04_EventBindings_EventHandling_TkConcepts.rb

# coding: utf-8

# Copyright (C) 2019 Mark D. Blackwell.

require 'tk'
require 'tkextlib/tile'

module ::EventBindings
  module GraphicalHelper

    def f_content
      $f_content_private ||= begin
        f = ::Tk::Tile::Frame.new root
        f.grid sticky: :wnes
      end
    end

    def root
      $root_private ||= begin
        tell_tk_which_encoding_to_use
        ::TkRoot.new
      end
    end

    def weights_column_and_row_default_set_up(*args)
      first = 0
      args.reverse_each do |e|
        ::TkGrid.columnconfigure e, first, weight: 1
        ::TkGrid.   rowconfigure e, first, weight: 1
      end
      nil
    end

    private

    def tell_tk_which_encoding_to_use
      ::Tk::Encoding.encoding = ''.encoding
      nil
    end
  end
end

module ::EventBindings
  module GraphicalObjects

    def l_label
      @l_label_private ||= begin
        l = ::Tk::Tile::Label.new f_content
        l.grid
      end
    end
  end
end

module ::EventBindings
  module Graphical
    extend GraphicalHelper
    extend GraphicalObjects
    extend self

    def main
      f_content.padding '3 3 3 3'
      weights_column_and_row_set_up
      l_label[:text] = 'Starting...'
      label_bind
      ::Tk.mainloop
      nil
    end

    private

    def label_bind
      label_bind_drag
      label_bind_text_fixed
      nil
    end

    def label_bind_drag
      l_label.bind 'B3-Motion', lambda_drag, '%x %y'
      nil
    end

    def label_bind_text_fixed
      key_symbol = %w[  1  Double-1  Enter  Leave  ]
      text = %w[
          Clicked\ left\ mouse\ button
          Double\ clicked
          Moved\ mouse\ inside
          Moved\ mouse\ outside
          ]
      key_symbol.zip(text).each do |k,t|
        l_label.bind k do
          l_label[:text] = t
        end
      end
      nil
    end

    def lambda_drag
      @lambda_drag_private ||= ::Kernel.lambda do |x,y|
        l_label[:text] = "Right button drag to #{x}, #{y}"
        nil
      end
    end

    def weights_column_and_row_set_up
      weights_column_and_row_default_set_up f_content, root
      nil
    end
  end
end

::EventBindings::Graphical.main