Make screensize() fetch the values dynamically instead of using variables

that are set on startup. This is needed to support the C128, which can switch
the screen size at runtime.


git-svn-id: svn://svn.cc65.org/cc65/trunk@2042 b7a2c559-68d2-44c3-8de9-860c34a00d81

libsrc/pet/_scrsize.s

@@ -4,27 +4,16 @@
 ; Screen size variables
 ;
 
-
-	.export		xsize, ysize
-       	.constructor	initscrsize
+	.export		screensize
 
 	.include	"pet.inc"
 
-.code
+.proc   screensize
 
-initscrsize:
        	ldx	SCR_LINELEN
 	inx			; Variable is one less
-       	stx 	xsize
-	lda	#25
-	sta    	ysize
+       	ldy	#25
 	rts
 
-
-.bss
-
-xsize: 	.res	1
-ysize:	.res	1
-
-
+.endproc
 

libsrc/pet/clrscr.s

@@ -7,7 +7,6 @@
 	.export	    	_clrscr
 	.import		plot
        	.importzp   	ptr1
-	.import	    	xsize
 
 	.include    	"pet.inc"
 
@@ -23,9 +22,9 @@ _clrscr:
 ; Determine, how many pages to fill
 
 	ldx 	#4
-	lda	xsize
-	cmp	#40
-       	beq	L1
+	lda	SCR_LINELEN     ; Check length of one line
+	cmp	#40+1
+       	bcc    	L1
 	ldx	#8
 
 ; Clear the screen

libsrc/pet/cputc.s

@@ -8,10 +8,8 @@
     	.export	       	_cputcxy, _cputc, cputdirect, putchar
 	.export		newline, plot
 	.import		popa, _gotoxy
-	.import		xsize
 
 	.include	"pet.inc"
-;	.include	"../cbm/cbm.inc"
 
 _cputcxy:
 	pha	    	    	; Save C
@@ -48,17 +46,17 @@ cputdirect:
 ; Advance cursor position
 
 advance:
-        iny
-        cpy     xsize
+        cpy     SCR_LINELEN     ; xsize-1
         bne     L3
         jsr     newline         ; new line
-        ldy     #0              ; + cr
-L3:     sty     CURS_X
+        ldy     #$FF            ; + cr
+L3:     iny
+        sty     CURS_X
         rts
 
 newline:
-   	clc
-   	lda	xsize
+   	lda    	SCR_LINELEN     ; xsize-1
+        sec                     ; Account for -1 above
    	adc	SCREEN_PTR
    	sta	SCREEN_PTR
    	bcc	L4
@@ -84,9 +82,9 @@ plot:	ldy	CURS_Y
 	lda	ScrLo,y
 	sta	SCREEN_PTR
 	lda	ScrHi,y
-	ldy	xsize
-	cpy	#40
-       	beq	@L1
+	ldy	SCR_LINELEN
+	cpy	#40+1
+       	bcc     @L1
        	asl    	SCREEN_PTR		; 80 column mode
  	rol	a
 @L1:	ora	#$80			; Screen at $8000