Simplify checking for near water sfx change

Rather than checking every frame you're near the water, only check when the
current cell changed (the sfx will only change when moving between interior and
exterior). It also doesn't need to look through all playing sounds, as it's a
local one not attached to a Ptr.

apps/openmw/mwsound/soundmanagerimp.cpp

@@ -72,8 +72,8 @@ namespace MWSound
         mNearWaterPoints = mFallback.getFallbackInt("Water_NearWaterPoints");
         mNearWaterIndoorTolerance = mFallback.getFallbackFloat("Water_NearWaterIndoorTolerance");
         mNearWaterOutdoorTolerance = mFallback.getFallbackFloat("Water_NearWaterOutdoorTolerance");
-        mNearWaterIndoorID = mFallback.getFallbackString("Water_NearWaterIndoorID");
-        mNearWaterOutdoorID = mFallback.getFallbackString("Water_NearWaterOutdoorID");
+        mNearWaterIndoorID = Misc::StringUtils::lowerCase(mFallback.getFallbackString("Water_NearWaterIndoorID"));
+        mNearWaterOutdoorID = Misc::StringUtils::lowerCase(mFallback.getFallbackString("Water_NearWaterOutdoorID"));
 
         mBufferCacheMin = std::max(Settings::Manager::getInt("buffer cache min", "Sound"), 1);
         mBufferCacheMax = std::max(Settings::Manager::getInt("buffer cache max", "Sound"), 1);
@@ -873,16 +873,18 @@ namespace MWSound
 
     void SoundManager::updateWaterSound(float /*duration*/)
     {
+        static const ESM::Cell *LastCell;
         MWBase::World* world = MWBase::Environment::get().getWorld();
         const MWWorld::ConstPtr player = world->getPlayerPtr();
         osg::Vec3f pos = player.getRefData().getPosition().asVec3();
+        const ESM::Cell *curcell = player.getCell()->getCell();
 
         float volume = 0.0f;
         const std::string& soundId = player.getCell()->isExterior() ? mNearWaterOutdoorID : mNearWaterIndoorID;
 
         if (!mListenerUnderwater)
         {
-            if (player.getCell()->getCell()->hasWater())
+            if (curcell->hasWater())
             {
                 float dist = std::abs(player.getCell()->getWaterLevel() - pos.z());
 
@@ -929,25 +931,24 @@ namespace MWSound
                 mOutput->finishSound(mNearWaterSound);
                 mNearWaterSound = nullptr;
             }
-            else
+            else if(LastCell != curcell)
             {
                 bool soundIdChanged = false;
 
-                Sound_Buffer* sfx = lookupSound(Misc::StringUtils::lowerCase(soundId));
-
-                for (SoundMap::const_iterator snditer = mActiveSounds.begin(); snditer != mActiveSounds.end(); ++snditer)
+                Sound_Buffer* sfx = lookupSound(soundId);
+                SoundMap::const_iterator snditer = mActiveSounds.find(MWWorld::Ptr());
+                if(snditer != mActiveSounds.end())
                 {
-                    for (SoundBufferRefPairList::const_iterator pairiter = snditer->second.begin(); pairiter != snditer->second.end(); ++pairiter)
-                    {
-                        if (pairiter->first == mNearWaterSound)
-                        {
-                            if (pairiter->second != sfx)
-                                soundIdChanged = true;
-                            break;
-                        }
-                    }
+                    SoundBufferRefPairList::const_iterator pairiter = std::find_if(
+                        snditer->second.begin(), snditer->second.end(),
+                        [this](const SoundBufferRefPairList::value_type &item) -> bool
+                        { return mNearWaterSound == item.first; }
+                    );
+                    if (pairiter != snditer->second.end() && pairiter->second != sfx)
+                        soundIdChanged = true;
                 }
 
+                LastCell = curcell;
                 if (soundIdChanged)
                 {
                     mOutput->finishSound(mNearWaterSound);
@@ -958,7 +959,10 @@ namespace MWSound
             }
         }
         else if (volume > 0.0f)
+        {
+            LastCell = curcell;
             mNearWaterSound = playSound(soundId, volume, 1.0f, Play_TypeSfx, Play_Loop);
+        }
     }
 
     void SoundManager::updateSounds(float duration)