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cc65/libsrc/apple2/cputc.s
Oliver Schmidt e47485f925 Added CONIO cursor support.
For quite some time I deliberately didn't add cursor support to the Apple II CONIO imöplementation. I consider it inappropriate to increase the size of cgetc() unduly for a rather seldom used feature.

There's no hardware cursor on the Apple II so displaying a cursor during keyboard input means reading the character stored at the cursor location, writing the cursor character, reading the keyboard and finally writing back the character read initially.

The naive approach is to reuse the part of cputc() that determines the memory location of the character at the cursor position in order to read the character stored there. However that means to add at least one additional JSR / RTS pair to cputc() adding 4 bytes and 12 cycles :-( Apart from that this approach means still a "too" large cgetc().

The approach implemented instead is to include all functionality required by cgetc() into cputc() - which is to read the current character before writing a new one. This may seem surprising at first glance but an LDA(),Y / TAX sequence adds only 3 bytes and 7 cycles so it cheaper than the JSR / RTS pair and allows to brings down the code increase in cgetc() down to a reasonable value.

However so far the internal cputc() code in question saved the X register. Now it uses the X register to return the old character present before writing the new character for cgetc(). This requires some rather small adjustments in other functions using that internal cputc() code.
2016-06-19 15:03:20 +02:00

98 lines
2.7 KiB
ArmAsm

;
; Ullrich von Bassewitz, 06.08.1998
;
; void __fastcall__ cputcxy (unsigned char x, unsigned char y, char c);
; void __fastcall__ cputc (char c);
;
.ifdef __APPLE2ENH__
.constructor initconio
.endif
.export _cputcxy, _cputc
.export cputdirect, newline, putchar, putchardirect
.import gotoxy, VTABZ
.include "apple2.inc"
.segment "ONCE"
.ifdef __APPLE2ENH__
initconio:
sta SETALTCHAR ; Switch in alternate charset
bit LORES ; Limit SET80COL-HISCR to text
rts
.endif
.code
; Plot a character - also used as internal function
_cputcxy:
pha ; Save C
jsr gotoxy ; Call this one, will pop params
pla ; Restore C and run into _cputc
_cputc:
cmp #$0D ; Test for \r = carrage return
beq left
cmp #$0A ; Test for \n = line feed
beq newline
ora #$80 ; Turn on high bit
.ifndef __APPLE2ENH__
cmp #$E0 ; Test for lowercase
bcc cputdirect
and #$DF ; Convert to uppercase
.endif
cputdirect:
jsr putchar
inc CH ; Bump to next column
lda CH
cmp WNDWDTH
bcc :+
left: lda #$00 ; Goto left edge of screen
sta CH
: rts
newline:
inc CV ; Bump to next line
lda CV
cmp WNDBTM
bcc :+
lda WNDTOP ; Goto top of screen
sta CV
: jmp VTABZ
putchar:
.ifdef __APPLE2ENH__
ldy INVFLG
cpy #$FF ; Normal character display mode?
beq putchardirect
cmp #$E0 ; Lowercase?
bcc mask
and #$7F ; Inverse lowercase
bra putchardirect
.endif
mask: and INVFLG ; Apply normal, inverse, flash
putchardirect:
pha
ldy CH
.ifdef __APPLE2ENH__
bit RD80VID ; In 80 column mode?
bpl put ; No, just go ahead
tya
lsr ; Div by 2
tay
bcs put ; Odd cols go in main memory
bit HISCR ; Assume SET80COL
.endif
put: lda (BASL),Y ; Get current character
tax ; Return old character for _cgetc
pla
sta (BASL),Y
.ifdef __APPLE2ENH__
bit LOWSCR ; Doesn't hurt in 40 column mode
.endif
rts