'=========================================================================== ' Subject: BLANK SCREEN SAVER Date: 06-20-99 (02:09) ' Author: John A. Kiernan Code: ASIC ' Origin: kiernan@uwo.ca Packet: ASIC.ABC '=========================================================================== rem SCRSAVE.ASI Blank the screen; exact restoration with any keypress. rem Version 1.00 by J. A. Kiernan (c) October 1997 rem (kiernan@uwo.ca) rem Version 1.10 by J. A. Kiernan (c) February 1999 rem remembers and then replace the screen colour rem attributes that were in effect before saving rem the screen. (Avoids a blank black line below the rem cursor on the restored screen, seen with Ver 1.0) rem Freeware! Feel free to modify the code or rem incorporate it into your own programmes, but rem don't blame me if your changes don't work. rem This is an annotated example of an ASIC programme made rem almost entirely with objects CALLed as SUBs from the rem ASILIB library. The commands are preceded by explanatory rem rem lines. rem The ASILIB library is available as shareware ($25) rem from its author: rem Douglas R. Herr rem P. O. Box 207 rem Sacramento, CA 95812 rem U. S. A. rem telephone (916) 721-8762, voice only rem CompuServe 71247,3542 rem It's good value for money, in my opinion. rem Compilation: rem To make the EXE file, you need ASICC.EXE from ASIC version 5, rem a linker (LINK.EXE) and ASI5LIB.LIB (from the ASILIB library). rem The directory paths in the command lines below are the ones rem on my C: drive. Other people will organize their files rem in other ways. The LINK.EXE is Version 2.3, the one that rem went with IBM DOS 3.2. The two command lines that follow rem (with duly modified path specs) are best put into a batch file, rem because every letter and comma is significant. rem COMMAND LINES FOR (1) compilation by ASICC; (2) linking with LINK - rem C:\PROG\ASIC\ASICC SCRSAVE e b/obj rem C:\PROG\ASIC\LINK SCRSAVE.OBJ,SCRSAVE.EXE,nul.map,C:\PROG\ASIC\ASILIB\ASI5LIB rem If this code is included in a programme that also makes calls rem to other libraries, ASILIB must be last on libraries list in the rem LINK command line (a requirement of the AllocDOS subroutine; rem see the ASILIB documentation.) rem The executable file (SCRSAVE.EXE) can be compressed with rem PKLITE, TINYPROG, XPACK or LZEXE (and probably others). rem Of these four, LZEXE gave the best compression (5871 --> 2442 bytes). rem SUBs are all from ASI5LIB.LIB, which is the ASILIB library rem file that works with ASIC 5.0 rem ____________ Programme code begins here _____________ rem Get the cursor position. This is one Line down from the rem DOS command line that calls the programme, and in rem column (Col) zero, because there isn't a DOS prompt rem any more once we are within this programme. rem Get the present screen colour attribute and rem translate it to foreground & background integer rem variables (Fg and Bg) rem The "TGetChr" sub also gets the Line, Column and Character rem at the cursor. Line=CSRLIN Col=POS(0) rem ASILIB uses 1-based coordinates Line=Line+1 Col=Col+1 CALL SUB "TGetChr"(Line,Col,Char,Colour) Fg=Colour MOD 16 Bg=Colour/16 Line=Line-1 Col=Col-1 rem The "AllocDOS" SUB will need DOS 3 or higher, so get DOS version rem now, and display a message if it is below 3.0. CALL SUB "GetDOSver" Major Minor IF Major < 3 THEN PRINT "This program needs a DOS version 3 or higher." PRINT "Version "; Major$=STR$(Major) Major$=LTRIM$(Major$) Minor$=STR$(Minor) Minor$=LTRIM$(Minor$) Version$=Major$+"." Version$=Version$+Minor$ PRINT Version$; PRINT " cannot evaluate the screen dimensions." PRINT "The original screen may not be accurately restored. Sorry!" GOSUB Wait: ENDIF rem Calculate bytes required to save a text screen page. The ASILIB rem subroutine requires an extended integer, hence the "&" and also rem the need to have an "e" in the ASICC compiler's command line. CALL SUB "ScreenMem", ScreenBytes& rem AllocDOS permits dynamic memory allocation for an ASIC programme. rem AllocDOS needs DOS 3 or higher. rem ScreenBytes& is the number of bytes you want to allocate. rem This number was returned by ASILIB's "ScreenMem" SUB. rem If the segment address returned by AllocDOS = 0, then rem insufficient memory is available for the requested memory rem block. The IF ... ENDIF below is to check for and respond to rem this unlikely event. CALL SUB "AllocDOS", ScreenBytes&, BlockSeg IF BlockSeg=0 THEN PRINT "Not enough memory to save the screen!" GOTO TheEnd: ENDIF rem Acquire the screen. CALL SUB "GetScreen", BlockSeg, 0 rem Make a blank, black screen CLS rem Make the cursor invisible CALL SUB "CursorOff" rem The Wait: subroutine is to wait (with screen black) until rem any key is pressed. GOSUB Wait: rem Restore the screen. CALL SUB "PutScreen", BlockSeg, 0 rem The next job is to delete the command line that called this rem programme, so that the screen will look exactly as it was rem before this programme did its stuff. rem This necessitates a bit of cursor moving: up from the Line rem originally saved with CSRLIN. The column (Col) saved with rem POS(0) is 0 so a whole 80-column line can be overwritten rem with "space" (ASCII 32) characters. The DOS prompt will rem reappear on top of the deleted line, with the cursor rem poised to receive a new command. rem It is also necessary to restore the colour attributes rem (Fg, Bg) to their previous values. rem If you use 4DOS.COM instead rem of COMMAND.COM you can still rem invoke earlier commands with rem the PgUp and arrow keys, just rem as if this screen blanking rem programme had never been rem executed. Line=Line-1 LOCATE Line,Col COLOR Fg,Bg BlankLine$=SPACE$(80) PRINT BlankLine$; Line=Line-1 LOCATE Line,Col TheEnd: END rem Subroutines for use by GOSUBs are placed after rem the programme's END statement. rem This programme has only one GOSUB. Wait: Key$=INKEY$ IF Key$="" THEN Wait: RETURN rem ________ The very end _________