; =============================================================================
;  Project  : Custom BIOS / ROM
;  File     : bda.asm
;  Author   : frater
;
;  License  : GNU General Public License v3.0 or later (GPL-3.0+)
;
;  This program is free software: you can redistribute it and/or modify
;  it under the terms of the GNU General Public License as published by
;  the Free Software Foundation, either version 3 of the License, or
;  (at your option) any later version.
;
;  This program is distributed in the hope that it will be useful,
;  but WITHOUT ANY WARRANTY; without even the implied warranty of
;  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
;  GNU General Public License for more details.
;
;  You should have received a copy of the GNU General Public License
;  along with this program.  If not, see <https://www.gnu.org/licenses/>.
;
; =============================================================================

; compatible with IBM PC BIOS Data Area (BDA):
; https://wiki.nox-rhea.org/back2root/ibm-pc-ms-dos/hardware/informations/bios_data_area
;

%define SEG_BDA		   		0x0040			    ; segment BDA (historically)
%define SEG_BDA_CUSTOM	    0x0050              ; custom data (mouse, gfx cursor, etc..)
%define SEG_GUI     		0x0070              ; Segment de données UI (Safe: après Stack, avant Heap)

%define PTR_MOUSE           0x0000
%define PTR_GFX             (PTR_MOUSE + mouse_size)

; video related information (compatible with VGA bios)
%define BDA_VIDEO_CURR_MODE	0x0049
%define BDA_VIDEO_COLUMNS	0x004A
%define BDA_VIDEO_BUF_SIZE	0x004C
%define BDA_VIDEO_OFS_PAGE	0x004E
;
; information relative à la souris
;

%define BDA_BitPPixel    		4

%define BKG_DWORDS_PER_LINE     1          ; 1 dword stocké par ligne
%define BKG_LINES               16
%define BKG_TOTAL_DWORDS        (BKG_LINES * BKG_DWORDS_PER_LINE) ; 16
%define BKG_TOTAL_BYTES         (BKG_TOTAL_DWORDS * 4)            ; 64

struc  mouse
	.buffer         resb    4       ; i8042 input buffer
	.idx            resb    1       ; index in the buffer
	.packetlen      resb    1       ; max buffer len (3 ou 4)
	.status         resb    1       ; mouse status (button etc)
	.wheel          resb    1       ; if a packet size is 4; experimental
	.x              resw    1       ;
	.y              resw    1       ;
	; cursor management
	.cur_x          resw    1       ; preservation des x,y du background
	.cur_y          resw    1       ;
	.cur_addr_start resw    1       ; adresse de départ de la sauvegarde
	.cur_drawing    resb    1       ;
	.cur_counter    resb    1       ; compteur de fois que le curseur a été caché (0 = visible, <0 = invisible)
	.cur_seg        resw    1       ; segment / offset of the pointer
	.cur_ofs        resw    1       ;
	.bkg_saved      resb    1       ; background saved
	alignb                  4       ; alignement 4 bytes
	; buffer for saved background
	.bkg_buffer     resd    16*BDA_BitPPixel
endstruc

struc   gfx
	.cur_x          resw    1       ; x,y en pixel
	.cur_y          resw    1
	.cur_mode       resw    1       ; mode text
	.cur_offset     resw    1       ; offset calculé pour le prochain caractère
	.cur_line_ofs   resw    1       ; "interligne" +2000h ou -2000h
	.cur_shift      resb    1       ; x&7 (0..7)

endstruc

; -----------------------------------------------------------------------------------
;  bda_setup
;  Initialise la BDA à zéro
; -----------------------------------------------------------------------------------
bda_setup:
			pusha
			push        ds

			mov 	ax, SEG_BDA_CUSTOM
			mov 	es, ax

			mov 	ax, 0x5F
			mov 	cx,0xFF
			xor 	di, di
			rep         stosb                ; clear BDA area

			pop 	ds
			popa
			ret