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: //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); Glib::RefPtr<Gdk::Window> m_refGdkWindow; Glib::RefPtr<Gdk::GC> m_refGC; }; #endif //GTKMM_CUSTOM_WIDGET_MYWIDGET_H
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(); }
File: main.cc
#include <gtkmm/main.h> #include "examplewindow.h" int main(int argc, char *argv[]) { Gtk::Main kit(argc, argv); ExampleWindow window; Gtk::Main::run(window); //Shows the window and returns when it is closed. return 0; }
File: mywidget.cc
#include "mywidget.h" MyWidget::MyWidget() { set_flags(Gtk::NO_WINDOW); } MyWidget::~MyWidget() { } 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(); 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()); //Allocate a GC for use in on_expose_event(): m_refGC = Gdk::GC::create(m_refGdkWindow); } } void MyWidget::on_unrealize() { m_refGdkWindow.clear(); m_refGC.clear(); //Call base class: Gtk::Widget::on_unrealize(); } bool MyWidget::on_expose_event(GdkEventExpose* /* event */) { if(m_refGdkWindow) { //Draw on the Gdk::Window: m_refGdkWindow->clear(); double scale_x = (double)get_allocation().get_width() /1000; double scale_y = (double)get_allocation().get_height() /1000; m_refGdkWindow->draw_line(m_refGC, (int)(155*scale_x), (int)(165*scale_y), (int)(155*scale_x), (int)(838*scale_y)); m_refGdkWindow->draw_line(m_refGC, (int)(155*scale_x), (int)(838*scale_y), (int)(265*scale_x), (int)(900*scale_y)); m_refGdkWindow->draw_line(m_refGC, (int)(265*scale_x), (int)(900*scale_y), (int)(849*scale_x), (int)(564*scale_y)); m_refGdkWindow->draw_line(m_refGC, (int)(849*scale_x), (int)(564*scale_y), (int)(849*scale_x), (int)(438*scale_y)); m_refGdkWindow->draw_line(m_refGC, (int)(849*scale_x), (int)(438*scale_y), (int)(265*scale_x), (int)(100*scale_y)); m_refGdkWindow->draw_line(m_refGC, (int)(265*scale_x), (int)(100*scale_y), (int)(155*scale_x), (int)(165*scale_y)); m_refGdkWindow->draw_line(m_refGC, (int)(265*scale_x), (int)(100*scale_y), (int)(265*scale_x), (int)(652*scale_y)); m_refGdkWindow->draw_line(m_refGC, (int)(265*scale_x), (int)(652*scale_y), (int)(526*scale_x), (int)(502*scale_y)); m_refGdkWindow->draw_line(m_refGC, (int)(369*scale_x), (int)(411*scale_y), (int)(633*scale_x), (int)(564*scale_y)); m_refGdkWindow->draw_line(m_refGC, (int)(369*scale_x), (int)(286*scale_y), (int)(369*scale_x), (int)(592*scale_y)); m_refGdkWindow->draw_line(m_refGC, (int)(369*scale_x), (int)(286*scale_y), (int)(849*scale_x), (int)(564*scale_y)); m_refGdkWindow->draw_line(m_refGC, (int)(633*scale_x), (int)(564*scale_y), (int)(155*scale_x), (int)(838*scale_y)); } return true; }