APNotes.txt

FE8U

See also decomp files src/ap.c and include/ap.h.
(https://github.com/FireEmblemUniverse/fireemblem8u)

AP is the name I'll give to the RAM struct initialized with the "Other Pointer" in the Moving Map Sprite table. With time I discovered that it was used in some other cases, like the prep menu/warp move unit cursor. The big thing is that is can be used to animate shit, using a definition in ROM (we back to the MMS "Other Pointer") (see ROMAP).

AP: (Size: 0x28) Array of 20 of those located at 03000108
	00 | word  | Pointer to AP Data
	04 | word  | Pointer to Frame Data Ref (from AP Data)
	08 | word  | Pointer to Current Anim Data (Start, where you go back on loop)
	0C | word  | Pointer to Current Anim Data (Cursor)
	10 | word  | Pointer to Current Frame/OAM Data
	14 | word  | Pointer to Current Rot/Scale Data
	18 | short | Cycle Timer
	1A | short | Cycle Time Step (0x100 is one frame)
	1C | short | Sub frame time offset or something
	1E | short | OAM Index?
	20 | byte  | bool defining whether gfx needs update
	21 | byte  | Rotation/Scale OAM Index
	22 | short | OAM Extra Data (Tile Index Root & OAM2 Stuff)
	24 | word  | Gfx Pointer

AP Data:
	00 | short | Relative Offset to Frame Data Ref Array
	02 | short | Relative Offset to Anim Data Ref Array

	AP Data Ref Arrays:
		Arrays of shorts that are relative offsets (relative *to the array*) to the relevant data

	Anim Data:
		Arrays of pairs of shorts:
			00 | short | cycle time of this anim frame
		if cycle time is non 0:
			02 | short | Frame index of this anim frame
		if cycle time is 0:
			02 | short | 0 = End animation (AP_Update returns 0), 1 = End/Free Anim/AP, FFFF = Loop back to start of Anim, other = same as with std cycle

	Frame Data:
		Your standard OAM Data (first short is number of parts, then array of three shorts that define base OAM data for that part)
		OR, when the top bit of the first short is set, then the OAM Data is at FrameData + 2 + [first short ignoring the top bit], the part before it is used to do some trigonometry and shit, so I guess that thing handles transformations as well? neat
		Ok so Rot Scale Data:
			First short: count (with the top bit set as mentionned).
			Then array of three shorts:
				00 | short | alpha
				02 | short | xScale
				04 | short | yScale

ROUTINES:
	0800927C | AP_New | Creates a new AP
		Arguments: r0 = Source AP Data, r1 = OAM Index? idk
		Returns:   r0 = AP Pointer
	
	080092A4 | AP_Free | Frees/Deletes/Ends a AP
		Arguments: r0 = AP
		Returns:   nothing
	
	080092BC | AP_Update | Updates AP Logic and Graphics
		Arguments: r0 = AP, r1 = display x, r2 = display y
		Returns:   0 on error, 1 otherwise
	
	08009518 | AP_SetAnim | Sets Anim of AP
		Arguments: r0 = AP, r1 = Anim Index
		Returns:   nothing
	
	08009548 | AP_SetAPData | Sets (Changes) AP Data of AP
		Arguments: r0 = AP, r1 = AP Data
		Returns:   nothing
	
	Other routines that seem to only be used internally:
		08009260:AP_ClearAll
		080092E4:AP_RegisterGraphics
		08009340:AP_Exec
		08009430:AP_QueueRotScaleData
		08009568:AP_QueueTileGfx
		08009674:AP_Load
		08009698:AP_ExecOneFrame
		080096B8:AP_Init
		080096F0:AP_Alloc

AP Proc: (Code at 0859168C)
	50 | word | AP Pointer
	54 | word | X
	58 | word | Y
	
	ROUTINES:
		08009718 | APProc_Start | Makes a new 6C in thread 3 that wraps a AP
			Arguments: r0 = Source AP, r1 = X, r2 = Y, r3 = Tile Root, [sp] = Anim index, [sp+4] = OAM Index
			Returns:   r0 = AP Wrapper 6C Pointer
		
		08009798 | APProc_SetParameters | Sets AP Parameters
			Arguments: r0 = AP Wrapper 6C Pointer, r1 = X, r2 = Y, r3 = Tile Root
		
		080097B4 | APProc_Delete | delet
			Arguments: r0 = AP Wrapper 6C Pointer
		
		080097C0 | APProc_DeleteAll | delets all
			Arguments: none
		
		080097D0 | APProcExists | Returns 1 if one exists, 0 otherwise
			Returns: result