More VGA tests

tests/pc/vga/L29-1.ASM

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+; Program to put up a mode 10h EGA graphics screen, then save it
+; to the file SNAPSHOT.SCR.
+;
+VGA_SEGMENT	equ   0a000h
+GC_INDEX	equ   3ceh		;Graphics Controller Index register
+READ_MAP	equ   4			;Read Map register index in GC
+DISPLAYED_SCREEN_SIZE equ (640/8)*350	;# of displayed bytes per plane in a
+					; hi-res graphics screen
+;
+stack	segment para stack 'STACK'
+	db	512 dup (?)
+stack	ends
+;
+Data	segment word 'DATA'
+SampleText	db	'This is bit-mapped text, drawn in hi-res '
+		db	'EGA graphics mode 10h.', 0dh, 0ah, 0ah
+		db	'Saving the screen (including this text)...'
+		db	0dh, 0ah, '$'
+Filename	db	'SNAPSHOT.SCR',0;name of file we're saving to
+ErrMsg1		db	"*** Couldn't open SNAPSHOT.SCR ***",0dh,0ah,'$'
+ErrMsg2		db	'*** Error writing to SNAPSHOT.SCR ***',0dh,0ah,'$'
+WaitKeyMsg	db	0dh, 0ah, 'Done. Press any key to end...',0dh,0ah,'$'
+Handle		dw	?		;handle of file we're saving to
+Plane		db	?		;plane being read
+Data	ends
+;
+Code	segment
+	assume	cs:Code, ds:Data
+Start	proc	near
+	mov	ax,Data
+	mov	ds,ax
+;
+; Go to hi-res graphics mode.
+;
+	mov	ax,10h			;AH = 0 means mode set, AL = 10h selects
+					; hi-res graphics mode
+	int	10h			;BIOS video interrupt
+;
+; Put up some text, so the screen isn't empty.
+;
+	mov	ah,9			;DOS print string function
+	mov	dx,offset SampleText
+	int	21h
+;
+; Delete SNAPSHOT.SCR if it exists.
+;
+	mov	ah,41h			;DOS unlink file function
+	mov	dx,offset Filename
+	int	21h
+;
+; Create the file SNAPSHOT.SCR.
+;
+	mov	ah,3ch			;DOS create file function
+	mov	dx,offset Filename
+	sub	cx,cx			;make it a normal file
+	int	21h
+	mov	[Handle],ax		;save the handle
+	jnc	SaveTheScreen		;we're ready to save if no error
+	mov	ah,9			;DOS print string function
+	mov	dx,offset ErrMsg1
+	int	21h			;notify of the error
+	jmp	short Done		;and done
+;
+; Loop through the 4 planes, making each readable in turn and
+; writing it to disk. Note that all 4 planes are readable at
+; A000:0000; the Read Map register selects which plane is readable
+; at any one time.
+;
+SaveTheScreen:
+	mov	[Plane],0		;start with plane 0
+SaveLoop:
+	mov	dx,GC_INDEX
+	mov	al,READ_MAP	;set GC Index to Read Map register
+	out	dx,al
+	inc	dx
+	mov	al,[Plane]		;get the # of the plane we want
+					; to save
+	out	dx,al			;set to read from the desired plane
+	mov	ah,40h			;DOS write to file function
+	mov	bx,[Handle]
+	mov	cx,DISPLAYED_SCREEN_SIZE;# of bytes to save
+	sub	dx,dx			;write all displayed bytes at A000:0000
+	push	ds
+	mov	si,VGA_SEGMENT
+	mov	ds,si
+	int	21h			;write the displayed portion of this plane
+	pop	ds
+	cmp	ax,DISPLAYED_SCREEN_SIZE;did all bytes get written?
+	jz	SaveLoopBottom
+	mov	ah,9			;DOS print string function
+	mov	dx,offset ErrMsg2
+	int	21h			;notify about the error
+	jmp	short DoClose		;and done
+SaveLoopBottom:
+	mov	al,[Plane]
+	inc	ax			;point to the next plane
+	mov	[Plane],al
+	cmp	al,3			;have we done all planes?
+	jbe	SaveLoop		;no, so do the next plane
+;
+; Close SNAPSHOT.SCR.
+;
+DoClose:
+	mov	ah,3eh			;DOS close file function
+	mov	bx,[Handle]
+	int	21h
+;
+; Wait for a keypress.
+;
+	mov	ah,9			;DOS print string function
+	mov	dx,offset WaitKeyMsg
+	int	21h			;prompt
+	mov	ah,8			;DOS input without echo function
+	int	21h
+;
+; Restore text mode.
+;
+	mov	ax,3
+	int	10h
+;
+; Done.
+;
+Done:
+	mov	ah,4ch			;DOS terminate function
+	int	21h
+Start	endp
+Code	ends
+	end	Start