Save Screen Contents

[Steve Bouffe]

This is how I save the entire screen to disk for a 40x80 display

OldX% = pos(0) : OldY% = csrlin : OldColor% = pbvscrntxtattr
DEF SEG = &hB800 : BSAVE "SCREEN.TMP", 0, 4000 : DEF SEG

Then to restore the screen

CT% = OldColor% and 15 : cb% = OldColor% \ 16
color CT%, cb% : locate OldY%, OldX%
DEF SEG = &hB800 : BLOAD "SCREEN.TMP" : DEF SEG


What would be the values if the screen mode was 43 or 50 lines.

How is the screen data structured ?

I need to save a portion of the screen and I know that within the 4000 bytes, the character and the colour is stored.

[Denny Moore]

Check out Qsave() and Qrest() in ScrnUnit.bas that comes
with PB 3.5. Routines allow any portion of the screen to
be saved/restored.

SUB QSAVE(BYVAL Row AS INTEGER, BYVAL Col AS INTEGER, _
BYVAL Rows AS INTEGER, BYVAL Cols AS INTEGER, _
Where AS INTEGER) PUBLIC

For example, to save 25,80:
dim n(2000) as integer
call qsave(1,1,25,80,n(1))
To restore full screen:
call qrest(1,1,25,80,n(1))

To save/rest rows 2-4, cols 11-15
call qsave(2,11,3,5,n(1))
call qrest(2,11,3,5,n(1))

As to how the screen data is structured, it's been awhile
since I got into this, but if I remember correctly, the lower
8 bits contain the ascii character, the upper 8 bits contain
the color.

Dennis


------------------

[Denny Moore]

Steve,
Sorry for first response. I missed the opening sentence
referring to disk write.
Denny


------------------

[Tom Hanlin]

BSAVE stores data with no translation. There's a brief header which contains information such as a BSAVE "signature" and the original data segment. After that, it's just the actual data bytes. In the case of a text screen, this would be sequential bytes starting from the upper left corner of the screen and going column by column, wrapping for each row, until the end of the screen. Screen data is stored as character/color combinations, where the first byte is the ASCII character and the second byte is the color/attribute of that character on the screen. If you need information about color/attribute encoding, I can dig that up.

------------------
Tom Hanlin
PowerBASIC Staff

[Paul G. Penn]

Saving screen contents to disk

Have you considered DIM ABSOLUTE? I don't know what "40x80" is, but for an 80x25 screen (SCREEN 0) on a CGA, try:

TYPE ScreenLineType
ScreenLine AS STRING * 160 ' 80-character line x 2 bytes per character
END TYPE

DIM ABSOLUTE ScreenPage0(1:25) AS ScreenLineType AT &HB800

OPEN "SCRNPIC.DAT" FOR RANDOM AS #1, LEN = 160

FOR I? = 1? TO 25?
PUT #1, I?, ScreenPage0(I?)
NEXT I?

This will write the line exactly as it is stored in the video buffer. You could write a SUB if all you want are the ASCII characters in the line. For a 43- or 50-line display, you just have to change the 25 and &HB800 to whatever you need.