mirror of
https://github.com/hsoft/collapseos.git
synced 2024-11-17 10:18:05 +11:00
33 lines
702 B
NASM
33 lines
702 B
NASM
; Font management
|
|
;
|
|
; There can only ever be one active font.
|
|
;
|
|
; *** Defines ***
|
|
; FNT_DATA: Pointer to the beginning of the binary font data to work with.
|
|
; FNT_WIDTH: Width of the font.
|
|
; FNT_HEIGHT: Height of the font.
|
|
;
|
|
; *** Code ***
|
|
|
|
; If A is in the range 0x20-0x7e, make HL point to the beginning of the
|
|
; corresponding glyph and set Z to indicate success.
|
|
; If A isn't in the range, do nothing and unset Z.
|
|
fntGet:
|
|
cp 0x20
|
|
ret c ; A < 0x20. Z was unset by cp
|
|
cp 0x7f
|
|
jp nc, unsetZ ; A >= 0x7f. Z might be set
|
|
|
|
push af ; --> lvl 1
|
|
push bc ; --> lvl 2
|
|
sub 0x20
|
|
ld hl, FNT_DATA
|
|
ld b, FNT_HEIGHT
|
|
.loop:
|
|
call addHL
|
|
djnz .loop
|
|
pop bc ; <-- lvl 2
|
|
pop af ; <-- lvl 1
|
|
cp a ; set Z
|
|
ret
|