Highpass filter in SDL

Core/apu.h

@@ -103,6 +103,7 @@ typedef enum {
     GB_HIGHPASS_OFF, // Do not apply any filter, keep DC offset
     GB_HIGHPASS_ACCURATE, // Apply a highpass filter similar to the one used on hardware
     GB_HIGHPASS_REMOVE_DC_OFFSET, // Remove DC Offset without affecting the waveform
+    GB_HIGHPASS_MAX
 } GB_highpass_mode_t;
 
 typedef struct {

SDL/gui.c

@@ -58,6 +58,7 @@ configuration_t configuration =
         SDL_SCANCODE_SPACE
     },
     .color_correction_mode = GB_COLOR_CORRECTION_EMULATE_HARDWARE,
+    .highpass_mode = GB_HIGHPASS_ACCURATE,
     .scaling_mode = GB_SDL_SCALING_INTEGER_FACTOR,
     .blend_frames = true
 };
@@ -227,10 +228,12 @@ static void item_help(unsigned index)
 static void enter_graphics_menu(unsigned index);
 static void enter_controls_menu(unsigned index);
 static void enter_joypad_menu(unsigned index);
+static void enter_audio_menu(unsigned index);
 
 static const struct menu_item paused_menu[] = {
     {"Resume", NULL},
     {"Graphic Options", enter_graphics_menu},
+    {"Audio Options", enter_audio_menu},
     {"Keyboard", enter_controls_menu},
     {"Joypad", enter_joypad_menu},
     {"Help", item_help},
@@ -238,14 +241,7 @@ static const struct menu_item paused_menu[] = {
     {NULL,}
 };
 
-static const struct menu_item nonpaused_menu[] = {
+static const struct menu_item *const nonpaused_menu = &paused_menu[1];
-    {"Graphic Options", enter_graphics_menu},
-    {"Keyboard", enter_controls_menu},
-    {"Joypad", enter_joypad_menu},
-    {"Help", item_help},
-    {"Exit", item_exit},
-    {NULL,}
-};
 
 const char *current_scaling_mode(unsigned index)
 {
@@ -409,6 +405,41 @@ static void enter_graphics_menu(unsigned index)
     current_selection = 0;
 }
 
+const char *highpass_filter_string(unsigned index)
+{
+    return (const char *[]){"None (Keep DC Offset)", "Accurate", "Preserve Waveform"}
+        [configuration.highpass_mode];
+}
+
+void cycle_highpass_filter(unsigned index)
+{
+    configuration.highpass_mode++;
+    if (configuration.highpass_mode == GB_HIGHPASS_MAX) {
+        configuration.highpass_mode = 0;
+    }
+}
+
+void cycle_highpass_filter_backwards(unsigned index)
+{
+    if (configuration.highpass_mode == 0) {
+        configuration.highpass_mode = GB_HIGHPASS_MAX - 1;
+    }
+    else {
+        configuration.highpass_mode--;
+    }
+}
+
+static const struct menu_item audio_menu[] = {
+    {"Highpass Filter:", cycle_highpass_filter, highpass_filter_string, cycle_highpass_filter_backwards},
+    {"Back", return_to_root_menu},
+    {NULL,}
+};
+
+static void enter_audio_menu(unsigned index)
+{
+    current_menu = audio_menu;
+    current_selection = 0;
+}
 static const char *key_name(unsigned index)
 {
     return SDL_GetScancodeName(configuration.keys[index]);

SDL/gui.h

@@ -37,6 +37,8 @@ typedef struct {
     enum scaling_mode scaling_mode;
     bool blend_frames;
     
+    GB_highpass_mode_t highpass_mode;
+    
     bool div_joystick;
     bool flip_joystick_bit_1;
     bool swap_joysticks_bits_1_and_2;

SDL/main.c

@@ -119,8 +119,16 @@ static void handle_events(GB_gameboy_t *gb)
                     GB_set_turbo_mode(gb, event.type == SDL_JOYBUTTONDOWN, false);
                 }
                 else {
+                    bool audio_playing = SDL_GetAudioStatus() == SDL_AUDIO_PLAYING;
+                    if (audio_playing) {
+                        SDL_PauseAudio(true);
+                    }
                     run_gui(true);
+                    if (audio_playing) {
+                        SDL_PauseAudio(false);
+                    }
                     GB_set_color_correction_mode(gb, configuration.color_correction_mode);
+                    GB_set_highpass_filter_mode(gb, configuration.highpass_mode);
                 }
             break;
                 
@@ -137,11 +145,19 @@ static void handle_events(GB_gameboy_t *gb)
                 
             case SDL_KEYDOWN:
                 switch (event.key.keysym.scancode) {
-                    case SDL_SCANCODE_ESCAPE:
+                    case SDL_SCANCODE_ESCAPE: {
+                        bool audio_playing = SDL_GetAudioStatus() == SDL_AUDIO_PLAYING;
+                        if (audio_playing) {
+                            SDL_PauseAudio(true);
+                        }
                         run_gui(true);
+                        if (audio_playing) {
+                            SDL_PauseAudio(false);
+                        }
                         GB_set_color_correction_mode(gb, configuration.color_correction_mode);
+                        GB_set_highpass_filter_mode(gb, configuration.highpass_mode);
                         break;
-                        
+                    }
                     case SDL_SCANCODE_C:
                         if (event.type == SDL_KEYDOWN && (event.key.keysym.mod & KMOD_CTRL)) {
                             GB_debugger_break(gb);
@@ -318,6 +334,7 @@ restart:
         GB_set_rgb_encode_callback(&gb, rgb_encode);
         GB_set_sample_rate(&gb, have_aspec.freq);
         GB_set_color_correction_mode(&gb, configuration.color_correction_mode);
+        GB_set_highpass_filter_mode(&gb, configuration.highpass_mode);
     }
     
     bool error = false;
@@ -435,7 +452,6 @@ usage:
     SDL_OpenAudio(&want_aspec, &have_aspec);
     
     /* Start Audio */
-    SDL_PauseAudio(false);
 
     SDL_EventState(SDL_DROPFILE, SDL_ENABLE);
     
@@ -447,6 +463,7 @@ usage:
     if (filename == NULL) {
         run_gui(false);
     }
+    SDL_PauseAudio(false);
     run(); // Never returns
     return 0;
 }