Class: Glimmer::SWT::WidgetProxy

Inherits:
Object
  • Object
show all
Includes:
Packages
Defined in:
lib/glimmer/swt/widget_proxy.rb

Overview

Proxy for SWT Widget objects

Sets default SWT styles to widgets upon inititalizing as per DEFAULT_STYLES

Also, auto-initializes widgets as per initializer blocks in DEFAULT_INITIALIZERS (e.g. setting Composite default layout)

Follows the Proxy Design Pattern

Constant Summary collapse

DEFAULT_STYLES = 
{
  'arrow'               => [:arrow],
  'button'              => [:push],
  'checkbox'            => [:check],
  'check'               => [:check],
  'drag_source'         => [:drop_copy],
  'drop_target'         => [:drop_copy],
  'expand_bar'          => [:v_scroll],
  'list'                => [:border, :v_scroll],
  'menu_item'           => [:push],
  'radio'               => [:radio],
  'scrolled_composite'  => [:border, :h_scroll, :v_scroll],
  'spinner'             => [:border],
  'styled_text'         => [:border, :multi, :v_scroll, :h_scroll],
  'table'               => [:virtual, :border, :full_selection],
  'text'                => [:border],
  'toggle'              => [:toggle],
  'tool_bar'            => [:push],
  'tool_item'           => [:push],
  'tree'                => [:virtual, :border, :h_scroll, :v_scroll],
  'date_drop_down'      => [:date, :drop_down],
  'time'                => [:time],
  'calendar'            => [:calendar],
}
DEFAULT_INITIALIZERS = 
{
  composite: lambda do |composite|
    if composite.get_layout.nil?
      layout = GridLayout.new
      layout.marginWidth = 15
      layout.marginHeight = 15
      composite.layout = layout
    end
  end,
  scrolled_composite: lambda do |scrolled_composite|
    scrolled_composite.expand_horizontal = true
    scrolled_composite.expand_vertical = true
  end,
  table: lambda do |table|
    table.setHeaderVisible(true)
    table.setLinesVisible(true)
  end,
  table_column: lambda do |table_column|
    table_column.setWidth(80)
  end,
  group: lambda do |group|
    group.layout = GridLayout.new if group.get_layout.nil?
  end,
}
KEYWORD_ALIASES = 
{
  'arrow'          => 'button',
  'checkbox'       => 'button',
  'check'          => 'button',
  'radio'          => 'button',
  'toggle'         => 'button',
  'date'           => 'date_time',
  'date_drop_down' => 'date_time',
  'time'           => 'date_time',
  'calendar'       => 'date_time',
}

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Methods included from Packages

included

Constructor Details

#initialize(*init_args, swt_widget: nil) ⇒ WidgetProxy

Initializes a new SWT Widget

It is preferred to use ‘::create` method instead since it instantiates the right subclass per widget keyword

keyword, parent, swt_widget_args (including styles)

Styles is a comma separate list of symbols representing SWT styles in lower case



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# File 'lib/glimmer/swt/widget_proxy.rb', line 147

def initialize(*init_args, swt_widget: nil)
  if swt_widget.nil?
    underscored_widget_name, parent, args = init_args
    @parent_proxy = parent
    styles, extra_options = extract_args(underscored_widget_name, args)
    swt_widget_class = self.class.swt_widget_class_for(underscored_widget_name)
    @swt_widget = swt_widget_class.new(@parent_proxy.swt_widget, style(underscored_widget_name, styles), *extra_options)
  else
    @swt_widget = swt_widget
    underscored_widget_name = self.class.underscored_widget_name(@swt_widget)
    parent_proxy_class = self.class.widget_proxy_class(self.class.underscored_widget_name(@swt_widget.parent))
    parent = swt_widget.parent
    @parent_proxy = parent.get_data('proxy') || parent_proxy_class.new(swt_widget: parent)
  end
  if @swt_widget&.get_data('proxy').nil?
    @swt_widget.set_data('proxy', self)
    DEFAULT_INITIALIZERS[underscored_widget_name.to_s.to_sym]&.call(@swt_widget)
    @parent_proxy.post_initialize_child(self)
  end
end

Dynamic Method Handling

This class handles dynamic methods through the method_missing method

#method_missing(method, *args, &block) ⇒ Object 



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# File 'lib/glimmer/swt/widget_proxy.rb', line 608

def method_missing(method, *args, &block)
  if can_handle_observation_request?(method)
    handle_observation_request(method, &block)
  else
    swt_widget.send(method, *args, &block)
  end
rescue => e
  Glimmer::Config.logger.debug {"Neither WidgetProxy nor #{swt_widget.class.name} can handle the method ##{method}"}
  super
  # TODO consider get_attribute too
end

Instance Attribute Details

#drag_source_proxy ⇒ Object (readonly)

Returns the value of attribute drag_source_proxy.



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# File 'lib/glimmer/swt/widget_proxy.rb', line 137

def drag_source_proxy
  @drag_source_proxy
end

#drag_source_style ⇒ Object

Returns the value of attribute drag_source_style.



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# File 'lib/glimmer/swt/widget_proxy.rb', line 137

def drag_source_style
  @drag_source_style
end

#drag_source_transfer ⇒ Object

Returns the value of attribute drag_source_transfer.



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# File 'lib/glimmer/swt/widget_proxy.rb', line 137

def drag_source_transfer
  @drag_source_transfer
end

#drop_target_proxy ⇒ Object (readonly)

Returns the value of attribute drop_target_proxy.



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# File 'lib/glimmer/swt/widget_proxy.rb', line 137

def drop_target_proxy
  @drop_target_proxy
end

#drop_target_transfer ⇒ Object

Returns the value of attribute drop_target_transfer.



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# File 'lib/glimmer/swt/widget_proxy.rb', line 137

def drop_target_transfer
  @drop_target_transfer
end

#parent_proxy ⇒ Object (readonly)

Returns the value of attribute parent_proxy.



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# File 'lib/glimmer/swt/widget_proxy.rb', line 137

def parent_proxy
  @parent_proxy
end

#swt_widget ⇒ Object (readonly)

Returns the value of attribute swt_widget.



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# File 'lib/glimmer/swt/widget_proxy.rb', line 137

def swt_widget
  @swt_widget
end

Class Method Details

.create(*init_args, swt_widget: nil) ⇒ Object

Instantiates the right WidgetProxy subclass for passed in keyword Args are: keyword, parent, swt_widget_args (including styles)



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# File 'lib/glimmer/swt/widget_proxy.rb', line 111

def create(*init_args, swt_widget: nil)
  return swt_widget.get_data('proxy') if swt_widget&.get_data('proxy')
  keyword, parent, args = init_args
  selected_widget_proxy_class = widget_proxy_class(keyword || underscored_widget_name(swt_widget))
  if init_args.empty?
    selected_widget_proxy_class.new(swt_widget: swt_widget)
  else
    selected_widget_proxy_class.new(*init_args)
  end
end

.swt_widget_class_for(underscored_widget_name) ⇒ Object

This supports widgets in and out of basic SWT



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# File 'lib/glimmer/swt/widget_proxy.rb', line 474

def self.swt_widget_class_for(underscored_widget_name)
  underscored_widget_name = KEYWORD_ALIASES[underscored_widget_name] if KEYWORD_ALIASES[underscored_widget_name]
  swt_widget_name = underscored_widget_name.camelcase(:upper)
  swt_widget_class = eval(swt_widget_name)
  # TODO fix issue with not detecting DateTime because it's conflicting with the Ruby DateTime
  unless swt_widget_class.ancestors.include?(org.eclipse.swt.widgets.Widget)
    swt_widget_class = swt_widget_class_manual_entries[underscored_widget_name]
    if swt_widget_class.nil?
      Glimmer::Config.logger.debug {"Class #{swt_widget_class} matching #{underscored_widget_name} is not a subclass of org.eclipse.swt.widgets.Widget"}
      return nil
    end
  end
  swt_widget_class
rescue SyntaxError, NameError => e
  Glimmer::Config.logger.debug {e.full_message}
  # Glimmer::Config.logger.debug {"#{e.message}\n#{e.backtrace.join("\n")}"}
  nil
rescue => e
  Glimmer::Config.logger.debug {e.full_message}
  # Glimmer::Config.logger.debug {"#{e.message}\n#{e.backtrace.join("\n")}"}
  nil
end

.swt_widget_class_manual_entries ⇒ Object

Manual entries of SWT widget classes that conflict with Ruby classes



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# File 'lib/glimmer/swt/widget_proxy.rb', line 467

def self.swt_widget_class_manual_entries
  {
    'date_time' => Java::OrgEclipseSwtWidgets::DateTime
  }
end

.underscored_widget_name(swt_widget) ⇒ Object 



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# File 'lib/glimmer/swt/widget_proxy.rb', line 132

def underscored_widget_name(swt_widget)
  swt_widget.class.name.split(/::|\./).last.underscore
end

.widget_exists?(underscored_widget_name) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/glimmer/swt/widget_proxy.rb', line 462

def self.widget_exists?(underscored_widget_name)
  !!swt_widget_class_for(underscored_widget_name)
end

.widget_proxy_class(keyword) ⇒ Object 



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# File 'lib/glimmer/swt/widget_proxy.rb', line 122

def widget_proxy_class(keyword)
  begin
    keyword = KEYWORD_ALIASES[keyword] if KEYWORD_ALIASES[keyword]
    class_name = "#{keyword.camelcase(:upper)}Proxy".to_sym
    Glimmer::SWT.const_get(class_name)
  rescue
    Glimmer::SWT::WidgetProxy
  end
end

Instance Method Details

#add_observer(observer, property_name) ⇒ Object

Used for data-binding only. Consider renaming or improving to avoid the confusion it causes



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# File 'lib/glimmer/swt/widget_proxy.rb', line 521

def add_observer(observer, property_name)
  property_listener_installers = @swt_widget.class.ancestors.map {|ancestor| widget_property_listener_installers[ancestor]}.compact
  widget_listener_installers = property_listener_installers.map{|installer| installer[property_name.to_s.to_sym]}.compact if !property_listener_installers.empty?
  widget_listener_installers.to_a.first&.call(observer)
end

#async_exec(&block) ⇒ Object 



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# File 'lib/glimmer/swt/widget_proxy.rb', line 497

def async_exec(&block)
  DisplayProxy.instance.async_exec(&block)
end

#can_add_observer?(property_name) ⇒ Boolean

TODO Consider renaming these methods as they are mainly used for data-binding

Returns:

  • (Boolean) 


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# File 'lib/glimmer/swt/widget_proxy.rb', line 516

def can_add_observer?(property_name)
  @swt_widget.class.ancestors.map {|ancestor| widget_property_listener_installers[ancestor]}.compact.map(&:keys).flatten.map(&:to_s).include?(property_name.to_s)
end

#can_handle_drag_observation_request?(observation_request) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/glimmer/swt/widget_proxy.rb', line 559

def can_handle_drag_observation_request?(observation_request)
  return false unless swt_widget.is_a?(Control)
  potential_drag_source = @drag_source_proxy.nil?
  ensure_drag_source_proxy
  @drag_source_proxy.can_handle_observation_request?(observation_request).tap do |result|
    if potential_drag_source && !result
      @drag_source_proxy.swt_widget.dispose
      @drag_source_proxy = nil
    end
  end
rescue => e
  Glimmer::Config.logger.debug {e.full_message}
  false
end

#can_handle_drop_observation_request?(observation_request) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/glimmer/swt/widget_proxy.rb', line 574

def can_handle_drop_observation_request?(observation_request)
  return false unless swt_widget.is_a?(Control)
  potential_drop_target = @drop_target_proxy.nil?
  ensure_drop_target_proxy
  @drop_target_proxy.can_handle_observation_request?(observation_request).tap do |result|
    if potential_drop_target && !result
      @drop_target_proxy.swt_widget.dispose
      @drop_target_proxy = nil
    end
  end
end

#can_handle_observation_request?(observation_request) ⇒ Boolean

TODO eliminate duplication in the following methods perhaps by relying on exceptions

Returns:

  • (Boolean) 


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# File 'lib/glimmer/swt/widget_proxy.rb', line 548

def can_handle_observation_request?(observation_request)
  observation_request = observation_request.to_s
  if observation_request.start_with?('on_swt_')
    constant_name = observation_request.sub(/^on_swt_/, '')
    SWTProxy.has_constant?(constant_name)
  elsif observation_request.start_with?('on_')
    event = observation_request.sub(/^on_/, '')
    can_add_listener?(event) || can_handle_drag_observation_request?(observation_request) || can_handle_drop_observation_request?(observation_request)
  end
end

#content(&block) ⇒ Object 



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# File 'lib/glimmer/swt/widget_proxy.rb', line 604

def content(&block)
  Glimmer::DSL::Engine.add_content(self, Glimmer::DSL::SWT::WidgetExpression.new, &block)
end

#dispose ⇒ Object 



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# File 'lib/glimmer/swt/widget_proxy.rb', line 510

def dispose
  @swt_widget.dispose
end

#ensure_drag_source_proxy(style = []) ⇒ Object 



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# File 'lib/glimmer/swt/widget_proxy.rb', line 531

def ensure_drag_source_proxy(style=[])
  @drag_source_proxy ||= self.class.new('drag_source', self, style).tap do |proxy|
    proxy.set_attribute(:transfer, :text)
  end
end

#ensure_drop_target_proxy(style = []) ⇒ Object 



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# File 'lib/glimmer/swt/widget_proxy.rb', line 537

def ensure_drop_target_proxy(style=[])
  @drop_target_proxy ||= self.class.new('drop_target', self, style).tap do |proxy|
    proxy.set_attribute(:transfer, :text)
    proxy.on_drag_enter { |event|
      event.detail = DNDProxy[:drop_copy]
    }
  end
end

#extract_args(underscored_widget_name, args) ⇒ Object 



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# File 'lib/glimmer/swt/widget_proxy.rb', line 178

def extract_args(underscored_widget_name, args)
  @arg_extractor_mapping ||= {
    'menu_item' => lambda do |args|
      index = args.delete(args.last) if args.last.is_a?(Numeric)
      extra_options = [index].compact
      styles = args
      [styles, extra_options]
    end,
  }
  if @arg_extractor_mapping[underscored_widget_name]
    @arg_extractor_mapping[underscored_widget_name].call(args)
  else
    extra_options = []
    style_args = args.select {|arg| arg.is_a?(Symbol) || arg.is_a?(String)}
    if style_args.any?
      style_arg_start_index = args.index(style_args.first)
      style_arg_last_index = args.index(style_args.last)
      extra_options = args[style_arg_last_index+1..-1]
      args = args[style_arg_start_index..style_arg_last_index]
    elsif args.first.is_a?(Integer)
      extra_options = args[1..-1]
      args = args[0..0]
    end
    [args, extra_options]
  end
end

#get_attribute(attribute_name) ⇒ Object 



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# File 'lib/glimmer/swt/widget_proxy.rb', line 227

def get_attribute(attribute_name)
  widget_custom_attribute = widget_custom_attribute_mapping[attribute_name.to_s]
  if widget_custom_attribute
    if widget_custom_attribute[:getter][:invoker]
      widget_custom_attribute[:getter][:invoker].call(@swt_widget, [])
    else
      @swt_widget.send(widget_custom_attribute[:getter][:name])
    end
  elsif @swt_widget.respond_to?(attribute_getter(attribute_name))
    @swt_widget.send(attribute_getter(attribute_name))
  else
    send(attribute_name)
  end
end

#handle_observation_request(observation_request, &block) ⇒ Object 



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# File 'lib/glimmer/swt/widget_proxy.rb', line 586

def handle_observation_request(observation_request, &block)
  observation_request = observation_request.to_s
  if observation_request.start_with?('on_swt_')
    constant_name = observation_request.sub(/^on_swt_/, '')
    add_swt_event_listener(constant_name, &block)
  elsif observation_request.start_with?('on_')
    event = observation_request.sub(/^on_/, '')
    if can_add_listener?(event)
      event = observation_request.sub(/^on_/, '')
      add_listener(event, &block)
    elsif can_handle_drag_observation_request?(observation_request)
      @drag_source_proxy&.handle_observation_request(observation_request, &block)
    elsif can_handle_drop_observation_request?(observation_request)
      @drop_target_proxy&.handle_observation_request(observation_request, &block)
    end
  end
end

#has_attribute?(attribute_name, *args) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/glimmer/swt/widget_proxy.rb', line 205

def has_attribute?(attribute_name, *args)
  widget_custom_attribute = widget_custom_attribute_mapping[attribute_name.to_s]
  if widget_custom_attribute
    @swt_widget.respond_to?(widget_custom_attribute[:setter][:name])
  else
    @swt_widget.respond_to?(attribute_setter(attribute_name), args) || respond_to?(ruby_attribute_setter(attribute_name), args)
  end
end

#has_style?(style) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/glimmer/swt/widget_proxy.rb', line 505

def has_style?(style)
  comparison = interpret_style(style)
  (@swt_widget.style & comparison) == comparison
end

#pack_same_size ⇒ Object 



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# File 'lib/glimmer/swt/widget_proxy.rb', line 242

def pack_same_size
  bounds = @swt_widget.getBounds
  listener = on_control_resized {
    @swt_widget.setSize(bounds.width, bounds.height)
    @swt_widget.setLocation(bounds.x, bounds.y)
  }
  if @swt_widget.is_a?(Composite)
    @swt_widget.layout(true, true)
  else
    @swt_widget.pack(true)
  end
  @swt_widget.removeControlListener(listener.swt_listener)
end

#post_add_content ⇒ Object

Subclasses may override to perform post add_content work



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# File 'lib/glimmer/swt/widget_proxy.rb', line 174

def post_add_content
  # No Op by default
end

#post_initialize_child(child) ⇒ Object

Subclasses may override to perform post initialization work on an added child



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# File 'lib/glimmer/swt/widget_proxy.rb', line 169

def post_initialize_child(child)
  # No Op by default
end

#remove_observer(observer, property_name) ⇒ Object 



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# File 'lib/glimmer/swt/widget_proxy.rb', line 527

def remove_observer(observer, property_name)
  # TODO consider implementing if remove_observer is needed (consumers can remove listener via SWT API)
end

#respond_to?(method, *args, &block) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/glimmer/swt/widget_proxy.rb', line 620

def respond_to?(method, *args, &block)
  super ||
    can_handle_observation_request?(method) ||
    swt_widget.respond_to?(method, *args, &block)
end

#set_attribute(attribute_name, *args) ⇒ Object 



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# File 'lib/glimmer/swt/widget_proxy.rb', line 214

def set_attribute(attribute_name, *args)
  # TODO Think about widget subclasses overriding set_attribute to add more attributes vs adding as Ruby attributes directly
  widget_custom_attribute = widget_custom_attribute_mapping[attribute_name.to_s]
  if widget_custom_attribute
    widget_custom_attribute[:setter][:invoker].call(@swt_widget, args)
  elsif @swt_widget.respond_to?(attribute_setter(attribute_name))
    apply_property_type_converters(attribute_name, args)
    @swt_widget.send(attribute_setter(attribute_name), *args) unless @swt_widget.send(attribute_getter(attribute_name)) == args.first
  else
    send(ruby_attribute_setter(attribute_name), args)
  end
end

#sync_exec(&block) ⇒ Object 



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# File 'lib/glimmer/swt/widget_proxy.rb', line 501

def sync_exec(&block)
  DisplayProxy.instance.sync_exec(&block)
end

#widget_property_listener_installers ⇒ Object 



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# File 'lib/glimmer/swt/widget_proxy.rb', line 256

def widget_property_listener_installers
  @swt_widget_property_listener_installers ||= {
    Java::OrgEclipseSwtWidgets::Control => {
      :focus => lambda do |observer|
        on_focus_gained { |focus_event|
          observer.call(true)
        }
        on_focus_lost { |focus_event|
          observer.call(false)
        }
      end,
      :selection => lambda do |observer|
        on_widget_selected { |selection_event|
          observer.call(@swt_widget.getSelection)
        } if can_handle_observation_request?(:on_widget_selected)
      end,
      :text => lambda do |observer|
        on_modify_text { |modify_event|
          observer.call(@swt_widget.getText)
        } if can_handle_observation_request?(:on_modify_text)
      end,
    },
    Java::OrgEclipseSwtWidgets::Combo => {
      :text => lambda do |observer|
        on_modify_text { |modify_event|
          observer.call(@swt_widget.getText)
        }
      end,
    },
    Java::OrgEclipseSwtWidgets::Table => {
      :selection => lambda do |observer|
        on_widget_selected { |selection_event|
          if has_style?(:multi)
            observer.call(@swt_widget.getSelection.map(&:get_data))
          else
            observer.call(@swt_widget.getSelection.first&.get_data)
          end
        }
      end,
    },
    Java::OrgEclipseSwtWidgets::Text => {
      :text => lambda do |observer|
        on_modify_text { |modify_event|
          observer.call(@swt_widget.getText)
        }
      end,
      :caret_position => lambda do |observer|
        on_swt_keydown { |event|
          observer.call(@swt_widget.getCaretPosition)
        }
        on_swt_keyup { |event|
          observer.call(@swt_widget.getCaretPosition)
        }
        on_swt_mousedown { |event|
          observer.call(@swt_widget.getCaretPosition)
        }
        on_swt_mouseup { |event|
          observer.call(@swt_widget.getCaretPosition)
        }
      end,
      :selection => lambda do |observer|
        on_swt_keydown { |event|
          observer.call(@swt_widget.getSelection)
        }
        on_swt_keyup { |event|
          observer.call(@swt_widget.getSelection)
        }
        on_swt_mousedown { |event|
          observer.call(@swt_widget.getSelection)
        }
        on_swt_mouseup { |event|
          observer.call(@swt_widget.getSelection)
        }
      end,
      :selection_count => lambda do |observer|
        on_swt_keydown { |event|
          observer.call(@swt_widget.getSelectionCount)
        }
        on_swt_keyup { |event|
          observer.call(@swt_widget.getSelectionCount)
        }
        on_swt_mousedown { |event|
          observer.call(@swt_widget.getSelectionCount)
        }
        on_swt_mouseup { |event|
          observer.call(@swt_widget.getSelectionCount)
        }
      end,
      :top_index => lambda do |observer|
        @last_top_index = @swt_widget.getTopIndex
        on_paint_control { |event|
          if @swt_widget.getTopIndex != @last_top_index
            @last_top_index = @swt_widget.getTopIndex
            observer.call(@last_top_index)
          end
        }
      end,
    },
    Java::OrgEclipseSwtCustom::StyledText => {
      :text => lambda do |observer|
        on_modify_text { |modify_event|
          observer.call(@swt_widget.getText)
        }
      end,
      :caret_position => lambda do |observer|
        on_caret_moved { |event|
          observer.call(@swt_widget.getSelection.x) unless @swt_widget.getCaretOffset == 0 && @last_modify_text != text
        }
        on_swt_keyup { |event|
          observer.call(@swt_widget.getSelection.x) unless @swt_widget.getCaretOffset == 0 && @last_modify_text != text
        }
        on_swt_mouseup { |event|
          observer.call(@swt_widget.getSelection.x) unless @swt_widget.getCaretOffset == 0 && @last_modify_text != text
        }
      end,
      :caret_offset => lambda do |observer|
        on_caret_moved { |event|
          observer.call(@swt_widget.getCaretOffset) unless @swt_widget.getCaretOffset == 0 && @last_modify_text != text
        }
      end,
      :selection => lambda do |observer|
        on_widget_selected { |event|
          observer.call(@swt_widget.getSelection) unless @swt_widget.getCaretOffset == 0 && @last_modify_text != text
        }
        on_swt_keyup { |event|
          observer.call(@swt_widget.getSelection) unless @swt_widget.getCaretOffset == 0 && @last_modify_text != text
        }
        on_swt_mouseup { |event|
          observer.call(@swt_widget.getSelection) unless @swt_widget.getCaretOffset == 0 && @last_modify_text != text
        }
      end,
      :selection_count => lambda do |observer|
        on_widget_selected { |event|
          observer.call(@swt_widget.getSelectionCount) unless @swt_widget.getCaretOffset == 0 && @last_modify_text != text
        }
        on_swt_keyup { |event|
          observer.call(@swt_widget.getSelectionCount) unless @swt_widget.getCaretOffset == 0 && @last_modify_text != text
        }
        on_swt_mouseup { |event|
          observer.call(@swt_widget.getSelectionCount) unless @swt_widget.getCaretOffset == 0 && @last_modify_text != text
        }
      end,
      :selection_range => lambda do |observer|
        on_widget_selected { |event|
          observer.call(@swt_widget.getSelectionRange) unless @swt_widget.getCaretOffset == 0 && @last_modify_text != text
        }
        on_swt_keyup { |event|
          observer.call(@swt_widget.getSelectionRange) unless @swt_widget.getCaretOffset == 0 && @last_modify_text != text
        }
        on_swt_mouseup { |event|
          observer.call(@swt_widget.getSelectionRange) unless @swt_widget.getCaretOffset == 0 && @last_modify_text != text
        }
      end,
      :top_index => lambda do |observer|
        @last_top_index = @swt_widget.getTopIndex
        on_paint_control { |event|
          if @swt_widget.getTopIndex != @last_top_index
            @last_top_index = @swt_widget.getTopIndex
            observer.call(@last_top_index)
          end
        }
      end,
      :top_pixel => lambda do |observer|
        @last_top_pixel = @swt_widget.getTopPixel
        on_paint_control { |event|
          if @swt_widget.getTopPixel != @last_top_pixel
            @last_top_pixel = @swt_widget.getTopPixel
            observer.call(@last_top_pixel)
          end
        }
      end,
    },
    Java::OrgEclipseSwtWidgets::Button => {
      :selection => lambda do |observer|
        on_widget_selected { |selection_event|
          observer.call(@swt_widget.getSelection)
        }
      end
    },
    Java::OrgEclipseSwtWidgets::MenuItem => {
      :selection => lambda do |observer|
        on_widget_selected { |selection_event|
          observer.call(@swt_widget.getSelection)
        }
      end
    },
    Java::OrgEclipseSwtWidgets::Spinner => {
      :selection => lambda do |observer|
        on_widget_selected { |selection_event|
          observer.call(@swt_widget.getSelection)
        }
      end
    },
    Java::OrgEclipseSwtWidgets::DateTime =>
      [:year, :month, :day, :hours, :minutes, :seconds, :date_time, :date, :time].reduce({}) do |hash, attribute|
        hash.merge(
          attribute => lambda do |observer|
            on_widget_selected { |selection_event|
              observer.call(get_attribute(attribute))
            }
          end
        )
      end,
  }
end