Routines
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F1F3: Update Camera Follow
Used by the routine at GameStart.
Adjust the camera window at Pointer_CameraRoomOrigin to follow the target entity.
If the camera-follow delay is non-zero, tick it down; otherwise scroll the window toward the target.
Update_CameraFollow F1F3 LD A,($730A) Load A with the camera-follow delay (CameraFollowDelay).
F1F6 OR A Is the camera-follow delay (CameraFollowDelay) zero? If so, jump to Update_CameraFollow_Active.
F1F7 JR Z,Update_CameraFollow_Active
F1F9 DEC A Decrease A by one.
F1FA LD ($730A),A Set the camera-follow delay (CameraFollowDelay).
F1FD RET Return.
Camera delay expired: point at the follow entity (StateData_Berk) and track it against Pointer_CameraRoomOrigin.
Update_CameraFollow_Active F1FE LD IX,$909B Point IX at the camera-follow entity (StateData_Berk).
F202 LD DE,($72FB) Load DE with the camera room-origin pointer (Pointer_CameraRoomOrigin).
F206 LD B,$20 Load B with loop count 20.
Probe whether the follow entity sits inside the camera X window.
Update_CameraFollow_ProbeX F208 LD A,(IX+$07) Load A with the current entity's x-coordinate.
F20B ADD A,$02 A+=02.
F20D CP E Is A less than E? If so, jump to Update_CameraFollow_ScrollLeft.
F20E JR C,Update_CameraFollow_ScrollLeft
F210 LD C,A Keep A in C for the next calculation.
F211 LD A,D Copy D into A for later use.
F212 CP C Is A less than C? If so, jump to Update_CameraFollow_ScrollRight.
F213 JR C,Update_CameraFollow_ScrollRight
F215 RET Return.
Scroll the camera origin right by 20 until the follow entity is centred.
Update_CameraFollow_ScrollRight F216 LD A,E Copy the saved low byte from E into A.
F217 CP $A0 Is A equal to A0? If so, jump to Update_CameraFollow_WrapLeft.
F219 JR Z,Update_CameraFollow_WrapLeft
F21B ADD A,B A+=B.
F21C LD E,A Copy A into E as a saved coordinate / value.
F21D LD D,A Copy A into D as a saved coordinate / value.
F21E ADD A,B A+=B.
F21F LD D,A Copy A into D as a saved coordinate / value.
F220 LD ($72FB),DE Store DE in Pointer: Camera Room Origin (Pointer_CameraRoomOrigin).
F224 JR Update_CameraFollow_ProbeX Jump to Update_CameraFollow_ProbeX to continue the loop.
Wrap the follow entity left by A0 when the camera hits the right edge.
Update_CameraFollow_WrapLeft F226 LD A,(IX+$07) Load A with the current entity's x-coordinate.
F229 SUB $A0 A-=A0.
F22B LD (IX+$07),A Set the current entity's x-coordinate.
F22E JR Update_CameraFollow_AdjustXExtent Jump to Update_CameraFollow_AdjustXExtent to refresh the follow entity's x-extent.
Scroll the camera origin left by 20 until the follow entity is centred.
Update_CameraFollow_ScrollLeft F230 LD A,E Copy the saved low byte from E into A.
F231 CP $20 Is A equal to 20? If so, jump to Update_CameraFollow_WrapRight.
F233 JR Z,Update_CameraFollow_WrapRight
F235 SUB B Subtract B from A.
F236 LD E,A Copy A into E as a saved coordinate / value.
F237 LD A,D Copy D into A for later use.
F238 SUB B Subtract B from A.
F239 LD D,A Copy A into D as a saved coordinate / value.
F23A LD ($72FB),DE Store DE in Pointer: Camera Room Origin (Pointer_CameraRoomOrigin).
F23E JR Update_CameraFollow_ProbeX Jump to Update_CameraFollow_ProbeX to continue the loop.
Wrap the follow entity right by A0 when the camera hits the left edge.
Update_CameraFollow_WrapRight F240 LD A,(IX+$07) Load A with the current entity's x-coordinate.
F243 ADD A,$A0 A+=A0.
F245 LD (IX+$07),A Set the current entity's x-coordinate.
Refresh the follow entity's X-extent after a wrap and keep probing.
Update_CameraFollow_AdjustXExtent F248 ADD A,$05 A+=05.
F24A LD (IX+$08),A Set the current entity's x-extent.
F24D JR Update_CameraFollow_ProbeX Jump to Update_CameraFollow_ProbeX to continue the loop.
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