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collapseos
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Mirror of CollapseOS
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collapseos/kernel/fnt/mgm.asm

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  1. ; Font management

  2. ;

  3. ; There can only ever be one active font.

  4. ;

  5. ; *** Defines ***

  6. ; FNT_DATA: Pointer to the beginning of the binary font data to work with.

  7. ; FNT_WIDTH: Width of the font.

  8. ; FNT_HEIGHT: Height of the font.

  9. ;

  10. ; *** Code ***

  11. 

  12. ; If A is in the range 0x20-0x7e, make HL point to the beginning of the

  13. ; corresponding glyph and set Z to indicate success.

  14. ; If A isn't in the range, do nothing and unset Z.

  15. fntGet:

  16. 	cp	0x20

  17. 	ret	c	; A < 0x20. Z was unset by cp

  18. 	cp	0x7f

  19. 	jp	nc, unsetZ	; A >= 0x7f. Z might be set

  20. 	

  21. 	push	af	; --> lvl 1

  22. 	push	bc	; --> lvl 2

  23. 	sub	0x20

  24. 	ld	hl, FNT_DATA

  25. 	ld	b, FNT_HEIGHT

  26. .loop:

  27. 	call	addHL

  28. 	djnz	.loop

  29. 	pop	bc	; <-- lvl 2

  30. 	pop	af	; <-- lvl 1

  31. 	cp	a	; set Z

  32. 	ret