Re: Display file puzzlement

[Simon Coulter <shc@xxxxxxxxxxxxxxxxx>]

On 23/04/2008, at 12:10 AM, John McKee wrote:
> Interesting....your example works exactly as you describe.  BUT,  
> when I add
> COLOR(YLW) or COLOR(BLU) to the first data field, that field does  
> not dp RI.

I see Lim Hock-Chai has provided a documentation reference showing  
this is expected behaviour. I see Dave McKenzie (among others) has  
provided a format showing all the valid 5250 display attributes.

The reason the OS does not set RI when the the field has both UL and  
HI (or UL plus colour BLU, WHT, or YLW) is simple. That combination  
(effectively UL+HI+RI) equals Non-display. Thus if ERRMSG and  
ERRMSGID did enable RI the field and its content would be invisible.

There are four possible attribute values that all result in non- 
display: x'27', x'2f', x'37', and x'3f'. You can see from the hex  
codes that the common pattern is xxxxx111. These last 3 bits control  
UL, HI, RI.

A given attribute byte is formatted as follows:

                          |  Zone   |    Digit    |
|Bit position in byte     | 0 1 2 3 | 4  5  6  7  |
|Bit Binary value         | 0 0 1 0 | 0  0  0  0  |
|Bit value within nibble  | 8 4 2 1 | 8  4  2  1  |
|Display attribute        |       CS| BL UL HI RI |

Bits 0, 1, and 2 are always OFF, OFF, ON. The remaining bits control  
each of the supported attributes. If bits 5, 6, and 7 are ON the  
field in non-display.

These bit patterns are originally from monochrome displays. When  
colour displays became available these bit patterns perform double  
duty by mapping to colours.

	RED = BL
	GRN = Normal
	WHT = HI
	TRQ = CS
	YLW = CS + HI
	PNK = CS + BL
	BLU = CS + BL + HI

Interestingly PNK and BLU set CS but don't cause column-separators to  
be displayed. This also explains why RED does not blink on colour  
terminals unless HI is also specified.

Given that input fields default to UL, and WHT, YLW, BLU all set HI,  
when ERRMSG or ERRMSGID sets RI we have instant invisibility.

Regards,
Simon Coulter.
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