Chase H.Q.: Routine at B627

B627: Draws a car part

One part is the shadow, the windscreen, the wheels or a side panel. The y-offset and the row count come from the graphic def, the part's y is subtracted from the car's y and draw_masked_sprite_rel_car does the drawing. flip_car picks the start offset in C': zero when unflipped, byte width minus one when flipped. The returned pointer is the following graphic def, so callers chain the parts together.

Used by the routine at draw_hero_car.

Input
C	Byte width
D	Y/Vertical position (in rows)
E	X/Horizontal position (in pixels)
HL	Address of graphic def (y_offset, nrows, data address)

Output
D	Preserved
E	Preserved
HL	Address of next graphic def

draw_hero_car_part

B627

LD A,D

A = Y

B628

PUSH DE

Preserve X,Y

B629

SUB (HL)

D = Y - y_offset

B62A

LD D,A

B62B

INC HL

Advance to nrows field

B62C

LD B,(HL)

Read nrows

B62D

INC HL

Advance to data address field

B62E

LD A,(HL)

Read data address while stacking HL+1

B62F

INC HL

B630

PUSH HL

B631

LD H,(HL)

B632

LD L,A

B633

PUSH BC

Preserve byte width over bank

D = y_offset, B = nrows, HL -> data

B634

EXX

Bank

B635

POP BC

Restore byte width

B636

LD A,($A251)

Load flip_car into B

B639

LD B,A

B63A

LD E,C

E = byte width -- becomes E' which is source data stride

B63B

DEC C

C = byte width - 1

B63C

AND A

Test flip_car flag, if clear then C = 0 else C = (byte width - 1)

B63D

JR NZ,dcp_cont

B63F

LD C,A

dcp_cont

B640

EXX

Unbank

B641

CALL draw_masked_sprite_rel_car

Draws all masked parts of the car (using car_y)

B644

POP HL

Restore graphic def ptr

B645

INC HL

Skip final byte - already consumed

B646

POP DE

Restore X,Y

B647

RET

Return