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From: rlh2@ukc.ac.uk (Richard Hesketh)
Newsgroups: comp.windows.x
Subject: Re: Application resource file etiquette
Message-ID: <5637@harrier.ukc.ac.uk>
Date: 6 Oct 90 16:07:13 GMT
References: <69294@lll-winken.LLNL.GOV> <1990Oct5.155651.7094@smsc.sony.com>
Reply-To: rlh2@ukc.ac.uk (Richard Hesketh)
Organization: Computing Lab, University of Kent at Canterbury, UK.
Lines: 91
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In article <1990Oct5.155651.7094@smsc.sony.com> dce@smsc.sony.com (David Elliott) writes:

>2. Modify the color namespace to handle "fallback" colors, which would

>	XTerm*background:	black
>	XTerm*foreground:	green(white)
>
>   So that instead of the foreground going back to the default (black)
>   if green can't be handled, white is used.
>
>The second idea here is OK (please allow me at least some vanity ;-), but
>could be too confusing.

Whilst a complete (or at least better) solution is being developed this
actually looks quite useful right now.  For toolkit programs all it requires is
a change in the StringToPixel converter which checks to see what type of 
screen this conversion is being made on and chooses the appropriate colour.

Here's a patch to mit/Xt/Converters.c [patchlevel 18] (you can apply the
patch then rip the converter out and put it in your own programs) that
changes the StringToPixel converter to recognize the following format:

	XTerm*foreground:	green/white

I use a slash "/" because its easier to parse 8-).  I really don't think it
is any more confusing than specifying any other resource!  The first colour
is chosen if the screen has a depth greater than one.

*** Converters.c.dist	Sat Sep 29 16:46:26 1990
--- Converters.c	Sat Oct  6 16:46:10 1990
***************
*** 351,357 ****
      XrmValuePtr	toVal;
      XtPointer	*closure_ret;
  {
!     String	    str = (String)fromVal->addr;
      XColor	    screenColor;
      XColor	    exactColor;
      Screen	    *screen;
--- 351,357 ----
      XrmValuePtr	toVal;
      XtPointer	*closure_ret;
  {
!     static String   str = NULL;
      XColor	    screenColor;
      XColor	    exactColor;
      Screen	    *screen;
***************
*** 360,365 ****
--- 360,366 ----
      Status	    status;
      String          params[1];
      Cardinal	    num_params=1;
+     String	    slash;
  
      if (*num_args != 2)
       XtAppErrorMsg(pd->appContext, XtNwrongParameters, "cvtStringToPixel",
***************
*** 369,374 ****
--- 370,393 ----
  
      screen = *((Screen **) args[0].addr);
      colormap = *((Colormap *) args[1].addr);
+ 
+     if (str != NULL)
+ 	XtFree(str);
+ 
+     str = XtNewString((String)fromVal->addr);
+     slash = str;
+     while (*slash && *slash != '/')
+ 	slash++;
+ 
+     if (*slash) {
+     	if (DefaultDepthOfScreen(screen) == 1) {
+ 		/* use fallback colour for monochrome screens */
+ 		slash = XtNewString(slash+1);
+ 		XtFree(str);
+ 		str = slash;
+ 	} else
+ 		*slash = '\0';
+     }
  
      if (CompareISOLatin1(str, XtDefaultBackground) == 0) {
  	*closure_ret = False;

---
Richard Hesketh   :   @nsfnet-relay.ac.uk:rlh2@ukc.ac.uk
		  :   rlh2@ukc.ac.uk    ..!{mcsun|mcvax}!ukc!rlh2
Computing Officer, Computing Lab., University of Kent at Canterbury,
Canterbury, Kent, CT2 7NF, United Kingdom.
        Tel: +44 227 764000 ext 7620/7590      Fax: +44 227 762811