id_vw_a.asm

; Keen Dreams Source Code
; Copyright (C) 2014 Javier M. Chavez
;
; 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 2 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, write to the Free Software Foundation, Inc.,
; 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.

; ID_VW_A.ASM

IDEAL
MODEL	MEDIUM,C

INCLUDE	"ID_ASM.EQU"

WAITFORVBL	=	1			; setting to 0 causes setscreen and waitvbl
							; to skip waiting for VBL (for timing things)

;============================================================================

DATASEG

EXTRN	screenseg			:WORD
EXTRN	drawofs				:WORD
EXTRN	bufferofs			:WORD
EXTRN	displayofs			:WORD
EXTRN	drawofs				:WORD
EXTRN	panadjust			:WORD
EXTRN	ylookup				:WORD
EXTRN	linewidth			:WORD
EXTRN	grsegs				:WORD
EXTRN	updateptr			:WORD
EXTRN	blockstarts			:WORD	;offsets from drawofs for each update block
EXTRN	fontspace			:WORD


planemask	db	?
planenum	db	?
screendest	dw	?
linedelta	dw	?

LABEL shiftdata0 WORD
	dw     0,    1,    2,    3,    4,    5,    6,    7,    8,    9,   10,   11,   12,   13
	dw    14,   15,   16,   17,   18,   19,   20,   21,   22,   23,   24,   25,   26,   27
	dw    28,   29,   30,   31,   32,   33,   34,   35,   36,   37,   38,   39,   40,   41
	dw    42,   43,   44,   45,   46,   47,   48,   49,   50,   51,   52,   53,   54,   55
	dw    56,   57,   58,   59,   60,   61,   62,   63,   64,   65,   66,   67,   68,   69
	dw    70,   71,   72,   73,   74,   75,   76,   77,   78,   79,   80,   81,   82,   83
	dw    84,   85,   86,   87,   88,   89,   90,   91,   92,   93,   94,   95,   96,   97
	dw    98,   99,  100,  101,  102,  103,  104,  105,  106,  107,  108,  109,  110,  111
	dw   112,  113,  114,  115,  116,  117,  118,  119,  120,  121,  122,  123,  124,  125
	dw   126,  127,  128,  129,  130,  131,  132,  133,  134,  135,  136,  137,  138,  139
	dw   140,  141,  142,  143,  144,  145,  146,  147,  148,  149,  150,  151,  152,  153
	dw   154,  155,  156,  157,  158,  159,  160,  161,  162,  163,  164,  165,  166,  167
	dw   168,  169,  170,  171,  172,  173,  174,  175,  176,  177,  178,  179,  180,  181
	dw   182,  183,  184,  185,  186,  187,  188,  189,  190,  191,  192,  193,  194,  195
	dw   196,  197,  198,  199,  200,  201,  202,  203,  204,  205,  206,  207,  208,  209
	dw   210,  211,  212,  213,  214,  215,  216,  217,  218,  219,  220,  221,  222,  223
	dw   224,  225,  226,  227,  228,  229,  230,  231,  232,  233,  234,  235,  236,  237
	dw   238,  239,  240,  241,  242,  243,  244,  245,  246,  247,  248,  249,  250,  251
	dw   252,  253,  254,  255

LABEL shiftdata1 WORD
	dw     0,32768,    1,32769,    2,32770,    3,32771,    4,32772,    5,32773,    6,32774
	dw     7,32775,    8,32776,    9,32777,   10,32778,   11,32779,   12,32780,   13,32781
	dw    14,32782,   15,32783,   16,32784,   17,32785,   18,32786,   19,32787,   20,32788
	dw    21,32789,   22,32790,   23,32791,   24,32792,   25,32793,   26,32794,   27,32795
	dw    28,32796,   29,32797,   30,32798,   31,32799,   32,32800,   33,32801,   34,32802
	dw    35,32803,   36,32804,   37,32805,   38,32806,   39,32807,   40,32808,   41,32809
	dw    42,32810,   43,32811,   44,32812,   45,32813,   46,32814,   47,32815,   48,32816
	dw    49,32817,   50,32818,   51,32819,   52,32820,   53,32821,   54,32822,   55,32823
	dw    56,32824,   57,32825,   58,32826,   59,32827,   60,32828,   61,32829,   62,32830
	dw    63,32831,   64,32832,   65,32833,   66,32834,   67,32835,   68,32836,   69,32837
	dw    70,32838,   71,32839,   72,32840,   73,32841,   74,32842,   75,32843,   76,32844
	dw    77,32845,   78,32846,   79,32847,   80,32848,   81,32849,   82,32850,   83,32851
	dw    84,32852,   85,32853,   86,32854,   87,32855,   88,32856,   89,32857,   90,32858
	dw    91,32859,   92,32860,   93,32861,   94,32862,   95,32863,   96,32864,   97,32865
	dw    98,32866,   99,32867,  100,32868,  101,32869,  102,32870,  103,32871,  104,32872
	dw   105,32873,  106,32874,  107,32875,  108,32876,  109,32877,  110,32878,  111,32879
	dw   112,32880,  113,32881,  114,32882,  115,32883,  116,32884,  117,32885,  118,32886
	dw   119,32887,  120,32888,  121,32889,  122,32890,  123,32891,  124,32892,  125,32893
	dw   126,32894,  127,32895

LABEL shiftdata2 WORD
	dw     0,16384,32768,49152,    1,16385,32769,49153,    2,16386,32770,49154,    3,16387
	dw 32771,49155,    4,16388,32772,49156,    5,16389,32773,49157,    6,16390,32774,49158
	dw     7,16391,32775,49159,    8,16392,32776,49160,    9,16393,32777,49161,   10,16394
	dw 32778,49162,   11,16395,32779,49163,   12,16396,32780,49164,   13,16397,32781,49165
	dw    14,16398,32782,49166,   15,16399,32783,49167,   16,16400,32784,49168,   17,16401
	dw 32785,49169,   18,16402,32786,49170,   19,16403,32787,49171,   20,16404,32788,49172
	dw    21,16405,32789,49173,   22,16406,32790,49174,   23,16407,32791,49175,   24,16408
	dw 32792,49176,   25,16409,32793,49177,   26,16410,32794,49178,   27,16411,32795,49179
	dw    28,16412,32796,49180,   29,16413,32797,49181,   30,16414,32798,49182,   31,16415
	dw 32799,49183,   32,16416,32800,49184,   33,16417,32801,49185,   34,16418,32802,49186
	dw    35,16419,32803,49187,   36,16420,32804,49188,   37,16421,32805,49189,   38,16422
	dw 32806,49190,   39,16423,32807,49191,   40,16424,32808,49192,   41,16425,32809,49193
	dw    42,16426,32810,49194,   43,16427,32811,49195,   44,16428,32812,49196,   45,16429
	dw 32813,49197,   46,16430,32814,49198,   47,16431,32815,49199,   48,16432,32816,49200
	dw    49,16433,32817,49201,   50,16434,32818,49202,   51,16435,32819,49203,   52,16436
	dw 32820,49204,   53,16437,32821,49205,   54,16438,32822,49206,   55,16439,32823,49207
	dw    56,16440,32824,49208,   57,16441,32825,49209,   58,16442,32826,49210,   59,16443
	dw 32827,49211,   60,16444,32828,49212,   61,16445,32829,49213,   62,16446,32830,49214
	dw    63,16447,32831,49215

LABEL shiftdata3 WORD
	dw     0, 8192,16384,24576,32768,40960,49152,57344,    1, 8193,16385,24577,32769,40961
	dw 49153,57345,    2, 8194,16386,24578,32770,40962,49154,57346,    3, 8195,16387,24579
	dw 32771,40963,49155,57347,    4, 8196,16388,24580,32772,40964,49156,57348,    5, 8197
	dw 16389,24581,32773,40965,49157,57349,    6, 8198,16390,24582,32774,40966,49158,57350
	dw     7, 8199,16391,24583,32775,40967,49159,57351,    8, 8200,16392,24584,32776,40968
	dw 49160,57352,    9, 8201,16393,24585,32777,40969,49161,57353,   10, 8202,16394,24586
	dw 32778,40970,49162,57354,   11, 8203,16395,24587,32779,40971,49163,57355,   12, 8204
	dw 16396,24588,32780,40972,49164,57356,   13, 8205,16397,24589,32781,40973,49165,57357
	dw    14, 8206,16398,24590,32782,40974,49166,57358,   15, 8207,16399,24591,32783,40975
	dw 49167,57359,   16, 8208,16400,24592,32784,40976,49168,57360,   17, 8209,16401,24593
	dw 32785,40977,49169,57361,   18, 8210,16402,24594,32786,40978,49170,57362,   19, 8211
	dw 16403,24595,32787,40979,49171,57363,   20, 8212,16404,24596,32788,40980,49172,57364
	dw    21, 8213,16405,24597,32789,40981,49173,57365,   22, 8214,16406,24598,32790,40982
	dw 49174,57366,   23, 8215,16407,24599,32791,40983,49175,57367,   24, 8216,16408,24600
	dw 32792,40984,49176,57368,   25, 8217,16409,24601,32793,40985,49177,57369,   26, 8218
	dw 16410,24602,32794,40986,49178,57370,   27, 8219,16411,24603,32795,40987,49179,57371
	dw    28, 8220,16412,24604,32796,40988,49180,57372,   29, 8221,16413,24605,32797,40989
	dw 49181,57373,   30, 8222,16414,24606,32798,40990,49182,57374,   31, 8223,16415,24607
	dw 32799,40991,49183,57375

LABEL shiftdata4 WORD
	dw     0, 4096, 8192,12288,16384,20480,24576,28672,32768,36864,40960,45056,49152,53248
	dw 57344,61440,    1, 4097, 8193,12289,16385,20481,24577,28673,32769,36865,40961,45057
	dw 49153,53249,57345,61441,    2, 4098, 8194,12290,16386,20482,24578,28674,32770,36866
	dw 40962,45058,49154,53250,57346,61442,    3, 4099, 8195,12291,16387,20483,24579,28675
	dw 32771,36867,40963,45059,49155,53251,57347,61443,    4, 4100, 8196,12292,16388,20484
	dw 24580,28676,32772,36868,40964,45060,49156,53252,57348,61444,    5, 4101, 8197,12293
	dw 16389,20485,24581,28677,32773,36869,40965,45061,49157,53253,57349,61445,    6, 4102
	dw  8198,12294,16390,20486,24582,28678,32774,36870,40966,45062,49158,53254,57350,61446
	dw     7, 4103, 8199,12295,16391,20487,24583,28679,32775,36871,40967,45063,49159,53255
	dw 57351,61447,    8, 4104, 8200,12296,16392,20488,24584,28680,32776,36872,40968,45064
	dw 49160,53256,57352,61448,    9, 4105, 8201,12297,16393,20489,24585,28681,32777,36873
	dw 40969,45065,49161,53257,57353,61449,   10, 4106, 8202,12298,16394,20490,24586,28682
	dw 32778,36874,40970,45066,49162,53258,57354,61450,   11, 4107, 8203,12299,16395,20491
	dw 24587,28683,32779,36875,40971,45067,49163,53259,57355,61451,   12, 4108, 8204,12300
	dw 16396,20492,24588,28684,32780,36876,40972,45068,49164,53260,57356,61452,   13, 4109
	dw  8205,12301,16397,20493,24589,28685,32781,36877,40973,45069,49165,53261,57357,61453
	dw    14, 4110, 8206,12302,16398,20494,24590,28686,32782,36878,40974,45070,49166,53262
	dw 57358,61454,   15, 4111, 8207,12303,16399,20495,24591,28687,32783,36879,40975,45071
	dw 49167,53263,57359,61455

LABEL shiftdata5 WORD
	dw     0, 2048, 4096, 6144, 8192,10240,12288,14336,16384,18432,20480,22528,24576,26624
	dw 28672,30720,32768,34816,36864,38912,40960,43008,45056,47104,49152,51200,53248,55296
	dw 57344,59392,61440,63488,    1, 2049, 4097, 6145, 8193,10241,12289,14337,16385,18433
	dw 20481,22529,24577,26625,28673,30721,32769,34817,36865,38913,40961,43009,45057,47105
	dw 49153,51201,53249,55297,57345,59393,61441,63489,    2, 2050, 4098, 6146, 8194,10242
	dw 12290,14338,16386,18434,20482,22530,24578,26626,28674,30722,32770,34818,36866,38914
	dw 40962,43010,45058,47106,49154,51202,53250,55298,57346,59394,61442,63490,    3, 2051
	dw  4099, 6147, 8195,10243,12291,14339,16387,18435,20483,22531,24579,26627,28675,30723
	dw 32771,34819,36867,38915,40963,43011,45059,47107,49155,51203,53251,55299,57347,59395
	dw 61443,63491,    4, 2052, 4100, 6148, 8196,10244,12292,14340,16388,18436,20484,22532
	dw 24580,26628,28676,30724,32772,34820,36868,38916,40964,43012,45060,47108,49156,51204
	dw 53252,55300,57348,59396,61444,63492,    5, 2053, 4101, 6149, 8197,10245,12293,14341
	dw 16389,18437,20485,22533,24581,26629,28677,30725,32773,34821,36869,38917,40965,43013
	dw 45061,47109,49157,51205,53253,55301,57349,59397,61445,63493,    6, 2054, 4102, 6150
	dw  8198,10246,12294,14342,16390,18438,20486,22534,24582,26630,28678,30726,32774,34822
	dw 36870,38918,40966,43014,45062,47110,49158,51206,53254,55302,57350,59398,61446,63494
	dw     7, 2055, 4103, 6151, 8199,10247,12295,14343,16391,18439,20487,22535,24583,26631
	dw 28679,30727,32775,34823,36871,38919,40967,43015,45063,47111,49159,51207,53255,55303
	dw 57351,59399,61447,63495

LABEL shiftdata6 WORD
	dw     0, 1024, 2048, 3072, 4096, 5120, 6144, 7168, 8192, 9216,10240,11264,12288,13312
	dw 14336,15360,16384,17408,18432,19456,20480,21504,22528,23552,24576,25600,26624,27648
	dw 28672,29696,30720,31744,32768,33792,34816,35840,36864,37888,38912,39936,40960,41984
	dw 43008,44032,45056,46080,47104,48128,49152,50176,51200,52224,53248,54272,55296,56320
	dw 57344,58368,59392,60416,61440,62464,63488,64512,    1, 1025, 2049, 3073, 4097, 5121
	dw  6145, 7169, 8193, 9217,10241,11265,12289,13313,14337,15361,16385,17409,18433,19457
	dw 20481,21505,22529,23553,24577,25601,26625,27649,28673,29697,30721,31745,32769,33793
	dw 34817,35841,36865,37889,38913,39937,40961,41985,43009,44033,45057,46081,47105,48129
	dw 49153,50177,51201,52225,53249,54273,55297,56321,57345,58369,59393,60417,61441,62465
	dw 63489,64513,    2, 1026, 2050, 3074, 4098, 5122, 6146, 7170, 8194, 9218,10242,11266
	dw 12290,13314,14338,15362,16386,17410,18434,19458,20482,21506,22530,23554,24578,25602
	dw 26626,27650,28674,29698,30722,31746,32770,33794,34818,35842,36866,37890,38914,39938
	dw 40962,41986,43010,44034,45058,46082,47106,48130,49154,50178,51202,52226,53250,54274
	dw 55298,56322,57346,58370,59394,60418,61442,62466,63490,64514,    3, 1027, 2051, 3075
	dw  4099, 5123, 6147, 7171, 8195, 9219,10243,11267,12291,13315,14339,15363,16387,17411
	dw 18435,19459,20483,21507,22531,23555,24579,25603,26627,27651,28675,29699,30723,31747
	dw 32771,33795,34819,35843,36867,37891,38915,39939,40963,41987,43011,44035,45059,46083
	dw 47107,48131,49155,50179,51203,52227,53251,54275,55299,56323,57347,58371,59395,60419
	dw 61443,62467,63491,64515

LABEL shiftdata7 WORD
	dw     0,  512, 1024, 1536, 2048, 2560, 3072, 3584, 4096, 4608, 5120, 5632, 6144, 6656
	dw  7168, 7680, 8192, 8704, 9216, 9728,10240,10752,11264,11776,12288,12800,13312,13824
	dw 14336,14848,15360,15872,16384,16896,17408,17920,18432,18944,19456,19968,20480,20992
	dw 21504,22016,22528,23040,23552,24064,24576,25088,25600,26112,26624,27136,27648,28160
	dw 28672,29184,29696,30208,30720,31232,31744,32256,32768,33280,33792,34304,34816,35328
	dw 35840,36352,36864,37376,37888,38400,38912,39424,39936,40448,40960,41472,41984,42496
	dw 43008,43520,44032,44544,45056,45568,46080,46592,47104,47616,48128,48640,49152,49664
	dw 50176,50688,51200,51712,52224,52736,53248,53760,54272,54784,55296,55808,56320,56832
	dw 57344,57856,58368,58880,59392,59904,60416,60928,61440,61952,62464,62976,63488,64000
	dw 64512,65024,    1,  513, 1025, 1537, 2049, 2561, 3073, 3585, 4097, 4609, 5121, 5633
	dw  6145, 6657, 7169, 7681, 8193, 8705, 9217, 9729,10241,10753,11265,11777,12289,12801
	dw 13313,13825,14337,14849,15361,15873,16385,16897,17409,17921,18433,18945,19457,19969
	dw 20481,20993,21505,22017,22529,23041,23553,24065,24577,25089,25601,26113,26625,27137
	dw 27649,28161,28673,29185,29697,30209,30721,31233,31745,32257,32769,33281,33793,34305
	dw 34817,35329,35841,36353,36865,37377,37889,38401,38913,39425,39937,40449,40961,41473
	dw 41985,42497,43009,43521,44033,44545,45057,45569,46081,46593,47105,47617,48129,48641
	dw 49153,49665,50177,50689,51201,51713,52225,52737,53249,53761,54273,54785,55297,55809
	dw 56321,56833,57345,57857,58369,58881,59393,59905,60417,60929,61441,61953,62465,62977
	dw 63489,64001,64513,65025

shifttabletable	dw	shiftdata0,shiftdata1,shiftdata2,shiftdata3
		dw	shiftdata4,shiftdata5,shiftdata6,shiftdata7

PUBLIC	shifttabletable


;============================================================================

CODESEG

IFE GRMODE-CGAGR
INCLUDE	"ID_VW_AC.ASM"
ENDIF

IFE GRMODE-EGAGR
INCLUDE	"ID_VW_AE.ASM"
ENDIF

IFE GRMODE-VGAGR
INCLUDE	"ID_VW_AV.ASM"
ENDIF

;============================================================================
;
;                           MISC VIDEO ROUTINES
;
;============================================================================

;========
;
; VW_WaitVBL (int number)
;
;========

PROC	VW_WaitVBL number:WORD
PUBLIC	VW_WaitVBL

if WAITFORVBL				; skip wait if profiling

	mov	dx,STATUS_REGISTER_1

	mov	cx,[number]

waitvbl1:
	in	al,dx
	test	al,00001000b	;look for vbl
	jnz	waitvbl1

waitvbl2:
	in	al,dx
	test	al,00001000b	;look for vbl
	jz	waitvbl2

	loop	waitvbl1

endif

	ret

ENDP


;===========================================================================


	MASM
;ÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ
;
; Name:	VW_VideoID
;
; Function:	Detects the presence of various video subsystems
;
; int VideoID;
;
; Subsystem ID values:
; 	 0  = (none)
; 	 1  = MDA
; 	 2  = CGA
; 	 3  = EGA
; 	 4  = MCGA
; 	 5  = VGA
; 	80h = HGC
; 	81h = HGC+
; 	82h = Hercules InColor
;
;ÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ

;ÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ
;
; Equates
;
;ÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ
VIDstruct	STRUC		; corresponds to C data structure

Video0Type	DB	?	; first subsystem type
Display0Type	DB	? 	; display attached to first subsystem

Video1Type	DB	?	; second subsystem type
Display1Type	DB	?	; display attached to second subsystem

VIDstruct	ENDS


Device0	EQU	word ptr Video0Type[di]
Device1	EQU	word ptr Video1Type[di]


MDA	EQU	1	; subsystem types
CGA	EQU	2
EGA	EQU	3
MCGA	EQU	4
VGA	EQU	5
HGC	EQU	80h
HGCPlus	EQU	81h
InColor	EQU	82h

MDADisplay	EQU	1	; display types
CGADisplay	EQU	2
EGAColorDisplay	EQU	3
PS2MonoDisplay	EQU	4
PS2ColorDisplay	EQU	5

TRUE	EQU	1
FALSE	EQU	0

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;
; Program
;
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Results	VIDstruct <>	;results go here!

EGADisplays	DB	CGADisplay	; 0000b, 0001b	(EGA switch values)
	DB	EGAColorDisplay	; 0010b, 0011b
	DB	MDADisplay	; 0100b, 0101b
	DB	CGADisplay	; 0110b, 0111b
	DB	EGAColorDisplay	; 1000b, 1001b
	DB	MDADisplay	; 1010b, 1011b

DCCtable	DB	0,0	; translate table for INT 10h func 1Ah
	DB	MDA,MDADisplay
	DB	CGA,CGADisplay
	DB	0,0
	DB	EGA,EGAColorDisplay
	DB	EGA,MDADisplay
	DB	0,0
	DB	VGA,PS2MonoDisplay
	DB	VGA,PS2ColorDisplay
	DB	0,0
	DB	MCGA,EGAColorDisplay
	DB	MCGA,PS2MonoDisplay
	DB	MCGA,PS2ColorDisplay

TestSequence	DB	TRUE	; this list of flags and addresses
	DW	FindPS2	;  determines the order in which this
			;  program looks for the various
EGAflag	DB	?	;  subsystems
	DW	FindEGA

CGAflag	DB	?
	DW	FindCGA

Monoflag	DB	?
	DW	FindMono

NumberOfTests	EQU	($-TestSequence)/3


PUBLIC	VW_VideoID
VW_VideoID	PROC

	push	bp	; preserve caller registers
	mov	bp,sp
	push	ds
	push	si
	push	di

	push	cs
	pop	ds
	ASSUME	DS:@Code

; initialize the data structure that will contain the results

	lea	di,Results	; DS:DI -> start of data structure

	mov	Device0,0	; zero these variables
	mov	Device1,0

; look for the various subsystems using the subroutines whose addresses are
; tabulated in TestSequence; each subroutine sets flags in TestSequence
; to indicate whether subsequent subroutines need to be called

	mov	byte ptr CGAflag,TRUE
	mov	byte ptr EGAflag,TRUE
	mov	byte ptr Monoflag,TRUE

	mov	cx,NumberOfTests
	mov	si,offset TestSequence

@@L01:	lodsb		; AL := flag
	test	al,al
	lodsw		; AX := subroutine address
	jz	@@L02	; skip subroutine if flag is false

	push	si
	push	cx
	call	ax	; call subroutine to detect subsystem
	pop	cx
	pop	si

@@L02:	loop	@@L01

; determine which subsystem is active

	call	FindActive

	mov	al,Results.Video0Type
	mov	ah,0	; was:  Results.Display0Type

	pop	di	; restore caller registers and return
	pop	si
	pop	ds
	mov	sp,bp
	pop	bp
	ret

VW_VideoID	ENDP


;
; FindPS2
;
; This subroutine uses INT 10H function 1Ah to determine the video BIOS
; Display Combination Code (DCC) for each video subsystem present.
;

FindPS2	PROC	near

	mov	ax,1A00h
	int	10h	; call video BIOS for info

	cmp	al,1Ah
	jne	@@L13	; exit if function not supported (i.e.,
			;  no MCGA or VGA in system)

; convert BIOS DCCs into specific subsystems & displays

	mov	cx,bx
	xor	bh,bh	; BX := DCC for active subsystem

	or	ch,ch
	jz	@@L11	; jump if only one subsystem present

	mov	bl,ch	; BX := inactive DCC
	add	bx,bx
	mov	ax,[bx+offset DCCtable]

	mov	Device1,ax

	mov	bl,cl
	xor	bh,bh	; BX := active DCC

@@L11:	add	bx,bx
	mov	ax,[bx+offset DCCtable]

	mov	Device0,ax

; reset flags for subsystems that have been ruled out

	mov	byte ptr CGAflag,FALSE
	mov	byte ptr EGAflag,FALSE
	mov	byte ptr Monoflag,FALSE

	lea	bx,Video0Type[di]  ; if the BIOS reported an MDA ...
	cmp	byte ptr [bx],MDA
	je	@@L12

	lea	bx,Video1Type[di]
	cmp	byte ptr [bx],MDA
	jne	@@L13

@@L12:	mov	word ptr [bx],0    ; ... Hercules can't be ruled out
	mov	byte ptr Monoflag,TRUE

@@L13:	ret

FindPS2	ENDP


;
; FindEGA
;
; Look for an EGA.  This is done by making a call to an EGA BIOS function
;  which doesn't exist in the default (MDA, CGA) BIOS.

FindEGA	PROC	near	; Caller:	AH = flags
			; Returns:	AH = flags
			;		Video0Type and
			;		 Display0Type updated

	mov	bl,10h	; BL := 10h (return EGA info)
	mov	ah,12h	; AH := INT 10H function number
	int	10h	; call EGA BIOS for info
			; if EGA BIOS is present,
			;  BL <> 10H
			;  CL = switch setting
	cmp	bl,10h
	je	@@L22	; jump if EGA BIOS not present

	mov	al,cl
	shr	al,1	; AL := switches/2
	mov	bx,offset EGADisplays
	xlat		; determine display type from switches
	mov	ah,al	; AH := display type
	mov	al,EGA	; AL := subystem type
	call	FoundDevice

	cmp	ah,MDADisplay
	je	@@L21	; jump if EGA has a monochrome display

	mov	CGAflag,FALSE	; no CGA if EGA has color display
	jmp	short @@L22

@@L21:	mov	Monoflag,FALSE	; EGA has a mono display, so MDA and
			;  Hercules are ruled out
@@L22:	ret

FindEGA	ENDP

;
; FindCGA
;
; This is done by looking for the CGA's 6845 CRTC at I/O port 3D4H.
;
FindCGA	PROC	near	; Returns:	VIDstruct updated

	mov	dx,3D4h	; DX := CRTC address port
	call	Find6845
	jc	@@L31	; jump if not present

	mov	al,CGA
	mov	ah,CGADisplay
	call	FoundDevice

@@L31:	ret

FindCGA	ENDP

;
; FindMono
;
; This is done by looking for the MDA's 6845 CRTC at I/O port 3B4H.  If
; a 6845 is found, the subroutine distinguishes between an MDA
; and a Hercules adapter by monitoring bit 7 of the CRT Status byte.
; This bit changes on Hercules adapters but does not change on an MDA.
;
; The various Hercules adapters are identified by bits 4 through 6 of
; the CRT Status value:
;
; 000b = HGC
; 001b = HGC+
; 101b = InColor card
;

FindMono	PROC	near	; Returns:	VIDstruct updated

	mov	dx,3B4h	; DX := CRTC address port
	call	Find6845
	jc	@@L44	; jump if not present

	mov	dl,0BAh	; DX := 3BAh (status port)
	in	al,dx
	and	al,80h
	mov	ah,al	; AH := bit 7 (vertical sync on HGC)

	mov	cx,8000h	; do this 32768 times
@@L41:	in	al,dx
	and	al,80h	; isolate bit 7
	cmp	ah,al
	loope	@@L41	; wait for bit 7 to change
	jne	@@L42	; if bit 7 changed, it's a Hercules

	mov	al,MDA	; if bit 7 didn't change, it's an MDA
	mov	ah,MDADisplay
	call	FoundDevice
	jmp	short @@L44

@@L42:	in	al,dx
	mov	dl,al	; DL := value from status port
	and	dl,01110000b	; mask bits 4 thru 6

	mov	ah,MDADisplay	; assume it's a monochrome display

	mov	al,HGCPlus	; look for an HGC+
	cmp	dl,00010000b
	je	@@L43	; jump if it's an HGC+

	mov	al,HGC	; look for an InColor card or HGC
	cmp	dl,01010000b
	jne	@@L43	; jump if it's not an InColor card

	mov	al,InColor	; it's an InColor card
	mov	ah,EGAColorDisplay

@@L43:	call	FoundDevice

@@L44:	ret

FindMono	ENDP

;
; Find6845
;
; This routine detects the presence of the CRTC on a MDA, CGA or HGC.
; The technique is to write and read register 0Fh of the chip (cursor
; low).  If the same value is read as written, assume the chip is
; present at the specified port addr.
;

Find6845	PROC	near	; Caller:  DX = port addr
			; Returns: cf set if not present
	mov	al,0Fh
	out	dx,al	; select 6845 reg 0Fh (Cursor Low)
	inc	dx
	in	al,dx	; AL := current Cursor Low value
	mov	ah,al	; preserve in AH
	mov	al,66h	; AL := arbitrary value
	out	dx,al	; try to write to 6845

	mov	cx,100h
@@L51:	loop	@@L51	; wait for 6845 to respond

	in	al,dx
	xchg	ah,al	; AH := returned value
			; AL := original value
	out	dx,al	; restore original value

	cmp	ah,66h	; test whether 6845 responded
	je	@@L52	; jump if it did (cf is reset)

	stc		; set carry flag if no 6845 present

@@L52:	ret

Find6845	ENDP


;
; FindActive
;
; This subroutine stores the currently active device as Device0.  The
; current video mode determines which subsystem is active.
;

FindActive	PROC	near

	cmp	word ptr Device1,0
	je	@@L63	; exit if only one subsystem

	cmp	Video0Type[di],4	; exit if MCGA or VGA present
	jge	@@L63	;  (INT 10H function 1AH
	cmp	Video1Type[di],4	;  already did the work)
	jge	@@L63

	mov	ah,0Fh
	int	10h	; AL := current BIOS video mode

	and	al,7
	cmp	al,7	; jump if monochrome
	je	@@L61	;  (mode 7 or 0Fh)

	cmp	Display0Type[di],MDADisplay
	jne	@@L63	; exit if Display0 is color
	jmp	short @@L62

@@L61:	cmp	Display0Type[di],MDADisplay
	je	@@L63	; exit if Display0 is monochrome

@@L62:	mov	ax,Device0	; make Device0 currently active
	xchg	ax,Device1
	mov	Device0,ax

@@L63:	ret

FindActive	ENDP


;
; FoundDevice
;
; This routine updates the list of subsystems.
;

FoundDevice	PROC	near	; Caller:    AH = display #
			;	     AL = subsystem #
			; Destroys:  BX
	lea	bx,Video0Type[di]
	cmp	byte ptr [bx],0
	je	@@L71	; jump if 1st subsystem

	lea	bx,Video1Type[di]	; must be 2nd subsystem

@@L71:	mov	[bx],ax	; update list entry
	ret

FoundDevice	ENDP

IDEAL



END