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https://github.com/cc65/cc65.git
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Scrolling text working
This commit is contained in:
Dave Plummer
parent
4ceeb9c4ab
commit
22d5dc6e32
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@ -27,12 +27,14 @@
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SCREEN = $A000
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SCREEN_WIDTH = 320
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SCREEN_HEIGHT = 200
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SCREEN_BYTES = SCREEN_WIDTH * SCREEN_HEIGHT / 8
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CHARWIDTH = 8
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CHARHEIGHT = 8
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BYTESPERROW = (SCREEN_WIDTH / 8)
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BYTESPERCHARROW = (BYTESPERROW * 8)
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CHARSPERROW = (SCREEN_WIDTH / CHARWIDTH)
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ROWSPERCOLUMN = (SCREEN_HEIGHT / CHARHEIGHT)
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LASTROW = SCREEN + SCREEN_BYTES - BYTESPERCHARROW
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.segment "ZEROPAGE"
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@ -54,6 +56,14 @@ adp2:
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adp2_lo: .res 1
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adp2_hi: .res 1
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scroll_src:
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scroll_src_lo: .res 1
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scroll_src_hi: .res 1
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scroll_dest:
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scroll_dest_lo: .res 1
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scroll_dest_hi: .res 1
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.segment "DATA"
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_x1cord: .res 2
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@ -67,6 +77,9 @@ xval: .res 2 ; These could move to zeropage for perf, but
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yval: .res 2 ; we want to minimize the amount we grow zero page use
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err: .res 2
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temp: .res 2
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tempa: .res 1
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tempx: .res 1
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tempy: .res 1
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temp2: .res 2
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x0: .res 2
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y0: .res 2
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@ -208,49 +221,61 @@ _ClearScreen:
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; ScrollScreen - Scrolls the entire video memory (and thus the screen) up one row
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;-----------------------------------------------------------------------------------
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_ScrollScreen: pha
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BYTES_TO_MOVE = SCREEN_BYTES - BYTESPERCHARROW
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PAGES_TO_MOVE = BYTES_TO_MOVE / 256
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_ScrollScreen:
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pha
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tya
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pha
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txa
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pha
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; Load the source (A140) and destination (A000) addresses. Each row of characters
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; occupies 320 bytes, so we start source as being one line ahead of the destination
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; which will have the effect of scrolling the screen up one text line.
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lda #<(SCREEN+320)
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sta src_lo
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lda #>(SCREEN+320)
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sta src_hi
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; Load the source (A140) and destination (A000) addresses
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lda #<(SCREEN+BYTESPERCHARROW)
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sta scroll_src_lo
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lda #>(SCREEN+BYTESPERCHARROW)
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sta scroll_src_hi
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lda #<SCREEN
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sta dest_lo
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sta scroll_dest_lo
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lda #>SCREEN
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sta dest_hi
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sta scroll_dest_hi
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ldy #$00
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:
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lda (src),y
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sta (dest),y
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ldx #PAGES_TO_MOVE
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@outerLoop:
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ldy #0
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@innerLoop:
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lda (scroll_src),y
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sta (scroll_dest),y
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iny
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bne :-
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bne @innerLoop ; If Y overflows, it will be 0, so won't branch
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inc scroll_src_hi
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inc scroll_dest_hi
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dex
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bne @outerLoop
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inc dest_hi ; When the source hits $BF00 we're done, as we've copied
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inc src_hi ; everything up to that point so far
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ldx src_hi
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cpx #$BE
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bne :-
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lda #$00 ; Clear the last line (320 bytes, or A0 twice)
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ldy #$A0
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: sta SCREEN+$1EA0, y
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sta SCREEN+$1E00, y
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dey
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bne :-
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; Clear the last line
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lda #<LASTROW
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sta scroll_dest_lo
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lda #>LASTROW
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sta scroll_dest_hi
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lda #$00
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ldy #0
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fullPageLoop:
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sta (scroll_dest_lo),y
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iny
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bne fullPageLoop
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inc scroll_dest_hi
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partialPageLoop:
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sta (scroll_dest_lo),y
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iny
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cpy #BYTESPERCHARROW - 256 ; Only clear up to the 64th byte (256 + 64 == 320)
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bne partialPageLoop
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pla
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txa
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tax
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pla
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tya
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tay
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pla
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rts
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@ -634,10 +659,12 @@ ScreenLineAddresses:
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;-----------------------------------------------------------------------------------
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; 0 <= x < 40
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; 0 <= y < 25
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; Preserves all registers
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; Preserves all registers, but its not very threadsafe or reentrant
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;-----------------------------------------------------------------------------------
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_DrawChar: pha
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_DrawChar: sty tempy
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stx tempx
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sta tempa
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tya ; Get the address in screen memory where this
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asl ; character X/Y cursor pos should be drawn
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@ -653,7 +680,7 @@ _DrawChar: pha
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lda #0 ; Get the address in font memory where this
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sta src_hi ; Petscii chracter lives (after conversion from
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pla ; ascii)
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lda tempa ; ascii)
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sty temp2
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jsr _AscToPet
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@ -688,10 +715,11 @@ _DrawChar: pha
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cpy #8
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bne :-
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ldy tempy
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ldx tempx
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lda tempa
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rts
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;-----------------------------------------------------------------------------------
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; DrawText - Draws an ASCII string at the current cursor position
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;-----------------------------------------------------------------------------------
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@ -701,27 +729,24 @@ _DrawChar: pha
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_DrawText: stx adp1_lo
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sty adp1_hi
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ldy #0
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@char: lda (adp1), y
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sta tempchar
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checkHWrap: lda _cursorX
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cmp #CHARSPERROW
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bcc checkVWrap
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lda #0
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sta _cursorX
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inc _cursorY
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checkVWrap: lda _cursorY
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cmp #ROWSPERCOLUMN
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bcc loadChar
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jsr _ScrollScreen
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lda #ROWSPERCOLUMN-1
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sta _cursorY
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loadChar: lda (adp1), y
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beq doneText
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lda _cursorX ; if X >= CHARSPERROW, we need to advance to the next line
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cmp #CHARSPERROW-1
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bcc :+
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lda #0 ; Back to the left edge
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sta _cursorX
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inc _cursorY ; Advance to the next line
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: lda _cursorY
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cmp #ROWSPERCOLUMN - 1 ; Check to see if we've gone off the bottom of the screen
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bcc :+
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lda #ROWSPERCOLUMN - 1 ; If we have, we scroll the screen and back up to the last line again
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sta _cursorY
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jsr _ScrollScreen
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: lda tempchar ; If the character is 0A, we advance to the next line
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cmp #$0a
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bne :+
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@ -729,20 +754,16 @@ _DrawText: stx adp1_lo
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sta _cursorX
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inc _cursorY ; Advance to the next line
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iny
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bne @char
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bne checkHWrap
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: tya
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pha
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lda tempchar
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: sty temp
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ldx _cursorX
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ldy _cursorY
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jsr _DrawChar
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pla
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tay
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ldy temp
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inc _cursorX
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iny
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bne @char
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bne checkHWrap
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doneText: rts
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@ -750,13 +771,20 @@ demoText1: .byte " *** COMMODORE KIM-1 SHELL V0.1 ***", $0A, $0A
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.byte " 60K RAM SYSTEM. 49152 BYTES FREE.", $0A, $0A
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.byte "READY.", $0A, 00
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alphabet: .byte "ABCDEFGHIJKLMNOPQRSTUVWXYZ", 00, "*****", 00
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_Demo: lda #0
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sta _cursorX
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sta _cursorY
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ldx #<demoText1
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ldy #>demoText1
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jsr _DrawText
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rts
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: ldx #<alphabet
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ldy #>alphabet
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jsr _DrawText
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jmp :-
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