Re: unable to set black text color for cdk

[Thomas Dickey]

----- Original Message -----
| From: "daggs" <address@hidden>
| To: address@hidden
| Cc: address@hidden
| Sent: Wednesday, June 3, 2015 5:33:21 AM
| Subject: Re: unable to set black text color for cdk
| 
| Greetings Thomas,
| 
| > Sent: Wednesday, June 03, 2015 at 4:24 AM
| > From: "Thomas Dickey" <address@hidden>
| > To: daggs <address@hidden>
| > Cc: address@hidden, address@hidden
| > Subject: Re: unable to set black text color for cdk
| >
| > On Thu, May 28, 2015 at 01:43:49PM +0200, daggs wrote:
| > > Greeting Thomas
| > > 
| > > > Sent: Thursday, April 02, 2015 at 12:28 PM
| > > > From: "Thomas Dickey" <address@hidden>
| > > > To: daggs <address@hidden>
| > > > Cc: address@hidden
| > > > Subject: Re: unable to set black text color for cdk
| > > >
| > > > On Thu, Apr 02, 2015 at 07:43:09AM +0200, daggs wrote:
| > > > > 
| > > > > 
| > > > > > Sent: Thursday, April 02, 2015 at 4:01 AM
| > > > > > From: "Thomas Dickey" <address@hidden>
| > > > > > To: daggs <address@hidden>
| > > > > > Cc: address@hidden
| > > > > > Subject: Re: unable to set black text color for cdk
| > > > > >
| > > > > > On Wed, Apr 01, 2015 at 10:50:26AM +0200, daggs wrote:
| > > > > > > 
| > > > > > > 
| > > > > > > > Sent: Wednesday, April 01, 2015 at 3:54 AM
| > > > > > > > From: "Thomas Dickey" <address@hidden>
| > > > > > > > To: daggs <address@hidden>
| > > > > > > > Cc: address@hidden
| > > > > > > > Subject: Re: unable to set black text color for cdk
| > > > > > > >
| > > > > > > > On Mon, Mar 30, 2015 at 12:31:33PM +0200, daggs wrote:
| > > > > > > > > Greetings,
| > > > > > > > > 
| > > > > > > > > I'm trying to setup a text in black color and it ends
| > > > > > > > > up in gray, looping
| > > > > > > > > over the first 49 colors (with and without bold)
| > > > > > > > > didn't returned any label
| > > > > > > > > with black text color, is it possible that there is
| > > > > > > > > no black color text in
| > > > > > > > > cdk?
| > > > > > > > 
| > > > > > > > hmm - it's more complicated than that - partly Cdk and
| > > > > > > > partly (n)curses.
| > > > > > > > 
| > > > > > > > The initCDKColor function is probably what you're
| > > > > > > > looking at, since
| > > > > > > > it is the only place that calls init_pair().  It's a
| > > > > > > > little odd (I think)
| > > > > > > > because it maps the colors 0-7 in this order:
| > > > > > > > 
| > > > > > > >       COLOR_WHITE, COLOR_RED, COLOR_GREEN,
| > > > > > > >       COLOR_YELLOW, COLOR_BLUE, COLOR_MAGENTA,
| > > > > > > >       COLOR_CYAN, COLOR_BLACK
| > > > > > > > 
| > > > > > > > If the terminal supports more than 8, cdk uses only 8.
| > > > > > > >  You can always
| > > > > > > > override that by calling init_pair() in your
| > > > > > > > application.
| > > > > > > > 
| > > > > > > > Normally in curses, black is zero.  That raises a
| > > > > > > > point, i.e., that color
| > > > > > > > pair 0 is special in curses (no colors as such).  So
| > > > > > > > cdk does not use that.
| > > > > > > > 
| > > > > > > > In any case, since black is last, you would see black
| > > > > > > > text on pairs 57-64,
| > > > > > > > due to the way the loops are ordered.
| > > > > > > 
| > > > > > > Greeting Thomas,
| > > > > > > 
| > > > > > > my issue in fact is with the (0,0) pair, e.g. black text
| > > > > > > over black background.
| > > > > > > you might ask why one need such option, well using black
| > > > > > > background color ober a background image gives me a
| > > > > > > transparency affect.
| > > > > > > for example, I want to create a background image that has
| > > > > > > a white square in it and write inside it text.
| > > > > > 
| > > > > > I see.  I think the issue is that Cdk is putting
| > > > > > black-on-black in the last
| > > > > > color pair which it requests -- the 65th slot.  However,
| > > > > > for an 8-color
| > > > > > terminal, the description would say the terminal supports
| > > > > > only 64 = 8*8
| > > > > > color pairs.
| > > > > >  
| > > > > 
| > > > > tried to print the 65th color, the it was the same like the
| > > > > 64th color (no change)
| > > > 
| > > > But ncurses only uses 0 through 63
| > > > 
| > > > See attached sample testcase and debugging trace -- look at the
| > > > return values
| > > > from init_pair().
| > > > 
| > > 
| > > sorry it took so long to answer, I was reassigned to another
| > > project for a while.
| > > 
| > > according to the trace in the case you've provided I see that the
| > > valid colors range from 1 to 80 (including).
| > > running a matching test on that range return a "hit" for pair 64,
| > > however, the color on screen stays the same.
| > > running the same matching test on a range from 0 to 63 return a
| > > "hit" for pair 0 (which you claim to be invalid). however, the
| > > color on screen stays the same.
| > > 
| > > so I want to understand what exactly is the right colors range.
| > 
| > That is 0 .. PAIRS-1
| > 
| > (zero up to one less than the number of color pairs in the terminal
| > description).
| > 
| > That's because -- even though it is tempting to consider zero as a
| > special
| > case that would just shift everything up -- the color pair is
| > stored as
| > an unsigned value in a bit-field in chtype's for instance.  ncurses
| > allows
| > 8 bits for that in ncurses5 (ncurses6 will allow 16 bits).
| > 
| 
| so assuming that color 0 is invalid, we have 62 colors to use.

63.

For a more complete discussion of color pair 0, I added to the
manual page (actually for a different discussion), see

http://invisible-island.net/ncurses/man/curs_color.3x.html#h3-Color-Rendering

| e.g. what I need (black over black) is not there. how can I insert
| the color pair? can I replace an existing on that I don't need with
| that pair?
| 

-- 
Thomas E. Dickey <address@hidden>
http://invisible-island.net
ftp://invisible-island.net