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Old January 26th, 2013 (9:59 PM). Edited January 27th, 2013 by Shiny Quagsire.
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Shiny Quagsire Shiny Quagsire is offline
I'm Still Alive, Elsewhere
     
    Join Date: May 2009
    Location: Hoenn Safari Zone
    Age: 19
    Gender: Male
    Nature: Jolly
    Posts: 700
    Using the Berry Bag for Item Selection

    So, recently I've been working on making a complete berry system based on JPAN's Berry System on Fire Red. For a planting script, it required some sort of berry selection, and having a scripted multichoice menu for it was a no-go for me. So, I got to work, searching and searching, and I got it!

    While you may think doing this would be complicated, there are is actually only one ASM routine required for this. Basically, what it does is it forces the bag into thinking every item is the Exit item, which will exit the bag immediately as it's selected. Along the way to exiting the routine, it stores the berry ID to variable 0x800E, or 0x0 if the user didn't select anything or pressed B. Under normal circumstances, this is wiped upon exiting the bag, but because of the way we call the bag, it preserves this variable.

    hijackbag.asm:
    Code:
    @Forces the bag to exit instead of opening the menu.
    @Insert bx r3 at (18 47) 0813DB18, and the pointer to this routine (+1) at 0813DB30
    
    .thumb
    .thumb_func
    .global hijackbag
    
    main:
    	ldr r3, var_8000
    	ldrh r3, [r3]
    	cmp r3, #0x7E
    	beq hack
    	ldr r3, unk_0203F370
    	mov r8, r3
    	ldrb r0, [r3,#0x4]
    	b return
    hack:
    	ldr r3, unk_0203F370
    	mov r8, r3
    	mov r0, #0x5
    return:
    	ldr r3, returnaddress
    	bx r3
    .align 2
    returnaddress: 		.word 0x0813DB1D
    unk_0203F370:		.word 0x0203F370
    var_8000:		.word 0x020370B8
    All this does it it checks variable 0x8000 (you can change it to use the variable decrypter if you wish) for a strange value that wouldn't misfire our hack. In this case, I chose 0x7E. Any other weird values will work if you feel 0x7E isn't apropriate.

    To insert this, place 18 47 at 0x13DB18, and the pointer to this routine + 1 at 0x13DB30.

    Now, to use this hack, simply place the following into a script:
    Code:
    fadescreen 1        'Fade the screen to prevent any graphical glitches from being visible. And it looks nice. :)
    setvar 0x8000 0x7E  'Set 0x8000 to trigger our script
    setvar 0x800E 0x0   'Make sure 0x800E isn't set, because if it is, weird things happen.
    callasm 0x0a1881    'Call the berry bag. This is stored internally in the ROM
    waitmsg             'I'll explain this later.
    setvar 0x8000 0x0   'Reset our hack to prevent weirdness.
    Ok, so basically this fades the screen, sets our trigger variable, calls the routine, and resets. However, if your a scripter, you might be thinking "What the heck is up with that waitmsg? Did we even call an msgbox?" Well, there's a reason for doing that. When the ASM code is called, it basically hands it to a table so that it is updated every time the game runs the main loop. However, this also means that the script keeps going during this time, which can be bad if you're calling a bufferitem 0x0 0x800E afterwards, or anything that borrows the value at 0x800E. So, the waitmsg acts as a delay so that the script waits until our player is finished choosing which berry he wants.

    As for applications to apply this to, here's an example script I wrote to test this:
    Spoiler:

    #dynamic 0x100011B
    #include stditems.rbh

    #org @start
    lock
    faceplayer
    msgbox @msg 0x5
    compare 0x800d 0x1
    if 0x1 goto @plant
    release
    end

    #org @plant
    giveitem ITEM_ORANBERRY 3 0
    giveitem ITEM_CHERIBERRY 1 0
    giveitem ITEM_SITRUSBERRY 1 0
    fadescreen 1
    setvar 0x8000 0x7E
    setvar 0x800E 0x0
    callasm 0x0a1881
    waitmsg
    setvar 0x8000 0x0
    compare 0x800E 0x0
    if 0x1 goto @noberry
    bufferitem 0x0 0x800E
    msgbox @planted 2
    release
    end

    #org @noberry
    msgbox @noplant 2
    release
    end

    #org @msg
    = There is a dude standing here.\pWould you like to plant a berry?
    #org @planted
    = You planted a [buffer0].
    #org @noplant
    = The trees cried because you\ndidn't plant anything. :'(


    Final Notes (and things to consider)
    So, this is an interesting hack, but what if we could use it with the normal bag, and have a way to manually give items to someone, ie a junk dealer, or a quest where you have to guess what the person likes? EDIT: Done! See section below!

    As a final note, if you find any bugs, report them, and suggestions are welcome. Also, be sure to give credits. It's a good morale booster for me.


    Using the Normal Bag for Item Selection

    So after completing my berry bag hack, I posted some final notes and things I thought about afterwards. Since both bags functioned relatively the same, I decided to port the same hack from the Berry Bag to the Main Bag.

    Since I'm lazy, I'm going to use quotes:
    Quote:
    Originally Posted by Shiny Quagsire View Post
    ... there are is actually only one ASM routine required for this. Basically, what it does is it forces the bag into thinking every item is the Exit item, which will exit the bag immediately as it's selected. Along the way to exiting the routine, it stores the berry ID to variable 0x800E, or 0x0 if the user didn't select anything or pressed B. Under normal circumstances, this is wiped upon exiting the bag, but because of the way we call the bag, it preserves this variable.
    hijacknormbag.asm
    Code:
    @Forces the bag to exit instead of showing the item menu.
    @Place the pointer to this routine at 0x081090D0, and place bx r1 (08 47) at 0x081090B6
    
    .thumb
    .thumb_func
    .global BagHack
    
    main:
    	ldr r1, var_8000
    	ldrh r1, [r1]
    	cmp r1, #0x7F
    	beq skip
    	ldr r1, var_800E
    	strh r0, [r1]
    	ldr r1, return
    	bx r1
    skip:
    	ldr r1, var_800E
    	strh r0, [r1]
    	ldr r1, skipaddr
    	bx r1
    	
    var_8000:	.word 0x020370B8
    var_800E:	.word 0x0203AD30
    skipaddr:	.word 0x08109065
    return:	.word 0x081090B9
    To insert this, place the pointer to the compiled routine (+ 1) at 0x1090D0, and place 08 47 at 0x1090B6.

    Now, one thing to notice if you can read this is that there is one major difference from the berry bag hack, and that's in this section of code:
    Code:
    cmp r1, #0x7F
    Instead of using 0x7E like the berry bag, I wanted to distinguish this hack from the other one to avoid confusion while scripting. so I made it check variable 0x8000 for 0x7F instead.

    Now, since this is almost exactly like the berry bag hack, the script calling is pretty much the same. I'll comment out any major differences.
    Code:
    fadescreen 1
    setvar 0x8000 0x7F    'Set 0x8000 to 0x7F instead of 0x7E
    setvar 0x800E 0x0
    callasm 0x10a67d       'This calls the bag. If you ever want to use this without the hack, it works.
    waitmsg
    setvar 0x8000 0x0
    Final Notes (and things to consider)
    As for applications for this, pretty much anything you want. Truthfully, I just reused my berry script for testing, because I was too lazy to do anything special or cool with it as seen by this pic:


    However, some ideas for this are:
    • A Junk Dealer who buys random items
    • An event where you have to give a certain item
    • An event where you trade items
    • A script where you have to guess an item that someone wants
    • Fossil scripts
    • Etc.

    As usual, report any bugs associated with the routine and suggestions are welcome. Also, be sure to give credits. It's a good morale booster for me.
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