Made tk_setPalette guess a reasonable default for the foreground colour.

2 files changed, 17 insertions, 3 deletions

diff --git a/ChangeLog b/ChangeLog
index 5df447c..6da7c18 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+2001-11-29  Donal K. Fellows  <fellowsd@cs.man.ac.uk>
+
+	* library/palette.tcl (tk_setPalette): Added heuristic to guess
+	from the background whether to use black or white for the
+	foreground when not told specifically.  Suggested by Chris Nelson.
+
 2001-11-27  David Gravereaux <davygrvy@pobox.com>
 
 	* win/makefile.vc: Fixed CAT32 target.  cat.c is located in the Tcl
diff --git a/library/palette.tcl b/library/palette.tcl
index 7542ef5..55834d3 100644
--- a/library/palette.tcl
+++ b/library/palette.tcl
@@ -3,7 +3,7 @@
 # This file contains procedures that change the color palette used
 # by Tk.
 #
-# RCS: @(#) $Id: palette.tcl,v 1.7 2001/11/15 14:02:47 dkf Exp $
+# RCS: @(#) $Id: palette.tcl,v 1.8 2001/11/29 10:54:21 dkf Exp $
 #
 # Copyright (c) 1995-1997 Sun Microsystems, Inc.
 #
@@ -40,10 +40,18 @@ proc ::tk_setPalette {args} {
     if {![info exists new(background)]} {
 	error "must specify a background color"
     }
+    set bg [winfo rgb . $new(background)]
     if {![info exists new(foreground)]} {
-	set new(foreground) black
+	# Note that the range of each value in the triple returned by
+	# [winfo rgb] is 0-65535, and your eyes are more sensitive to
+	# green than to red, and more to red than to blue.
+	foreach {r g b} $bg {break}
+	if {$r+1.5*$g+0.5*$b > 100000} {
+	    set new(foreground) black
+	} else {
+	    set new(foreground) white
+	}
     }
-    set bg [winfo rgb . $new(background)]
     set fg [winfo rgb . $new(foreground)]
     set darkerBg [format #%02x%02x%02x [expr {(9*[lindex $bg 0])/2560}] \
 	    [expr {(9*[lindex $bg 1])/2560}] [expr {(9*[lindex $bg 2])/2560}]]