;; #LAYOUT# STD *        #TAKE
;; #LAYOUT# *   KERNAL_0 #TAKE
;; #LAYOUT# *   *        #IGNORE

;
; Official Kernal routine, described in:
;
; - [RG64] C64 Programmers Reference Guide   - page 290
; - [CM64] Computes Mapping the Commodore 64 - page 215
;
; CPU registers that has to be preserved (see [RG64]): none
;


PLOT:

	bcs plot_get

	; Note: the 'set' part has to start from $E50C, as this is a known address
	; - https://www.lemon64.com/forum/viewtopic.php?t=3296&amp%3Bstart=15
	; - https://sys64738.org/2019/05/c64-bedtime-coding-eng-printing-08/
	; - 'Duotris' game calls $E50C during startup screen initialization

plot_set:

	sty PNTR
	stx TBLX

!ifndef CONFIG_ARNITECH_BLADE {

	jsr screen_calculate_pointers

} else {

	; On a Blade the cursor is the Terminal Card's, which clamps it to the 80x25 screen;
	; PNTR and TBLX keep the last place set or read, which is all there is without a Card

	jsr terminal_find
	bcs plot_get_kept
	lda PNTR
	sta TERMINAL_COLUMN, x
	lda TBLX
	sta TERMINAL_ROW, x
}

	; FALLTROUGH to save one byte on RTS

plot_get:

!ifdef CONFIG_ARNITECH_BLADE {

	jsr terminal_find
	bcs plot_get_kept
	lda TERMINAL_COLUMN, x
	sta PNTR
	lda TERMINAL_ROW, x
	sta TBLX

plot_get_kept:
}

	ldy PNTR
	ldx TBLX
	rts