Core/Spells: Creature spellcast facing rework:

- Fixes creatures turning just before a spellcast finishes and smacking players with supposedly-unavoidable damage. Fixes and closes #15393, #10803, and probably others.
- Fixes visual effects not lining up with the correct target for spells that have their visual aligned with the caster's orientation (examples: Anub'rekhan Impale, Ingvar's Smash/Dark Smash, etc.). Fixes and closes #2947 and probably a bunch of others, including the aforementioned #15393 and #10803.
- Creatures' displayed target now properly matches the unit they are targeting with spells for a split second (blizzlike). This is necessary to get proper client-side orientation.

1 files changed, 45 insertions, 7 deletions

diff --git a/src/server/game/Spells/Spell.cpp b/src/server/game/Spells/Spell.cpp
index cb573f4ec3d..2878b2e4da6 100644
--- a/src/server/game/Spells/Spell.cpp
+++ b/src/server/game/Spells/Spell.cpp
@@ -602,6 +602,8 @@ m_caster((info->HasAttribute(SPELL_ATTR6_CAST_BY_CHARMER) && caster->GetCharmerO
 
     //Auto Shot & Shoot (wand)
     m_autoRepeat = m_spellInfo->IsAutoRepeatRangedSpell();
+    
+    m_isDelayedInstantCast = false;
 
     m_runesState = 0;
     m_powerCost = 0;                                        // setup to correct value in Spell::prepare, must not be used before.
@@ -2936,6 +2938,27 @@ void Spell::prepare(SpellCastTargets const* targets, AuraEffect const* triggered
     else
         m_casttime = m_spellInfo->CalcCastTime(this);
 
+    if (m_caster->GetTypeId() == TYPEID_UNIT && !m_caster->HasFlag(UNIT_FIELD_FLAGS, UNIT_FLAG_PLAYER_CONTROLLED)) // _UNIT actually means creature. for some reason.
+        if (!(IsNextMeleeSwingSpell() || IsAutoRepeat() || _triggeredCastFlags & TRIGGERED_IGNORE_SET_FACING))
+        {
+            if (m_targets.GetObjectTarget() && m_caster != m_targets.GetObjectTarget())
+            {
+                if (m_caster->ToCreature()->FocusTarget(this, m_targets.GetObjectTarget()))
+                {
+                    m_isDelayedInstantCast = true;
+                    m_timer = 100; // 100ms delay ensures client has updated creature orientation when cast goes off
+                }
+            }
+            else if (m_spellInfo->HasAttribute(SPELL_ATTR5_DONT_TURN_DURING_CAST))
+            {
+                if (m_caster->ToCreature()->FocusTarget(this, nullptr))
+                {
+                    m_isDelayedInstantCast = true;
+                    m_timer = 100;
+                }
+            }
+        }
+
     // don't allow channeled spells / spells with cast time to be cast while moving
     // (even if they are interrupted on moving, spells with almost immediate effect get to have their effect processed before movement interrupter kicks in)
     if ((m_spellInfo->IsChanneled() || m_casttime) && m_caster->GetTypeId() == TYPEID_PLAYER && m_caster->isMoving() && m_spellInfo->InterruptFlags & SPELL_INTERRUPT_FLAG_MOVEMENT)
@@ -2971,18 +2994,14 @@ void Spell::prepare(SpellCastTargets const* targets, AuraEffect const* triggered
         }
 
         m_caster->SetCurrentCastSpell(this);
-        SendSpellStart();
-
-        // set target for proper facing
-        if ((m_casttime || m_spellInfo->IsChanneled()) && !(_triggeredCastFlags & TRIGGERED_IGNORE_SET_FACING))
-            if (m_caster->GetTypeId() == TYPEID_UNIT && m_targets.GetObjectTarget() && m_caster != m_targets.GetObjectTarget())
-                m_caster->ToCreature()->FocusTarget(this, m_targets.GetObjectTarget());
+        if (!m_isDelayedInstantCast)
+            SendSpellStart();
 
         if (!(_triggeredCastFlags & TRIGGERED_IGNORE_GCD))
             TriggerGlobalCooldown();
 
         //item: first cast may destroy item and second cast causes crash
-        if (!m_casttime && !m_spellInfo->StartRecoveryTime && !m_castItemGUID && GetCurrentContainer() == CURRENT_GENERIC_SPELL)
+        if (!m_casttime && !m_isDelayedInstantCast && !m_spellInfo->StartRecoveryTime && !m_castItemGUID && GetCurrentContainer() == CURRENT_GENERIC_SPELL)
             cast(true);
     }
 }
@@ -2991,6 +3010,9 @@ void Spell::cancel()
 {
     if (m_spellState == SPELL_STATE_FINISHED)
         return;
+    // delayed instant casts are used for client-side visual orientation; they are treated as instant for all intents and purposes server-side, and thus cannot be interrupted by another cast
+    if (m_isDelayedInstantCast)
+        return;
 
     uint32 oldState = m_spellState;
     m_spellState = SPELL_STATE_FINISHED;
@@ -3060,6 +3082,9 @@ void Spell::cast(bool skipCheck)
         return;
     }
 
+    if (m_isDelayedInstantCast)
+        SendSpellStart();
+
     if (Player* playerCaster = m_caster->ToPlayer())
     {
         // now that we've done the basic check, now run the scripts
@@ -3139,6 +3164,16 @@ void Spell::cast(bool skipCheck)
         }
     }
 
+    // if the spell allows the creature to turn while casting, then adjust server-side orientation to face the target now
+    // client-side orientation is handled by the client itself, as the cast target is targeted due to Creature::FocusTarget
+    if (m_caster->GetTypeId() == TYPEID_UNIT && !m_caster->HasFlag(UNIT_FIELD_FLAGS, UNIT_FLAG_PLAYER_CONTROLLED))
+        if (!m_spellInfo->HasAttribute(SPELL_ATTR5_DONT_TURN_DURING_CAST))
+            if (WorldObject* objTarget = m_targets.GetObjectTarget())
+            {
+                m_caster->SetInFront(objTarget);
+                m_caster->SetFacingToObject(objTarget);
+            }
+
     SelectSpellTargets();
 
     // Spell may be finished after target map check
@@ -3242,6 +3277,9 @@ void Spell::cast(bool skipCheck)
     }
 
     SetExecutedCurrently(false);
+
+    if (Creature* creatureCaster = m_caster->ToCreature())
+        creatureCaster->ReleaseFocus(this);
 }
 
 void Spell::handle_immediate()