separate functions for EAL/SAL preservation during screen routines

c64/kernal/screen/e8ea.screen_scroll_up.s

@@ -10,7 +10,38 @@ screen_scroll_up:
 
 	// First handle CTRL and NO_SCRL keys
 
-	jsr screen_scroll_delay
+#if CONFIG_KEYBOARD_C128 || CONFIG_KEYBOARD_C65
+
+	// Do not scroll if NO_SCRL is pressed and interrupts are enabled
+!:
+	php
+	pla
+	and #%00000010
+	bne !+                             // branch if IRQs disabled, we cannot detect NO_SCRL status
+
+	lda SHFLAG
+	and #KEY_FLAG_NO_SCRL
+	bne !-
+!:
+
+#endif
+
+	// Check if CTRL key pressed - if so, perform a delay
+
+	lda SHFLAG
+	and #KEY_FLAG_CTRL
+	beq screen_scroll_up_delay_done
+
+	ldy #$09
+!:
+	ldx #$FF
+	jsr wait_x_bars
+	dey
+	bne !-
+
+	// FALLTROUGH
+
+screen_scroll_up_delay_done:
 
 	// Scroll the LDTBL (line link table)
 
@@ -27,14 +58,7 @@ screen_scroll_up:
 
 	// Preserve SAL and EAL
 
-	lda SAL+0
+	jsr screen_preserve_sal_eal
-	pha
-	lda SAL+1
-	pha	
-	lda EAL+0
-	pha
-	lda EAL+1
-	pha
 
 	// Now, we need to scroll both screen memory and color memory; first create start/end pointers
 
@@ -87,14 +111,7 @@ screen_scroll_up_loop_done:
 
 	// Restore SAL and EAL
 
- 	pla
+	jsr screen_restore_sal_eal
- 	sta EAL+1
- 	pla
- 	sta EAL+0
- 	pla
- 	sta SAL+1
- 	pla
- 	sta SAL+0
 
 	// Clear the newly introduced line
 

c64/kernal/screen/screen_grow_logical_line.s

@@ -8,7 +8,6 @@ screen_grow_logical_line_done:
 screen_grow_logical_line:
 
 	// Do not grow line if previus one is grown
-
 	ldy TBLX
 	lda LDTBL,y
 	bpl screen_grow_logical_line_done
@@ -28,12 +27,27 @@ screen_grow_logical_line:
 	lda #$00
 	sta LDTBL,y
 
+	// Preserve SAL and EAL
+	jsr screen_preserve_sal_eal
+
 	// Now we have to scroll lines downwards to make space
 
 
+	// YYY implement here
 
 	.break
-	rts
+
+
+
+
+
+
+
+	// Restore SAL and EAL
+	jsr screen_restore_sal_eal
+
+ 	// Recalculate PNT and USER    YYY is it needed?
+	jmp screen_calculate_PNT_USER
 
 
 

c64/kernal/screen/screen_preserve_sal_eal.s

@@ -0,0 +1,23 @@
+
+
+screen_preserve_sal_eal:
+
+	plx_trash_a
+	ply_trash_a
+
+	lda SAL+0
+	pha
+	lda SAL+1
+	pha	
+	lda EAL+0
+	pha
+	lda EAL+1
+	pha
+
+	// FALLTROUGH
+
+screen_common_sal_eal:
+
+	phy_trash_a
+	phx_trash_a
+	rts

c64/kernal/screen/screen_restore_sal_eal.s

@@ -0,0 +1,18 @@
+
+
+screen_restore_sal_eal:
+
+	plx_trash_a
+	ply_trash_a
+
+ 	pla
+ 	sta EAL+1
+ 	pla
+ 	sta EAL+0
+ 	pla
+ 	sta SAL+1
+ 	pla
+ 	sta SAL+0
+
+ 	jmp screen_common_sal_eal
+ 

c64/kernal/screen/screen_scroll_delay.s

@@ -1,40 +0,0 @@
-
-//
-// Handles CTRL and NO_SCRL during screen scroll
-//
-
-
-screen_scroll_delay:
-
-#if CONFIG_KEYBOARD_C128 || CONFIG_KEYBOARD_C65
-
-	// Do not scroll if NO_SCRL is pressed and interrupts are enabled
-!:
-	php
-	pla
-	and #%00000010
-	bne !+                             // branch if IRQs disabled, we cannot detect NO_SCRL status
-
-	lda SHFLAG
-	and #KEY_FLAG_NO_SCRL
-	bne !-
-!:
-
-#endif
-
-	// Check if CTRL key pressed - if so, perform a delay
-
-	lda SHFLAG
-	and #KEY_FLAG_CTRL
-	beq screen_scroll_delay_done
-
-	ldy #$09
-!:
-	ldx #$FF
-	jsr wait_x_bars
-	dey
-	bne !-
-
-screen_scroll_delay_done:
-	
-	rts