Add volume control to SDL

SDL/gui.c

@@ -106,7 +106,8 @@ configuration_t configuration =
     .scaling_mode = GB_SDL_SCALING_INTEGER_FACTOR,
     .blending_mode = GB_FRAME_BLENDING_MODE_ACCURATE,
     .rewind_length = 60 * 2,
-    .model = MODEL_CGB
+    .model = MODEL_CGB,
+    .volume = 100,
 };
 
 
@@ -681,8 +682,32 @@ void cycle_highpass_filter_backwards(unsigned index)
     }
 }
 
+const char *volume_string(unsigned index)
+{
+    static char ret[5];
+    sprintf(ret, "%d%%", configuration.volume);
+    return ret;
+}
+
+void increase_volume(unsigned index)
+{
+    configuration.volume += 5;
+    if (configuration.volume > 100) {
+        configuration.volume = 100;
+    }
+}
+
+void decrease_volume(unsigned index)
+{
+    configuration.volume -= 5;
+    if (configuration.volume > 100) {
+        configuration.volume = 0;
+    }
+}
+
 static const struct menu_item audio_menu[] = {
     {"Highpass Filter:", cycle_highpass_filter, highpass_filter_string, cycle_highpass_filter_backwards},
+    {"Volume:", increase_volume, volume_string, decrease_volume},
     {"Back", return_to_root_menu},
     {NULL,}
 };

SDL/gui.h

@@ -104,6 +104,7 @@ typedef struct {
     /* v0.13 */
     uint8_t dmg_palette;
     GB_border_mode_t border_mode;
+    uint8_t volume;
 } configuration_t;
 
 extern configuration_t configuration;

SDL/main.c

@@ -420,6 +420,11 @@ static void gb_audio_callback(GB_gameboy_t *gb, GB_sample_t *sample)
         return;
     }
     
+    if (configuration.volume != 100) {
+        sample->left = sample->left * configuration.volume / 100;
+        sample->right = sample->right * configuration.volume / 100;
+    }
+    
     SDL_QueueAudio(device_id, sample, sizeof(*sample));
     
 }