Merge pull request #1549 from ghoulslash/last_ball

add last used ball

graphics/battle_interface/ability_pop_up.pal

@@ -0,0 +1,19 @@
+JASC-PAL
+0100
+16
+1 177 91
+143 129 149
+103 91 111
+79 65 85
+59 31 81
+103 89 109
+231 239 245
+249 253 255
+0 0 0
+0 0 0
+107 115 115
+74 66 82
+0 0 0
+214 214 206
+132 140 140
+0 0 0

include/battle.h

@@ -37,6 +37,7 @@
 #define B_ACTION_CANCEL_PARTNER         12 // when choosing an action
 #define B_ACTION_NOTHING_FAINTED        13 // when choosing an action
 #define B_ACTION_DEBUG                  20
+#define B_ACTION_THROW_BALL             21 // R to throw last used ball
 #define B_ACTION_NONE                   0xFF
 
 #define MAX_TRAINER_ITEMS 4
@@ -602,6 +603,7 @@ struct BattleStruct
     u8 quickClawBattlerId;
     struct StolenItem itemStolen[PARTY_SIZE];  // Player's team that had items stolen (two bytes per party member)
     u8 blunderPolicy:1; // should blunder policy activate
+    u8 ballSpriteIds[2];    // item gfx, window gfx
 };
 
 #define GET_MOVE_TYPE(move, typeArg)                        \
@@ -905,5 +907,6 @@ extern u8 gNumberOfMovesToChoose;
 extern u8 gBattleControllerData[MAX_BATTLERS_COUNT];
 extern bool8 gHasFetchedBall;
 extern u8 gLastUsedBall;
+extern u16 gLastThrownBall;
 
 #endif // GUARD_BATTLE_H

include/battle_interface.h

@@ -93,5 +93,9 @@ u8 GetScaledHPFraction(s16 hp, s16 maxhp, u8 scale);
 u8 GetHPBarLevel(s16 hp, s16 maxhp);
 void CreateAbilityPopUp(u8 battlerId, u32 ability, bool32 isDoubleBattle);
 void DestroyAbilityPopUp(u8 battlerId);
+bool32 CanThrowLastUsedBall(void);
+void TryHideLastUsedBall(void);
+void TryRestoreLastUsedBall(void);
+void TryAddLastUsedBallItemSprites(void);
 
 #endif // GUARD_BATTLE_INTERFACE_H

include/battle_util.h

@@ -47,6 +47,7 @@ struct TypePower
 
 extern const struct TypePower gNaturalGiftTable[];
 
+void HandleAction_ThrowBall(void);
 bool32 IsAffectedByFollowMe(u32 battlerAtk, u32 defSide, u32 move);
 void HandleAction_UseMove(void);
 void HandleAction_Switch(void);

include/constants/battle_config.h

@@ -166,6 +166,10 @@
 // Item Theft Settings
 #define B_TRAINERS_KNOCK_OFF_ITEMS  TRUE  // If TRUE, trainers can steal/swap your items (non-berries are restored after battle). In vanilla games trainers cannot steal items.
 
+// Last Used Ball
+#define B_LAST_USED_BALL            TRUE        // If TRUE, the "last used ball" feature from Gen 7 will be implemented
+#define B_LAST_USED_BALL_BUTTON     R_BUTTON    // If last used ball is implemented, this button (or button combo) will trigger throwing the last used ball.
+
 // Other
 #define B_DOUBLE_WILD_CHANCE        0     // % chance of encountering two Pokémon in a Wild Encounter.
 #define B_SLEEP_TURNS               GEN_7 // In Gen5+, sleep lasts for 1-3 turns instead of 2-5 turns.

include/item_use.h

@@ -33,5 +33,6 @@ void ItemUseInBattle_EnigmaBerry(u8);
 void Task_UseDigEscapeRopeOnField(u8 taskId);
 u8 CanUseDigOrEscapeRopeOnCurMap(void);
 u8 CheckIfItemIsTMHMOrEvolutionStone(u16 itemId);
+u32 CanThrowBall(void);
 
 #endif // GUARD_ITEM_USE_H

src/battle_controller_player.c

@@ -249,7 +249,8 @@ static void HandleInputChooseAction(void)
     if (JOY_NEW(A_BUTTON))
     {
         PlaySE(SE_SELECT);
-
+        TryHideLastUsedBall();
+        
         switch (gActionSelectionCursor[gActiveBattler])
         {
         case 0:
@@ -336,6 +337,15 @@ static void HandleInputChooseAction(void)
         BtlController_EmitTwoReturnValues(1, B_ACTION_DEBUG, 0);
         PlayerBufferExecCompleted();
     }
+    #if B_LAST_USED_BALL == TRUE
+    else if (JOY_NEW(B_LAST_USED_BALL_BUTTON) && CanThrowLastUsedBall())
+    {
+        PlaySE(SE_SELECT);
+        TryHideLastUsedBall();
+        BtlController_EmitTwoReturnValues(1, B_ACTION_THROW_BALL, 0);
+        PlayerBufferExecCompleted();
+    }
+    #endif
 }
 
 static void UnusedEndBounceEffect(void)
@@ -372,6 +382,7 @@ static void HandleInputChooseTarget(void)
         else
             BtlController_EmitTwoReturnValues(1, 10, gMoveSelectionCursor[gActiveBattler] | (gMultiUsePlayerCursor << 8));
         EndBounceEffect(gMultiUsePlayerCursor, BOUNCE_HEALTHBOX);
+        TryHideLastUsedBall();
         HideMegaTriggerSprite();
         PlayerBufferExecCompleted();
     }
@@ -514,6 +525,7 @@ static void HandleInputShowTargets(void)
         else
             BtlController_EmitTwoReturnValues(1, 10, gMoveSelectionCursor[gActiveBattler] | (gMultiUsePlayerCursor << 8));
         HideMegaTriggerSprite();
+        TryHideLastUsedBall();
         PlayerBufferExecCompleted();
     }
     else if (gMain.newKeys & B_BUTTON || gPlayerDpadHoldFrames > 59)
@@ -606,6 +618,7 @@ static void HandleInputChooseMove(void)
             else
                 BtlController_EmitTwoReturnValues(1, 10, gMoveSelectionCursor[gActiveBattler] | (gMultiUsePlayerCursor << 8));
             HideMegaTriggerSprite();
+            TryHideLastUsedBall();
             PlayerBufferExecCompleted();
         }
         else if (canSelectTarget == 1)
@@ -2696,6 +2709,7 @@ static void PlayerHandleChooseAction(void)
     for (i = 0; i < 4; i++)
         ActionSelectionDestroyCursorAt(i);
 
+    TryRestoreLastUsedBall();
     ActionSelectionCreateCursorAt(gActionSelectionCursor[gActiveBattler], 0);
     BattleStringExpandPlaceholdersToDisplayedString(gText_WhatWillPkmnDo);
     BattlePutTextOnWindow(gDisplayedStringBattle, 1);

src/battle_interface.c

@@ -27,6 +27,10 @@
 #include "constants/battle_config.h"
 #include "data.h"
 #include "pokemon_summary_screen.h"
+#include "item_icon.h"
+#include "item_use.h"
+#include "item.h"
+#include "constants/items.h"
 
 enum
 {   // Corresponds to gHealthboxElementsGfxTable (and the tables after it) in graphics.c
@@ -196,6 +200,9 @@ static u8 CalcBarFilledPixels(s32 maxValue, s32 oldValue, s32 receivedValue, s32
 static void SpriteCb_AbilityPopUp(struct Sprite *sprite);
 static void Task_FreeAbilityPopUpGfx(u8 taskId);
 
+static void SpriteCB_LastUsedBall(struct Sprite *sprite);
+static void SpriteCB_LastUsedBallWin(struct Sprite *sprite);
+
 // const rom data
 static const struct OamData sUnknown_0832C138 =
 {
@@ -723,6 +730,12 @@ u8 GetMegaIndicatorSpriteId(u32 healthboxSpriteId)
     return gSprites[spriteId].hOther_IndicatorSpriteId;
 }
 
+static void InitLastUsedBallAssets(void)
+{
+    gBattleStruct->ballSpriteIds[0] = MAX_SPRITES;
+    gBattleStruct->ballSpriteIds[1] = MAX_SPRITES;
+}
+
 u8 CreateBattlerHealthboxSprites(u8 battlerId)
 {
     s16 data6 = 0;
@@ -812,6 +825,9 @@ u8 CreateBattlerHealthboxSprites(u8 battlerId)
         gSprites[megaIndicatorSpriteId].invisible = TRUE;
     }
 
+    gBattleStruct->ballSpriteIds[0] = MAX_SPRITES;
+    gBattleStruct->ballSpriteIds[1] = MAX_SPRITES;
+
     return healthboxLeftSpriteId;
 }
 
@@ -3123,3 +3139,200 @@ static void Task_FreeAbilityPopUpGfx(u8 taskId)
         DestroyTask(taskId);
     }
 }
+
+// last used ball
+#define LAST_BALL_WINDOW_TAG 0xD721
+
+static const struct OamData sOamData_LastUsedBall =
+{
+	.y = 0,
+	.affineMode = 0,
+	.objMode = 0,
+	.mosaic = 0,
+	.bpp = 0,
+	.shape = SPRITE_SHAPE(32x32),
+	.x = 0,
+	.matrixNum = 0,
+	.size = SPRITE_SIZE(32x32),
+	.tileNum = 0,
+	.priority = 1,
+	.paletteNum = 0,
+	.affineParam = 0,
+};
+
+static const struct SpriteTemplate sSpriteTemplate_LastUsedBallWindow =
+{
+    .tileTag = LAST_BALL_WINDOW_TAG,
+    .paletteTag = ABILITY_POP_UP_TAG,
+    .oam = &sOamData_LastUsedBall,
+    .anims = gDummySpriteAnimTable,
+    .images = NULL,
+    .affineAnims = gDummySpriteAffineAnimTable,
+    .callback = SpriteCB_LastUsedBallWin
+};
+
+#if B_LAST_USED_BALL_BUTTON == R_BUTTON
+    static const u8 sLastUsedBallWindowGfx[] = INCBIN_U8("graphics/battle_interface/last_used_ball_r.4bpp");
+#else
+    static const u8 sLastUsedBallWindowGfx[] = INCBIN_U8("graphics/battle_interface/last_used_ball_l.4bpp");
+#endif
+static const struct SpriteSheet sSpriteSheet_LastUsedBallWindow =
+{
+    sLastUsedBallWindowGfx, sizeof(sLastUsedBallWindowGfx), LAST_BALL_WINDOW_TAG
+};
+
+#define LAST_USED_BALL_X_F    15
+#define LAST_USED_BALL_X_0    -15
+#define LAST_USED_BALL_Y      ((IsDoubleBattle()) ? 78 : 68)
+
+#define LAST_BALL_WIN_X_F       (LAST_USED_BALL_X_F - 1)
+#define LAST_BALL_WIN_X_0       (LAST_USED_BALL_X_0 - 0)
+#define LAST_USED_WIN_Y         (LAST_USED_BALL_Y - 8)
+
+#define sHide  data[0]
+
+bool32 CanThrowLastUsedBall(void)
+{
+    #if B_LAST_USED_BALL == FALSE
+        return FALSE;
+    #else
+        return (!(CanThrowBall() != 0
+         || (gBattleTypeFlags & BATTLE_TYPE_TRAINER)
+         || !CheckBagHasItem(gLastThrownBall, 1)));
+     #endif
+}
+
+
+void TryAddLastUsedBallItemSprites(void)
+{
+    #if B_LAST_USED_BALL == TRUE
+    if (gLastThrownBall == 0
+      || (gLastThrownBall != 0 && !CheckBagHasItem(gLastThrownBall, 1)))
+    {
+        // we're out of the last used ball, so just set it to the first ball in the bag
+        // we have to compact the bag first bc it is typically only compacted when you open it
+        CompactItemsInBagPocket(&gBagPockets[BALLS_POCKET]);
+        gLastThrownBall = gBagPockets[BALLS_POCKET].itemSlots[0].itemId;
+    }
+    
+    if (CanThrowBall() != 0
+     || (gBattleTypeFlags & BATTLE_TYPE_TRAINER)
+     || !CheckBagHasItem(gLastThrownBall, 1))
+        return;
+
+    // ball
+    if (gBattleStruct->ballSpriteIds[0] == MAX_SPRITES)
+    {
+        gBattleStruct->ballSpriteIds[0] = AddItemIconSprite(102, 102, gLastThrownBall);
+        gSprites[gBattleStruct->ballSpriteIds[0]].x = LAST_USED_BALL_X_0;
+        gSprites[gBattleStruct->ballSpriteIds[0]].y = LAST_USED_BALL_Y;
+        gSprites[gBattleStruct->ballSpriteIds[0]].sHide = FALSE;   // restore
+        gSprites[gBattleStruct->ballSpriteIds[0]].callback = SpriteCB_LastUsedBall;
+    }
+
+    // window
+    LoadSpritePalette(&sSpritePalette_AbilityPopUp);
+    if (GetSpriteTileStartByTag(LAST_BALL_WINDOW_TAG) == 0xFFFF)
+        LoadSpriteSheet(&sSpriteSheet_LastUsedBallWindow);
+
+    if (gBattleStruct->ballSpriteIds[1] == MAX_SPRITES)
+    {
+        gBattleStruct->ballSpriteIds[1] = CreateSprite(&sSpriteTemplate_LastUsedBallWindow,
+           LAST_BALL_WIN_X_0,
+           LAST_USED_WIN_Y, 5);
+        gSprites[gBattleStruct->ballSpriteIds[0]].sHide = FALSE;   // restore
+    }
+    #endif
+}
+
+static void DestroyLastUsedBallWinGfx(struct Sprite *sprite)
+{
+    FreeSpriteTilesByTag(LAST_BALL_WINDOW_TAG);
+    FreeSpritePaletteByTag(ABILITY_POP_UP_TAG);
+    DestroySprite(sprite);
+    gBattleStruct->ballSpriteIds[1] = MAX_SPRITES;
+}
+
+static void DestroyLastUsedBallGfx(struct Sprite *sprite)
+{
+    FreeSpriteTilesByTag(102);
+    FreeSpritePaletteByTag(102);
+    DestroySprite(sprite);
+    gBattleStruct->ballSpriteIds[0] = MAX_SPRITES;
+}
+
+static void SpriteCB_LastUsedBallWin(struct Sprite *sprite)
+{    
+    if (sprite->sHide)
+    {
+        if (sprite->x != LAST_BALL_WIN_X_0)
+            sprite->x--;
+
+        if (sprite->x == LAST_BALL_WIN_X_0)
+            DestroyLastUsedBallWinGfx(sprite);
+    }
+    else
+    {
+        if (sprite->x != LAST_BALL_WIN_X_F)
+            sprite->x++;
+    }
+}
+
+static void SpriteCB_LastUsedBall(struct Sprite *sprite)
+{    
+    if (sprite->sHide)
+    {
+        if (sprite->x != LAST_USED_BALL_X_0)
+            sprite->x--;
+
+        if (sprite->x == LAST_USED_BALL_X_0)
+            DestroyLastUsedBallGfx(sprite);
+    }
+    else
+    {
+        if (sprite->x != LAST_USED_BALL_X_F)
+            sprite->x++;
+    }
+}
+
+static void TryHideOrRestoreLastUsedBall(u8 caseId)
+{
+    #if B_LAST_USED_BALL == TRUE
+    if (gBattleStruct->ballSpriteIds[0] == MAX_SPRITES)
+        return;
+
+    switch (caseId)
+    {
+    case 0: // hide
+        if (gBattleStruct->ballSpriteIds[0] != MAX_SPRITES)
+            gSprites[gBattleStruct->ballSpriteIds[0]].sHide = TRUE;   // hide
+        if (gBattleStruct->ballSpriteIds[1] != MAX_SPRITES)
+            gSprites[gBattleStruct->ballSpriteIds[1]].sHide = TRUE;   // hide
+        break;
+    case 1: // restore
+        if (gBattleStruct->ballSpriteIds[0] != MAX_SPRITES)
+            gSprites[gBattleStruct->ballSpriteIds[0]].sHide = FALSE;   // restore
+        if (gBattleStruct->ballSpriteIds[1] != MAX_SPRITES)
+            gSprites[gBattleStruct->ballSpriteIds[1]].sHide = FALSE;   // restore
+        break;
+    }
+    #endif
+}
+
+void TryHideLastUsedBall(void)
+{
+    #if B_LAST_USED_BALL == TRUE
+    TryHideOrRestoreLastUsedBall(0);
+    #endif
+}
+
+void TryRestoreLastUsedBall(void)
+{
+    #if B_LAST_USED_BALL == TRUE
+    if (gBattleStruct->ballSpriteIds[0] != MAX_SPRITES)
+        TryHideOrRestoreLastUsedBall(1);
+    else
+        TryAddLastUsedBallItemSprites();
+    #endif
+}
+

src/battle_main.c

@@ -230,6 +230,7 @@ EWRAM_DATA u16 gPartnerSpriteId = 0;
 EWRAM_DATA struct TotemBoost gTotemBoosts[MAX_BATTLERS_COUNT] = {0};
 EWRAM_DATA bool8 gHasFetchedBall = FALSE;
 EWRAM_DATA u8 gLastUsedBall = 0;
+EWRAM_DATA u16 gLastThrownBall = 0;
 
 // IWRAM common vars
 void (*gPreBattleCallback1)(void);
@@ -401,6 +402,7 @@ static void (* const sTurnActionsFuncsTable[])(void) =
     [B_ACTION_TRY_FINISH] = HandleAction_TryFinish,
     [B_ACTION_FINISHED] = HandleAction_ActionFinished,
     [B_ACTION_NOTHING_FAINTED] = HandleAction_NothingIsFainted,
+    [B_ACTION_THROW_BALL] = HandleAction_ThrowBall,
 };
 
 static void (* const sEndTurnFuncsTable[])(void) =
@@ -4073,6 +4075,10 @@ static void HandleTurnActionSelectionState(void)
                 case B_ACTION_SAFARI_BALL:
                     gBattleCommunication[gActiveBattler]++;
                     break;
+                case B_ACTION_THROW_BALL:
+                    gBattleStruct->throwingPokeBall = TRUE;
+                    gBattleCommunication[gActiveBattler]++;
+                    break;
                 case B_ACTION_SAFARI_POKEBLOCK:
                     if ((gBattleResources->bufferB[gActiveBattler][1] | (gBattleResources->bufferB[gActiveBattler][2] << 8)) != 0)
                     {
@@ -4186,6 +4192,13 @@ static void HandleTurnActionSelectionState(void)
     if (gBattleCommunication[ACTIONS_CONFIRMED_COUNT] == gBattlersCount)
     {
         sub_818603C(1);
+        
+        if (WILD_DOUBLE_BATTLE && gBattleStruct->throwingPokeBall) {
+            // if we choose to throw a ball with our second mon, skip the action of the first
+            // (if we have chosen throw ball with first, second's is already skipped)
+            gChosenActionByBattler[B_POSITION_PLAYER_LEFT] = B_ACTION_NOTHING_FAINTED;
+        }
+        
         gBattleMainFunc = SetActionsAndBattlersTurnOrder;
 
         if (gBattleTypeFlags & BATTLE_TYPE_INGAME_PARTNER)
@@ -4507,7 +4520,9 @@ static void SetActionsAndBattlersTurnOrder(void)
         {
             for (gActiveBattler = 0; gActiveBattler < gBattlersCount; gActiveBattler++)
             {
-                if (gChosenActionByBattler[gActiveBattler] == B_ACTION_USE_ITEM || gChosenActionByBattler[gActiveBattler] == B_ACTION_SWITCH)
+                if (gChosenActionByBattler[gActiveBattler] == B_ACTION_USE_ITEM
+                  || gChosenActionByBattler[gActiveBattler] == B_ACTION_SWITCH
+                  || gChosenActionByBattler[gActiveBattler] == B_ACTION_THROW_BALL)
                 {
                     gActionsByTurnOrder[turnOrderId] = gChosenActionByBattler[gActiveBattler];
                     gBattlerByTurnOrder[turnOrderId] = gActiveBattler;
@@ -4516,7 +4531,9 @@ static void SetActionsAndBattlersTurnOrder(void)
             }
             for (gActiveBattler = 0; gActiveBattler < gBattlersCount; gActiveBattler++)
             {
-                if (gChosenActionByBattler[gActiveBattler] != B_ACTION_USE_ITEM && gChosenActionByBattler[gActiveBattler] != B_ACTION_SWITCH)
+                if (gChosenActionByBattler[gActiveBattler] != B_ACTION_USE_ITEM
+                  && gChosenActionByBattler[gActiveBattler] != B_ACTION_SWITCH
+                  && gChosenActionByBattler[gActiveBattler] != B_ACTION_THROW_BALL)
                 {
                     gActionsByTurnOrder[turnOrderId] = gChosenActionByBattler[gActiveBattler];
                     gBattlerByTurnOrder[turnOrderId] = gActiveBattler;
@@ -4532,7 +4549,9 @@ static void SetActionsAndBattlersTurnOrder(void)
                     if (gActionsByTurnOrder[i] != B_ACTION_USE_ITEM
                         && gActionsByTurnOrder[j] != B_ACTION_USE_ITEM
                         && gActionsByTurnOrder[i] != B_ACTION_SWITCH
-                        && gActionsByTurnOrder[j] != B_ACTION_SWITCH)
+                        && gActionsByTurnOrder[j] != B_ACTION_SWITCH
+                        && gActionsByTurnOrder[i] != B_ACTION_THROW_BALL
+                        && gActionsByTurnOrder[j] != B_ACTION_THROW_BALL)
                     {
                         if (GetWhoStrikesFirst(battler1, battler2, FALSE))
                             SwapTurnOrder(i, j);

src/battle_script_commands.c

@@ -12512,7 +12512,8 @@ static void Cmd_handleballthrow(void)
     {
         u32 odds;
         u8 catchRate;
-
+    
+        gLastThrownBall = gLastUsedItem;
         if (gLastUsedItem == ITEM_SAFARI_BALL)
             catchRate = gBattleStruct->safariCatchFactor * 1275 / 100;
         else

src/battle_util.c

@@ -756,6 +756,17 @@ void HandleAction_SafariZoneBallThrow(void)
     gCurrentActionFuncId = B_ACTION_EXEC_SCRIPT;
 }
 
+void HandleAction_ThrowBall(void)
+{
+    gBattlerAttacker = gBattlerByTurnOrder[gCurrentTurnActionNumber];
+    gBattle_BG0_X = 0;
+    gBattle_BG0_Y = 0;
+    gLastUsedItem = gLastThrownBall;
+    RemoveBagItem(gLastUsedItem, 1);
+    gBattlescriptCurrInstr = BattleScript_BallThrow;
+    gCurrentActionFuncId = B_ACTION_EXEC_SCRIPT;
+}
+
 void HandleAction_ThrowPokeblock(void)
 {
     gBattlerAttacker = gBattlerByTurnOrder[gCurrentTurnActionNumber];

src/item_use.c

@@ -936,42 +936,46 @@ void ItemUseOutOfBattle_EvolutionStone(u8 taskId)
     SetUpItemUseCallback(taskId);
 }
 
-void ItemUseInBattle_PokeBall(u8 taskId)
+u32 CanThrowBall(void)
 {
     if (IsBattlerAlive(GetBattlerAtPosition(B_POSITION_OPPONENT_LEFT))
-        && IsBattlerAlive(GetBattlerAtPosition(B_POSITION_OPPONENT_RIGHT))) // There are two present pokemon.
+        && IsBattlerAlive(GetBattlerAtPosition(B_POSITION_OPPONENT_RIGHT))) 
     {
-        static const u8 textCantThrowPokeBall[] = _("Cannot throw a ball!\nThere are two pokemon out there!\p");
-
-        if (!InBattlePyramid())
-            DisplayItemMessage(taskId, 1, textCantThrowPokeBall, CloseItemMessage);
-        else
-            DisplayItemMessageInBattlePyramid(taskId, textCantThrowPokeBall, Task_CloseBattlePyramidBagMessage);
+        return 1;   // There are two present pokemon.
     }
-    else if (gBattlerInMenuId == GetBattlerAtPosition(B_POSITION_PLAYER_RIGHT)
-             && IsBattlerAlive(GetBattlerAtPosition(B_POSITION_PLAYER_LEFT))) // Attempting to throw a ball with the second pokemon while both are alive.
+    else if (IsPlayerPartyAndPokemonStorageFull() == TRUE)
     {
-        static const u8 textCantThrowPokeBall[] = _("Cannot throw a ball!\p");
-
-        if (!InBattlePyramid())
-            DisplayItemMessage(taskId, 1, textCantThrowPokeBall, CloseItemMessage);
-        else
-            DisplayItemMessageInBattlePyramid(taskId, textCantThrowPokeBall, Task_CloseBattlePyramidBagMessage);
+        return 2;   // No room for mon
     }
-    else if (IsPlayerPartyAndPokemonStorageFull() == FALSE) // have room for mon?
+    
+    return 0;   // usable 
+}
+
+static const u8 sText_CantThrowPokeBall_TwoMons[] = _("Cannot throw a ball!\nThere are two pokemon out there!\p");
+void ItemUseInBattle_PokeBall(u8 taskId)
+{
+    switch (CanThrowBall())
     {
+    case 0: // usable
+    default:
         RemoveBagItem(gSpecialVar_ItemId, 1);
         if (!InBattlePyramid())
             Task_FadeAndCloseBagMenu(taskId);
         else
             CloseBattlePyramidBag(taskId);
-    }
-    else
-    {
+        break;
+    case 1:  // There are two present pokemon.
+        if (!InBattlePyramid())
+            DisplayItemMessage(taskId, 1, sText_CantThrowPokeBall_TwoMons, CloseItemMessage);
+        else
+            DisplayItemMessageInBattlePyramid(taskId, sText_CantThrowPokeBall_TwoMons, Task_CloseBattlePyramidBagMessage);
+        break;
+    case 2: // No room for mon
         if (!InBattlePyramid())
             DisplayItemMessage(taskId, 1, gText_BoxFull, CloseItemMessage);
         else
             DisplayItemMessageInBattlePyramid(taskId, gText_BoxFull, Task_CloseBattlePyramidBagMessage);
+        break;
     }
 }
 

src/new_game.c

@@ -45,6 +45,7 @@
 #include "berry_powder.h"
 #include "mevent.h"
 #include "union_room_chat.h"
+#include "constants/items.h"
 
 extern const u8 EventScript_ResetAllMapFlags[];