initial LNMX calculation routine

c64/aliases/,aliases_ram_lowmem.s

@@ -155,7 +155,7 @@
 	.label PNT       = $D1  // $D1-$D2  pointer to the current screen line
 	.label PNTR      = $D3  //          current screen X position (logical column), 0-79
 	.label QTSW      = $D4  //          quote mode flag
-	.label LNMX      = $D5  //          logical line length, [!] our usage probably differs in details
+	.label LNMX      = $D5  //          logical line length, 39 or 79
 	.label TBLX      = $D6  //          current screen Y position (row), 0-24
 	.label SCHAR     = $D7  //          ASCII value of the last printed character
 	.label INSRT     = $D8  //          insert mode flag/counter

c64/kernal/screen/chrout_screen.s

@@ -120,11 +120,12 @@ chrout_screen_literal:
 chrout_screen_calc_lptr_done:
 
 	jsr screen_calculate_PNT_USER
-	jsr screen_fix_PNTR
+	jsr screen_calculate_PNTR
+	jsr screen_calculate_LNMX
 
 	// FALLTROUGH
 
-chrout_screen_done:
+chrout_screen_done: // YYY review all the jumps here
 
 	// YYY should we update character under cursor here? or in cursor_show_if_enabled?
 

c64/kernal/screen/screen_calculate_lnmx.s

@@ -0,0 +1,36 @@
+
+//
+// Sets LNMX to 39 or 79
+//
+
+
+// YYY value is improper shortly after linee growth!
+
+
+screen_calculate_LNMX: // YYY review all the code, mayybe some optimizations are possible using this value
+
+	ldy TBLX
+	lda LDTBL, y
+	bpl screen_calculate_lnmx_79       // this line is a continuation
+
+	cpy #24
+	beq screen_calculate_lnmx_39       // this is the last line, which is not a continuation
+
+	iny
+	lda LDTBL, y
+	bpl screen_calculate_lnmx_79       // line is continued
+
+	// FALLTROUGH
+
+screen_calculate_lnmx_39:
+
+	lda #39
+	skip_2_bytes_trash_nvz
+
+	// FALLTROUGH
+
+screen_calculate_lnmx_79:
+
+	lda #79
+	sta LNMX
+	rts

c64/kernal/screen/screen_calculate_pntr.s

@@ -4,18 +4,18 @@
 //
 
 
-screen_fix_PNTR:
+screen_calculate_PNTR:
 
 	ldy TBLX
 	lda LDTBL, y
 	php
 	jsr screen_get_clipped_PNTR
 	plp
-	bmi screen_fix_PNTR_0_39
+	bmi screen_calculate_PNTR_0_39
 
 	// FALLTROUGH
 
-screen_fix_PNTR_40_79:
+screen_calculate_PNTR_40_79:
 
 	tya
 	clc
@@ -24,7 +24,7 @@ screen_fix_PNTR_40_79:
 
 	// FALLTROUGH
 
-screen_fix_PNTR_0_39:
+screen_calculate_PNTR_0_39:
 
 	sty PNTR
 	rts