Update BookLever related functions to use Rectangle.

This is mainly to help isolate functionality in the hopes of adding a specialised object class for this type of object as suggested by @julealgon in https://github.com/diasurgical/devilutionX/pull/2344#discussion_r667415019

For example, AddSCambBook performs almost the same logic but uses var6 instead of var8 for the trigger condition/identifier.

Source/loadsave.cpp

@@ -741,7 +741,7 @@ static void LoadObject(LoadHelper *file, int i)
 	pObject->_oVar4 = file->NextLE<int32_t>();
 	pObject->_oVar5 = file->NextLE<int32_t>();
 	pObject->_oVar6 = file->NextLE<uint32_t>();
-	pObject->_oVar7 = static_cast<_speech_id>(file->NextLE<int32_t>());
+	pObject->bookMessage = static_cast<_speech_id>(file->NextLE<int32_t>());
 	pObject->_oVar8 = file->NextLE<int32_t>();
 }
 
@@ -1783,7 +1783,7 @@ static void SaveObject(SaveHelper *file, int i)
 	file->WriteLE<int32_t>(pObject->_oVar4);
 	file->WriteLE<int32_t>(pObject->_oVar5);
 	file->WriteLE<uint32_t>(pObject->_oVar6);
-	file->WriteLE<int32_t>(pObject->_oVar7);
+	file->WriteLE<int32_t>(pObject->bookMessage);
 	file->WriteLE<int32_t>(pObject->_oVar8);
 }
 

Source/objects.cpp

@@ -476,7 +476,16 @@ void AddCandles()
 	AddObject(OBJ_STORYCANDLE, { tx + 2, ty + 2 });
 }
 
-void AddBookLever(int x1, int y1, int x2, int y2, _speech_id msg)
+/**
+ * @brief Attempts to spawn a book somewhere on the current floor which when activated will change a region of the map.
+ *
+ * This object acts like a lever and will cause a change to the map based on what quest is active. The exact effect is
+ * determined by OperateBookLever().
+ *
+ * @param affectedArea The map region to be updated when this object is activated by the player.
+ * @param msg The quest text to play when the player activates the book.
+*/
+void AddBookLever(Rectangle affectedArea, _speech_id msg)
 {
 	int cnt = 0;
 	int xp;
@@ -509,8 +518,8 @@ void AddBookLever(int x1, int y1, int x2, int y2, _speech_id msg)
 		AddObject(OBJ_BLOODBOOK, { xp, yp });
 	}
 	int ob = dObject[xp][yp] - 1;
-	Objects[ob].SetMapRange({ x1, y1 }, { x2, y2 }, leverid);
-	SetBookMsg(ob, msg);
+	Objects[ob].SetMapRange(affectedArea, leverid);
+	Objects[ob].bookMessage = msg;
 	leverid++;
 	Objects[ob]._oVar6 = Objects[ob]._oAnimFrame + 1;
 }
@@ -1062,7 +1071,7 @@ void InitObjects()
 					break;
 				}
 				Quests[Q_BLIND]._qmsg = spId;
-				AddBookLever(setpc_x, setpc_y, setpc_w + setpc_x + 1, setpc_h + setpc_y + 1, spId);
+				AddBookLever({ { setpc_x, setpc_y }, { setpc_w + 1, setpc_h + 1 } }, spId);
 				LoadMapObjs("Levels\\L2Data\\Blind2.DUN", { 2 * setpc_x, 2 * setpc_y });
 			}
 			if (QuestStatus(Q_BLOOD)) {
@@ -1088,7 +1097,7 @@ void InitObjects()
 					break;
 				}
 				Quests[Q_BLOOD]._qmsg = spId;
-				AddBookLever(setpc_x, setpc_y + 3, setpc_x + 2, setpc_y + 7, spId);
+				AddBookLever({ { setpc_x, setpc_y + 3 }, { 2, 4 } }, spId);
 				AddObject(OBJ_PEDISTAL, { 2 * setpc_x + 25, 2 * setpc_y + 32 });
 			}
 			InitRndBarrels();
@@ -1121,7 +1130,7 @@ void InitObjects()
 					break;
 				}
 				Quests[Q_WARLORD]._qmsg = spId;
-				AddBookLever(setpc_x, setpc_y, setpc_x + setpc_w, setpc_y + setpc_h, spId);
+				AddBookLever({ { setpc_x, setpc_y }, { setpc_w, setpc_h } }, spId);
 				LoadMapObjs("Levels\\L4Data\\Warlord.DUN", { 2 * setpc_x, 2 * setpc_y });
 			}
 			if (QuestStatus(Q_BETRAYER) && !gbIsMultiplayer)
@@ -1247,11 +1256,6 @@ void SetupObject(int i, Point position, _object_id ot)
 	Objects[i]._oDoorFlag = false;
 }
 
-void SetBookMsg(int i, _speech_id msg)
-{
-	Objects[i]._oVar7 = msg;
-}
-
 void AddL1Door(int i, Point position, _object_id objectType)
 {
 	Objects[i]._oDoorFlag = true;
@@ -2936,7 +2940,7 @@ void OperateBookLever(int pnum, int i)
 			}
 		}
 		Objects[i]._oAnimFrame = Objects[i]._oVar6;
-		InitQTextMsg(Objects[i]._oVar7);
+		InitQTextMsg(Objects[i].bookMessage);
 		if (pnum == MyPlayerId)
 			NetSendCmdParam1(false, CMD_OPERATEOBJ, i);
 	}

Source/objects.h

@@ -48,7 +48,12 @@ struct ObjectStruct {
 	int _oVar4;
 	int _oVar5;
 	uint32_t _oVar6;
-	_speech_id _oVar7;
+	/**
+	 * @brief ID of a quest message to play when this object is activated.
+	 *
+	 * Used by spell book objects which trigger quest progress for Halls of the Blind, Valor, or Warlord of Blood
+	 */
+	_speech_id bookMessage;
 	int _oVar8;
 
 	/**
@@ -58,16 +63,16 @@ struct ObjectStruct {
 	 * antechamber levers). The coordinates used for this region are based on a 40*40 grid overlaying the central
 	 * 80*80 region of the dungeon.
 	 *
-	 * @param topLeft corner of the map region closest to the origin
-	 * @param bottomRight corner of the map region furthest from the origin
+	 * @param topLeftPosition corner of the map region closest to the origin
+	 * @param bottomRightPosition corner of the map region furthest from the origin
 	 * @param v ID/discriminator for the object type? Needs to be investigated further
 	 */
-	constexpr void SetMapRange(Point topLeft, Point bottomRight, int v)
+	constexpr void SetMapRange(Point topLeftPosition, Point bottomRightPosition, int v)
 	{
-		_oVar1 = topLeft.x;
-		_oVar2 = topLeft.y;
-		_oVar3 = bottomRight.x;
-		_oVar4 = bottomRight.y;
+		_oVar1 = topLeftPosition.x;
+		_oVar2 = topLeftPosition.y;
+		_oVar3 = bottomRightPosition.x;
+		_oVar4 = bottomRightPosition.y;
 		_oVar8 = v;
 	}
 
@@ -95,7 +100,6 @@ void AddL1Objs(int x1, int y1, int x2, int y2);
 void AddL2Objs(int x1, int y1, int x2, int y2);
 void InitObjects();
 void SetMapObjects(const uint16_t *dunData, int startx, int starty);
-void SetBookMsg(int i, _speech_id msg);
 void GetRndObjLoc(int randarea, int *xx, int *yy);
 void AddMushPatch();
 void AddSlainHero();