[Bugfix] More correct way to fix camera glitching

In commit 0aab576 we have attempts to fix camera glitching when one of effectors finishes working. The root of glitches is effector's deletion in CCameraManager::ProcessCameraEffector. Cycle in CCameraManager::UpdateCamEffectors uses reverse iterator and doesn't expect that entry in the list would be removed. Due to specific behavior of reverse iterator it really points to the next element relative to element which it dereferenced to. So, when ProcessCameraEffector deletes currently dereferenced element, iterator automatically starts point to element before deleted one. But the UpdateCamEffectors doesn't know about it, and cycle changes iterator on next iteration. So, processing of one camera effect would be skipped in this moment.
Changes in 0aab576 don't seems to be the best solution, because
1) vector is less suitable for situations where we are often want to add or remove random elements
2) Deletion of current effector in ProcessCameraEffector seems to be not safe. For example, we could have CCameraManager's childs with overridden ProcessCameraEffector method. They could be deadly surprised if pointer to current effector would start pointing to non-existent element.
So, this commit:
1) Reverts changes from 0aab576
2) Removes effector's deletion from CCameraManager::ProcessCameraEffector; now the method returns false if it should be deleted, or true otherwise
3) Adds code for removing 'old' effectors to UpdateCamEffectors method.

Author: gunslingermod

src/xrEngine/CameraManager.cpp

@@ -86,7 +86,7 @@ void CCameraManager::UpdateDeffered()
         RemoveCamEffector((*it)->eType);
 
         if ((*it)->AbsolutePositioning())
-            m_EffectorsCam.insert(m_EffectorsCam.begin(), *it);
+            m_EffectorsCam.push_front(*it);
         else
             m_EffectorsCam.push_back(*it);
     }
@@ -222,23 +222,19 @@ void CCameraManager::Update(const Fvector& P, const Fvector& D, const Fvector& N
 
 bool CCameraManager::ProcessCameraEffector(CEffectorCam* eff)
 {
+    // Do NOT delete effector here! It's unsafe because:
+    // 1. Leads to failed iterators in UpdateCamEffectors
+    // 2. Child classes with overrided ProcessCameraEffector would be surprised if eff becames invalid pointer
+    // The best way - return 'false' when the effector should be deleted, and delete it in ProcessCameraEffector
+
     bool res = false;
     if (eff->Valid() && eff->ProcessCam(m_cam_info))
     {
         res = true;
     }
-    else
+    else if (eff->AllowProcessingIfInvalid())
     {
-        if (eff->AllowProcessingIfInvalid())
-        {
-            eff->ProcessIfInvalid(m_cam_info);
-            res = true;
-        }
-
-        EffectorCamVec::iterator it = std::find(m_EffectorsCam.begin(), m_EffectorsCam.end(), eff);
-
-        m_EffectorsCam.erase(it);
-        OnEffectorReleased(eff);
+        eff->ProcessIfInvalid(m_cam_info);
     }
     return res;
 }
@@ -247,8 +243,22 @@ void CCameraManager::UpdateCamEffectors()
 {
     if (m_EffectorsCam.empty())
         return;
-    for (int i = m_EffectorsCam.size() - 1; i >= 0; --i)
-		ProcessCameraEffector(m_EffectorsCam[i]);
+
+    auto r_it = m_EffectorsCam.rbegin();
+    while (r_it != m_EffectorsCam.rend())
+    {
+        if (ProcessCameraEffector(*r_it))
+            ++r_it;
+        else
+        {
+            // Dereferencing reverse iterator returns previous element of the list, r_it.base() returns current element
+            // So, we should use base()-1 iterator to delete just processed element. 'Previous' element would be 
+            // automatically changed after deletion, so r_it would dereferencing to another value, no need to change it
+            OnEffectorReleased(*r_it);
+            auto r_to_del = r_it.base();
+            m_EffectorsCam.erase(--r_to_del);
+        }
+    }
 
     m_cam_info.d.normalize();
     m_cam_info.n.normalize();

src/xrEngine/CameraManager.h

@@ -3,7 +3,7 @@
 #include "CameraDefs.h"
 #include "xrCore/PostProcess/PPInfo.hpp"
 
-using EffectorCamVec = xr_vector<CEffectorCam*>;
+using EffectorCamVec = xr_list<CEffectorCam*>;
 using EffectorPPVec = xr_vector<CEffectorPP*>;
 
 #define effCustomEffectorStartID 10000