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<th width="60%" align="center">Chapter 23. Keyboard and Mouse Events</th>
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<div class="titlepage"><div><div><h2 class="title" style="clear: both">
<a name="sec-keyboardevents-mouse"></a>Mouse Events</h2></div></div></div>
  

  <p>
    Mouse events are similar to keyboard events. There are some differences, though.
    </p>
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem"><p>You use <code class="classname">Gtk::GestureClick</code> instead of
        <code class="classname">Gtk::EventControllerKey</code>.</p></li>
<li class="listitem"><p>There are other event classes that can be used for handling
        mouse events, for instance <code class="classname">Gtk::EventControllerMotion</code> and
        <code class="classname">Gtk::EventControllerScroll</code>.</p></li>
<li class="listitem"><p>Many signal handlers don't return a <code class="literal">bool</code>.
        You can't stop those events from propagating.</p></li>
</ul></div>
<p>
  </p>

  <p>
    The event classes that handle mouse events are also useful for handling
    events from touchscreens. There are also many subclasses of
    <code class="classname">Gtk::EventController</code> which are only (or mainly) useful
    for touchscreens. Examples: <code class="classname">Gtk::GestureRotate</code>,
    <code class="classname">Gtk::GestureZoom</code>, <code class="classname">Gtk::GestureSwipe</code>,
    <code class="classname">Gtk::GestureLongPress</code>.
  </p>

  <p><a class="ulink" href="https://gnome.pages.gitlab.gnome.org/gtkmm/classGtk_1_1EventController.html" target="_top">Reference</a></p>

    <div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="keyboardevents-mouse-example"></a>Example</h3></div></div></div>
    
      <p>
        This is an expanded version of the simple keyboard events example.
      </p>

      <div class="figure">
<a name="figure-keyboardevents-mouse"></a><p class="title"><b>Figure 23.3. Keyboard and Mouse Events</b></p>
<div class="figure-contents">
        
        <div class="screenshot">
          <div class="mediaobject"><img src="figures/events_mouse.png" alt="Keyboard and Mouse Events"></div>
        </div>
      </div>
</div>
<br class="figure-break">

<p><a class="ulink" href="https://gitlab.gnome.org/GNOME/gtkmm-documentation/tree/master/examples/book/events/mouse/" 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();
  ~ExampleWindow() override;

private:
  // Signal handlers:
  void on_window_mouse_pressed(int n_press, double x, double y);
  void on_first_button_mouse_pressed(int n_press, double x, double y);
  void on_second_button_mouse_pressed(int n_press, double x, double y);
  void on_third_button_mouse_pressed(int n_press, double x, double y);
  void on_third_button_clicked();
  void on_mouse_released(int n_press, double x, double y);
  void on_mouse_motion(double x, double y);
  bool on_mouse_scroll(double dx, double dy);
  bool on_key_pressed(guint keyval, guint keycode, Gdk::ModifierType state);

  Gtk::Box m_box;
  Gtk::CheckButton m_first;
  Gtk::CheckButton m_second;
  Gtk::Button m_third;

  Glib::RefPtr&lt;Gtk::GestureClick&gt; m_window_click;
  Glib::RefPtr&lt;Gtk::GestureClick&gt; m_first_button_click;
  Glib::RefPtr&lt;Gtk::GestureClick&gt; m_second_button_click;
};

#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;map&gt;
#include &lt;iostream&gt;

namespace
{
std::map&lt;unsigned int, Glib::ustring&gt; mouse_buttons
{
  {0, "No button"},
  {GDK_BUTTON_PRIMARY, "Primary"},
  {GDK_BUTTON_MIDDLE, "Middle"},
  {GDK_BUTTON_SECONDARY, "Secondary"},
};
}

ExampleWindow::ExampleWindow()
: m_first("First"),
  m_second("Second"),
  m_third("Click me")
{
  set_title("Keyboard and Mouse Events");
  m_box.set_margin(10);
  set_child(m_box);

  // Radio buttons
  m_second.set_group(m_first);
  m_first.set_active();

  // Main container
  m_box.set_orientation(Gtk::Orientation::HORIZONTAL);
  m_box.append(m_first);
  m_box.append(m_second);
  m_box.append(m_third);

  // Keyboard events
  auto key_controller = Gtk::EventControllerKey::create();
  key_controller-&gt;signal_key_pressed().connect(
    sigc::mem_fun(*this, &amp;ExampleWindow::on_key_pressed), false);
  add_controller(key_controller);

  // Mouse events, window
  auto motion_controller = Gtk::EventControllerMotion::create();
  motion_controller-&gt;signal_motion().connect(
    sigc::mem_fun(*this, &amp;ExampleWindow::on_mouse_motion));
  add_controller(motion_controller);

  m_window_click = Gtk::GestureClick::create();
  m_window_click-&gt;set_button(0); // All mouse buttons
  m_window_click-&gt;signal_pressed().connect(
    sigc::mem_fun(*this, &amp;ExampleWindow::on_window_mouse_pressed));
  add_controller(m_window_click);

  auto mouse_click = Gtk::GestureClick::create();
  mouse_click-&gt;set_button(GDK_BUTTON_PRIMARY);
  mouse_click-&gt;signal_released().connect(sigc::mem_fun(*this, &amp;ExampleWindow::on_mouse_released));
  add_controller(mouse_click);

  auto mouse_scroll = Gtk::EventControllerScroll::create();
  mouse_scroll-&gt;set_flags(Gtk::EventControllerScroll::Flags::VERTICAL);
  // Handle mouse wheel rotations
  mouse_scroll-&gt;signal_scroll().connect(
    sigc::mem_fun(*this, &amp;ExampleWindow::on_mouse_scroll), true);
  add_controller(mouse_scroll);

  // Mouse events, buttons
  m_first_button_click = Gtk::GestureClick::create();
  m_first_button_click-&gt;set_button(GDK_BUTTON_PRIMARY);
  m_first_button_click-&gt;signal_pressed().connect(
    sigc::mem_fun(*this, &amp;ExampleWindow::on_first_button_mouse_pressed));
  m_first.add_controller(m_first_button_click);

  m_second_button_click = Gtk::GestureClick::create();
  m_second_button_click-&gt;set_button(GDK_BUTTON_PRIMARY);
  m_second_button_click-&gt;signal_pressed().connect(
    sigc::mem_fun(*this, &amp;ExampleWindow::on_second_button_mouse_pressed));
  m_second.add_controller(m_second_button_click);

  mouse_click = Gtk::GestureClick::create();
  // This mouse event must be handled in the capture phase.
  // The GtkButton C class handles the event in the capture phase and
  // does not let it propagate to the bubble phase where events are
  // handled by default.
  mouse_click-&gt;set_propagation_phase(Gtk::PropagationPhase::CAPTURE);
  mouse_click-&gt;set_button(GDK_BUTTON_PRIMARY);
  mouse_click-&gt;signal_pressed().connect(
    sigc::mem_fun(*this, &amp;ExampleWindow::on_third_button_mouse_pressed));
  m_third.add_controller(mouse_click);
  m_third.signal_clicked().connect(
    sigc::mem_fun(*this, &amp;ExampleWindow::on_third_button_clicked));
}

void ExampleWindow::on_window_mouse_pressed(int n_press, double x, double y)
{
  const auto current_button = mouse_buttons[m_window_click-&gt;get_current_button()];
  std::cout &lt;&lt; "Mouse pressed in window: " &lt;&lt; current_button
    &lt;&lt; ", " &lt;&lt; n_press &lt;&lt; ", " &lt;&lt; x &lt;&lt; ", " &lt;&lt; y &lt;&lt; std::endl;
}

void ExampleWindow::on_first_button_mouse_pressed(int n_press, double x, double y)
{
  const auto current_button = mouse_buttons[m_first_button_click-&gt;get_current_button()];
  std::cout &lt;&lt; "Mouse pressed in first button: " &lt;&lt; current_button
    &lt;&lt; ", " &lt;&lt; n_press &lt;&lt; ", " &lt;&lt; x &lt;&lt; ", " &lt;&lt; y &lt;&lt; std::endl;
}

void ExampleWindow::on_second_button_mouse_pressed(int n_press, double x, double y)
{
  const auto current_button = mouse_buttons[m_second_button_click-&gt;get_current_button()];
  std::cout &lt;&lt; "Mouse pressed in second button: " &lt;&lt; current_button
    &lt;&lt; ", " &lt;&lt; n_press &lt;&lt; ", " &lt;&lt; x &lt;&lt; ", " &lt;&lt; y &lt;&lt; std::endl;
}

void ExampleWindow::on_third_button_mouse_pressed(int n_press, double x, double y)
{
  std::cout &lt;&lt; "Mouse pressed in third button: "
    &lt;&lt; n_press &lt;&lt; ", " &lt;&lt; x &lt;&lt; ", " &lt;&lt; y &lt;&lt; std::endl;
}

void ExampleWindow::on_third_button_clicked()
{
  std::cout &lt;&lt; "Third button clicked" &lt;&lt; std::endl;
}

void ExampleWindow::on_mouse_released(int n_press, double x, double y)
{
  std::cout &lt;&lt; "Mouse released: " &lt;&lt; n_press &lt;&lt; ", " &lt;&lt; x &lt;&lt; ", " &lt;&lt; y &lt;&lt; std::endl;
}

void ExampleWindow::on_mouse_motion(double x, double y)
{
  std::cout &lt;&lt; "Mouse motion: "  &lt;&lt; x &lt;&lt; ", " &lt;&lt; y &lt;&lt; std::endl;
}

bool ExampleWindow::on_mouse_scroll(double dx, double dy)
{
  std::cout &lt;&lt; "Mouse scroll: "  &lt;&lt; dx &lt;&lt; ", " &lt;&lt; dy &lt;&lt; std::endl;
  return true; // handled
}

bool ExampleWindow::on_key_pressed(guint keyval, guint, Gdk::ModifierType state)
{
  // Gdk::ModifierType::ALT_MASK -&gt; the 'Alt' key(mask)
  // GDK_KEY_1 -&gt; the '1' key
  // GDK_KEY_2 -&gt; the '2' key

  // Select the first radio button, when we press Alt + 1
  if ((keyval == GDK_KEY_1) &amp;&amp;
    (state &amp; (Gdk::ModifierType::SHIFT_MASK | Gdk::ModifierType::CONTROL_MASK | Gdk::ModifierType::ALT_MASK)) == Gdk::ModifierType::ALT_MASK)
  {
    m_first.set_active();
    // Returning true, cancels the propagation of the event
    return true;
  }
  else if ((keyval == GDK_KEY_2) &amp;&amp;
    (state &amp; (Gdk::ModifierType::SHIFT_MASK | Gdk::ModifierType::CONTROL_MASK | Gdk::ModifierType::ALT_MASK)) == Gdk::ModifierType::ALT_MASK)
  {
    // and the second radio button, when we press Alt + 2
    m_second.set_active();
    return true;
  }
  else if (keyval == GDK_KEY_Escape)
  {
    // Close the window, when the 'Esc' key is pressed
    set_visible(false);
    return true;
  }

  // The event has not been handled
  return false;
}

ExampleWindow::~ExampleWindow()
{
}
</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[])
{
  auto app = Gtk::Application::create("org.gtkmm.example");

  //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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