Add enemy health bar fading and use relevant GMSTs

apps/openmw/mwgui/hud.cpp

@@ -618,6 +618,11 @@ namespace MWGui
         // Health is usually cast to int before displaying. Actors die whenever they are < 1 health.
         // Therefore any value < 1 should show as an empty health bar. We do the same in statswindow :)
         mEnemyHealth->setProgressPosition(int(stats.getHealth().getCurrent()) / stats.getHealth().getModified() * 100);
+
+        static const float fNPCHealthBarFade = MWBase::Environment::get().getWorld()->getStore().get<ESM::GameSetting>().find("fNPCHealthBarFade")->getFloat();
+        if (fNPCHealthBarFade > 0.f)
+            mEnemyHealth->setAlpha(std::max(0.f, std::min(1.f, mEnemyHealthTimer/fNPCHealthBarFade)));
+
     }
 
     void HUD::update()
@@ -639,7 +644,7 @@ namespace MWGui
     void HUD::setEnemy(const MWWorld::Ptr &enemy)
     {
         mEnemyActorId = enemy.getClass().getCreatureStats(enemy).getActorId();
-        mEnemyHealthTimer = 5;
+        mEnemyHealthTimer = MWBase::Environment::get().getWorld()->getStore().get<ESM::GameSetting>().find("fNPCHealthBarTime")->getFloat();
         if (!mEnemyHealth->getVisible())
             mWeaponSpellBox->setPosition(mWeaponSpellBox->getPosition() - MyGUI::IntPoint(0,20));
         mEnemyHealth->setVisible(true);