Chase H.Q.: Routine at EBFF

EBFF: Renders a string

The top bit of the attribute byte is the double-height flag; it is shifted out into the carry and banked in F' before the character loop starts, so that menu_draw_char can test it per character.

Used by the routines at menu_draw_strings and define_a_key.

Input
HL	Address of a message structure (byte: attribute byte, word: destination screen address, bytes: top bit set terminated ASCII string)

Output
HL	Address of next unconsumed byte

menu_draw_string

EBFF

LD C,(HL)

Load attribute byte

EC00

RL C

Extract top bit of attribute byte as carry flag then bank (this is the single height flag)

EC02

EX AF,AF'

EC03

SRL C

EC05

INC HL

Advance

EC06

LD E,(HL)

Load screen address into DE

EC07

INC HL

EC08

LD D,(HL)

EC09

INC HL

EC0A

PUSH HL

Stack screen address

Calculate attribute address from screen address

EC0B

LD A,D

H = $58 + ((D >> 3) & 3)

EC0C

RRA

EC0D

RRA

EC0E

RRA

EC0F

AND $03

EC11

ADD A,$58

EC13

LD H,A

EC14

LD L,E

L = E

EC15

EXX

Bank for when calling menu_draw_char

HL' is screen address, DE' is attribute address

EC16

EX (SP),HL

Get screen address and preserve old HL

EC17

PUSH DE

Preserve regs

EC18

PUSH BC

menu_draw_string_loop

EC19

LD A,(HL)

Isolate terminator bit

EC1A

AND $7F

EC1C

PUSH HL

Draw character in A

EC1D

CALL menu_draw_char

EC20

POP HL

EC21

BIT 7,(HL)

End of string?

EC23

INC HL

Advance to next char irrespective

EC24

JR Z,menu_draw_string_loop

Loop if not

EC26

EXX

EC27

POP BC

Restore regs

EC28

POP DE

EC29

POP HL

EC2A

EXX

Unbank

EC2B

RET

Return