PSSST: Routine at 30160

30160: Erase Sprite

Used by the routines at 29861 and 29980.

Input
B	Loop counter
C	Actor Y position, or zero?
DE	Address into a sprite/buffer
HL	Address in the DISPLAY_FILE

MaskSprite

30160

LD A,C

Jump to MaskSprite_4 if the sprites vertical position is zero.

30161

AND A

30162

JR Z,MaskSprite_4

30164

DEC C

Else decrement.

30165

PUSH BC

Stash BC and HL on the stack.

30166

PUSH HL

Loop to create a mask of the sprite and it write to the screen.

MaskSprite_0

30167

LD A,(DE)

A=sprite byte.

30168

CPL

Create mask and write to screen.

30169

AND (HL)

30170

LD (HL),A

30171

INC DE

Move onto the next byte.

30172

INC L

Move onto the next column.

30173

DJNZ MaskSprite_0

Decrease counter by one and loop back to MaskSprite_0 until counter is zero.

30175

POP HL

Restore HL from the stack.

30176

CALL ScreenPos1PixelAbove

Call ScreenPos1PixelAbove.

30179

POP BC

Restore BC from the stack.

30180

EXX

30181

LD A,C

Jump to MaskSprite_3 if C is zero.

30182

AND A

30183

JR Z,MaskSprite_3

MaskSprite_1

30185

DEC C

30186

PUSH BC

Stash BC and HL on the stack.

30187

PUSH HL

MaskSprite_2

30188

LD A,(DE)

30189

OR (HL)

30190

LD (HL),A

30191

INC DE

30192

INC L

30193

DJNZ MaskSprite_2

30195

POP HL

Restore HL from the stack.

30196

CALL ScreenPos1PixelAbove

Call ScreenPos1PixelAbove.

30199

POP BC

Restore BC from the stack.

MaskSprite_3

30200

EXX

30201

JR MaskSprite

MaskSprite_4

30203

EXX

30204

LD A,C

30205

AND A

30206

JR NZ,MaskSprite_1

This entry point is used by the routine at 29861.

MaskSprite_5

30208

EXX

This entry point is used by the routine at 29861.

MaskSprite_6

30209

LD A,(24080)

30212

LD C,A

30213

LD A,(24081)

30216

OR C

30217

RET Z

30218

XOR A

30219

LD (24080),A

30222

EXX

30223

LD A,(24081)

30226

LD C,A

30227

XOR A

This entry point is used by the routine at 29861.

MaskSprite_7

30228

LD (24081),A

30231

EXX

30232

JR MaskSprite