Routines
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CB44: Script Routine: (4B) Task-four entity action
Nudge the task-four creature one character toward its target.
Input
IX Address of complex state data for an entity
ScriptRoutine_TaskFourStepToward CB44 LD A,(IX+$0D) Load A with the current entity's extra state.
CB47 BIT 4,A Is bit 04 of the current entity's extra state set? If not, jump to ScriptRoutine_TaskFourStepToward_RequireExtraBit2.
CB49 JR Z,ScriptRoutine_TaskFourStepToward_RequireExtraBit2
CB4B RES 4,A Clear bit 04 of the flag byte in A.
CB4D LD (IX+$0D),A Set the current entity's extra state.
CB50 JR ScriptRoutine_TaskFourStepToward_MaybeNegateDelta Jump to ScriptRoutine_TaskFourStepToward_MaybeNegateDelta to continue this routine.
Require extra-state bit 02 before stepping; otherwise bail to the next script.
ScriptRoutine_TaskFourStepToward_RequireExtraBit2 CB52 BIT 2,A Is bit 02 of the current entity's extra state set? If so, jump to AdvanceScriptInstruction.
CB54 JP NZ,AdvanceScriptInstruction
At extra-state ends (0B or 00), reverse the signed step via ScriptRoutine_TaskFourStepToward_NegateDirection.
ScriptRoutine_TaskFourStepToward_MaybeNegateDelta CB57 LD A,(IX+$0C) Load A with the current entity's extra state.
CB5A CP $0B Is the current entity's extra state equal to 0B? If so, call ScriptRoutine_TaskFourStepToward_NegateDirection.
CB5C CALL Z,ScriptRoutine_TaskFourStepToward_NegateDirection
CB5F OR A Is A zero? If so, call ScriptRoutine_TaskFourStepToward_NegateDirection.
CB60 CALL Z,ScriptRoutine_TaskFourStepToward_NegateDirection
Apply the signed step: grow or shrink extra state, then rewrite X / X-extent.
ScriptRoutine_TaskFourStepToward_ApplySignedStep CB63 LD C,(IX+$09) Load C with the current entity's direction / state.
CB66 BIT 7,C Is bit 07 of the direction/state in C set (negative delta)? If so, jump to ScriptRoutine_TaskFourStepToward_DecExtraState.
CB68 JR NZ,ScriptRoutine_TaskFourStepToward_DecExtraState
CB6A INC A Advance the current entity's extra state by one.
CB6B JR ScriptRoutine_TaskFourStepToward_WriteCoordsAndFlags Jump to ScriptRoutine_TaskFourStepToward_WriteCoordsAndFlags to continue this routine.
Negative delta path: shrink extra state before rewriting coordinates.
ScriptRoutine_TaskFourStepToward_DecExtraState CB6D DEC A Step the current entity's extra state back by one.
Commit the stepped X band, clear latch bit 04, and at X=6C raise it and maybe reverse.
ScriptRoutine_TaskFourStepToward_WriteCoordsAndFlags CB6E LD (IX+$0C),A Set the current entity's extra state.
CB71 LD A,C Copy the saved count/flag from C into A.
CB72 ADD A,(IX+$07) Add the current entity's x-coordinate to A.
CB75 LD (IX+$07),A Set the current entity's x-coordinate.
CB78 LD A,C Copy the saved count/flag from C into A.
CB79 ADD A,(IX+$08) Add the current entity's x-extent to A.
CB7C LD (IX+$08),A Set the current entity's x-extent.
CB7F LD A,($72B3) Load A with the game event flags (GameEventFlags).
CB82 RES 4,A Clear bit 04 of the flag byte in A.
CB84 LD ($72B3),A Set the game event flags (GameEventFlags).
CB87 LD A,(IX+$07) Load A with the current entity's x-coordinate.
CB8A CP $6C Is the current entity's x-coordinate equal to 6C? If not, jump to AdvanceScriptInstruction.
CB8C JP NZ,AdvanceScriptInstruction
CB8F LD A,($72B3) Load A with the game event flags (GameEventFlags).
CB92 SET 4,A Set bit 04 of game event flags.
CB94 LD ($72B3),A Set the game event flags (GameEventFlags).
CB97 BIT 1,A Is bit 01 of game event flags set? If not, jump to ScriptRoutine_TaskFourStepToward_MatchCreatureThenRetrace.
CB99 JR Z,ScriptRoutine_TaskFourStepToward_MatchCreatureThenRetrace
CB9B LD HL,$CA9B Point HL at task-four script entry CA9B.
CB9E JP ScriptInstruction Jump to ScriptInstruction to execute the script instruction at HL.
At the turnaround X, retrace only when aligned with the vat (StateData_Complex_28) in room 03.
ScriptRoutine_TaskFourStepToward_MatchCreatureThenRetrace CBA1 LD IY,$9071 Point IY at the vat entity at StateData_Complex_28.
CBA5 LD A,(IX+$07) Load A with the current entity's x-coordinate.
CBA8 CP (IY+$07) Does this entity's x match the referenced entity's x (IY+07)? If not, jump to AdvanceScriptInstruction.
CBAB JP NZ,AdvanceScriptInstruction
CBAE LD A,(IY+$04) Load A with the referenced entity's room index.
CBB1 CP $03 Is referenced entity's room index equal to 03? If not, jump to AdvanceScriptInstruction.
CBB3 JP NZ,AdvanceScriptInstruction
CBB6 JR ScriptRoutine_TaskFourStepToward_ApplySignedStep Jump to ScriptRoutine_TaskFourStepToward_ApplySignedStep to continue this routine.
Negate the stored direction / step delta so the entity walks the other way.
ScriptRoutine_TaskFourStepToward_NegateDirection CBB8 PUSH AF Stash AF on the stack.
CBB9 LD A,(IX+$09) Load A with the current entity's direction / state.
CBBC NEG Negate A (flip a delta/direction).
CBBE LD (IX+$09),A Set the current entity's direction / state.
CBC1 POP AF Restore AF from the stack.
CBC2 RET Return.
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