Re: Display & Color Attributes In SDA Using A Color Terminal ...

[dhandy@xxxxxxxxxxx (Douglas Handy)]

Bill,

>there seems to 
>be no way to use these colors without the dots.  

It depends on your terminal (or terminal emulation).  Those colors
always include "column separators", but some devices let you configure
the style of column separators or let you turn them off completely.

For example, with Client Access you'd use the menu item Appearance |
Color Mapping, then select Category Others and Element: Column
Separators.

On some dumb terminals you can press the Setup key and follow the
on-screen instructions.

>Any why are some colors, pink for example, not able to display HI, CS, and 
>BL, but they will RI and UL?

It is due to design constraints in the original 5250 data stream.
Unlike PCs, the design called for a single display buffer the size of
the screen instead of twice the size with one half keeping the
displayed characters and the other half keeping the attributes for a
given location.

Therefore, display attributes consume one byte each on the display,
and remain in effect until the next attribute byte is found in the
buffer.  Since attributes therefore coexist with displayed data, it
follows you have fewer possible choices for "characters" which are
interpreted as display attributes.  The design called for only those
characters in the range of x'20' through x'3F' to be considered
display attributes.  This basically means there are only five bits
available to control all normal attribute combinations.  These were
assigned to high intensity, reverse image, underline, blink, and
column separator.  You could do any combination of those, except if
the first three listed above were turned on together, it represented
non-display.  (Remember at the time, there were no such thing as color
displays.)

When color came along, there were still only 5 bits available.  So
colors were mapped to the various combinations.  Given the design
constraints, the mapping is IMHO pretty reasonable. 

Later, the 5250 data stream was enhanced to provide the ability to
have "extended attributes" which do not consume a position on the
display.  However, these also require devices which support the "write
extended attributes" 5250 data stream order.  With these devices, it
is possible to get lots of different color and attribute combinations,
even in adjacent positions on the display.

However, support for doing so has never been added to DDS, so you need
to use DSM or UDDS to make much use of it.  Why doesn't DDS support
it?  Probably because not enough people complain, so IBM likely
doesn't consider it high enough on the priority list.

A user program which attempts to do it via DSM or UDDS needs to first
query the WS controller and device to make sure the WEA (write
extended attribute) order is supported.  If it is sent to an older
controller or WS which does not recognize it, an escape message is
issued for a device error.

Doug
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