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Conference bulova::decw_jan-89_to_nov-90

Title:	DECWINDOWS 26-JAN-89 to 29-NOV-90
Notice:	See 1639.0 for VMS V5.3 kit; 2043.0 for 5.4 IFT kit
Moderator:	STAR::VATNE

Created:	Mon Oct 30 1989
Last Modified:	Mon Dec 31 1990
Last Successful Update:	Fri Jun 06 1997
Number of topics:	3726
Total number of notes:	19516

1772.0. "help with named colors" by EPIK::J_JOSEPH (Living in the Pasture) Mon Nov 20 1989 19:17

When you alloc a named color using XAllocNamedColor, two color definitions
are returned.  The screen color definition and the exact color definition.
I can't understand why these should be any different on my 8 plane GPX.  But
consistently, the exact color definition has RGB values which are smaller than
those in the screen color definition (In fact, for all named colors, the 
exact color value is .996108949 of the screen color value for each of RGB).

Can anyone explain this and give the reasoning behind it? 

-Jonathan

T.R	Title	User	Personal Name	Date	Lines
1772.1	Difference between definition and capability	MELTIN::dick	Gvriel::Schoeller	`Mon Nov 20 1989 19:32`	7
	The value of a named color is described by a set of RGB information (in logicals on VMS). This information may be in a format with more significant digits than the display you are on. Therefore, you get a returned value in the screen color that is slightly (sometimes substantially) different than the exact color. Dick
1772.2	That's not the problem	EPIK::J_JOSEPH	Living in the Pasture	`Tue Nov 21 1989 11:15`	11
	>The value of a named color is described by a set of RGB information >(in logicals on VMS). This information may be in a format with more >significant digits than the display you are on. Therefore, you get >a returned value in the screen color that is slightly (sometimes >substantially) different than the exact color. The thing is, if you do an XAllocColor, you can get precisely the RGB values described in the file DECW$RGB.COM. Why should XAllocNamedColor give you anything different if you CAN get the exact values described? -Jonathan
1772.3	That still may be the issue	GVRIEL::SCHOELLER	Who's on first?	`Tue Nov 21 1989 11:49`	9
	>The thing is, if you do an XAllocColor, you can get precisely the RGB values >described in the file DECW$RGB.COM. Why should XAllocNamedColor give you >anything different if you CAN get the exact values described? If you XAllocColor with the RGB returned in XAllocNamedColor's exact value. Do you get that RGB or the one returned in the screen value? Dick