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<div class="chapter">
<div class="titlepage"><div><div><h1 class="title">
<a name="chapter-keyboardevents"></a>Chapter 23. Keyboard and Mouse Events</h1></div></div></div>
<div class="toc">
<p><b>Table of Contents</b></p>
<ul class="toc">
<li><span class="section"><a href="chapter-keyboardevents.html#sec-keyboardevents-overview">Overview</a></span></li>
<li><span class="section"><a href="sec-keyboardevents-propagation.html">Event Propagation</a></span></li>
<li><span class="section"><a href="sec-keyboardevents-mouse.html">Mouse Events</a></span></li>
</ul>
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<p>
Event signals differ in some ways from other signals. These differences are described
in the <a class="link" href="sec-eventsignals.html" title="Event signals">Event signals</a> section in
the appendix. Here we will use keyboard events and mouse events to show how
events can be used in a program.
</p>
<div class="section">
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
<a name="sec-keyboardevents-overview"></a>Overview</h2></div></div></div>
<p>
Whenever you press or release a key, an event is emitted. You can add an
event controller and connect a signal handler to handle such events.
</p>
<p>
The event signal handler will receive arguments that depend on the type of event.
For key press events the arguments are (<span class="type">guint</span> <code class="varname">keyval</code>,
<span class="type">guint</span> <code class="varname">keycode</code>, <span class="type">Gdk::ModifierType</span> <code class="varname">state</code>).
As described in the <a class="link" href="sec-eventsignals.html" title="Event signals">appendix</a>,
the key press event signal handler returns a <span class="type">bool</span> value, to indicate that
the signal is fully handled (<code class="literal">true</code>) or allow event propagation
(<code class="literal">false</code>).
</p>
<p>
To determine which key was pressed or released, you read the value of
the <code class="varname">keyval</code> argument and compare it with a constant in the
<a class="ulink" href="https://gitlab.gnome.org/GNOME/gtk/tree/main/gdk/gdkkeysyms.h" target="_top">
<code class="filename"><gdk/gdkkeysyms.h></code></a> header file. The states of
modifier keys (shift, ctrl, etc.) are available as bit-flags in
<code class="varname">state</code>.
</p>
<p>
Here's a simple example:
</p>
<pre class="programlisting"><code class="code">
bool MyClass::on_key_pressed(guint keyval, guint, Gdk::ModifierType state)
{
if (keyval == GDK_KEY_1 &&
(state & (Gdk::ModifierType::SHIFT_MASK | Gdk::ModifierType::CONTROL_MASK |
Gdk::ModifierType::ALT_MASK)) == Gdk::ModifierType::ALT_MASK)
{
handle_alt_press();
return true;
}
return false;
}
// in MyClass constructor
auto controller = Gtk::EventControllerKey::create();
controller->signal_key_pressed().connect(
sigc::mem_fun(*this, &MyClass::on_key_pressed), false);
add_controller(controller);
</code></pre>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="keyboardevents-simple-example"></a>Example</h3></div></div></div>
<p>
In this example there are three keyboard shortcuts:
<span class="keycap"><strong>Alt</strong></span>+<span class="keycap"><strong>1</strong></span> selects the first radio button,
<span class="keycap"><strong>Alt</strong></span>+<span class="keycap"><strong>2</strong></span> selects the second one, and the
<span class="keycap"><strong>Esc</strong></span> key hides (closes) the window.
</p>
<div class="figure">
<a name="figure-keyboardevents-simple"></a><p class="title"><b>Figure 23.1. Keyboard Events - Simple</b></p>
<div class="figure-contents">
<div class="screenshot">
<div class="mediaobject"><img src="figures/events_simple.png" alt="Keyboard Events - 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/events/keyboard_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 <gtkmm.h>
class ExampleWindow : public Gtk::Window
{
public:
ExampleWindow();
virtual ~ExampleWindow();
private:
// Signal handler:
bool on_window_key_pressed(guint keyval, guint keycode, Gdk::ModifierType state);
Gtk::Box m_container;
Gtk::CheckButton m_first;
Gtk::CheckButton m_second;
};
#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"
ExampleWindow::ExampleWindow()
{
set_title("Keyboard Events");
m_container.set_margin(10);
set_child(m_container);
// Radio buttons:
m_first.set_label("First");
m_second.set_label("Second");
m_second.set_group(m_first);
m_first.set_active();
// Main Container:
m_container.set_orientation(Gtk::Orientation::HORIZONTAL);
m_container.append(m_first);
m_container.append(m_second);
// Events.
auto controller = Gtk::EventControllerKey::create();
controller->signal_key_pressed().connect(
sigc::mem_fun(*this, &ExampleWindow::on_window_key_pressed), false);
add_controller(controller);
}
bool ExampleWindow::on_window_key_pressed(guint keyval, guint, Gdk::ModifierType state)
{
//Gdk::ModifierType::ALT_MASK -> the 'Alt' key(mask)
//GDK_KEY_1 -> the '1' key
//GDK_KEY_2 -> the '2' key
//select the first radio button, when we press alt + 1
if((keyval == GDK_KEY_1) &&
(state & (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) &&
(state & (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 <gtkmm/application.h>
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->make_window_and_run<ExampleWindow>(argc, argv);
}
</code></pre>
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