From: Morton Goldberg <m_goldberg@...>
Date: 2006-09-23T17:14:39+09:00
Subject: Re: Ruby TK list question

On Sep 22, 2006, at 2:21 PM, Harry Truax wrote:

> Hi everyone,
>
> I am trying to do the following: I am trying to have one list re- 
> display
> it's contents with new information based upon a selection made in  
> another
> list without having the user click on a button. So the user would  
> click on
> one list's element (highlighting it in the process) and the other  
> list would
> dynamically re-draw it's list of info with new list elements being
> displayed.
>
> Thanks for your help,

The following is a little program I wrote to explore the exact  
question you're asking. It displays a two-stage color browser for X11  
colors. The first stage is a list of color categories and the second  
is a list of color names. Disclaimer: this has only been tested on OS  
X (10.4). In particular, the path to rgb.txt probably isn't valid on  
other platforms.

<code>
#! /usr/bin/ruby -w
# Author: Morton Goldberg
#
# Date: August 26, 2006
#
# X11 color browser

require 'tk'

DEBUG = []

class X11ColorCategory

    # Full path name of the X11 colors file.
    RGB_TXT = "/usr/X11R6/lib/X11/rgb.txt"

    #Dictionary of rgb values keyed by color name.
    COLORS = {}

    def X11ColorCategory.read_rgb_table
       # read and parse the X11 colors file.
       File.foreach(RGB_TXT) do |rgb|
          next if rgb =~ /^!/ # skip header line
          rgb = rgb.lstrip.split(/\s+/)
          r = rgb.shift
          g = rgb.shift
          b = rgb.shift
          key = rgb.join(' ')
          COLORS[key] = "r:#{r} g:#{g} b:#{b}"
       end
       COLORS
    end

    def X11ColorCategory.all
       ALL_CATEGORIES
    end

    def X11ColorCategory.rgb(color_name)
       COLORS[color_name]
    end

    def extract(pattern)
       @members, OTHER.members =
          OTHER.members.partition {|m| m =~ pattern}
       self
    end

    def initialize(name)
       @name = name
       @members = []
    end

    attr_accessor :name, :members

    ALL = X11ColorCategory.new('ALL')
    X11ColorCategory.read_rgb_table.each {|key,| ALL.members << key}
    ALL.members.sort!
    OTHER = X11ColorCategory.new('OTHER')
    ALL.members.each {|m| OTHER.members << m}
    REDS = X11ColorCategory.new('REDS').
       extract(/red|rose|pink|salmon|fire/i)
    GREENS = X11ColorCategory.new('GREENS').
       extract(/green|chartreuse|olive|honeydew/i)
    BLUES = X11ColorCategory.new('BLUES').
       extract(/blue|navy/i)
    CYANS = X11ColorCategory.new('CYANS').
       extract(/cyan|aqua|azure|turquoise/i)
    MAGENTAS = X11ColorCategory.new('MAGENTAS').
       extract(/magenta|maroon|violet|plum|purple|orchid|thistle/i)
    YELLOWS = X11ColorCategory.new('YELLOWS').
       extract(/yellow|gold|lemon|corn/i)
    ORANGES = X11ColorCategory.new('ORANGES').
       extract(/orange|tomato|peach|coral/i)
    BROWNS = X11ColorCategory.new('BROWNS').
       extract(/brown|tan|wood|choc|sienna|wheat|peru/i)
    WHITES = X11ColorCategory.new('WHITES').
       extract(/white|ivory|snow|lace/i)
    GRAYS = X11ColorCategory.new('GRAYS').
       extract(/gr[ae]y|gainsboro/i)

    ALL_CATEGORIES = [
       REDS,
       ORANGES,
       YELLOWS,
       GREENS,
       CYANS,
       BLUES,
       MAGENTAS,
       BROWNS,
       WHITES,
       GRAYS,
       OTHER
    ]

end

class X11ColorBrowser

    # Action performed when category selection is made.
    def category_selected_action
       @category_names.focus
       @selected_category =
          X11ColorCategory.all[@category_names.curselection[0]]
       @color_names.delete(0, 'end')
       @selected_category.members.each {|m| @color_names.insert 
("end", m)}
       @color_names.selection_set(0)
       color_selected_action
    end

    # Action performed when color selection is made.
    def color_selected_action
       color = @selected_category.members[@color_names.curselection[0]]
       @color_rect.background(color)
       @rgb_lbl.text(X11ColorCategory.rgb(color))
    end

    #Action performed when browser window is mapped.
    def window_mapped_action
       return if @mapped
       @mapped = true
       X11ColorCategory.all.each do |category|
          @category_names.insert("end", category.name)
       end
       @category_names.selection_set(0)
       category_selected_action
    end

    def initialize
       # Flag indicating that window has been mapped at least once.
       @mapped = false
       # Holder for currently selected color category
       @selected_category = nil
       # Set up the browser window.
       root = TkRoot.new {title 'Color Browser'}
       # Panel at top of browser containing scrolling list of X11  
colors and
       # label displaying selected color.
       top_pnl = TkFrame.new(root)
          # List box displaying names of X11 color categories.
          @category_names = TkListbox.new(top_pnl)
          # Scroll bar for the color names list.
          vbar1 = TkScrollbar.new(top_pnl)
          @category_names.yscrollbar(vbar1)
          # List box displaying names of X11 colors within selected  
category.
          @color_names = TkListbox.new(top_pnl)
          # Scroll bar for the color names list.
          vbar2 = TkScrollbar.new(top_pnl)
          @color_names.yscrollbar(vbar2)
          # Label displaying selected color.
          @color_rect = TkLabel.new(top_pnl, 'width'=>25)
       # Request layout of top panel.
       @category_names.pack("side"=>"left", "fill"=>"both",  
"expand"=>true,
                            "padx"=>5)
       vbar1.pack("side"=>"left", "after"=>@category_names, "fill"=>"y")
       @color_names.pack("side"=>"left", "after"=>vbar1, "fill"=>"both",
                         "expand"=>true, "padx"=>5)
       vbar2.pack("side"=>"left", "after"=>@color_names, "fill"=>"y")
       @color_rect.pack("side"=>"right", "fill"=>"both", "expand"=>true,
                        "padx"=>5)
       top_pnl.pack("side"=>"top", "fill"=>"both", "expand"=>true,
                    "padx"=>5, "pady"=>8)
       # Panel at bottom of browser containing exit button and label
       # displaying RGB values of selected color.
       btm_pnl = TkFrame.new(root)
          # Label displaying rgb values of selected color.
          @rgb_lbl = TkLabel.new(btm_pnl) {
             text "r:xxx g:xxx b:xxx"
          }
          # Exit button.
          @quit_btn = TkButton.new(btm_pnl) {
             text "Exit"
             command {Tk.root.destroy}
          }
       # Request layout of bottom panel.
       @rgb_lbl.pack("side"=>"left", "anchor"=>"w")
       @quit_btn.pack("side"=>"right")
       btm_pnl.pack("side"=>"bottom", "fill"=>"x", "padx"=>10,  
"pady"=>8)
       # Set initial window geometry; i.e., size and placement.
       win_w, win_h = 750, 300
       root.minsize(win_w, win_h)
       win_x = (root.winfo_screenwidth - win_w) / 2
       root.geometry("#{win_w}x#{win_h}+#{win_x}+50")
       # Make Cmnd+Q work as expected.
       root.bind('Command-q') {@quit_btn.invoke}
       # Bind mouse button-1, space bar, window map event to their  
actions.
       @category_names.bind('Map') {window_mapped_action}
       ev = TkVirtualEvent.new('ButtonRelease-1', 'space')
       @category_names.bind(ev) {category_selected_action}
       ev = TkVirtualEvent.new('ButtonRelease-1', 'space')
       @color_names.bind(ev) {color_selected_action}
       Tk.mainloop
    end

end

begin
    X11ColorBrowser.new
ensure
    puts DEBUG unless DEBUG.empty?
end
</code>

Sorry to push all this code on you. I'm afraid I'm too busy at the  
moment to edit it down to just the parts that will answer your question.

Regards, Morton