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XMAIN.ASM
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Assembly Source File
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1992-11-12
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39KB
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1,256 lines
;-----------------------------------------------------------------------
; MODULE XMAIN
;
; Initialization, panning and split screen functions for all MODE X 256
; Color resolutions
;
; Compile with Tasm.
; C callable.
;
;
; ****** XLIB - Mode X graphics library ****************
; ****** ****************
; ****** Written By Themie Gouthas ****************
;
; egg@dstos3.dsto.gov.au
; teg@bart.dsto.gov.au
;
; MODIFICATIONS:
; 26-9-92: Pel panning code added
; Dates forgotten: Numerous ;^)
;-----------------------------------------------------------------------
include xlib.inc
include xmain.inc
.data
; Mode X CRTC register tweaks for various resolutions
X320Y200 label word
db 0e3h ; dot clock
db 02 ; Number of CRTC Registers to update
dw 00014h ; turn off dword mode
dw 0e317h ; turn on byte mode
dw 320 ; width
dw 200 ; height
X320Y240 label word
db 0e3h ; dot clock
db 10 ; Number of CRTC Registers to update
dw 00d06h ; vertical total
dw 03e07h ; overflow (bit 8 of vertical counts)
dw 04109h ; cell height (2 to double-scan)
dw 0ea10h ; v sync start
dw 0ac11h ; v sync end and protect cr0-cr7
dw 0df12h ; vertical displayed
dw 00014h ; turn off dword mode
dw 0e715h ; v blank start
dw 00616h ; v blank end
dw 0e317h ; turn on byte mode
dw 320 ; width
dw 240 ; height
X360Y200 label word
db 0e7h ; dot clock
db 08 ; Number of CRTC Registers to update
dw 06b00h ; horz total
dw 05901h ; horz displayed
dw 05a02h ; start horz blanking
dw 08e03h ; end horz blanking
dw 05e04h ; start h sync
dw 08a05h ; end h sync
dw 00014h ; turn off dword mode
dw 0e317h ; turn on byte mode
dw 360 ; width
dw 200 ; height
X360Y240 label word
db 0e7h ; dot clock
db 17 ; Number of CRTC Registers to update
dw 06b00h ; horz total
dw 05901h ; horz displayed
dw 05a02h ; start horz blanking
dw 08e03h ; end horz blanking
dw 05e04h ; start h sync
dw 08a05h ; end h sync
dw 00d06h ; vertical total
dw 03e07h ; overflow (bit 8 of vertical counts)
dw 04109h ; cell height (2 to double-scan)
dw 0ea10h ; v sync start
dw 0ac11h ; v sync end and protect cr0-cr7
dw 0df12h ; vertical displayed
dw 02d13h ; offset;
dw 00014h ; turn off dword mode
dw 0e715h ; v blank start
dw 00616h ; v blank end
dw 0e317h ; turn on byte mode
dw 360
dw 240
X376Y282 label word
db 0e7h
db 18
dw 06e00h ; horz total
dw 05d01h ; horz displayed
dw 05e02h ; start horz blanking
dw 09103h ; end horz blanking
dw 06204h ; start h sync
dw 08f05h ; end h sync
dw 06206h ; vertical total
dw 0f007h ; overflow
dw 06109h ; cell height
dw 0310fh ;
dw 03710h ; v sync start
dw 08911h ; v sync end and protect cr0-cr7
dw 03312h ; vertical displayed
dw 02f13h ; offset
dw 00014h ; turn off dword mode
dw 03c15h ; v blank start
dw 05c16h ; v blank end
dw 0e317h ; turn on byte mode
dw 376
dw 564
X320Y400 label word
db 0e3h ; dot clock
db 03 ; Number of CRTC Registers to update
dw 04009h ; cell height
dw 00014h ; turn off dword mode
dw 0e317h ; turn on byte mode
dw 320 ; width
dw 400 ; height
X320Y480 label word
db 0e3h ; dotclock
db 10 ; Number of CRTC Registers to update
dw 00d06h ; vertical total
dw 03e07h ; overflow (bit 8 of vertical counts)
dw 04009h ; cell height (2 to double-scan)
dw 0ea10h ; v sync start
dw 0ac11h ; v sync end and protect cr0-cr7
dw 0df12h ; vertical displayed
dw 00014h ; turn off dword mode
dw 0e715h ; v blank start
dw 00616h ; v blank end
dw 0e317h ; turn on byte mode
dw 320 ; width
dw 480 ; height
X360Y400 label word
db 0e7h ; dot clock
db 09 ; Number of CRTC Registers to update
dw 06b00h ; horz total
dw 05901h ; horz displayed
dw 05a02h ; start horz blanking
dw 08e03h ; end horz blanking
dw 05e04h ; start h sync
dw 08a05h ; end h sync
dw 04009h ; cell height
dw 00014h ; turn off dword mode
dw 0e317h ; turn on byte mode
dw 360 ; width
dw 400 ; height
X360Y480 label word
db 0e7h
db 17
dw 06b00h ; horz total
dw 05901h ; horz displayed
dw 05a02h ; start horz blanking
dw 08e03h ; end horz blanking
dw 05e04h ; start h sync
dw 08a05h ; end h sync
dw 00d06h ; vertical total
dw 03e07h ; overflow
dw 04009h ; cell height
dw 0ea10h ; v sync start
dw 0ac11h ; v sync end and protect cr0-cr7
dw 0df12h ; vertical displayed
dw 02d13h ; offset
dw 00014h ; turn off dword mode
dw 0e715h ; v blank start
dw 00616h ; v blank end
dw 0e317h ; turn on byte mode
dw 360
dw 480
X360Y360 label word
db 0e7h
db 15
dw 06b00h ; horz total
dw 05901h ; horz displayed
dw 05a02h ; start horz blanking
dw 08e03h ; end horz blanking
dw 05e04h ; start h sync
dw 08a05h ; end h sync
dw 04009h ; cell height
dw 08810h ; v sync start
dw 08511h ; v sync end and protect cr0-cr7
dw 06712h ; vertical displayed
dw 02d13h ; offset
dw 00014h ; turn off dword mode
dw 06d15h ; v blank start
dw 0ba16h ; v blank end
dw 0e317h ; turn on byte mode
dw 360
dw 360
X376Y308 label word
db 0e7h
db 18
dw 06e00h ; horz total
dw 05d01h ; horz displayed
dw 05e02h ; start horz blanking
dw 09103h ; end horz blanking
dw 06204h ; start h sync
dw 08f05h ; end h sync
dw 06206h ; vertical total
dw 00f07h ; overflow
dw 04009h ;
dw 0310fh ;
dw 03710h ; v sync start
dw 08911h ; v sync end and protect cr0-cr7
dw 03312h ; vertical displayed
dw 02f13h ; offset
dw 00014h ; turn off dword mode
dw 03c15h ; v blank start
dw 05c16h ; v blank end
dw 0e317h ; turn on byte mode
dw 376
dw 308
X376Y564 label word
db 0e7h
db 18
dw 06e00h ; horz total
dw 05d01h ; horz displayed
dw 05e02h ; start horz blanking
dw 09103h ; end horz blanking
dw 06204h ; start h sync
dw 08f05h ; end h sync
dw 06206h ; vertical total
dw 0f007h ; overflow
dw 06009h ;
dw 0310fh ;
dw 03710h ; v sync start
dw 08911h ; v sync end and protect cr0-cr7
dw 03312h ; vertical displayed
dw 02f13h ; offset
dw 00014h ; turn off dword mode
dw 03c15h ; v blank start
dw 05c16h ; v blank end
dw 0e317h ; turn on byte mode
dw 376
dw 564
LAST_X_MODE equ 11
ModeTable label word ; Mode X tweak table
dw offset X320Y200
dw offset X320Y240
dw offset X360Y200
dw offset X360Y240
dw offset X376Y282
dw offset X320Y400
dw offset X320Y480
dw offset X360Y400
dw offset X360Y480
dw offset X360Y360
dw offset X376Y308
dw offset X376Y564
PARAMS label byte
_CurrXMode dw 0 ; Current graphics mode index
_InGraphics db 0 ; Flag indicating graphics activity
_ScrnPhysicalByteWidth dw 0 ; Physical width in bytes of screen
_ScrnPhysicalPixelWidth dw 0 ; Physical width in pixels of screen
_ScrnPhysicalHeight dw 0 ; Physical Height of screen
_ErrorValue db 0 ; Set after function calls
_SplitScrnActive db 0 ; Flag indicating Split scrn activity
_DoubleBufferActive dw 0 ; Flag indicating double buffering
_SplitScrnScanLine dw 0 ; Split Screen's starting scan line
_SplitScrnVisibleHeight dw 0 ; Split Screen's height on screen
_SplitScrnOffs dw 0 ; Offset in video ram of Split Screen
; always = 0
_Page0_Offs dw 0 ; Ofset in video ram of Main virtual
; screen ( = 0 if no split screen
; otherwise = offset of first byte
; after split screen
_Page1_Offs dw 0 ; Ofset in video ram of Second virtual
; screen ( = 0 if no split screen
; otherwise = offset of first byte
; after split screen
; = Page0_Offs if Doubble buffering
; not enabled
_NonVisual_Offs dw 0 ; Ofset in video ram of first byte
; of non visible ram
_ScrnLogicalByteWidth dw 0 ; Logical width in bytes of screen
_ScrnLogicalPixelWidth dw 0 ; Logical width in pixels of screen
_ScrnLogicalHeight dw 0 ; Logical Height of screen
_MaxScrollX dw 0 ; Max X start position of Physical
; screen within virtual screen (in
; bytes)
_MaxScrollY dw 0 ; Max Y start position of Physical
; screen within virtual screen
_VisiblePageIdx dw 0 ; Index of currently visible D.B.
; page
PageAddrTable label word
_VisiblePageOffs dw 0 ; Table containing starting offsets
_HiddenPageOffs dw 0 ; of the double buffer pages
_TopClip dw 0 ; Clipping Rectangle
_BottomClip dw 0 ;
_LeftClip dw 0 ; Left/Right coordinates in bytes
_RightClip dw 0 ;
_PhysicalStartByteX dw 0 ; X byte coord of physical screen
; relative to virtual virtual screen
_PhysicalStartPixelX dw 0 ; X pixel coord of physical screen
; relative to virtual screen
_PhysicalStartY dw 0 ; Y pixel coord of physical screen
; relative to virtual screen
PARAMS_END label byte
PARAM_COUNT equ ($-PARAMS)
; Index/data pairs for CRT Controller registers that differ between
; mode 13h and mode X.
;Pelpan values for 0,1,2,3 pixel panning to the left, respectively
PelPanMask db 000h,002h,004h,006h
DoubleScanFlag db ? ; Flag to indicate double scanned mode
.code
;-------------------------------------------------------------------------
; Local Logical Screen Width setting function
; cx = Requitrd Logical Width
;
; WARNING: no registers are preserved
SetLogicalScrWidth proc
mov dx,CRTC_INDEX
mov al,CRTC_OFFSET
out dx,al
inc dx
mov ax,cx
cmp ax,[_ScrnPhysicalPixelWidth]; Is logical width >= physical width
jge @@ValidLogicalWidth ; yes - continue
mov ax,bx ; no - set logical width = physical
@@ValidLogicalWidth:
shr ax,3
out dx,al
; The EXACT logical pixel width may not have been possible since
; it should be divisible by 8. Round down to the closest possible
; width and update the status variables
shl ax,1
mov bx,ax
mov [_ScrnLogicalByteWidth],ax ; Store the byte width of virtual
mov [_RightClip],ax ; Set default Right clip column
; screen
sub ax,[_ScrnPhysicalByteWidth] ; Calculate and store Max X position
shl ax,2 ; of physical screen in virtual
mov [_MaxScrollX],ax ; screen in pixels
mov ax,bx ; set ax to byte width of virt scrn
shl ax,2 ; convert to pixels
mov [_ScrnLogicalPixelWidth],ax ; store virt scrn pixel width
mov cx,ax ; save ax (return value)
; calculate no. non split screen rows in video ram
mov ax,0ffffh ; cx = Maximum video ram offset
sub dx,dx ; DX:AX is divide operand, set DX = 0
div bx ; divide ax by ScrnLogicalByteWidth
mov [_ScrnLogicalHeight],ax ; Save Screen Logical Height
mov [_BottomClip],ax ; Set default bottom clip row
sub ax,[_ScrnPhysicalHeight] ; Update the maximum Y position of
mov [_MaxScrollY],ax ; Physical screen in logical screen
mov ax,cx ; restore ax (return value)
; calculate initial NonVisual
mov ax,[_ScrnLogicalByteWidth]
mul [_ScrnPhysicalHeight]
mov [_NonVisual_Offs],ax
@@Done: ret
SetLogicalScrWidth endp
;-----------------------------------------------------------------------
; Mode X graphics mode set with a virtual screen
; logical screen width.
; C near-callable as:
;
; int x_set_mode(unsigned int mode,unsigned int WidthInPixels);
;
; returns the actual width of the allocated virtual screen in pixels
; if a valid mode was selected otherwise returns -1
;
; Saves virtual screen pixel width in _ScrnLogicalPixelWidth.
; Saves virtual screen byte width in _ScrnLogicalByteWidth.
; Physical screen dimensions are set in _ScrnPhysicalPixelWidth,
; _ScrnPhysicalByteWidth and _ScrnPhysicalHeight
;
;
; Modes: 0 = 320 x 200 (256 color) NOTE: Some of these modes require
; 1 = 320 x 240 (256 color) vertical size adjustment.
; 2 = 360 x 200 (256 color)
; 3 = 360 x 240 (256 color)
; 4 = 320 x 400 (256 color)
; 5 = 320 x 480 (256 color)
; 6 = 360 x 200 (256 color)
; 7 = 360 x 480 (256 color)
; 8 = 360 x 360 (256 color)
; 9 = 376 x 308 (256 color)
; 10 = 376 x 564 (256 color)
;
; Written by Themie Gouthas,
; parts adapted from M. Abrash code.
;------------------------------------------------------------------------
_x_set_mode proc
ARG mode:word,logicalscrwidth:word
push bp ;preserve caller's stack frame
mov bp,sp
push si ;preserve C register vars
push di ; (don't count on BIOS preserving anything)
cld
mov ax,ds
mov es,ax
mov di,offset PARAMS
xor ax,ax
mov cx,PARAM_COUNT
rep stosb
mov cx,[mode]
cmp cx,LAST_X_MODE ; have we selected a valid mode
jle @@ValidMode ; Yes !
mov [_InGraphics],FALSE ; No return -1
mov ax,-1
pop di
pop si
pop bp
ret
@@ValidMode:
mov [_CurrXMode],cx
mov [_InGraphics],TRUE
xor al,al
cmp cx,3
jg @@SetDoubleScanFlag
mov al,TRUE
@@SetDoubleScanFlag:
mov [DoubleScanFlag],al
mov ax,13h ; let the BIOS set standard 256-color
int 10h ; mode (320x200 linear)
mov dx,SC_INDEX
mov ax,0604h
out dx,ax ; disable chain4 mode
mov ax,0100h
out dx,ax ; synchronous reset while setting Misc
; Output for safety, even though clock
; unchanged
mov bx,offset ModeTable
shl cx,1
add bx,cx
mov si, word ptr [bx]
lodsb
mov dx,MISC_OUTPUT
out dx,al ; select the dot clock and Horiz
; scanning rate
mov dx,SC_INDEX
mov ax,0300h
out dx,ax ; undo reset (restart sequencer)
mov dx,CRTC_INDEX ; reprogram the CRT Controller
mov al,11h ; VSync End reg contains register write
out dx,al ; protect bit
inc dx ; CRT Controller Data register
in al,dx ; get current VSync End register setting
and al,07fh ; remove write protect on various
out dx,al ; CRTC registers
dec dx ; CRT Controller Index
cld
xor cx,cx
lodsb
mov cl,al
@@SetCRTParmsLoop:
lodsw ; get the next CRT Index/Data pair
out dx,ax ; set the next CRT Index/Data pair
loop @@SetCRTParmsLoop
mov dx,SC_INDEX
mov ax,0f02h
out dx,ax ; enable writes to all four planes
mov ax,SCREEN_SEG ; now clear all display memory, 8 pixels
mov es,ax ; at a time
sub di,di ; point ES:DI to display memory
sub ax,ax ; clear to zero-value pixels
mov cx,8000h ; # of words in display memory
rep stosw ; clear all of display memory
; Set pysical screen dimensions
lodsw ; Load scrn pixel width
mov [_ScrnPhysicalPixelWidth],ax ; from tweak table and store
mov [_SplitScrnScanLine],ax ; No splitscrn ==
; splitscrn=PhysicalscrnHeight
mov bx,ax ; Copy width for later use
shr ax,2 ; Convert to byte width
mov [_ScrnPhysicalByteWidth],ax ; Store for later use
lodsw ; Load Screen Phys. Height
mov [_ScrnPhysicalHeight],ax ; Store for later use
; Mode X is set, now set the required logical page width.
mov cx,[logicalscrwidth]
call SetLogicalScrWidth
pop di ;restore C register vars
pop si
pop bp ;restore caller's stack frame
ret
_x_set_mode endp
;----------------------------------------------------------------------
; Mode X (256 color mode) set default access video plane
;
; C near-callable as:
; void x_select_default_plane(unsigned char plane);
;
; Enables Read/Write access to a plane using general memory access
; methods
;
; Written by Themie Gouthas
;----------------------------------------------------------------------
_x_select_default_plane proc
ARG Plane:byte
push bp
mov bp,sp ; set up stack frame
mov cl,byte ptr [Plane]
; SELECT WRITE PLANE
and cl,011b ;CL = plane
mov ax,0100h + MAP_MASK ;AL = index in SC of Map Mask reg
shl ah,cl ;set only the bit for the required
; plane to 1
mov dx,SC_INDEX ;set the Map Mask to enable only the
out dx,ax ; pixel's plane
; SELECT READ PLANE
mov ah,cl ;AH = plane
mov al,READ_MAP ;AL = index in GC of the Read Map reg
mov dx,GC_INDEX ;set the Read Map to read the pixel's
out dx,ax ; plane
pop bp
ret
_x_select_default_plane endp
;----------------------------------------------------------------------
; Mode X (256 color mode) Set Mode X split screen starting row
; The split screen resides on the bottom half of the screen and has a
; starting address of A000:0000
;
; C near-callable as:
; void x_set_splitscreen(unsigned int line);
;
; Updates _Page0_Offs to reflect the existence of the split screen region
; ie _MainScrnOffset is set to the offset of the first pixel beyond the split
; screen region
;
; Written by Themie Gouthas
;----------------------------------------------------------------------
_x_set_splitscreen proc
ARG Line:word
push bp
mov bp,sp ; set up stack frame
push si
xor si,si ; si=0 -> x virtual page start coord
cmp [_DoubleBufferActive],0
jne @@error
cmp [_SplitScrnActive],0
je @@NotPreviouslyCalled
@@error:
mov [_ErrorValue],ERROR
pop si
pop bp ; Return if previously called
ret
@@NotPreviouslyCalled:
; Turn on split screen pal pen suppression, so the split screen
; wo'nt be subject to pel panning as is the non split screen portion.
mov dx,INPUT_STATUS_0
in al,dx ; Reset the AC Index/Data toggle to
; index state
mov al,AC_MODE_CONTROL+20h ; Bit 5 set to prevent screen blanking
mov dx,AC_INDEX ; Point AC to Index/Data register
out dx,al
inc dx ; Point to AC Data reg (for reads only)
in al,dx ; Get the current AC Mode Control reg
or al,20h ; Enable split scrn Pel panning suppress.
dec dx ; Point to AC Index/Data reg (for writes only)
out dx,al ; Write the new AC Mode Control setting
; with split screen pel panning
; suppression turned on
mov [_PhysicalStartByteX],ax ; Set the Phisical screen start
mov [_PhysicalStartPixelX],ax ; offset within virtual screen
mov [_PhysicalStartY],ax
mov [_SplitScrnActive],TRUE
mov ax,[Line]
jns @@NotNeg ; Check that Split Scrn start scan line is +ve
mov ax,0 ; Since -ve set to 0
@@NotNeg:
mov [_SplitScrnScanLine],ax ; save the scanline
mov cl,[DoubleScanFlag]
shl ax,cl ; Mode X 200 and 240 line modes are actually
; 400 and 480 lines that are double scanned
; so for start scanline multiply required ModeX
; scan line by 2 if its a double scanned mode
mov bx,ax ; save the scanline
WaitVsyncStart ; wait for vertical retrace
cli ; Dont allow register setting to be interrupted
mov dx,CRTC_INDEX
mov ah,bl
mov al,LINE_COMPARE
out dx,ax ; Bits 7-0 of the split screen scan line
mov ah,bh
and ah,1
shl ah,4
mov al,OVERFLOW ; Bit 4 of overflow register = Bit 8 of split
out dx,al ; screen scan line,
inc dx ; So using readability of VGA registers
in al,dx ; Read the OVERFLOW register, and set the
and al, not 10h ; bit corresponding to Bit 8 (above)
or al,ah
out dx,al
dec dx
mov ah,bh
and ah,2
ror ah,3
mov al,MAX_SCAN_LINE ; Bit 6 of max scan line register =
out dx,al ; Bit 9 of split screen scan line
inc dx ; As we did before, update the apropriate
in al,dx ; bit without disturbing the rest
and al, not 40h
or al,ah
out dx,al
sti ; Registers are set, so interrupts are safe
mov ax,[_ScrnPhysicalHeight] ; Determine where the first byte
sub ax,[_SplitScrnScanLine] ; of the non split screen video ram
mov [_SplitScrnVisibleHeight],bx ; starts and store it for reference
mov bx,[_ScrnLogicalByteWidth]
mul bx
mov [_Page0_Offs],ax
mov [_Page1_Offs],ax
; calculate no. non split screen rows in video ram
mov cx,0ffffh ; cx = Maximum video ram offset
sub cx,ax ; cx = cx - _Page0_Offs
xchg cx,ax ; swap cx and ax
sub dx,dx ; DX:AX is divide operand, set DX = 0
div bx ; divide ax (prev cx) by
; ScrnLogicalByteWidth
mov [_ScrnLogicalHeight],ax ; Save Screen Logical Height
cmp ax,[_BottomClip]
jle @@BottomClipOK ; Adjust Clip Rectangle if necessary
mov [_BottomClip],ax
@@BottomClipOK:
sub ax,[_SplitScrnScanLine] ; Update the maximum Y position of
mov [_MaxScrollY],ax ; Physical screen in logical screen
xchg cx,ax ; restore original ax (MainScrnOfs)
mov bh,al ; Set the visible screen start address
mov ch,ah ; to the top left corner of the virtual
jmp short StartAddrEntry ; screen
_x_set_splitscreen endp
;-----------------------------------------------------------------------
; Mode X (256 color mode) Page flip primer
; No clipping is performed.
; C near-callable as:
;
; void x_page_flip(unsigned int x, unsigned int y);
;
; Swaps visible and hidden page offsets and then executes the SetStartAddr
; to achieve a page flip.
;
; SEE x_set_start_addr below
;
; Written by Themie Gouthas
;------------------------------------------------------------------------
_x_page_flip proc
ARG x:word,y:word
push bp ;preserve caller's stack frame
mov bp,sp ;point to local stack frame
push si
mov si,[x]
mov ax,[_ScrnLogicalByteWidth] ; Calculate Offset increment
mov cx,[y]
mul cx ; for Y
cmp [_DoubleBufferActive],TRUE ; Do we have double buffering ?
jne PageFlipEntry1
mov bx,[_HiddenPageOffs]
xchg bx,[_VisiblePageOffs] ; Swap the Page Offsete
xchg [_HiddenPageOffs],bx
xor [_VisiblePageIdx],01h ; Set the Visible page index
jmp short PageFlipEntry2
_x_page_flip endp
;-----------------------------------------------------------------------
; Mode X (256 color mode) Set Mode X non split screen start address
; of logical screen.
; C near-callable as:
;
; void x_set_start_addr(unsigned int x, unsigned int y);
;
; Params: StartOffset is offset of first byte of logical screen ram
; (Useful if you want to double buffer by splitting your non
; split screen video ram into 2 pages)
; X,Y coordinates of the top left hand corner of the physical screen
; within the logical screen
; X must not exceed (Logical screen width - Physical screen width)
; Y must not exceed (Logical screen height - Physical screen height)
;
;
; Written by Themie Gouthas,
; Parts addapted from M. Abrash code published in DDJ Mag.
;------------------------------------------------------------------------
_x_set_start_addr proc
ARG x:word,y:word
push bp
mov bp,sp
push si
mov si,[x]
mov ax,[_ScrnLogicalByteWidth] ; Calculate Offset increment
mov cx,[y] ; for Y
mul cx
cmp [_DoubleBufferActive],TRUE ; Do we have double buffering ?
je @@PageResolution
PageFlipEntry1:
add ax,[_Page0_Offs] ; no - add page 0 offset
jmp short @@AddColumn
PageFlipEntry2:
mov [_PhysicalStartPixelX],si
mov [_PhysicalStartY],cx
@@PageResolution:
add ax,[_VisiblePageOffs] ; Add visible page offset
@@AddColumn:
mov cx,si
shr cx,2
mov [_PhysicalStartByteX],cx
add ax,cx ; add the column offset for X
mov bh,al ; setup CRTC start addr regs and
; values in word registers for
mov ch,ah ; fast word outs
StartAddrEntry:
mov bl,ADDR_LOW
mov cl,ADDR_HIGH
mov dx,INPUT_STATUS_0 ;Wait for trailing edge of Vsync pulse
@@WaitDE:
in al,dx
test al,01h
jnz @@WaitDE ;display enable is active low (0 = active)
mov dx,CRTC_INDEX
mov ax,bx
out dx,ax ;start address low
mov ax,cx
out dx,ax ;start address high
mov dx,AC_INDEX
mov al,PEL_PANNING+20h ; Point the attribute controller to pel pan
out dx,al ; reg. Bit 5 also set to prevent blanking
and si,0003h ; select pel pan register value for the
mov al,PelPanMask[si] ; required x coordinate
out dx,al ; load new Pel Pan setting.
; Now wait for vertical sync, so the other page will be invisible when
; we start drawing to it.
WaitVsyncStart
mov [_ErrorValue],OK
pop si
pop bp
ret
_x_set_start_addr endp
;-----------------------------------------------------------------------
; Mode X (256 color mode) Mode X split screen hide
; C near-callable as:
;
; void x_hide_splitscreen()
;
; Hides an existing split screen by setting its starting scan line to
; the last physical screen scan line
;
; WARNING: Only to be used if SplitScrnLine has been previously called
; WARNING: DO NOT USE with mode 5-11 (320x400-376x564). The memory for
; the initial split screen is reserved and the size limitations
; of these modes means any change in the split screen scan line
; will encroach on the split screen ram
;
; Written by Themie Gouthas
;------------------------------------------------------------------------
_x_hide_splitscreen proc
push bp
mov bp,sp
cmp [_SplitScrnActive],TRUE
je @@SplitScreenEnabled
@@error:
mov [_ErrorValue],ERROR
pop bp
ret
@@SplitScreenEnabled:
cmp [_CurrXMode],4 ; Do nothing for Modes > 2
jg @@error
mov bx,[_ScrnPhysicalHeight]
mov ax,[_ScrnLogicalHeight]
sub ax,bx
mov [_MaxScrollY],ax
xor ax,ax
mov [_SplitScrnVisibleHeight],ax
mov cl,[DoubleScanFlag] ; Compensate for double scanned modes
shl bx,cl
WaitVsyncStart ; wait for vertical retrace
cli ; Dont allow register setting to be interrupted
mov dx,CRTC_INDEX
mov ah,bl
mov al,LINE_COMPARE
out dx,ax ; Bits 7-0 of the split screen scan line
mov ah,bh
and ah,1
shl ah,4
mov al,OVERFLOW ; Bit 4 of overflow register = Bit 8 of split
out dx,al ; screen scan line,
inc dx ; So using readability of VGA registers
in al,dx ; Read the OVERFLOW register, and set the
and al, not 10h ; bit corresponding to Bit 8 (above)
or al,ah
out dx,al
dec dx
mov ah,bh
and ah,2
ror ah,3
mov al,MAX_SCAN_LINE ; Bit 6 of max scan line register =
out dx,al ; Bit 9 of split screen scan line
inc dx ; As we did before, update the apropriate
in al,dx ; bit without disturbing the rest
and al, not 40h
or al,ah
out dx,al
sti ; Registers are set, so interrupts are safe
@@done:
mov [_ErrorValue],OK
pop bp
ret
_x_hide_splitscreen endp
;-----------------------------------------------------------------------
; Mode X (256 color mode) Mode X split screen show
; C near-callable as:
;
; void x_show_splitscreen()
;
; Restores split screen start scan line to the initial split screen
; starting scan line as set by SplitScrnLine.
;
; WARNING: Only to be used if SplitScrnLine has been previously called
; WARNING: DO NOT USE with mode 5-11 (320x400-376x564). The memory for
; the initial split screen is reserved and the size limitations
; of these modes means any change in the split screen scan line
; will encroach on the split screen ram
; Update: Now disabled for these modes
;
; Written by Themie Gouthas
;------------------------------------------------------------------------
_x_show_splitscreen proc
push bp
mov bp,sp
cmp [_SplitScrnActive],TRUE
je @@SplitScreenEnabled
@@error:
mov [_ErrorValue],ERROR
pop bp
ret
@@SplitScreenEnabled:
cmp [_CurrXMode],4 ; Do nothing for Modes > 2
jg @@error
mov bx,[_SplitScrnScanLine]
mov ax,[_ScrnLogicalHeight] ; Update Max Scroll Y
sub ax,bx
mov [_MaxScrollY],ax
mov ax,[_ScrnPhysicalHeight]
sub ax,bx
mov [_SplitScrnVisibleHeight],ax
mov cl,[DoubleScanFlag] ; Compensate for double scanned modes
shl bx,cl
WaitVsyncStart ; wait for vertical retrace
cli ; Dont allow register setting to be interrupted
mov dx,CRTC_INDEX
mov ah,bl
mov al,LINE_COMPARE
out dx,ax ; Bits 7-0 of the split screen scan line
mov ah,bh
and ah,1
shl ah,4
mov al,OVERFLOW ; Bit 4 of overflow register = Bit 8 of split
out dx,al ; screen scan line,
inc dx ; So using readability of VGA registers
in al,dx ; Read the OVERFLOW register, and set the
and al, not 10h ; bit corresponding to Bit 8 (above)
or al,ah
out dx,al
dec dx
mov ah,bh
and ah,2
ror ah,3
mov al,MAX_SCAN_LINE ; Bit 6 of max scan line register =
out dx,al ; Bit 9 of split screen scan line
inc dx ; As we did before, update the apropriate
in al,dx ; bit without disturbing the rest
and al, not 40h
or al,ah
out dx,al
sti ; Registers are set, so interrupts are safe
@@Done:
mov [_ErrorValue],0
pop bp
ret
_x_show_splitscreen endp
;-----------------------------------------------------------------------
; Mode X (256 color mode) Modify Mode X split screen starting scan line
; C near-callable as:
;
; void x_adjust_splitscreen(unsigned int ScanLine)
;
; Sets the split screen start scan line to a new scan line. Valid scan lines
; are between the initial split screen starting scan line and the last
; physical screen scan line.
;
; WARNING: Only to be used if SplitScrnLine has been previously called
; WARNING: DO NOT USE with mode 5-11 (320x400-376x564). The memory for
; the initial split screen is reserved and the size limitations
; of these modes means any change in the split screen scan line
; will encroach on the split screen ram
; Update: Now disabled for these modes
;
;
; Written by Themie Gouthas
;------------------------------------------------------------------------
_x_adjust_splitscreen proc
ARG ScanLine
push bp
mov bp,sp
cmp [_SplitScrnActive],TRUE
je @@SplitScreenEnabled
@@error:
mov [_ErrorValue],ERROR
pop bp
ret
@@SplitScreenEnabled:
cmp [_CurrXMode],4 ; Do nothing for Modes > 2
jg @@error
mov bx,[ScanLine] ; Is the required starting scan line
cmp bx,[_SplitScrnScanLine] ; valid ?
js @@Done ; No - Then do nothing
@@ValidScanLine:
mov ax,[_ScrnLogicalHeight] ; Update Max Scroll Y
sub ax,bx
mov [_MaxScrollY],ax
mov ax,[_ScrnPhysicalHeight]
sub ax,bx
mov [_SplitScrnVisibleHeight],ax
mov cl,[DoubleScanFlag] ; Compensate for double scanned modes
shl bx,cl
WaitVsyncStart ; wait for vertical retrace
cli ; Dont allow register setting to be interrupted
mov dx,CRTC_INDEX
mov ah,bl
mov al,LINE_COMPARE
out dx,ax ; Bits 7-0 of the split screen scan line
mov ah,bh
and ah,1
shl ah,4
mov al,OVERFLOW ; Bit 4 of overflow register = Bit 8 of split
out dx,al ; screen scan line,
inc dx ; So using readability of VGA registers
in al,dx ; Read the OVERFLOW register, and set the
and al, not 10h ; bit corresponding to Bit 8 (above)
or al,ah
out dx,al
dec dx
mov ah,bh
and ah,2
ror ah,3
mov al,MAX_SCAN_LINE ; Bit 6 of max scan line register =
out dx,al ; Bit 9 of split screen scan line
inc dx ; As we did before, update the apropriate
in al,dx ; bit without disturbing the rest
and al, not 40h
or al,ah
out dx,al
sti ; Registers are set, so interrupts are safe
@@Done:
mov [_ErrorValue],OK
pop bp
ret
_x_adjust_splitscreen endp
;-----------------------------------------------------------------------
; Mode X (256 color mode) Enable DoubleBuffering on non split screen area
; C near-callable as:
;
; int x_set_doublebuffer(unsigned int PageHeight);
;
; Params: PageHeight is the height of the virtual screen to double buffer
; Returns the closest possible height to the specified.
;
; Sets up two double buffering virtual pages
; GLOBAL variables set:
;
; _Page1_Offs Offset of second virtual page
; _NonVisual_Offs Offset of first non visible video ram byte
; _DoubleBufferActive Flag
; _PageAddrTable Table of Double buffering pages start offsets
; _ScrnLogicalHeight Logical height of the double buffering pages
;
;
; Written by Themie Gouthas
;------------------------------------------------------------------------
_x_set_doublebuffer proc
ARG PageHeight:word
push bp
mov bp,sp
cmp [_DoubleBufferActive],0
je @@OkToContinue
@error:
mov [_ErrorValue],ERROR
pop bp
ret
@@OkToContinue:
mov [_VisiblePageIdx],0 ; Set visible Page to 0
mov ax,[_ScrnLogicalHeight] ; Set Maximum D.B. Page height to
shr ax,1 ; _ScrnLogicalHeight / 2
mov bx,[PageHeight] ; Is the require D.B. Page Height
cmp ax,bx ; > the Maximum D.B. Page Height ?
js @@InvalidHeight ; no - jump
mov ax,bx ; yes - Set the D.B. Page height to
; to the maximum allowed.
@@InvalidHeight:
mov [_ScrnLogicalHeight],ax ; Update logical screen height to
; reflect the height of a D.B. page
cmp ax,[_BottomClip]
jle @@BottomClipOK ; Adjust Clip Rectangle if necessary
mov [_BottomClip],ax
@@BottomClipOK:
mov dx,ax
mul [_ScrnLogicalByteWidth] ; Calculate the offset of the second
mov cx,ax ; D.B. Page in video ram
mov bx,[_Page0_Offs]
mov [_VisiblePageOffs],bx
add ax,bx
mov [_Page1_Offs],ax ; Save it
mov [_HiddenPageOffs],ax
add ax,cx ; Calculate the offset of first byte
mov [_NonVisual_Offs],ax ; beyond the D.B. pages and save it
mov [_DoubleBufferActive],TRUE ; Set flag indicating D.B'ing mode on
mov ax,dx
sub ax,[_ScrnPhysicalHeight]
add ax,[_SplitScrnVisibleHeight]
mov [_MaxScrollY],ax
mov ax,dx ; return the D.B. pages' height
mov [_ErrorValue],OK
pop bp
ret
_x_set_doublebuffer endp
;-----------------------------------------------------------------------
; Set Clipping rectangle
; C callable as:
;
;
; int x_set_cliprect(WORD left,WORD top, WORD right, WORD bottom);
;
;
; NOTE clipping is byte oriented. "left" and "right" are in bytes not pixels.
; Only selected functions perform any clipping at all.
;
; Written by Themie Gouthas
;------------------------------------------------------------------------
_x_set_cliprect proc
ARG left:word,top:word,right:word,bottom:word
push bp
mov bp,sp
mov ax,[left]
mov bx,[right]
cmp bx,ax
jns @@CorrectXOrder
xchg bx,ax
@@CorrectXOrder:
mov [_LeftClip],ax
mov [_RightClip],bx
mov ax,[top]
mov bx,[bottom]
cmp bx,ax
jns @@CorrectYOrder
xchg bx,ax
@@CorrectYOrder:
mov [_TopClip],ax
mov [_BottomClip],bx
pop bp
ret
_x_set_cliprect endp
;----------------------------------------------------------------------
; Return to text mode
;
_x_text_mode proc
push bp
mov ax,03h ; Restore Text Mode
int 10h
pop bp
ret
_x_text_mode endp
end
