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<th width="60%" align="center">Chapter 20. The Clipboard</th>
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<div class="titlepage"><div><div><h2 class="title" style="clear: both">
<a name="sec-clipboard-examples"></a>Examples</h2></div></div></div>


<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="sec-clipboard-example-simple"></a>Simple</h3></div></div></div>

<p>
This example allows copy and pasting of application-specific data, using the
standard text format. Although this is simple, it's not ideal because it does
not identify the <code class="classname">Clipboard</code> data as being of a particular
type.
</p>

<div class="figure">
<a name="figure-clipboard-simple"></a><p class="title"><b>Figure 20.1. Clipboard - Simple</b></p>
<div class="figure-contents">
  
  <div class="screenshot">
    <div class="mediaobject"><img src="figures/clipboard_simple.png" alt="Clipboard - Simple"></div>
  </div>
</div>
</div>
<br class="figure-break">

<p><a class="ulink" href="https://gitlab.gnome.org/GNOME/gtkmm-documentation/tree/master/examples/book/clipboard/simple/" target="_top">Source Code</a></p>

<p>File: <code class="filename">examplewindow.h</code> (For use with gtkmm 4)</p>
<pre class="programlisting"><code class="code">#ifndef GTKMM_EXAMPLEWINDOW_H
#define GTKMM_EXAMPLEWINDOW_H

#include &lt;gtkmm.h&gt;

class ExampleWindow : public Gtk::Window
{
public:
  ExampleWindow();
  virtual ~ExampleWindow();

protected:
  //Signal handlers:
  void on_button_copy();
  void on_button_paste();

  void on_clipboard_text_received(Glib::RefPtr&lt;Gio::AsyncResult&gt;&amp; result);

  Glib::ustring m_strData;

  //Child widgets:
  Gtk::Box m_VBox;

  Gtk::Label m_Label;

  Gtk::Grid m_Grid;
  Gtk::ToggleButton m_ButtonA1, m_ButtonA2, m_ButtonB1, m_ButtonB2;

  Gtk::Box m_ButtonBox;
  Gtk::Button m_Button_Copy, m_Button_Paste;
};

#endif //GTKMM_EXAMPLEWINDOW_H
</code></pre>
<p>File: <code class="filename">examplewindow.cc</code> (For use with gtkmm 4)</p>
<pre class="programlisting"><code class="code">#include "examplewindow.h"
#include &lt;iostream&gt;

ExampleWindow::ExampleWindow()
: m_VBox(Gtk::Orientation::VERTICAL),
  m_Label("Select cells in the grid, click Copy, then open a second "
        "instance of this example to try pasting the copied data."),
  m_ButtonA1("A1"), m_ButtonA2("A2"), m_ButtonB1("B1"), m_ButtonB2("B2"),
  m_Button_Copy("_Copy", /* mnemonic= */ true), m_Button_Paste("_Paste", true)
{
  set_title("Gtk::Clipboard example");

  m_VBox.set_margin(12);
  set_child(m_VBox);

  m_VBox.append(m_Label);

  //Fill Grid:
  m_VBox.append(m_Grid);
  m_Grid.set_expand(true);
  m_Grid.set_row_homogeneous(true);
  m_Grid.set_column_homogeneous(true);
  m_Grid.attach(m_ButtonA1, 0, 0);
  m_Grid.attach(m_ButtonA2, 1, 0);
  m_Grid.attach(m_ButtonB1, 0, 1);
  m_Grid.attach(m_ButtonB2, 1, 1);

  //Add ButtonBox to bottom:
  m_VBox.append(m_ButtonBox);
  m_VBox.set_spacing(6);

  //Fill ButtonBox:
  m_ButtonBox.append(m_Button_Copy);
  m_Button_Copy.set_hexpand(true);
  m_Button_Copy.set_halign(Gtk::Align::END);
  m_Button_Copy.signal_clicked().connect(sigc::mem_fun(*this,
              &amp;ExampleWindow::on_button_copy) );
  m_ButtonBox.append(m_Button_Paste);
  m_Button_Paste.signal_clicked().connect(sigc::mem_fun(*this,
              &amp;ExampleWindow::on_button_paste) );
}

ExampleWindow::~ExampleWindow()
{
}

void ExampleWindow::on_button_copy()
{
  //Build a string representation of the stuff to be copied:
  //Ideally you would use XML, with an XML parser here:
  m_strData = m_ButtonA1.get_active() ? "1" : "0";
  m_strData += m_ButtonA2.get_active() ? "1" : "0";
  m_strData += m_ButtonB1.get_active() ? "1" : "0";
  m_strData += m_ButtonB2.get_active() ? "1" : "0";

  // Gdk::Clipboard::set_text() does not take a copy of the text.
  // The text can only be pasted (in this program or in some other program)
  // for as long as it exists.
  get_clipboard()-&gt;set_text(m_strData);
}

void ExampleWindow::on_button_paste()
{
  //Tell the clipboard to call our method when it is ready:
  get_clipboard()-&gt;read_text_async(sigc::mem_fun(*this,
              &amp;ExampleWindow::on_clipboard_text_received));
}

void ExampleWindow::on_clipboard_text_received(Glib::RefPtr&lt;Gio::AsyncResult&gt;&amp; result)
{
  Glib::ustring text;
  try
  {
    text = get_clipboard()-&gt;read_text_finish(result);
  }
  catch (const Glib::Error&amp; err)
  {
    // Print an error about why pasting failed.
    // Usually you probably want to ignore such failures,
    // but for demonstration purposes, we show the error.
    std::cout &lt;&lt; "Pasting failed: " &lt;&lt; err.what() &lt;&lt; std::endl;
  }

  //See comment in on_button_copy() about this silly clipboard format.
  if(text.size() &gt;= 4)
  {
    m_ButtonA1.set_active( text[0] == '1' );
    m_ButtonA2.set_active( text[1] == '1' );
    m_ButtonB1.set_active( text[2] == '1' );
    m_ButtonB2.set_active( text[3] == '1' );
  }
}
</code></pre>
<p>File: <code class="filename">main.cc</code> (For use with gtkmm 4)</p>
<pre class="programlisting"><code class="code">#include "examplewindow.h"
#include &lt;gtkmm/application.h&gt;

int main(int argc, char *argv[])
{
  // Gio::Application::Flags::NON_UNIQUE because it shall be possible to run
  // several instances of this application simultaneously.
  auto app = Gtk::Application::create(
    "org.gtkmm.example", Gio::Application::Flags::NON_UNIQUE);

  //Shows the window and returns when it is closed.
  return app-&gt;make_window_and_run&lt;ExampleWindow&gt;(argc, argv);
}
</code></pre>


</div>

<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="sec-clipboard-example-ideal"></a>Ideal</h3></div></div></div>

<p>This is like the simple example, but it
</p>
<div class="orderedlist"><ol class="orderedlist" type="1">
<li class="listitem">Defines a custom clipboard target, though the format is still text.</li>
<li class="listitem">It uses the <code class="methodname">Gdk::ContentFormats::signal_changed()</code>
  signal and disables the Paste button if it can't use anything on the clipboard.</li>
</ol></div>
<p>
</p>

<div class="figure">
<a name="figure-clipboard-ideal"></a><p class="title"><b>Figure 20.2. Clipboard - Ideal</b></p>
<div class="figure-contents">
  
  <div class="screenshot">
    <div class="mediaobject"><img src="figures/clipboard_ideal.png" alt="Clipboard - Ideal"></div>
  </div>
</div>
</div>
<br class="figure-break">

<p><a class="ulink" href="https://gitlab.gnome.org/GNOME/gtkmm-documentation/tree/master/examples/book/clipboard/ideal/" target="_top">Source Code</a></p>

<p>File: <code class="filename">examplewindow.h</code> (For use with gtkmm 4)</p>
<pre class="programlisting"><code class="code">#ifndef GTKMM_EXAMPLEWINDOW_H
#define GTKMM_EXAMPLEWINDOW_H

#include &lt;gtkmm.h&gt;

class ExampleWindow : public Gtk::Window
{
public:
  ExampleWindow();
  virtual ~ExampleWindow();

protected:
  //Signal handlers:
  void on_button_copy();
  void on_button_paste();

  void on_clipboard_content_changed();

  void on_clipboard_received(Glib::RefPtr&lt;Gio::AsyncResult&gt;&amp; result);
  void on_clipboard_received_status(Glib::RefPtr&lt;Gio::AsyncResult&gt;&amp; result);

  void update_paste_status(); //Disable the paste button if there is nothing to paste.

  Glib::ustring m_strData;

  //Child widgets:
  Gtk::Box m_VBox;

  Gtk::Label m_Label;

  Gtk::Grid m_Grid;
  Gtk::ToggleButton m_ButtonA1, m_ButtonA2, m_ButtonB1, m_ButtonB2;

  Gtk::Box m_ButtonBox;
  Gtk::Button m_Button_Copy, m_Button_Paste;
};

#endif //GTKMM_EXAMPLEWINDOW_H
</code></pre>
<p>File: <code class="filename">examplewindow.cc</code> (For use with gtkmm 4)</p>
<pre class="programlisting"><code class="code">#include "examplewindow.h"
#include &lt;iostream&gt;
#include &lt;string&gt;

namespace
{

const char example_format_custom[] = "gtkmmclipboardexample";

} // anonymous namespace


ExampleWindow::ExampleWindow()
: m_VBox(Gtk::Orientation::VERTICAL),
  m_Label("Select cells in the grid, click Copy, then open a second instance "
          "of this example to try pasting the copied data.\nOr try pasting the "
          "text representation into gedit."),
  m_ButtonA1("A1"), m_ButtonA2("A2"), m_ButtonB1("B1"), m_ButtonB2("B2"),
  m_Button_Copy("_Copy", /* mnemonic= */ true), m_Button_Paste("_Paste", true)
{
  set_title("Gtk::Clipboard example");

  m_VBox.set_margin(12);
  set_child(m_VBox);

  m_VBox.append(m_Label);

  //Fill Grid:
  m_VBox.append(m_Grid);
  m_Grid.set_expand(true);
  m_Grid.set_row_homogeneous(true);
  m_Grid.set_column_homogeneous(true);
  m_Grid.attach(m_ButtonA1, 0, 0);
  m_Grid.attach(m_ButtonA2, 1, 0);
  m_Grid.attach(m_ButtonB1, 0, 1);
  m_Grid.attach(m_ButtonB2, 1, 1);

  //Add ButtonBox to bottom:
  m_VBox.append(m_ButtonBox);
  m_VBox.set_spacing(6);

  //Fill ButtonBox:
  m_ButtonBox.append(m_Button_Copy);
  m_Button_Copy.set_hexpand(true);
  m_Button_Copy.set_halign(Gtk::Align::END);
  m_Button_Copy.signal_clicked().connect(sigc::mem_fun(*this,
              &amp;ExampleWindow::on_button_copy) );
  m_ButtonBox.append(m_Button_Paste);
  m_Button_Paste.signal_clicked().connect(sigc::mem_fun(*this,
              &amp;ExampleWindow::on_button_paste) );

  //Connect a signal handler that will be called when the contents of
  //the clipboard change.
  get_clipboard()-&gt;signal_changed().connect(sigc::mem_fun(*this,
              &amp;ExampleWindow::on_clipboard_content_changed));

  update_paste_status();
}

ExampleWindow::~ExampleWindow()
{
}

void ExampleWindow::on_button_copy()
{
  //Build a string representation of the stuff to be copied:
  //Ideally you would use XML, with an XML parser here:
  m_strData = example_format_custom;
  m_strData += m_ButtonA1.get_active() ? " A1" : "";
  m_strData += m_ButtonA2.get_active() ? " A2" : "";
  m_strData += m_ButtonB1.get_active() ? " B1" : "";
  m_strData += m_ButtonB2.get_active() ? " B2" : "";

  // Gdk::Clipboard::set_text() does not take a copy of the text.
  // The text can only be pasted (in this program or in some other program)
  // for as long as it exists.
  get_clipboard()-&gt;set_text(m_strData);
}

void ExampleWindow::on_button_paste()
{
  //Tell the clipboard to call our method when it is ready:
  get_clipboard()-&gt;read_text_async(sigc::mem_fun(*this,
              &amp;ExampleWindow::on_clipboard_received));
}

void ExampleWindow::on_clipboard_content_changed()
{
  update_paste_status();
}

void ExampleWindow::on_clipboard_received(Glib::RefPtr&lt;Gio::AsyncResult&gt;&amp; result)
{
  Glib::ustring text;
  try
  {
    text = get_clipboard()-&gt;read_text_finish(result);
  }
  catch (const Glib::Error&amp; err)
  {
    // Print an error about why pasting failed.
    // Usually you probably want to ignore such failures,
    // but for demonstration purposes, we show the error.
    std::cout &lt;&lt; "Pasting failed: " &lt;&lt; err.what() &lt;&lt; std::endl;
  }

  if (text.find(example_format_custom) == 0)
  {
    // It's the expected format.
    m_ButtonA1.set_active(text.find("A1") != std::string::npos);
    m_ButtonA2.set_active(text.find("A2") != std::string::npos);
    m_ButtonB1.set_active(text.find("B1") != std::string::npos);
    m_ButtonB2.set_active(text.find("B2") != std::string::npos);
  }
  else
  {
    // Unexpected format. Disable the Paste button.
    std::cout &lt;&lt; "Unexpected pasted text: \"" &lt;&lt; text &lt;&lt; "\"" &lt;&lt; std::endl;
    m_Button_Paste.set_sensitive(false);
  }
}

void ExampleWindow::update_paste_status()
{
  // Disable the paste button if there is nothing to paste.
  get_clipboard()-&gt;read_text_async(sigc::mem_fun(*this,
              &amp;ExampleWindow::on_clipboard_received_status));
}

void ExampleWindow::on_clipboard_received_status(Glib::RefPtr&lt;Gio::AsyncResult&gt;&amp; result)
{
  Glib::ustring text;
  try
  {
    text = get_clipboard()-&gt;read_text_finish(result);
  }
  catch (const Glib::Error&amp;)
  {
  }

  const bool bPasteIsPossible = text.find(example_format_custom) == 0;

  // Enable/Disable the Paste button appropriately:
  m_Button_Paste.set_sensitive(bPasteIsPossible);
}
</code></pre>
<p>File: <code class="filename">main.cc</code> (For use with gtkmm 4)</p>
<pre class="programlisting"><code class="code">#include "examplewindow.h"
#include &lt;gtkmm/application.h&gt;

int main(int argc, char *argv[])
{
  // Gio::Application::Flags::NON_UNIQUE because it shall be possible to run
  // several instances of this application simultaneously.
  auto app = Gtk::Application::create(
    "org.gtkmm.example", Gio::Application::Flags::NON_UNIQUE);

  //Shows the window and returns when it is closed.
  return app-&gt;make_window_and_run&lt;ExampleWindow&gt;(argc, argv);
}
</code></pre>


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