Fix #4938

- Set the minimum sound volume to 0.025f instead of effectively 0.1f. This is particularly helpful for headphone users.
- Make the step between each volume setting exponential.
- Add parameters to remember the parameters of the audio spinners.
- Increase the default number of values the audio spinners can take from 10 to 15. Old config files will keep using 10.
- Set the default values to 10 (spinners), which translates to 0.2678 (volume fraction) instead of 0.6 (previous default)

src/config/user_config.hpp

@@ -414,16 +414,22 @@ namespace UserConfigParams
             PARAM_DEFAULT(  BoolUserConfigParam(true, "music_on",
             &m_audio_group,
             "Whether musics are enabled or not (true or false)") );
+    PARAM_PREFIX IntUserConfigParam         m_sfx_numerator
+            PARAM_DEFAULT(  IntUserConfigParam(10, "sfx_numerator",
+            &m_audio_group, "The value in the audio options SFX spinner") );
     PARAM_PREFIX FloatUserConfigParam       m_sfx_volume
-            PARAM_DEFAULT(  FloatUserConfigParam(0.6f, "sfx_volume",
+            PARAM_DEFAULT(  FloatUserConfigParam(0.2678f, "sfx_volume",
             &m_audio_group, "Volume for sound effects, see openal AL_GAIN "
                             "for interpretation") );
+    PARAM_PREFIX IntUserConfigParam         m_music_numerator
+            PARAM_DEFAULT(  IntUserConfigParam(10, "music_numerator",
+            &m_audio_group, "The value in the audio options music spinner") );
     PARAM_PREFIX FloatUserConfigParam       m_music_volume
-            PARAM_DEFAULT(  FloatUserConfigParam(0.5f, "music_volume",
+            PARAM_DEFAULT(  FloatUserConfigParam(0.2678f, "music_volume",
             &m_audio_group, "Music volume from 0.0 to 1.0") );
 
     PARAM_PREFIX IntUserConfigParam          m_volume_denominator
-            PARAM_DEFAULT(  IntUserConfigParam(10, "volume_denominator",
+            PARAM_DEFAULT(  IntUserConfigParam(15, "volume_denominator",
                             &m_audio_group,
                             "Number of steps for volume adjustment") );
 

src/states_screens/options/options_screen_audio.cpp

@@ -67,14 +67,12 @@ void OptionsScreenAudio::init()
     SpinnerWidget* gauge = this->getWidget<SpinnerWidget>("sfx_volume");
     assert(gauge != NULL);
     gauge->setMax(UserConfigParams::m_volume_denominator);
-    gauge->setValue((int)(SFXManager::get()->getMasterSFXVolume() *
+    gauge->setValue(UserConfigParams::m_sfx_numerator);
-        float(UserConfigParams::m_volume_denominator)));
 
     gauge = this->getWidget<SpinnerWidget>("music_volume");
     assert(gauge != NULL);
     gauge->setMax(UserConfigParams::m_volume_denominator);
-    gauge->setValue((int)(music_manager->getMasterMusicVolume() *
+    gauge->setValue(UserConfigParams::m_music_numerator);
-        float(UserConfigParams::m_volume_denominator)));
 
     // ---- music volume
     CheckBoxWidget* sfx = this->getWidget<CheckBoxWidget>("sfx_enabled");
@@ -136,8 +134,10 @@ void OptionsScreenAudio::eventCallback(Widget* widget, const std::string& name,
         SpinnerWidget* w = dynamic_cast<SpinnerWidget*>(widget);
         assert(w != NULL);
 
-        music_manager->setMasterMusicVolume(w->getValue() /
+        float new_volume = computeVolume(w->getValue(), UserConfigParams::m_volume_denominator);
-            float(UserConfigParams::m_volume_denominator));
+
+        UserConfigParams::m_music_numerator = w->getValue(); 
+        music_manager->setMasterMusicVolume(new_volume);
     }
     else if(name == "sfx_volume")
     {
@@ -149,10 +149,10 @@ void OptionsScreenAudio::eventCallback(Widget* widget, const std::string& name,
         if (sample_sound == NULL) sample_sound = SFXManager::get()->createSoundSource( "pre_start_race" );
         sample_sound->setVolume(1);
 
-        float new_vol = w->getValue() /
+        float new_volume = computeVolume(w->getValue(), UserConfigParams::m_volume_denominator);
-            float(UserConfigParams::m_volume_denominator);
+        SFXManager::get()->setMasterSFXVolume(new_volume);
-        SFXManager::get()->setMasterSFXVolume(new_vol);
+        UserConfigParams::m_sfx_numerator = w->getValue(); 
-        UserConfigParams::m_sfx_volume = new_vol;
+        UserConfigParams::m_sfx_volume = new_volume;
 
         // play a sample sound to show the user what this volume is like
         sample_sound->play();
@@ -194,6 +194,23 @@ void OptionsScreenAudio::eventCallback(Widget* widget, const std::string& name,
     }
 }   // eventCallback
 
+float OptionsScreenAudio::computeVolume(int numerator, int denominator)
+{
+    if (numerator <= 1)
+    {
+        return 0.025f;
+    }
+    else if (numerator == denominator)
+    {
+        return 1.0f;
+    }
+    else
+    {
+        float num_root = pow(40.0f, 1.0f / (float)(denominator - 1));
+        return 0.025f * pow(num_root, (float)(numerator - 1));
+    }
+}
+
 // -----------------------------------------------------------------------------
 
 void OptionsScreenAudio::unloaded()

src/states_screens/options/options_screen_audio.hpp

@@ -35,6 +35,9 @@ class OptionsScreenAudio : public GUIEngine::Screen, public GUIEngine::ScreenSin
 {
     OptionsScreenAudio();
 
+private:
+    float computeVolume(int numerator, int denominator);
+
 public:
     friend class GUIEngine::ScreenSingleton<OptionsScreenAudio>;