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<div class="titlepage"><div><div><h1 class="title">
<a name="chapter-widgets-without-xwindows"></a>Chapter 15. Widgets Without X-Windows</h1></div></div></div>
<div class="toc">
<p><b>Table of Contents</b></p>
<ul class="toc"><li><span class="sect1"><a href="chapter-widgets-without-xwindows.html#sec-eventbox">EventBox</a></span></li></ul>
</div>
<p>
Some Widgets do not have an associated X-Window, so they therefore do not
receive X events. This means that the signals described in the <a class="link" href="sec-xeventsignals.html" title="X Event signals">X event signals</a> section will not be
emitted. If you want to capture events for these widgets you can use a special
container called <code class="classname">Gtk::EventBox</code>, which is described in
the <a class="link" href="chapter-widgets-without-xwindows.html#sec-eventbox" title="EventBox">EventBox</a> section.
</p>
<p>
Here is a list of some of these Widgets:
</p>
<pre class="programlisting">Gtk::Alignment (deprecated from <span class="application">gtkmm</span> version 3.14)
Gtk::Arrow (deprecated from <span class="application">gtkmm</span> version 3.14)
Gtk::AspectFrame
Gtk::Bin
Gtk::Box
Gtk::Button
Gtk::CheckButton
Gtk::Fixed
Gtk::Frame
Gtk::Grid
Gtk::Image
Gtk::Label
Gtk::MenuItem
Gtk::Notebook
Gtk::Paned
Gtk::RadioButton
Gtk::Range
Gtk::ScrolledWindow
Gtk::Separator
Gtk::Table (deprecated from <span class="application">gtkmm</span> version 3.4)
Gtk::Toolbar</pre>
<p>
These widgets are mainly used for decoration or layout, so you won't often need
to capture events on them. They are intended to have no X-Window in order to improve performance.
</p>
<div class="sect1">
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
<a name="sec-eventbox"></a>EventBox</h2></div></div></div>
<p>
Some <span class="application">gtkmm</span> widgets don't have associated X windows; they draw on
their parents' windows. Because of this, they cannot receive events.
Also, if they are incorrectly sized, they don't clip, so you can get
messy overwriting etc. To receive events on one of these widgets, you can place it
inside an <code class="classname">EventBox</code> widget and then call
<code class="methodname">Gtk::Widget::set_events()</code> on the EventBox before showing it.</p>
<p>Although the name
<code class="classname">EventBox</code> emphasises the event-handling method, the
widget can also be used for clipping (and more; see the example below).
</p>
<p>
The constructor for <code class="classname">Gtk::EventBox</code> is:
</p>
<pre class="programlisting">Gtk::EventBox();</pre>
<p>
A child widget can be added to the <code class="classname">EventBox</code> using:
</p>
<pre class="programlisting">event_box.add(child_widget);</pre>
<p><a class="ulink" href="http://developer.gnome.org/gtkmm/3.24/classGtk_1_1EventBox.html" target="_top">Reference</a></p>
<div class="sect2">
<div class="titlepage"><div><div><h3 class="title">
<a name="eventbox-example"></a>Example</h3></div></div></div>
<p>
The following example demonstrates both uses of an
<code class="classname">EventBox</code> - a label is created that is clipped to a small
box, and set up so that a mouse-click on the label causes the program to exit.
Resizing the window reveals varying amounts of the label.
</p>
<div class="figure">
<a name="figure-eventbox"></a><p class="title"><b>Figure 15.1. EventBox</b></p>
<div class="figure-contents"><div class="screenshot"><div><img src="figures/eventbox.png" alt="EventBox"></div></div></div>
</div>
<br class="figure-break"><p><a class="ulink" href="http://git.gnome.org/browse/gtkmm-documentation/tree/examples/book/eventbox?h=gtkmm-3-24" target="_top">Source Code</a></p>
<p>File: <code class="filename">examplewindow.h</code> (For use with gtkmm 3, not gtkmm 2)
</p>
<pre class="programlisting">
#ifndef GTKMM_EXAMPLEWINDOW_H
#define GTKMM_EXAMPLEWINDOW_H
#include <gtkmm.h>
class ExampleWindow : public Gtk::Window
{
public:
ExampleWindow();
virtual ~ExampleWindow();
protected:
//Signal handlers:
bool on_eventbox_button_press(GdkEventButton* button_event);
//Child widgets:
Gtk::EventBox m_EventBox;
Gtk::Label m_Label;
};
#endif //GTKMM_EXAMPLEWINDOW_H
</pre>
<p>File: <code class="filename">main.cc</code> (For use with gtkmm 3, not gtkmm 2)
</p>
<pre class="programlisting">
#include "examplewindow.h"
#include <gtkmm/application.h>
int main(int argc, char *argv[])
{
auto app = Gtk::Application::create(argc, argv, "org.gtkmm.example");
ExampleWindow window;
//Shows the window and returns when it is closed.
return app->run(window);
}
</pre>
<p>File: <code class="filename">examplewindow.cc</code> (For use with gtkmm 3, not gtkmm 2)
</p>
<pre class="programlisting">
#include "examplewindow.h"
ExampleWindow::ExampleWindow()
: m_Label("Click here to quit, quit, quit, quit, quit")
{
set_title ("EventBox");
set_border_width(10);
add(m_EventBox);
m_EventBox.add(m_Label);
//Clip the label short:
set_default_size(110, 20);
m_Label.set_size_request(110, 20);
m_Label.set_ellipsize(Pango::ELLIPSIZE_END);
//And bind an action to it:
m_EventBox.set_events(Gdk::BUTTON_PRESS_MASK);
m_EventBox.signal_button_press_event().connect(
sigc::mem_fun(*this, &ExampleWindow::on_eventbox_button_press) );
m_EventBox.set_tooltip_text("Click me!");
show_all_children();
}
ExampleWindow::~ExampleWindow()
{
}
bool ExampleWindow::on_eventbox_button_press(GdkEventButton*)
{
hide();
return true;
}
</pre>
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