Added yet another trainer slide condition

Now a trainer NPC can also say something before the first turn of a battle starts for good.

include/battle.h

@@ -669,6 +669,7 @@ struct BattleStruct
     u8 trainerSlidePlayerMonUnaffectedMsgState:2;
     bool8 trainerSlideMegaEvolutionMsgDone:1;
     bool8 trainerSlideZMoveMsgDone:1;
+    bool8 trainerSlideBeforeFirstTurnMsgDone:1;
 };
 
 #define F_DYNAMIC_TYPE_1 (1 << 6)

include/battle_message.h

@@ -236,6 +236,7 @@ enum
     TRAINER_SLIDE_PLAYER_MON_UNAFFECTED,
     TRAINER_SLIDE_MEGA_EVOLUTION,
     TRAINER_SLIDE_Z_MOVE,
+    TRAINER_SLIDE_BEFORE_FIRST_TURN,
 };
 
 void BufferStringBattle(u16 stringID);

src/battle_main.c

@@ -3776,6 +3776,9 @@ static void TryDoEventsBeforeFirstTurn(void)
         StopCryAndClearCrySongs();
         BattleScriptExecute(BattleScript_ArenaTurnBeginning);
     }
+
+    if ((i = ShouldDoTrainerSlide(GetBattlerAtPosition(B_POSITION_OPPONENT_LEFT), TRAINER_SLIDE_BEFORE_FIRST_TURN)))
+        BattleScriptExecute(i == 1 ? BattleScript_TrainerASlideMsgEnd2 : BattleScript_TrainerBSlideMsgEnd2);
 }
 
 static void HandleEndTurn_ContinueBattle(void)

src/battle_message.c

@@ -3881,6 +3881,7 @@ struct TrainerSlide
     const u8 *msgPlayerMonUnaffected;
     const u8 *msgMegaEvolution;
     const u8 *msgZMove;
+    const u8 *msgBeforeFirstTurn;
 };
 
 static const struct TrainerSlide sTrainerSlides[] =
@@ -3899,6 +3900,7 @@ static const struct TrainerSlide sTrainerSlides[] =
         .msgPlayerMonUnaffected = sText_ButNoEffect,
         .msgMegaEvolution = sText_PowderExplodes,
         .msgZMove = sText_Electromagnetism,
+        .msgBeforeFirstTurn = sText_GravityIntensified,
     },
     */
 };
@@ -4044,6 +4046,14 @@ u32 ShouldDoTrainerSlide(u32 battlerId, u32 which)
                     return TRUE;
                 }
                 break;
+            case TRAINER_SLIDE_BEFORE_FIRST_TURN:
+                if (sTrainerSlides[i].msgBeforeFirstTurn != NULL && !gBattleStruct->trainerSlideBeforeFirstTurnMsgDone)
+                {
+                    gBattleStruct->trainerSlideBeforeFirstTurnMsgDone = TRUE;
+                    gBattleStruct->trainerSlideMsg = sTrainerSlides[i].msgBeforeFirstTurn;
+                    return TRUE;
+                }
+                break;
             }
             break;
         }