Acquiring the Clipboard
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## Acquiring the Clipboard

Let's begin by augmenting the GUI to include a row of buttons along the bottom of the main window for copying and pasting:

    require 'fox'
    require 'customer'

    include Fox

    class ClipMainWindow < FXMainWindow
      def initialize(anApp)
        # Initialize base class first
        super(anApp, "Clipboard Example", nil, nil, DECOR_ALL, 0, 0, 400, 300)

        # Horizontal frame contains buttons
        buttons = FXHorizontalFrame.new(self, LAYOUT_SIDE_BOTTOM|LAYOUT_FILL_X|PACK_UNIFORM_WIDTH)

        # Cut and paste buttons
        copyButton  = FXButton.new(buttons, "Copy")
        pasteButton = FXButton.new(buttons, "Paste")

        # Place the list in a sunken frame
        sunkenFrame = FXVerticalFrame.new(self, LAYOUT_FILL_X|LAYOUT_FILL_Y|FRAME_SUNKEN|FRAME_THICK,
          0, 0, 0, 0, 0, 0, 0, 0)

        # Customer list
        customerList = FXList.new(sunkenFrame, 6, nil, 0, LIST_BROWSESELECT|LAYOUT_FILL_X|LAYOUT_FILL_Y)
        $customers.each do |customer|
          customerList.appendItem(customer.name, nil, customer)
        end
      end

      def create
        super
        show(PLACEMENT_SCREEN)
      end
    end

    if __FILE__ == $0
      FXApp.new("ClipboardExample", "FXRuby") do |theApp|
        ClipMainWindow.new(theApp)
        theApp.create
        theApp.run
      end
    end

Note that the lines which appear in bold face are those which have been added (or changed) since the previous source code listing.

The clipboard is a kind of shared resource in the operating system. Copying (or cutting) data to the clipboard begins with some window in your application requesting "ownership" of the clipboard by calling the `acquireClipboard()` instance method. Let's add a handler for the "Copy" button press which does just that:

    # User clicks Copy
    copyButton.connect(SEL_COMMAND) do
      customer = customerList.getItemData(customerList.currentItem)
      types = [ FXWindow.stringType ]
      if acquireClipboard(types)
        @clippedCustomer = customer
      end
    end

The `acquireClipboard()` method takes as its input an array of drag types. A drag type is just a unique value, assigned by the window system, that identifies a particular kind of data. In this case, we're using one of FOX's pre-registered drag types (`stringType`) to indicate that we have some string data to place on the clipboard. Later, we'll see how to register customized, application-specific drag types as well.

The `acquireClipboard()` method returns `true` on success; since we called `acquireClipboard()` on the main window, this means that the main window is now the clipboard owner. At this time, we want to save a reference to the currently selected customer in the `@clippedCustomer` instance variable so that if its value is requested later, we'll be able to return the correct customer's information.

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Chapter 3. Working With the Clipboard | Home | Sending Data to the Clipboard