EBLAN_ENGINE/include/engine_simulation.inc

; Fixed 60 Hz simulation and QPC scheduler. No presentation or keyboard APIs in
; Engine_Tick. AdvanceSimulation accepts elapsed QPC counts for deterministic tests.
.code
QueryPerformanceCounter PROTO :DWORD
QueryPerformanceFrequency PROTO :DWORD

GetSimulationState PROC
    mov eax, SIM_UNFOCUSED
    cmp inputFocused, 0
    je state_ready
    mov eax, SIM_PAUSED
    cmp isGamePaused, 0
    jne state_ready
    mov eax, SIM_DIALOG
    cmp gameDialogActive, 0
    jne state_ready
    mov eax, SIM_TRANSITION
    cmp fadeState, 0
    jne state_ready
    mov eax, SIM_DEAD
    cmp isPlayerDead, 0
    jne state_ready
    mov eax, SIM_CUTSCENE
    cmp isCutsceneActive, 0
    jne state_ready
    cmp cutscenePending, 0
    jne state_ready
    mov eax, SIM_PLAYING
state_ready:
    ret
GetSimulationState ENDP

; UI edges execute on ticks, never during polling or drawing.
ApplyInputCommands PROC
    cmp keyPause, 0
    je command_menu
    xor isGamePaused, 1
    mov clockReset, 1
command_menu:
    cmp isGamePaused, 0
    je command_hud
    cmp keyMenu1, 0
    je @F
    mov isGamePaused, 0
    mov clockReset, 1
@@:
    cmp keyMenu2, 0
    je @F
    xor enableWeapons, 1
    mov eax, enableWeapons
    mov gameMode, eax
    mov showCrosshair, eax
    mov playerWeapon, WEAPON_NONE
    test eax, eax
    jz @F
    mov playerWeapon, WEAPON_PISTOL
@@:
    cmp keyMenu3, 0
    je @F
    xor hudStyle, 1
@@:
    cmp keyMenu4, 0
    je @F
    call RestartCurrentRoom
    ; A failed reload stays paused with all room/gameplay state intact.
@@:
    cmp keyMenu5, 0
    je command_done
    mov isRunning, 0
    ret
command_hud:
    cmp keyMap, 0
    je @F
    xor keyShowMap, 1
@@:
    cmp keyHud, 0
    je @F
    xor hudStyle, 1
@@:
    call GetSimulationState
    cmp eax, SIM_PLAYING
    jne command_done
    cmp keyFlashlight, 0
    je @F
    xor isFlashlightOn, 1
@@:
    cmp keyLightMode, 0
    je @F
    inc lightingMode
    cmp lightingMode, 3
    jb @F
    mov lightingMode, 0
@@:
    cmp enableWeapons, 0
    je command_done
    cmp gameMode, GAME_MODE_ACTION
    jne command_done
    cmp keyWeapon1, 0
    je @F
    mov playerWeapon, WEAPON_KNIFE
@@:
    cmp keyWeapon2, 0
    je @F
    mov playerWeapon, WEAPON_PISTOL
@@:
    cmp keyWeapon3, 0
    je command_done
    mov playerWeapon, WEAPON_SHOTGUN
command_done:
    ret
ApplyInputCommands ENDP

Engine_Tick PROC
    inc simulationTicks
    mov gameplayTickBlocked, 1
    call GetSimulationState
    mov simulationState, eax
    cmp eax, SIM_UNFOCUSED
    je tick_done
    call ApplyInputCommands
    cmp clockReset, 0
    jne tick_done
    call GetSimulationState
    mov simulationState, eax
    cmp eax, SIM_PAUSED
    je tick_done
    cmp eax, SIM_DIALOG
    je tick_dialog
    cmp eax, SIM_TRANSITION
    je tick_transition
    cmp eax, SIM_DEAD
    je tick_dead
    cmp mapErrorFrames, 0
    je @F
    dec mapErrorFrames
@@:
    call UpdatePlayer
    call IsGameplayBlocked
    test eax, eax
    jnz tick_cinematic
    call UpdateEntities
    call IsGameplayBlocked
    test eax, eax
    jnz tick_done
    call UpdateCombat
    call IsGameplayBlocked
    test eax, eax
    jnz tick_done
    call Game_OnTick
    call IsGameplayBlocked
    test eax, eax
    jnz tick_done
    call UpdateDynamicLights
    cmp gameToastTimer, 0
    jle tick_done
    dec gameToastTimer
    jmp tick_done
tick_cinematic:
    cmp isCutsceneActive, 0
    je tick_done
    call UpdateDynamicLights
    jmp tick_done
tick_dialog:
    mov al, keyAction
    or al, keyDismiss
    or al, keyAttack
    jz tick_done
    call CloseGameDialog
    mov clockReset, 1
    jmp tick_done
tick_transition:
    call UpdateScreenFade
    jmp tick_done
tick_dead:
    cmp keyRestart, 0
    je tick_done
    call RestartCurrentRoom
tick_done:
    call ConsumeInputEdges
    ret
Engine_Tick ENDP

InitSimulationClock PROC
    invoke QueryPerformanceFrequency, OFFSET qpcFrequency
    invoke QueryPerformanceCounter, OFFSET qpcPrevious
    mov DWORD PTR tickAccumulator, 0
    mov DWORD PTR tickAccumulator+4, 0
    mov clockReset, 0
    ret
InitSimulationClock ENDP

AdvanceSimulation PROC uses ebx esi edi, deltaLow:DWORD, deltaHigh:DWORD
    ; Drop elapsed stalls over 250ms, backwards time, and explicit pause/focus
    ; debt. Bound catch-up to 8 ticks even on an overloaded machine.
    cmp clockReset, 0
    jne clock_discard
    mov eax, DWORD PTR qpcFrequency
    mov edx, DWORD PTR qpcFrequency+4
    shrd eax, edx, 2
    shr edx, 2
    cmp deltaHigh, edx
    ja clock_discard
    jb clock_add
    cmp deltaLow, eax
    ja clock_discard
clock_add:
    mov eax, deltaLow
    mov ebx, 60
    mul ebx
    imul ebx, deltaHigh
    add edx, ebx
    add DWORD PTR tickAccumulator, eax
    adc DWORD PTR tickAccumulator+4, edx
    mov esi, 8
clock_tick:
    mov edx, DWORD PTR tickAccumulator+4
    cmp edx, DWORD PTR qpcFrequency+4
    jb clock_done
    ja clock_step
    mov eax, DWORD PTR tickAccumulator
    cmp eax, DWORD PTR qpcFrequency
    jb clock_done
clock_step:
    mov eax, DWORD PTR qpcFrequency
    mov edx, DWORD PTR qpcFrequency+4
    sub DWORD PTR tickAccumulator, eax
    sbb DWORD PTR tickAccumulator+4, edx
    call Engine_Tick
    cmp clockReset, 0
    jne clock_discard
    dec esi
    jnz clock_tick
clock_discard:
    mov DWORD PTR tickAccumulator, 0
    mov DWORD PTR tickAccumulator+4, 0
    mov clockReset, 0
clock_done:
    ret
AdvanceSimulation ENDP

PumpSimulationClock PROC uses ebx
    invoke QueryPerformanceCounter, OFFSET qpcNow
    mov eax, DWORD PTR qpcNow
    mov edx, DWORD PTR qpcNow+4
    sub eax, DWORD PTR qpcPrevious
    sbb edx, DWORD PTR qpcPrevious+4
    mov ebx, DWORD PTR qpcNow
    mov DWORD PTR qpcPrevious, ebx
    mov ebx, DWORD PTR qpcNow+4
    mov DWORD PTR qpcPrevious+4, ebx
    invoke AdvanceSimulation, eax, edx
    ret
PumpSimulationClock ENDP