By deriving directly from Gtk::Widget you can
do all the drawing for your widget directly, instead of just arranging
child widgets. For instance, a Gtk::Label draws
the text of the label, but does not do this by using other
widgets.
This example implements a widget which draws a Penrose triangle.
File: examplewindow.h
#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:
virtual void on_button_quit();
//Child widgets:
Gtk::VBox m_VBox;
MyWidget m_MyWidget;
Gtk::HButtonBox m_ButtonBox;
Gtk::Button m_Button_Quit;
};
#endif //GTKMM_EXAMPLEWINDOW_H
File: mywidget.h
#ifndef GTKMM_CUSTOM_WIDGET_MYWIDGET_H
#define GTKMM_CUSTOM_WIDGET_MYWIDGET_H
#include <gtkmm/widget.h>
class MyWidget : public Gtk::Widget
{
public:
MyWidget();
virtual ~MyWidget();
protected:
#ifdef GLIBMM_DEFAULT_SIGNAL_HANDLERS_ENABLED
//Overrides:
virtual void on_size_request(Gtk::Requisition* requisition);
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_expose_event(GdkEventExpose* event);
#endif /* GLIBMM_DEFAULT_SIGNAL_HANDLERS_ENABLED */
Glib::RefPtr<Gdk::Window> m_refGdkWindow;
int m_scale;
};
#endif //GTKMM_CUSTOM_WIDGET_MYWIDGET_H
File: main.cc
#include <gtkmm/main.h>
#include "examplewindow.h"
int main(int argc, char *argv[])
{
Gtk::Main kit(argc, argv);
ExampleWindow window;
//Shows the window and returns when it is closed.
Gtk::Main::run(window);
return 0;
}
File: mywidget.cc
#include "mywidget.h"
#include <gdkmm/drawable.h>
#include <gdkmm/general.h> // for cairo helper functions
#include <iostream>
#include <string.h>
//#include <gtk/gtkwidget.h> //For GTK_IS_WIDGET()
MyWidget::MyWidget() :
//The GType name will actually be gtkmm__CustomObject_mywidget
Glib::ObjectBase("mywidget"),
Gtk::Widget(),
m_scale(1000)
{
set_flags(Gtk::NO_WINDOW);
//This shows the GType name, which must be used in the RC file.
std::cout << "GType name: " << G_OBJECT_TYPE_NAME(gobj()) << std::endl;
//This show 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 an RC
//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,
0,
G_PARAM_READABLE) );
gtk_rc_parse("custom_gtkrc");
}
MyWidget::~MyWidget()
{
}
#ifdef GLIBMM_DEFAULT_SIGNAL_HANDLERS_ENABLED
void MyWidget::on_size_request(Gtk::Requisition* requisition)
{
//Initialize the output parameter:
*requisition = Gtk::Requisition();
//Discover the total amount of minimum space needed by this widget.
//Let's make this simple example widget always need 50 by 50:
requisition->height = 50;
requisition->width = 50;
}
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()
{
//Call base class:
Gtk::Widget::on_realize();
ensure_style();
//Get the themed style from the RC file:
get_style_property("example_scale", m_scale);
std::cout << "m_scale (example_scale from the theme/rc-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_window() /* parent */, &attributes,
GDK_WA_X | GDK_WA_Y);
unset_flags(Gtk::NO_WINDOW);
set_window(m_refGdkWindow);
//set colors
modify_bg(Gtk::STATE_NORMAL , Gdk::Color("red"));
modify_fg(Gtk::STATE_NORMAL , Gdk::Color("blue"));
//make the widget receive expose events
m_refGdkWindow->set_user_data(gobj());
}
}
void MyWidget::on_unrealize()
{
m_refGdkWindow.clear();
//Call base class:
Gtk::Widget::on_unrealize();
}
bool MyWidget::on_expose_event(GdkEventExpose* event)
{
if(m_refGdkWindow)
{
double scale_x = (double)get_allocation().get_width() / m_scale;
double scale_y = (double)get_allocation().get_height() / m_scale;
Cairo::RefPtr<Cairo::Context> cr = m_refGdkWindow->create_cairo_context();
if (event)
{
// clip to the area that needs to be re-exposed so we don't draw any
// more than we need to.
cr->rectangle(event->area.x, event->area.y,
event->area.width, event->area.height);
cr->clip();
}
// paint the background
Gdk::Cairo::set_source_color(cr, get_style()->get_bg(Gtk::STATE_NORMAL));
cr->paint();
// draw the foreground
Gdk::Cairo::set_source_color(cr, get_style()->get_fg(Gtk::STATE_NORMAL));
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;
}
#endif /* GLIBMM_DEFAULT_SIGNAL_HANDLERS_ENABLED */
File: examplewindow.cc
#include "examplewindow.h"
ExampleWindow::ExampleWindow()
: 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();
}