Routines
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36215: Control Player
Used by the routines at HandlerWizard, HandlerSerf and HandlerKnight.
Moves the entity of a character, using the controls. Called by the handlers of the knight and the serf (and the wizard). The velocities of the entity are kept at offsets 6 (X) and 7 (Y), and have four bits after the point, so only the top four bits make up the whole pixels moved each frame. They are changed by UpdateVelocity, slowed by SlowVelocity and limited by CheckRoomBounds and CheckObstacles before ApplyMovement moves the entity. The bits at offset 2 are the number of steps still to be taken in the bottom four, and in bits 4-5 a flag that is set when movement is blocked along the X axis (bit 4) or the Y axis (bit 5).
Input
B The change made to a velocity each frame by the controls
C The fastest X velocity (the Y velocity is limited by B)
D The amount that the Y velocity is slowed by each frame
E The amount that the X velocity is slowed by each frame
IX The entity of the character
ControlPlayer 36215 LD A,(60049) Fetch the room of the player from PlayerRoom.
36218 LD (61017),A Write A to 61017 (the room of the entity at Initialisation_Blank).
36221 PUSH BC Stash the speed limits (BC), the slowing (DE) and HL on the stack.
36222 PUSH DE
36223 PUSH HL
36224 CALL AutoWalkStep Call AutoWalkStep to take a step of the auto walk.
36227 LD A,(IX+2) Fetch offset 2 of the entity.
36230 OR %00110000 Set bits 4-5, to stop all movement until a check shows it is possible.
36232 LD (IX+2),A Update offset 2 of the entity.
36235 CALL StoreEntity Call StoreEntity to save the position of the entity.
Read the controls (a bit is zero when the control is used) and work out the change in velocity for each axis.
36238 CALL ReadControls Call ReadControls to read the controls.
36241 LD C,A Keep the controls in C.
36242 POP HL Restore HL from the stack.
36243 LD DE,0 DE=0000 (no change in either velocity).
36246 BIT 1,C Jump to ControlPlayer_Right if bit 1 (left) is not used.
36248 JR NZ,ControlPlayer_Right
36250 LD A,B Fetch the change in velocity.
36251 NEG Reverse the change, so that it is negative.
36253 LD E,A E=A (the X change is -B).
ControlPlayer_Right 36254 BIT 0,C Jump to ControlPlayer_Down if bit 0 (right) is not used.
36256 JR NZ,ControlPlayer_Down
36258 LD E,B E=B (the X change is B).
ControlPlayer_Down 36259 BIT 2,C Jump to ControlPlayer_Up if bit 2 (down) is not used.
36261 JR NZ,ControlPlayer_Up
36263 LD D,B D=B (the Y change is B).
ControlPlayer_Up 36264 BIT 3,C Jump to ControlPlayer_Move if bit 3 (up) is not used.
36266 JR NZ,ControlPlayer_Move
36268 LD A,B Fetch the change in velocity.
36269 NEG Reverse the change, so that it is negative.
36271 LD D,A D=A (the Y change is -B).
Slow the velocities, change them, check for obstacles and then move the entity.
ControlPlayer_Move 36272 POP HL Restore the amounts of slowing from the stack into HL.
36273 CALL SlowVelocity Call SlowVelocity to slow the entity down.
36276 POP HL Restore the fastest velocities from the stack into HL.
36277 CALL UpdateVelocity Call UpdateVelocity to update the velocities of the entity.
36280 CALL CheckRoomBounds Call CheckRoomBounds to check whether the entity is inside the room.
36283 CALL CheckDoorway Call CheckDoorway to check the doorway.
36286 CALL CheckObstacles Call CheckObstacles to check whether the entity would hit an item.
36289 JP ApplyMovement Jump to ApplyMovement to move the entity by its velocities.
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