VIDEO.RW [Revelation On-Line Wiki]

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====== VIDEO.RW ======

^Published By^Date^Version^Knowledge Level^Keywords^
|Revelation Technologies|14 NOV 1989|2.X|EXPERT|VIDEO.RW, |

==== Description ====
 
VIDEO.RW reads, writes, or clears the  
specified display area. 
 
==== Arguments ====
 
=== lcol ===
 
An integer indicating the starting column of  
the display area

=== top.row ===
 
An integer indicating the top row of the  
display area. 

=== rcol ===
 
An integer indicating the ending column of  
the display area 

=== bot.row ===
 
An integer indicating the bottom row of the  
display area 

=== operator ===
 
One of the following operators specifying  
the function VIDEO.RW is to perform: 

^Operator^Function ^
|R|Save (read) the specified area of the display|
|W|Restore (write) the specified area of the display|
|C|Clear the specified area of the display|
 
=== image ===
 
A variable whose value is determined by the  
operator specified: 

^Operator^Value^
|R|A variable used by VIDEO.RW to save the display image described by the coordinates specified in the argument list.  Multiple full-screen save operations should be avoided to conserve memory.  Each screen saved requires approximately 4K.|
|W|The display image saved in the preceding read operation.  The display image is written to the coordinates specified in the argument list.|
|C|A two-byte sequence specifying the background character and foreground<$Ivideo attribute> video attribute.  The background character defaults to space, and the foreground attribute to Normal.  For a standard monochrome display, image may be null (see Appendix 3, Video Attributes).|
 
==== Values returned ====
 
If a read or write operation is specified,  
VIDEO.RW passes the display image in the image parameter of  
the argument list. 

==== Examples ====

<code>
*Initialization for each example 
DECLARE SUBROUTINE VIDEO.RW,MSG 
 
*Save full screen image, clear using default attributes, display *message, and restore 
VIDEO.RW(0,0,@CRTWIDE-1,@CRTMAXHIGH- 1,'R',IMAGE) 
VIDEO.RW(0,0,@CRTWIDE-1,@CRTMAXHIGH-1,'C','') 
MSG('Saved the status line as well','','','') 
VIDEO.RW(0,0,@CRTWIDE-1,@CRTMAXHIGH-1,'W',IMAGE) 
 
*Save half screen image, clear, display message, and restore 
VIDEO.RW(0,10,@CRTWIDE-1,@CRTHIGH-1,'R',IMAGE) 
VIDEO.RW(0,10,@CRTWIDE-1,@CRTHIGH-1,'C','') 
MSG('Cleared fully half','','','') 
VIDEO.RW(0,10,@CRTWIDE-1,@CRTHIGH-1,'W',IMAGE) 
 
*Save partial screen image, clear, display message, and restore 
VIDEO.RW(20,10,60,20,'R',IMAGE) 
VIDEO.RW(20,10,60,20,'C','') 
MAP = '' 
TYPE = 1 
COL = 3 
ROW = 4 
MAP<TYPE> = 'A' 
MAP<COL> = 24 
MAP<ROW> = 16 
MSG('Window',MAP,'','') 
VIDEO.RW(20,10,60,20,'W',IMAGE) 

*For color displays only: Save partial screen image, clear color *display and set background attributes, display message, and  
*restore (see Appendix 3, Video Attributes). 
BACK.CHAR = '*'          ;* background fill character 
BACKGROUND = 5           ;* background video attribute 
FOREGROUND = 14          ;* foreground video attribute 
COLOR = (BACKGROUND * 16) + FOREGROUND ;* color formula 
COLOR = CHAR(COLOR) 
ATTRIBUTES = BACK.CHAR:COLOR<E> 
 
VIDEO.RW(0,10,@CRTWIDE-1,@CRTHIGH-1,'R',IMAGE) 
VIDEO.RW(0,10,@CRTWIDE-1,@CRTHIGH-1,'C',ATTRIBUTES) 
MSG('Clear half with a background color change','','','') 
VIDEO.RW(0,10,@CRTWIDE-1,@CRTHIGH-1,'W',IMAGE) 
 
*For color displays only: the same example as above, but using *the current video settings in the system variable @ENVIRON.SET. 
$INSERT UTILITY.PROGS,ENVIRON.CONSTANTS 
*Background fill character 
BACK.CHAR = @ENVIRON.SET<E.BACK.CHAR>
*Background video attribute 
BACKGROUND = @ENVIRON.SET<E.BG.BACK.CHAR>[4,1]   
*Foreground video attribute 
FOREGROUND = @ENVIRON.SET<E.BG.FORE.COLOR>[4,1]   
COLOR = (BACKGROUND * 16) + FOREGROUND ;* color formula 
COLOR = CHAR(COLOR) 
ATTRIBUTES = BACK.CHAR:COLOR<E> 
 
VIDEO.RW(0,10,@CRTWIDE-1,@CRTHIGH-1,'R',IMAGE) 
VIDEO.RW(0,10,@CRTWIDE-1,@CRTHIGH-1,'C',ATTRIBUTES) 
MSG('Clear half with a background color change','','','') 
VIDEO.RW(0,10,@CRTWIDE-1,@CRTHIGH-1,'W',IMAGE)
</code>