_enabled,
+                     int *out_system_volume_following);
 
 #endif // VBX_CONFIG_IO_H