Screenblank 1/2

 BBS: Inland Empire Archive
Date: 11-11-92 (00:52)             Number: 399
From: MARK BUTLER                  Refer#: NONE
  To: ALL                           Recvd: NO  
Subj: Screenblank   1/2              Conf: (2) Quik_Bas

 Hi all, there's been a thread lately about screen blanking techniques
 so I played around with some ASM code I saw on 80XXX and came up with
 this. When you call 'ScreenBlank' from within QB/QBX it will clear
 the screen, turn off the cursor and wait for a keypress before
 returning. You will need to save the current screen before calling
 ScreenBlank and restore it afterwards. Maybe some of you ASM Wizards
 could write a screen save/restore right into ScreenBlank?

==========================8< Cut Here 8<=============================
'** QB/QBX code to demonstrate ScreenBlank.
'** A call to ScreenBlank will blank the screen, shut the
'** the cursor off and wait for a keypress to return.
'** M-H-B
'**
DEFINT A-Z
DECLARE SUB ScreenBlank ()

    COLOR 7, 1
    CLS
    FOR i = 1 TO 13             '*** throw some crapola
        FOR ch = 33 TO 176      '*** around on the screen
            PRINT CHR$(ch);
        NEXT ch
    NEXT i

    PCOPY 0, 1                  '*** save the screen

    DO UNTIL LEN(INKEY$): LOOP  '*** wait for a keypress

    ScreenBlank                 '*** now call ScreenBlank
                                '*** ScreenBlank will check for
                                '*** a keypress before returning

    PCOPY 1, 0                  '*** copy the old screen back

==========================8< Cut Here 8<=============================

                TITLE Scrnblnk.asm
                page    ,132
Comment~
=======
This is a modification of a bit of code I saw on the 80XXX echo.
Originally it would blank the screen by writing blank spaces to all
25 lines in 80 x 25 text mode and then return. I thought this would be
perfect as a callable screen blanker in QB/QBX if it would wait for a
keypress before returning so I added the code for a 'KeyPress' call.

Note: this routine is for _color_ 80 x 25 text mode, note the change
below that must be made for use with monochrome. ***

QB/QBX declaration ->   DECLARE SUB ScreenBlank ()
=======~

               .model  medium,basic
               .code
               public  ScreenBlank
ScreenBlank    proc    far
               push    es           ; Save registers
               push    di
               push    cx
               push    ax
               mov     ax,0b800h    ; *** Make this B000h for mono
               mov     es,ax
               xor     di,di        ; Zero DI
               mov     ax,0720h
               mov     cx,2000      ; 2000 Spaces to clear
               rep     stosw        ; Load spaces into all areas

               call    Cursoff      ; shut off the cursor
               pop     ax
               pop     cx
               pop     di
               pop     es
               call    KeyPress
               retf    0
ScreenBlank    endp
cursoff:
               mov     ah,01h
               mov     ch,20h
               int     10h
               retn
KeyPress:                           ; wait for a keypress
               mov     ah,08h
               int     21h
               cmp     al,00h
               jne     KeyWasHit
               int     21h
KeyWasHit:
               mov     ah,4ch
               retn
               end

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