provided screen scroll up unofficial routine

STATUS.md

@@ -235,7 +235,7 @@ Not all of them - only these we want to have implemented.
 | `$E518`   | legacy part of CINT          | DONE     |                                                    |
 | `$E51B`   | init screen keyboard, no VIC | DONE     |                                                    |
 | `$E544`   | clear screen                 | DONE     |                                                    |
-| `$E50C`   | set cursor position          | PARTIAL  |                                                    |
+| `$E50C`   | set cursor position          | DONE     |                                                    |
 | `$E566`   | home cursor                  | DONE     |                                                    |
 | `$E56C`   | set PNT and USER values      | DONE     |                                                    |
 | `$E5A0`   | setup VIC II & I/O           | DONE     |                                                    |
@@ -243,7 +243,7 @@ Not all of them - only these we want to have implemented.
 | `$E701`   | previous line                | NOT DONE |                                                    |
 | `$E716`   | screen CHROUT                | NOT DONE |                                                    |
 | `$E8DA`   | color code table             | DONE     |                                                    |
-| `$E8EA`   | scroll line                  | NOT DONE |                                                    |
+| `$E8EA`   | scroll logical line up       | DONE     |                                                    |
 | `$E96C`   | insert line on top           | NOT DONE |                                                    |
 | `$E9FF`   | clear line                   | DONE     |                                                    |
 | `$EA31`   | default IRQ                  | PARTIAL  |                                                    |

c64/kernal/,stubs/e8ea.scroll_line.s

@@ -1,4 +0,0 @@
-
-// XXX provide documentation and implementation
-
-    STUB_IMPLEMENTATION()

c64/kernal/screen/e8ea.screen_scroll_up.s

@@ -1,43 +1,18 @@
 
 //
-// Scroll the whole screen up by 1 logical line
+// Scroll the whole screen up by 1 logical line, described in:
+//
+// - [CM64] Computes Mapping the Commodore 64 - page 218
 //
 
 
 screen_scroll_up:
 
+	// First handle CTRL and NO_SCRL keys
 
-#if CONFIG_KEYBOARD_C128 || CONFIG_KEYBOARD_C65
+	jsr screen_scroll_delay
 
-	// Do not scroll if NO_SCRL is pressed and interrupts are enabled
+	// Scroll the LDTBL (line link table)
-!:
-	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 !-
-
-screen_scroll_up_delay_done:
-
-	// First scroll the LDTBL (line link table)
 
 	ldy #$00
 !:
@@ -133,49 +108,8 @@ screen_scroll_up_loop_done:
 	// If the first line is linked, scroll once more
 
 	bit LDTBL+0
-#if CONFIG_KEYBOARD_C128 || CONFIG_KEYBOARD_C65
-	bpl_far screen_scroll_up
-#else
 	bpl screen_scroll_up
-#endif
 
  	// Recalculate PNT and USER
 
 	jmp screen_calculate_PNT_USER
-
-
-
-
-
-
-/* YYY disabled for rework, add CTRL and NO_SCROLL support
-
-not_last_line:
-	rts
-
-screen_scroll_up_if_on_last_line:
-
-	// Colour RAM is always in fixed place, so is easiest
-	// to use to check if we are on the last line.
-	// The last line is at $D800 + 24*40 = $DBC0
-	lda USER+1
-	cmp #>$DBC0
-	bne not_last_line
-
-	lda USER+0
-	cmp #<$DBC0
-	beq is_last_line
-
-	jsr screen_get_current_line_logical_length
-	clc
-	adc USER+0
-	cmp #<$DBE7-1
-	bcc not_last_line
-
-is_last_line:
-
-	dec TBLX
-
-	// FALLTHROUGH to screen_scroll_up
-
-*/

c64/kernal/screen/screen_grow_logical_line.s

@@ -7,33 +7,38 @@ screen_grow_logical_line_done:
 
 screen_grow_logical_line:
 
-	jmp screen_grow_logical_line // YYY
+	// Do not grow line if previus one is grown
+
+	ldy TBLX
+	lda LDTBL,y
+	bpl screen_grow_logical_line_done
+
+	// If last line, scroll the screen up
+	cpy #24
+	bne !+
+	jsr screen_scroll_up
+	ldy TBLX
+!:
+	// Do not grow line if already grown
+	iny
+	lda LDTBL,y
+	bpl screen_grow_logical_line_done
+	
+	// Mark current line as grown
+	lda #$00
+	sta LDTBL,y
+
+	// Now we have to scroll lines downwards to make space
+
+
+
+	.break
+	rts
+
 
 
 /* YYY disabled for rework
 
-	// Do not grow line if it is already grown
-	ldy TBLX
-	lda LDTBL,y
-	bmi screen_grow_logical_line_done
-
-	// Do not grow line if previous grown
-	dey
-	bmi !+
-	lda LDTBL,y
-	bmi screen_grow_logical_line_done
-!:
-	iny
-
-	// Mark current line as grown
-	lda #$80
-	sta LDTBL,y
-
-	// Now make space for the extra line added.
-	// If we are on the last physical line of the screen,
-	// Then we need to scroll the screen up
-	jsr screen_scroll_up_if_on_last_line
-
 	// Count the number of physical lines to scroll down
 	ldx #$01
 	ldy TBLX

c64/kernal/screen/screen_scroll_delay.s

@@ -0,0 +1,40 @@
+
+//
+// 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