Tk::Doubleslider

A double-headed slider widget allows for a range to be specified. This implementation works for Ruby Tk and provides ways to provide customized formatting of values, non-linear values, and log-based sliders (i.e., lots of accuracy for low values, but not for high values).

This has been tested in:

• ruby-1.8.7-p371
• ruby-1.9.3-p392
• ruby-2.0.0-p0

RVM install command example (rvm doesn't install with tk or tcl by default):

rvm reinstall 1.9.3 --enable-shared --enable-pthread --with-tk --with-tcl

Installation

Add this line to your application's Gemfile:

gem 'tk-doubleslider'

And then execute:

$ bundle

Or install it yourself as:

$ gem install tk-doubleslider

Usage

Within a Tk project, you'll need to have a Window with a Frame to place the Doubleslider within. Here is a minimalistic example:

require 'tk'

def minimal_example()
    # create the root window for this Tk app
    root = TkRoot.new() {
        title "Tk::DoubleSlider Test"
        protocol('WM_DELETE_WINDOW', proc{ exit })
    }
    # bind ctrl-c to exit
    root.bind('Control-c', proc{ exit })
    # create a frame to place the Doubleslider within
    left_frame = TkFrame.new(root)
    left_frame.grid(:row=>0,:column=>0,:sticky=>'new')
    # create a "time window" from 7 days ago until now
    time_min = Time.now.to_i - (7*24*60*60)
    time_max = Time.now.to_i
    # create a "time slider" with a value formatter in HH:MM format and a delta formatter of 0.00 hours.
    timeslide = Tk::Doubleslider.new( left_frame, 
        :min=>time_min, # what's the minimal possible value
        :max=>time_max, # what's the maximum possible value
        :low=>time_min, # what's the current minimum value
        :high=>time_max, # what's the current max
        :snap => 300, # when you slide the slider, by what increments (for this example, it's every 5 minutes)
        :label=>'Time', # what do you call this slider
        :valuefmt => proc { |x| Time.at(x).strftime("%H:%M") }, # how shall we format the values
        :deltafmt => proc { |x| sprintf("%0.2f hours", (x/3600.0)) } # how shall we format the delta
    )
    # pack everything together
    timeslide.pack()
    # enter the main loop
    Tk.mainloop()
end

Great, so what options can Tk::Doubleslider take and what are their defaults?

height = 36.0    # height in pixels
width = 360.0    # width in pixel
min = 0.0        # minimum possible value
max = 0.0        # maximum possible value
low = 0.0        # the current minimum value
high = 0.0       # the current high value
ballsize = 5     # the size in pixels of the header (the knob)
snap = false     # snap increments in value
logbase = false  # use logirithms to scale the slider (pretty cool stuff)
# colors for the slider
colors = {
    :background => 'grey20',
    :line => 'grey75',
    :low_head => '#996666',
    :high_head => '#996666',
    :text => 'white',
    :delta => 'white',
}
# margins
left_margin = 10.0
right_margin = 20.0
top_margin = 6.0
bottom_margin = 4.0
change_cb = nil  # callback to call when a selection has changed, object must have a method called, "call", which must accept a low and high value (see example below)
# how to format the value
valuefmt = proc { |x| sprintf "%d", x }
# how to format the delta (defaults to valuefmt)
deltafmt = nil
# the label to display on the slider, a string
label = nil

Now, how about that callback that I promised you?

class TkDS_Callback
    def call(low, high)
        puts "#{low} #{high}"
        if low < 90
            puts "Maybe you should reconsider your answer"
        end
    end
end

timeslide = Tk::Doubleslider.new( left_frame, :min => 0, :max => 100, :low => 90, :high => 100,
    :cb => TkDS_Callback.new, :label => 'your love for TkDS')

Contributing

1. Fork it
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Add some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create new Pull Request

Copyright

Copyright (c) 2011 Chris Lee, PhD. See LICENSE.txt for further details.