How to display alternate lines of text in 2 columns?

Question

I have this part of code where all text lines come to the screen at once. Now I want for each lines to come on the screen from the other side (ie. first line from left, second from right etc.). Can anyone help?

Start                   SEI
                        LDX #$01
                        STX $0286
                        DEX
                        STX $D020
                        STX $D021
                        JSR $E544

mainLoop               LDA #$FA
waitRaster             CMP $D012
                        BNE waitRaster
waitRaster2            CMP $D012
                        BEQ waitRaster2

                        LDA #$0F
                        STA $D020
                        JSR UpdateThings
                        INC $D020
                        JMP mainLoop

UpdateThings        ; is state 0 ?
                        LDA State
                        BNE nextState
                    ; yes, call Move Text to Screen routine
                        JSR MoveTextIn
nextState              RTS

I tried with some change here..

MoveTextIn              LDX 02
                        LDY Counter
loop                   ; LDA TextLines1+(1*40),x
                       ; STA $0400+(1*40),X
                        LDA TextLines2+(1*40),y 
                        STA $0400+(1*40),X
                       ; LDA TextLines+(5*40),Y 
                       ; STA $0400+(5*40),X
                        INX 
                        INY
                        CPY #$28
                        BNE loop
and there....
                       ; LDX #$27
                        TXA
                        SEC 
                        SBC Counter
                        TAY

and again here...

loop2                   ;LDA TextLines1+(0*40),x
                        ;STA $0400+(0*40),X
                        LDA TextLines2+(0*40),y 
                        STA $0400+(0*40),X
                        ;LDA TextLines+(4*40),Y 
                        ;STA $0400+(4*40),X
                        DEX 
                        DEY
                        BPL loop2

                        LDA Counter
                        BEQ TextMoveDone

                        DEC Counter
                        RTS
TextMoveDone            INC State
                        RTS

State                   !byte 0

Counter                 !byte $10

TextLines1              !scr "!x-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-xx!"
TextLines2              !scr "!x      commodore master soft         x!"
                        !scr "!        -------------------           !"
                        !scr "!         somewhere in 2019.           !"
                        !scr "!          ----------------            !"
                        !scr "! -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-  !"

I'll never not upvote attempts to program on the C64! You might want to post this on [retrocomputing.SE] if you don't get good answers here. — fuz, May 15 '19 at 21:57
@fuz This question was also posted to Retrocomputing, but was deleted by OP. It wasn't on-topic there because it was (essentially) a generic programming question, not specific to retrocomputing. — Lorraine, May 21 '19 at 08:07
@simun9 It would be great if you could explain what you're trying to accomplish; as it stands your question is essentially a page of assembly. We can't really see what's going on. My first though is there's some kind of animation or a scrolly thing, but I'm not sure. So first thing is to *explain what you want to know*. — Lorraine, May 21 '19 at 08:10
@Wilson: I want each line come to screen one by one instead of all at same time. — simun9, May 21 '19 at 12:16
And where is your code that does that, and what's the problem with it? — Lorraine, May 21 '19 at 12:20
The code above is modified version where I tried with line by line. But I stucked. — simun9, May 21 '19 at 15:17

score 0 · Answer 1 · answered May 22 '19 at 18:10

Ok, thank you all. I found answer:

One possibility would be having counter that go from 0 to 240, and it would be updated once a frame adding +1 to it....

if value be 0 - 39 it would move line 1 and calculate locations it needs to put text to screen if value be 40 - 79 it would move line 2 + same ... if value be 200 - 239 it would move line 6 + same if value be 240, all moving has been done...

Other way would be to have counter that go 0..40 and when 40, it adds linecounter.

score 0 · Accepted Answer · answered May 28 '19 at 07:04

I'm copying my solution below. I think it is self explanatory.

counter must be set to zero before jumping to MoveTextIn

MoveTextIn
shiftRight      ldx #$00
                lda textLines1+(0*40),x
                sta $0400+(0*40),x
                lda textLines1(2*40),x
                sta $0400+(2*40),x
                lda textLines1(4*40),x
                sta $0400+(4*40),x

                inx
                cmp #$40
                bne shiftRight

shiftLeft       lda textLines1+(1*40),x
                sta $0400+(1*40),x
                lda textLines1(3*40),x
                sta $0400+(3*40),x
                lda textLines1(5*40),x
                sta $0400+(5*40),x

                dex
                bne shiftLeft

copyRight       ldx counter
                lda textLines1+(1*40),x
                sta $0400+(1*40)-1
                lda textLines1+(3*40),x
                sta $0400+(3*40)-1
                lda textLines1+(5*40),x
                sta $0400+(5*40)-1

copyLeft        sec
                lda #$40
                sbc counter
                tax
                lda textLines1+(0*40),x
                sta $0400+(0*40)-1
                lda textLines1+(2*40),x
                sta $0400+(2*40)-1
                lda textLines1+(4*40),x
                sta $0400+(4*40)-1

                inc counter
                lda counter
                cmp #$40
                beq textMoveDone
                rts

textMoveDone    inc state
                rts

How to display alternate lines of text in 2 columns?

2 Answers2