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215 lines
5.3 KiB
ArmAsm
215 lines
5.3 KiB
ArmAsm
;
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; 2022-04-03, Karri Kaksonen
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;
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; setcursor (unsigned char on);
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;
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; The Atari 7800 does not have a hw cursor.
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; This module emulates a cursor to be used with the conio
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; implementation.
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;
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; The actual cursor display is included in the conio dll
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; but every scanline has the element silenced by default
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; at the end of every zone.
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;
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; The way the cursor works is to silence it before the cursor
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; position changes and enable it afterwards.
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;
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; In order to get some performance we have a pointer to the
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; cursor header structure. This structure is always at the
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; end of the zone. So the pointer changes when CURS_Y changes.
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;
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; There is so many dependencies that it makes sense to
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; deal with all CURS_X, CURS_Y stuff in this file and
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; definitely not allow direct access to the variables.
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;
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.export gotoxy, _gotoxy, gotox, gotoy
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.constructor init_cursor
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.interruptor blink_cursor
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.importzp sp
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.import _zonecounter
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.import _zones
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.import cursor
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.import pusha, incsp1, pusha0, pushax, popa
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.include "atari7800.inc"
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.include "extzp.inc"
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.macpack generic
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.data
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;-----------------------------------------------------------------------------
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; The variables used by cursor functions
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;
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blink_time:
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.byte 200
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.code
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;---------------------------------------------------------------------------
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; 8x16 routine
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umula0:
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ldy #8 ; Number of bits
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lda #0
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lsr ptr7800 ; Get first bit into carry
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@L0: bcc @L1
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clc
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adc ptrtmp
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tax
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lda ptrtmp+1 ; hi byte of left op
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clc
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adc ptr7800+1
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sta ptr7800+1
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txa
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@L1: ror ptr7800+1
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ror a
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ror ptr7800
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dey
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bne @L0
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tax
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lda ptr7800 ; Load the result
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rts
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;-----------------------------------------------------------------------------
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; Calculate cursorzone address
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; You also need to set the cursorzone to point to the correct cursor Header
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; at the end of line CURS_Y.
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; Offset to cursor zone 5. To next line offset 11
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; cursorzone points to _zones + CURS_Y * 11 + 5
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; A = CURS_Y
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.proc calccursorzone
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sta ptr7800
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lda #11
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sta ptrtmp
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lda #0
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sta ptr7800+1
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sta ptrtmp+1
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jsr umula0
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clc
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adc #5
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bcc @L1
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inx
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@L1: clc
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adc #<_zones
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sta cursorzone ; calculate new cursorzone
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txa
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adc #>_zones
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sta cursorzone+1
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rts
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.endproc
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;-----------------------------------------------------------------------------
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; Set cursor to Y position.
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; You also need to set the cursorzone to point to the correct cursor Header
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; at the end of line CURS_Y.
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; Offset to cursor zone 5. To next line offset 11
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; cursorzone points to _zones + CURS_Y * 11 + 5
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;
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; cursorzone[1] = 0 when not CURS_Y, 30 if CURS_Y
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;
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; Disable cursor
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; cursorzone[1] = 0
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;
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; Enable cursor
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; if showcursor cursorzone[1] = 30
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;
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.proc gotoy
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pha
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lda CURS_Y
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jsr calccursorzone
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ldy #1
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lda #0
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sta (cursorzone),y ; disable cursor
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pla
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sta CURS_Y
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jsr calccursorzone
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lda cursor
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beq @L1
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lda #30 ; enable cursor
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@L1: ldy #1
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sta (cursorzone),y
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rts
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.endproc
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;-----------------------------------------------------------------------------
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; Set cursor to X position.
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; You also need to set the hpos offset to the correct value on this line
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; cursorzone[3] = 8 * CURS_X
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;
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.proc gotox
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sta CURS_X
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ldy #3
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clc
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rol
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rol
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rol
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sta (cursorzone),y
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rts
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.endproc
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;-----------------------------------------------------------------------------
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; Set cursor to desired position (X,Y)
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;
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.proc _gotoxy
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jsr gotoy
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jsr popa
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jsr gotox
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rts
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.endproc
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.proc gotoxy
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jsr popa
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jmp _gotoxy
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.endproc
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;-----------------------------------------------------------------------------
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; Initialize cursorzone at startup
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; Offset to cursor zone 5.
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;
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.proc blink_cursor
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lda _zonecounter
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and #01
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beq @L3
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inc blink_time
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bne @L3
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lda #200
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sta blink_time
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ldy #0
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lda (cursorzone),y
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bne @L1
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lda #254
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bne @L2
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@L1: lda #0
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@L2: sta (cursorzone),y
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@L3: rts
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.endproc
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;-----------------------------------------------------------------------------
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; Initialize cursorzone at startup
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; Offset to cursor zone 5.
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;
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.segment "ONCE"
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init_cursor:
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lda #0
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jsr calccursorzone
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lda #0
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sta blink_time
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rts
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;-----------------------------------------------------------------------------
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; force the init constructor to be imported
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.import initconio
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conio_init = initconio
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