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workaround for black square issue at start

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Irmen de Jong 2022-12-10 21:43:38 +01:00
parent 578969c34c
commit 832601b36b
2 changed files with 20 additions and 0 deletions
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3
compiler/res/prog8lib/cx16/syslib.p8
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@ -638,6 +638,9 @@ asmsub init_system() {
and #%11111000
ora P8ZP_SCRATCH_REG
sta VERA_DC_VIDEO ; keep old output mode
ldy #0
clc
jsr c64.PLOT ; force a call to PLOT to avoid autostart black square issue, also see textio.fix_autostart_square()
lda #$90 ; black
jsr c64.CHROUT
lda #1 ; swap fg/bg

17
compiler/res/prog8lib/cx16/textio.p8
View File

@ -21,6 +21,23 @@ sub home() {
txt.chrout(19)
}
sub fix_autostart_square() {
; Here's a possible work around for weird issue that prints a black character after first call to c64.PLOT()
; if you're also using c64.CINT() yourself. The default prog8 program initialization (which calls CINT) already performs this workaround.
; The problem occurs when a program is autostarded in the emulator with -run -prg test.prg,
; or when the program is saved as AUTOBOOT.X16 and loaded on boot like that.
%asm {{
sec
jsr c64.PLOT
clc
jsr c64.PLOT
lda #' '
jsr c64.CHROUT ; overwrite the black square
clc
jmp c64.PLOT ; cursor back to original position
}}
}
sub nl() {
txt.chrout('\n')
}