Add a new text scrolling speed

This tutorial details how to add an additional text speed option to the options screen. As an example we'll implement an option for instant text.

Contents

1. Define wram constant
2. Add instant text to options
3. Fix text speed while holding A or B
4. Fix <SCROLL> command

1. Define wram constant

Edit constants/wram_constants.asm:

; wOptions1::
DEF TEXT_DELAY_MASK EQU %111
	const_def 4
	const NO_TEXT_SCROLL ; 4
	const STEREO         ; 5
	const BATTLE_SHIFT   ; 6
	const BATTLE_SCENE   ; 7

+DEF TEXT_DELAY_NONE EQU %000 ; 0
DEF TEXT_DELAY_FAST EQU %001 ; 1
DEF TEXT_DELAY_MED  EQU %011 ; 3
DEF TEXT_DELAY_SLOW EQU %101 ; 5

As you can see we defined TEXT_DELAY_NONE as 0, which will print all characters with 0 frame delay.

2. Add instant text to options

Edit engine/menus/options_menu.asm:

 .Pointers:
 	dw Options_TextSpeed
 	...
 
 	const_def
 	const OPT_TEXT_SPEED_FAST ; 0
 	const OPT_TEXT_SPEED_MED  ; 1
 	const OPT_TEXT_SPEED_SLOW ; 2
+	const OPT_TEXT_SPEED_NONE ; 3
 
 Options_TextSpeed:
 	call GetTextSpeed
 	ldh a, [hJoyPressed]
 	bit D_LEFT_F, a
 	jr nz, .LeftPressed
 	bit D_RIGHT_F, a
 	jr z, .NonePressed
 	ld a, c ; right pressed
-	cp OPT_TEXT_SPEED_SLOW
+	cp OPT_TEXT_SPEED_NONE
 	jr c, .Increase
 	...
 
 .LeftPressed:
 	ld a, c
 	and a
 	jr nz, .Decrease
-       ld c, OPT_TEXT_SPEED_SLOW + 1
+ 	ld c, OPT_TEXT_SPEED_NONE + 1

This will make it cycleable in the options menu but it won't actually work quite yet. We still need to define its string and load the correct previous & next value into registers, otherwise it won't display the selected value correctly.

 .Strings:
 ; entries correspond to OPT_TEXT_SPEED_* constants
 	dw .Fast
 	dw .Mid
 	dw .Slow
+	dw .None
 
 .Fast: db "FAST@"
 .Mid:  db "MID @"
 .Slow: db "SLOW@"
+.None: db "NONE@"
 
 GetTextSpeed:
 ; converts TEXT_DELAY_* value in a to OPT_TEXT_SPEED_* value in c,
 ; with previous/next TEXT_DELAY_* values in d/e
 	ld a, [wOptions]
 	and TEXT_DELAY_MASK
 	cp TEXT_DELAY_SLOW
 	jr z, .slow
 	cp TEXT_DELAY_FAST
 	jr z, .fast
+	cp TEXT_DELAY_NONE
+	jr z, .none
 	; none of the above
 	ld c, OPT_TEXT_SPEED_MED
 	lb de, TEXT_DELAY_FAST, TEXT_DELAY_SLOW
 	ret
 
 .slow
 	ld c, OPT_TEXT_SPEED_SLOW
-	lb de, TEXT_DELAY_MED, TEXT_DELAY_FAST
+	lb de, TEXT_DELAY_MED, TEXT_DELAY_NONE
 	ret
 
 .fast
 	ld c, OPT_TEXT_SPEED_FAST
-	lb de, TEXT_DELAY_SLOW, TEXT_DELAY_MED
+	lb de, TEXT_DELAY_NONE, TEXT_DELAY_MED
+	ret
+
+.none
+	ld c, OPT_TEXT_SPEED_NONE
+	lb de, TEXT_DELAY_SLOW, TEXT_DELAY_FAST
 	ret

Note how lb de, <previous>, <next> correspond to the order defined with the OPT_TEXT_SPEED_<speed> constants. If your custom text speed is not 0 like mine you're done.

3. Fix text speed while holding A or B

There are a few extra quirks to fix. When you hold the A or B buttons while text is scrolling it does so at TEXT_DELAY_FAST. Since our custom text speed is faster than that we need to make sure this doesn't happen.

Edit home/print_text.asm:

 PrintLetterDelay::
 	...
 
 ; text speed
 	ld a, [wOptions]
 	and %111
+	jr z, .end
 	jr .updatedelay

4. Fix <SCROLL> command

Lastly, the <SCROLL> command, which is used when a stat is sharply raised or lowered (among a couple other cases), will cause the line to skip instantly, giving you no time to read it. We'll force a delay into it.

_ContText fallsthrough into _ContTextNoPause but it doesn't need the delay, so we'll replace the fallthrough with a jump

Edit home/text.asm:

_ContText::
 	...
        call z, UnloadBlinkingCursor
-       ; fallthrough
+	jr _ContTextNoPause.not_instant

_ContTextNoPause::
+	ld a, [wOptions]
+	and TEXT_DELAY_MASK
+	cp TEXT_DELAY_FAST
+	jr nz, .not_instant
+	ld c, 15
+	call DelayFrames
+.not_instant
	push de

And there you go.