<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Custom Widgets</title>
<link rel="stylesheet" type="text/css" href="style.css">
<meta name="generator" content="DocBook XSL Stylesheets V1.78.1">
<link rel="home" href="index.html" title="Programming with gtkmm 3">
<link rel="up" href="chapter-customwidgets.html" title="Chapter 28. Custom Widgets">
<link rel="prev" href="chapter-customwidgets.html" title="Chapter 28. Custom Widgets">
<link rel="next" href="chapter-multi-threaded-programs.html" title="Chapter 29. Multi-threaded programs">
</head>
<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
<div class="navheader">
<table width="100%" summary="Navigation header">
<tr><th colspan="3" align="center">Custom Widgets</th></tr>
<tr>
<td width="20%" align="left">
<a accesskey="p" href="chapter-customwidgets.html"><img src="icons/prev.png" alt="Prev"></a> </td>
<th width="60%" align="center">Chapter 28. Custom Widgets</th>
<td width="20%" align="right"> <a accesskey="n" href="chapter-multi-threaded-programs.html"><img src="icons/next.png" alt="Next"></a>
</td>
</tr>
</table>
<hr>
</div>
<div class="sect1">
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
<a name="sec-custom-widgets"></a>Custom Widgets</h2></div></div></div>
<p>By deriving directly from <code class="classname">Gtk::Widget</code> you can
do all the drawing for your widget directly, instead of just arranging
child widgets. For instance, a <code class="classname">Gtk::Label</code> draws
the text of the label, but does not do this by using other
widgets.</p>
<p>When deriving from <code class="classname">Gtk::Widget</code>, you should
override the following virtual methods. The methods marked (optional)
need not be overridden in all custom widgets. The base class's methods
may be appropriate.
</p>
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem"><p><code class="methodname">get_request_mode_vfunc()</code>: (optional) Return what <code class="literal">Gtk::SizeRequestMode</code> is preferred by the widget.</p></li>
<li class="listitem"><p><code class="methodname">get_preferred_width_vfunc()</code>: Calculate the minimum and natural width of the widget.</p></li>
<li class="listitem"><p><code class="methodname">get_preferred_height_vfunc()</code>: Calculate the minimum and natural height of the widget.</p></li>
<li class="listitem"><p><code class="methodname">get_preferred_width_for_height_vfunc()</code>: Calculate the minimum and natural width of the widget, if it would be given the specified height.</p></li>
<li class="listitem"><p><code class="methodname">get_preferred_height_for_width_vfunc()</code>: Calculate the minimum and natural height of the widget, if it would be given the specified width.</p></li>
<li class="listitem"><p><code class="methodname">on_size_allocate()</code>: Position the widget, given the height and width that it has actually been given.</p></li>
<li class="listitem"><p><code class="methodname">on_realize()</code>: Associate a <code class="classname">Gdk::Window</code> with the widget.</p></li>
<li class="listitem"><p><code class="methodname">on_unrealize()</code>: (optional) Break the association with the <code class="classname">Gdk::Window</code>. </p></li>
<li class="listitem"><p><code class="methodname">on_map()</code>: (optional)</p></li>
<li class="listitem"><p><code class="methodname">on_unmap()</code>: (optional)</p></li>
<li class="listitem"><p><code class="methodname">on_draw()</code>: Draw on the supplied <code class="classname">Cairo::Context</code>.</p></li>
</ul></div>
<p>
</p>
<p>The first 6 methods in the previous table are also overridden in custom
containers. They are briefly described in the
<a class="link" href="chapter-customwidgets.html#sec-custom-containers" title="Custom Containers">Custom Containers</a> section.
</p>
<p>Most custom widgets need their own <code class="classname">Gdk::Window</code>
to draw on. Then you can call
<code class="methodname">Gtk::Widget::set_has_window(true)</code> in your
constructor. (This is the default value.) If you do not call
<code class="methodname">set_has_window(false)</code>, you must override
<code class="methodname">on_realize()</code> and call
<code class="methodname">Gtk::Widget::set_realized()</code> and
<code class="methodname">Gtk::Widget::set_window()</code> from there.</p>
<div class="sect2">
<div class="titlepage"><div><div><h3 class="title">
<a name="custom-widget-example"></a>Example</h3></div></div></div>
<p>This example implements a widget which draws a Penrose triangle.</p>
<div class="figure">
<a name="figure-custom-widget"></a><p class="title"><b>Figure 28.2. Custom Widget</b></p>
<div class="figure-contents"><div class="screenshot"><div><img src="figures/custom_widget.png" alt="Custom Widget"></div></div></div>
</div>
<br class="figure-break"><p><a class="ulink" href="http://git.gnome.org/browse/gtkmm-documentation/tree/examples/book/custom/custom_widget/?h=master" 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>
#include "mywidget.h"
class ExampleWindow : public Gtk::Window
{
public:
ExampleWindow();
virtual ~ExampleWindow();
protected:
//Signal handlers:
void on_button_quit();
//Child widgets:
Gtk::Box m_VBox;
MyWidget m_MyWidget;
Gtk::ButtonBox m_ButtonBox;
Gtk::Button m_Button_Quit;
};
#endif //GTKMM_EXAMPLEWINDOW_H
</pre>
<p>File: <code class="filename">mywidget.h</code> (For use with gtkmm 3, not gtkmm 2)
</p>
<pre class="programlisting">
#ifndef GTKMM_CUSTOM_WIDGET_MYWIDGET_H
#define GTKMM_CUSTOM_WIDGET_MYWIDGET_H
#include <gtkmm/widget.h>
#include <gtkmm/cssprovider.h>
class MyWidget : public Gtk::Widget
{
public:
MyWidget();
virtual ~MyWidget();
protected:
//Overrides:
virtual Gtk::SizeRequestMode get_request_mode_vfunc() const;
virtual void get_preferred_width_vfunc(int& minimum_width, int& natural_width) const;
virtual void get_preferred_height_for_width_vfunc(int width, int& minimum_height, int& natural_height) const;
virtual void get_preferred_height_vfunc(int& minimum_height, int& natural_height) const;
virtual void get_preferred_width_for_height_vfunc(int height, int& minimum_width, int& natural_width) const;
virtual void on_size_allocate(Gtk::Allocation& allocation);
virtual void on_map();
virtual void on_unmap();
virtual void on_realize();
virtual void on_unrealize();
virtual bool on_draw(const Cairo::RefPtr<Cairo::Context>& cr);
Glib::RefPtr<Gdk::Window> m_refGdkWindow;
Glib::RefPtr<Gtk::CssProvider> m_refStyleProvider;
int m_scale;
};
#endif //GTKMM_CUSTOM_WIDGET_MYWIDGET_H
</pre>
<p>File: <code class="filename">mywidget.cc</code> (For use with gtkmm 3, not gtkmm 2)
</p>
<pre class="programlisting">
#include "mywidget.h"
#include <gdkmm/general.h> // for cairo helper functions
#include <iostream>
//#include <gtk/gtkwidget.h> //For GTK_IS_WIDGET()
#include <cstring>
MyWidget::MyWidget() :
//The GType name will actually be gtkmm__CustomObject_mywidget
Glib::ObjectBase("mywidget"),
Gtk::Widget(),
m_scale(1000)
{
set_has_window(true);
//This shows the GType name, which must be used in the CSS file.
std::cout << "GType name: " << G_OBJECT_TYPE_NAME(gobj()) << std::endl;
//This shows that the GType still derives from GtkWidget:
//std::cout << "Gtype is a GtkWidget?:" << GTK_IS_WIDGET(gobj()) << std::endl;
//Install a style so that an aspect of this widget may be themed via a CSS
//style sheet file:
gtk_widget_class_install_style_property(GTK_WIDGET_CLASS(
G_OBJECT_GET_CLASS(gobj())),
g_param_spec_int("example_scale",
"Scale of Example Drawing",
"The scale to use when drawing. This is just a silly example.",
G_MININT,
G_MAXINT,
500,
G_PARAM_READABLE) );
m_refStyleProvider = Gtk::CssProvider::create();
Glib::RefPtr<Gtk::StyleContext> refStyleContext = get_style_context();
refStyleContext->add_provider(m_refStyleProvider,
GTK_STYLE_PROVIDER_PRIORITY_APPLICATION);
try
{
m_refStyleProvider->load_from_path("custom_gtk.css");
}
catch(const Glib::Error& ex)
{
std::cerr << "Gtk::CssProvider::load_from_path() failed: " << ex.what() << std::endl;
}
}
MyWidget::~MyWidget()
{
}
Gtk::SizeRequestMode MyWidget::get_request_mode_vfunc() const
{
//Accept the default value supplied by the base class.
return Gtk::Widget::get_request_mode_vfunc();
}
//Discover the total amount of minimum space and natural space needed by
//this widget.
//Let's make this simple example widget always need minimum 60 by 50 and
//natural 100 by 70.
void MyWidget::get_preferred_width_vfunc(int& minimum_width, int& natural_width) const
{
minimum_width = 60;
natural_width = 100;
}
void MyWidget::get_preferred_height_for_width_vfunc(int /* width */,
int& minimum_height, int& natural_height) const
{
minimum_height = 50;
natural_height = 70;
}
void MyWidget::get_preferred_height_vfunc(int& minimum_height, int& natural_height) const
{
minimum_height = 50;
natural_height = 70;
}
void MyWidget::get_preferred_width_for_height_vfunc(int /* height */,
int& minimum_width, int& natural_width) const
{
minimum_width = 60;
natural_width = 100;
}
void MyWidget::on_size_allocate(Gtk::Allocation& allocation)
{
//Do something with the space that we have actually been given:
//(We will not be given heights or widths less than we have requested, though
//we might get more)
//Use the offered allocation for this container:
set_allocation(allocation);
if(m_refGdkWindow)
{
m_refGdkWindow->move_resize( allocation.get_x(), allocation.get_y(),
allocation.get_width(), allocation.get_height() );
}
}
void MyWidget::on_map()
{
//Call base class:
Gtk::Widget::on_map();
}
void MyWidget::on_unmap()
{
//Call base class:
Gtk::Widget::on_unmap();
}
void MyWidget::on_realize()
{
//Do not call base class Gtk::Widget::on_realize().
//It's intended only for widgets that set_has_window(false).
set_realized();
//Get the themed style from the CSS file:
get_style_property("example_scale", m_scale);
std::cout << "m_scale (example_scale from the theme/css-file) is: "
<< m_scale << std::endl;
if(!m_refGdkWindow)
{
//Create the GdkWindow:
GdkWindowAttr attributes;
memset(&attributes, 0, sizeof(attributes));
Gtk::Allocation allocation = get_allocation();
//Set initial position and size of the Gdk::Window:
attributes.x = allocation.get_x();
attributes.y = allocation.get_y();
attributes.width = allocation.get_width();
attributes.height = allocation.get_height();
attributes.event_mask = get_events () | Gdk::EXPOSURE_MASK;
attributes.window_type = GDK_WINDOW_CHILD;
attributes.wclass = GDK_INPUT_OUTPUT;
m_refGdkWindow = Gdk::Window::create(get_parent_window(), &attributes,
GDK_WA_X | GDK_WA_Y);
set_window(m_refGdkWindow);
//set colors
override_background_color(Gdk::RGBA("red"));
override_color(Gdk::RGBA("blue"));
//make the widget receive expose events
m_refGdkWindow->set_user_data(gobj());
}
}
void MyWidget::on_unrealize()
{
m_refGdkWindow.reset();
//Call base class:
Gtk::Widget::on_unrealize();
}
bool MyWidget::on_draw(const Cairo::RefPtr<Cairo::Context>& cr)
{
const double scale_x = (double)get_allocation().get_width() / m_scale;
const double scale_y = (double)get_allocation().get_height() / m_scale;
// paint the background
Gdk::Cairo::set_source_rgba(cr, get_style_context()->get_background_color());
cr->paint();
// draw the foreground
Gdk::Cairo::set_source_rgba(cr, get_style_context()->get_color());
cr->move_to(155.*scale_x, 165.*scale_y);
cr->line_to(155.*scale_x, 838.*scale_y);
cr->line_to(265.*scale_x, 900.*scale_y);
cr->line_to(849.*scale_x, 564.*scale_y);
cr->line_to(849.*scale_x, 438.*scale_y);
cr->line_to(265.*scale_x, 100.*scale_y);
cr->line_to(155.*scale_x, 165.*scale_y);
cr->move_to(265.*scale_x, 100.*scale_y);
cr->line_to(265.*scale_x, 652.*scale_y);
cr->line_to(526.*scale_x, 502.*scale_y);
cr->move_to(369.*scale_x, 411.*scale_y);
cr->line_to(633.*scale_x, 564.*scale_y);
cr->move_to(369.*scale_x, 286.*scale_y);
cr->line_to(369.*scale_x, 592.*scale_y);
cr->move_to(369.*scale_x, 286.*scale_y);
cr->line_to(849.*scale_x, 564.*scale_y);
cr->move_to(633.*scale_x, 564.*scale_y);
cr->line_to(155.*scale_x, 838.*scale_y);
cr->stroke();
return true;
}
</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_VBox(Gtk::ORIENTATION_VERTICAL),
m_Button_Quit("Quit")
{
set_title("Custom Widget example");
set_border_width(6);
set_default_size(400, 200);
add(m_VBox);
m_VBox.pack_start(m_MyWidget, Gtk::PACK_EXPAND_WIDGET);
m_MyWidget.show();
m_VBox.pack_start(m_ButtonBox, Gtk::PACK_SHRINK);
m_ButtonBox.pack_start(m_Button_Quit, Gtk::PACK_SHRINK);
m_ButtonBox.set_border_width(6);
m_ButtonBox.set_layout(Gtk::BUTTONBOX_END);
m_Button_Quit.signal_clicked().connect( sigc::mem_fun(*this, &ExampleWindow::on_button_quit) );
show_all_children();
}
ExampleWindow::~ExampleWindow()
{
}
void ExampleWindow::on_button_quit()
{
hide();
}
</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[])
{
Glib::RefPtr<Gtk::Application> 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>
</div>
</div>
<div class="navfooter">
<hr>
<table width="100%" summary="Navigation footer">
<tr>
<td width="40%" align="left">
<a accesskey="p" href="chapter-customwidgets.html"><img src="icons/prev.png" alt="Prev"></a> </td>
<td width="20%" align="center"><a accesskey="u" href="chapter-customwidgets.html"><img src="icons/up.png" alt="Up"></a></td>
<td width="40%" align="right"> <a accesskey="n" href="chapter-multi-threaded-programs.html"><img src="icons/next.png" alt="Next"></a>
</td>
</tr>
<tr>
<td width="40%" align="left" valign="top">Chapter 28. Custom Widgets </td>
<td width="20%" align="center"><a accesskey="h" href="index.html"><img src="icons/home.png" alt="Home"></a></td>
<td width="40%" align="right" valign="top"> Chapter 29. Multi-threaded programs</td>
</tr>
</table>
</div>
</body>
</html>
