Flashing Background [Revelation On-Line Wiki]

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====== Flashing Background=====

^Published By^Date^Version^Knowledge Level^Keywords^
|Sprezzatura Ltd|01 APR 1990|1.16+|EXPERT|BACKGROUND, VIDEO.RW, ESC.TO.ATTR, ATTR.TO.ESC, BITOR|

Users of VIDEO.RW will be aware that the colour attributes for each byte of
information on screen are stored in a single character, yet generally colour
escape sequences are four characters long. The conversion between these
formats is facilitated by the AREV functions ESC.TO.ATTR and ATTR.TO.ESC.
Thus to get the screen attribute for Yellow on Blue (Esc C1N) one would
simply say ATTR = ESC.TO.ATTR(CHAR(27) : "C1N"). Converting from attribute
to escape conversely uses the ATTR.TO.ESC.

The highest bit of the colour attribute determines whether or not the colour
has a flashing background. If the highest bit is set the background will
flash. If not the background will remain normal. To set the highest bit it
is necessary to BITOR the attribute with 128. Try running the following with
a (B option

<code>
          DECLARE FUNCTION ATTR.TO.ESC, ESC.TO.ATTR

          X = ESC.TO.ATTR(@AW<4>)
          X = BITOR(SEQ(X),128)
          X = ATTR.TO.ESC(CHAR(X))
          PRINT @AW<4> : "Hello"
          PRINT X : "Hello"
          INPUT X,1
</code>


(Volume 1, Issue 10, Page 9)