Beispielprogramme 12.11.2018

20181112/gtk-1.c

+#include <gtk/gtk.h>
+
+int main (int argc, char **argv)
+{
+  gtk_init (&argc, &argv);
+  GtkWidget *window = gtk_window_new (GTK_WINDOW_TOPLEVEL);
+  gtk_window_set_title (GTK_WINDOW (window), "Hello");
+  gtk_widget_show (window);
+  gtk_main ();
+  return 0;
+}

20181112/gtk-10.c

+#include <gtk/gtk.h>
+
+#define WIDTH 320
+#define HEIGHT 240
+
+double t = 0.0;
+
+double x = 10;
+double y = 200;
+double vx = 20;
+double vy = -60;
+double g = 9.81;
+
+gboolean draw (GtkWidget *widget, cairo_t *c, gpointer data)
+{
+  GdkRGBA blue = { 0.0, 0.5, 1.0, 1.0 };
+
+  gdk_cairo_set_source_rgba (c, &blue);
+  cairo_rectangle (c, x + vx * t, y + vy * t + 0.5 * g * t * t, 10, 10);
+  cairo_fill (c);
+
+  return FALSE;  /* TRUE to stop other handlers from being invoked for the event.
+                    FALSE to propagate the event further. */
+}
+
+gboolean timer (GtkWidget *widget)
+{
+  t += 0.05;
+  gtk_widget_queue_draw_area (widget, 0, 0, WIDTH, HEIGHT);
+  g_timeout_add (50, (GSourceFunc) timer, widget);
+  return FALSE;
+}
+
+int main (int argc, char **argv)
+{
+  gtk_init (&argc, &argv);
+
+  GtkWidget *window = gtk_window_new (GTK_WINDOW_TOPLEVEL);
+  gtk_widget_show (window);
+  gtk_window_set_title (GTK_WINDOW (window), "Hello");
+  g_signal_connect (window, "destroy", G_CALLBACK (gtk_main_quit), NULL);
+
+  GtkWidget *drawing_area = gtk_drawing_area_new ();
+  gtk_widget_show (drawing_area);
+  gtk_container_add (GTK_CONTAINER (window), drawing_area);
+  gtk_widget_set_size_request (drawing_area, WIDTH, HEIGHT);
+  g_signal_connect (drawing_area, "draw", G_CALLBACK (draw), NULL);
+
+  g_timeout_add (50, (GSourceFunc) timer, drawing_area);
+
+  gtk_main ();
+  return 0;
+}

20181112/gtk-11.c

+#include <gtk/gtk.h>
+
+#define WIDTH 320
+#define HEIGHT 240
+
+double t = 0.0;
+double dt = 0.05;
+
+double x = 10;
+double y = 200;
+double vx = 20;
+double vy = -60;
+double g = 9.81;
+
+gboolean draw (GtkWidget *widget, cairo_t *c, gpointer data)
+{
+  GdkRGBA blue = { 0.0, 0.5, 1.0, 1.0 };
+
+  gdk_cairo_set_source_rgba (c, &blue);
+  cairo_rectangle (c, x, y, 10, 10);
+  cairo_fill (c);
+
+  return FALSE;  /* TRUE to stop other handlers from being invoked for the event.
+                    FALSE to propagate the event further. */
+}
+
+gboolean timer (GtkWidget *widget)
+{
+  t += dt;
+  x += vx * dt;
+  y += vy * dt;
+  vy += g * dt;
+  gtk_widget_queue_draw_area (widget, 0, 0, WIDTH, HEIGHT);
+  g_timeout_add (50, (GSourceFunc) timer, widget);
+  return FALSE;
+}
+
+int main (int argc, char **argv)
+{
+  gtk_init (&argc, &argv);
+
+  GtkWidget *window = gtk_window_new (GTK_WINDOW_TOPLEVEL);
+  gtk_widget_show (window);
+  gtk_window_set_title (GTK_WINDOW (window), "Hello");
+  g_signal_connect (window, "destroy", G_CALLBACK (gtk_main_quit), NULL);
+
+  GtkWidget *drawing_area = gtk_drawing_area_new ();
+  gtk_widget_show (drawing_area);
+  gtk_container_add (GTK_CONTAINER (window), drawing_area);
+  gtk_widget_set_size_request (drawing_area, WIDTH, HEIGHT);
+  g_signal_connect (drawing_area, "draw", G_CALLBACK (draw), NULL);
+
+  g_timeout_add (50, (GSourceFunc) timer, drawing_area);
+
+  gtk_main ();
+  return 0;
+}

20181112/gtk-12.c

+#include <gtk/gtk.h>
+
+#define WIDTH 320
+#define HEIGHT 240
+
+double t = 0.0;
+double dt = 0.05;
+
+double x = 10;
+double y = 200;
+double vx = 20;
+double vy = -60;
+double g = 9.81;
+
+gboolean draw (GtkWidget *widget, cairo_t *c, gpointer data)
+{
+  GdkRGBA blue = { 0.0, 0.5, 1.0, 1.0 };
+
+  gdk_cairo_set_source_rgba (c, &blue);
+  cairo_rectangle (c, x, y, 10, 10);
+  cairo_fill (c);
+
+  return FALSE;  /* TRUE to stop other handlers from being invoked for the event.
+                    FALSE to propagate the event further. */
+}
+
+gboolean timer (GtkWidget *widget)
+{
+  t += dt;
+  x += vx * dt;
+  y += vy * dt;
+  vy += g * dt;
+  if (y >= HEIGHT)
+    vy = -vy;
+  if (x >= WIDTH)
+    vx = -vx;
+  if (x <= 0)
+    vx = -vx;
+  gtk_widget_queue_draw_area (widget, 0, 0, WIDTH, HEIGHT);
+  g_timeout_add (50, (GSourceFunc) timer, widget);
+  return FALSE;
+}
+
+int main (int argc, char **argv)
+{
+  gtk_init (&argc, &argv);
+
+  GtkWidget *window = gtk_window_new (GTK_WINDOW_TOPLEVEL);
+  gtk_widget_show (window);
+  gtk_window_set_title (GTK_WINDOW (window), "Hello");
+  g_signal_connect (window, "destroy", G_CALLBACK (gtk_main_quit), NULL);
+
+  GtkWidget *drawing_area = gtk_drawing_area_new ();
+  gtk_widget_show (drawing_area);
+  gtk_container_add (GTK_CONTAINER (window), drawing_area);
+  gtk_widget_set_size_request (drawing_area, WIDTH, HEIGHT);
+  g_signal_connect (drawing_area, "draw", G_CALLBACK (draw), NULL);
+
+  g_timeout_add (50, (GSourceFunc) timer, drawing_area);
+
+  gtk_main ();
+  return 0;
+}

20181112/gtk-13.c

+#include <gtk/gtk.h>
+
+#define WIDTH 320
+#define HEIGHT 240
+
+double t = 0.0;
+double dt = 0.2;
+
+int r = 5;
+
+double x = 10;
+double y = 200;
+double vx = 20;
+double vy = -60;
+double g = 9.81;
+
+gboolean draw (GtkWidget *widget, cairo_t *c, gpointer data)
+{
+  GdkRGBA blue = { 0.0, 0.5, 1.0, 1.0 };
+
+  gdk_cairo_set_source_rgba (c, &blue);
+  cairo_arc (c, x, y, r, 0, 2 * G_PI);
+  cairo_fill (c);
+
+  return FALSE;  /* TRUE to stop other handlers from being invoked for the event.
+                    FALSE to propagate the event further. */
+}
+
+gboolean timer (GtkWidget *widget)
+{
+  t += dt;
+  x += vx * dt;
+  y += vy * dt;
+  vy += g * dt;
+  if (y + r >= HEIGHT)
+    vy = -vy * 0.9;
+  if (x + r >= WIDTH)
+    vx = -vx * 0.9;
+  if (x - r <= 0)
+    vx = -vx * 0.9;
+  gtk_widget_queue_draw_area (widget, 0, 0, WIDTH, HEIGHT);
+  g_timeout_add (50, (GSourceFunc) timer, widget);
+  return FALSE;
+}
+
+int main (int argc, char **argv)
+{
+  gtk_init (&argc, &argv);
+
+  GtkWidget *window = gtk_window_new (GTK_WINDOW_TOPLEVEL);
+  gtk_widget_show (window);
+  gtk_window_set_title (GTK_WINDOW (window), "Hello");
+  g_signal_connect (window, "destroy", G_CALLBACK (gtk_main_quit), NULL);
+
+  GtkWidget *drawing_area = gtk_drawing_area_new ();
+  gtk_widget_show (drawing_area);
+  gtk_container_add (GTK_CONTAINER (window), drawing_area);
+  gtk_widget_set_size_request (drawing_area, WIDTH, HEIGHT);
+  g_signal_connect (drawing_area, "draw", G_CALLBACK (draw), NULL);
+
+  g_timeout_add (50, (GSourceFunc) timer, drawing_area);
+
+  gtk_main ();
+  return 0;
+}

20181112/gtk-3.c

+#include <gtk/gtk.h>
+
+int main (int argc, char **argv)
+{
+  gtk_init (&argc, &argv);
+  GtkWidget *window = gtk_window_new (GTK_WINDOW_TOPLEVEL);
+  gtk_window_set_title (GTK_WINDOW (window), "Hello");
+  g_signal_connect (window, "destroy", G_CALLBACK (gtk_main_quit), NULL);
+  GtkWidget *button = gtk_button_new_with_label ("Quit");
+  g_signal_connect (button, "clicked", G_CALLBACK (gtk_main_quit), NULL);
+  gtk_container_add (GTK_CONTAINER (window), button);
+  gtk_widget_show (button);
+  gtk_widget_show (window);
+  gtk_main ();
+  return 0;
+}

20181112/gtk-4a.c

+#include <gtk/gtk.h>
+
+int main (int argc, char **argv)
+{
+  gtk_init (&argc, &argv);
+
+  GtkWidget *window = gtk_window_new (GTK_WINDOW_TOPLEVEL);
+  gtk_widget_show (window);
+  gtk_window_set_title (GTK_WINDOW (window), "Hello");
+  g_signal_connect (window, "destroy", G_CALLBACK (gtk_main_quit), NULL);
+
+  GtkWidget *drawing_area = gtk_drawing_area_new ();
+  gtk_widget_show (drawing_area);
+  gtk_container_add (GTK_CONTAINER (window), drawing_area);
+
+  gtk_main ();
+  return 0;
+}

20181112/gtk-6.c

+#include <gtk/gtk.h>
+
+#define WIDTH 320
+#define HEIGHT 240
+
+gboolean draw (GtkWidget *widget, cairo_t *c, gpointer data)
+{
+  GdkRGBA red = { 1.0, 0.0, 0.0, 0.8 };
+  GdkRGBA yellow = { 1.0, 1.0, 0.0, 0.6 };
+  GdkRGBA blue = { 0.0, 0.5, 1.0, 0.4 };
+
+  gdk_cairo_set_source_rgba (c, &red);
+  cairo_rectangle (c, 10, 10, 60, 40);
+  cairo_fill (c);
+
+  gdk_cairo_set_source_rgba (c, &yellow);
+  cairo_arc (c, 65, 50, 30, 0, 2 * G_PI);
+  cairo_fill (c);
+
+  gdk_cairo_set_source_rgba (c, &blue);
+  cairo_move_to (c, 10, 70);
+  cairo_line_to (c, 70, 70);
+  cairo_line_to (c, 40, 18);
+  cairo_close_path (c);
+  cairo_fill (c);
+
+  return FALSE;  /* TRUE to stop other handlers from being invoked for the event.
+                    FALSE to propagate the event further. */
+}
+
+int main (int argc, char **argv)
+{
+  gtk_init (&argc, &argv);
+  GtkWidget *window = gtk_window_new (GTK_WINDOW_TOPLEVEL);
+  gtk_window_set_title (GTK_WINDOW (window), "Hello");
+  g_signal_connect (window, "destroy", G_CALLBACK (gtk_main_quit), NULL);
+
+  GtkWidget *vbox = gtk_box_new (GTK_ORIENTATION_VERTICAL, 5);
+  gtk_container_add (GTK_CONTAINER (window), vbox);
+
+  GtkWidget *button = gtk_button_new_with_label ("Quit");
+  g_signal_connect (button, "clicked", G_CALLBACK (gtk_main_quit), NULL);
+  gtk_container_add (GTK_CONTAINER (vbox), button);
+
+  GtkWidget *drawing_area = gtk_drawing_area_new ();
+  gtk_container_add (GTK_CONTAINER (vbox), drawing_area);
+  g_signal_connect (drawing_area, "draw", G_CALLBACK (draw), NULL);
+  gtk_widget_set_size_request (drawing_area, WIDTH, HEIGHT);
+
+  gtk_widget_show (drawing_area);
+  gtk_widget_show (button);
+  gtk_widget_show (vbox);
+  gtk_widget_show (window);
+  gtk_main ();
+  return 0;
+}

20181112/gtk-6a.c

+#include <gtk/gtk.h>
+
+#define WIDTH 320
+#define HEIGHT 240
+
+gboolean draw (GtkWidget *widget, cairo_t *c, gpointer data)
+{
+  GdkRGBA red = { 1.0, 0.0, 0.0, 0.8 };
+  GdkRGBA yellow = { 1.0, 1.0, 0.0, 0.6 };
+  GdkRGBA blue = { 0.0, 0.5, 1.0, 0.4 };
+
+  gdk_cairo_set_source_rgba (c, &red);
+  cairo_rectangle (c, 10, 10, 60, 40);
+  cairo_fill (c);
+
+  gdk_cairo_set_source_rgba (c, &yellow);
+  cairo_arc (c, 65, 50, 30, 0, 2 * G_PI);
+  cairo_fill (c);
+
+  gdk_cairo_set_source_rgba (c, &blue);
+  cairo_move_to (c, 10, 70);
+  cairo_line_to (c, 70, 70);
+  cairo_line_to (c, 40, 18);
+  cairo_close_path (c);
+  cairo_fill (c);
+
+  return FALSE;  /* TRUE to stop other handlers from being invoked for the event.
+                    FALSE to propagate the event further. */
+}
+
+int main (int argc, char **argv)
+{
+  gtk_init (&argc, &argv);
+
+  GtkWidget *window = gtk_window_new (GTK_WINDOW_TOPLEVEL);
+  gtk_widget_show (window);
+  gtk_window_set_title (GTK_WINDOW (window), "Hello");
+  g_signal_connect (window, "destroy", G_CALLBACK (gtk_main_quit), NULL);
+
+  GtkWidget *drawing_area = gtk_drawing_area_new ();
+  gtk_widget_show (drawing_area);
+  gtk_container_add (GTK_CONTAINER (window), drawing_area);
+  gtk_widget_set_size_request (drawing_area, WIDTH, HEIGHT);
+  g_signal_connect (drawing_area, "draw", G_CALLBACK (draw), NULL);
+
+  gtk_main ();
+  return 0;
+}

20181112/gtk-6b.c

+#include <gtk/gtk.h>
+
+#define WIDTH 320
+#define HEIGHT 240
+
+gboolean draw (GtkWidget *widget, cairo_t *c, gpointer data)
+{
+  GdkRGBA red = { 1.0, 0.0, 0.0, 0.8 };
+  GdkRGBA yellow = { 1.0, 1.0, 0.0, 0.6 };
+  GdkRGBA blue = { 0.0, 0.5, 1.0, 0.4 };
+
+  gdk_cairo_set_source_rgba (c, &red);
+  cairo_rectangle (c, 10, 10, 60, 40);
+  cairo_fill (c);
+
+  gdk_cairo_set_source_rgba (c, &yellow);
+  cairo_arc (c, 65, 50, 30, 0, 2 * G_PI);
+  cairo_fill (c);
+
+  gdk_cairo_set_source_rgba (c, &blue);
+  cairo_move_to (c, 10, 70);
+  cairo_line_to (c, 70, 70);
+  cairo_line_to (c, 40, 18);
+  cairo_close_path (c);
+  cairo_fill (c);
+
+  return FALSE;  /* TRUE to stop other handlers from being invoked for the event.
+                    FALSE to propagate the event further. */
+}
+
+int main (int argc, char **argv)
+{
+  gtk_init (&argc, &argv);
+
+  GtkWidget *window = gtk_window_new (GTK_WINDOW_TOPLEVEL);
+  gtk_widget_show (window);
+  gtk_window_set_title (GTK_WINDOW (window), "Hello");
+  g_signal_connect (window, "clicked", G_CALLBACK (gtk_main_quit), NULL);
+
+  GtkWidget *drawing_area = gtk_drawing_area_new ();
+  gtk_widget_show (drawing_area);
+  gtk_container_add (GTK_CONTAINER (window), drawing_area);
+  gtk_widget_set_size_request (drawing_area, WIDTH, HEIGHT);
+  g_signal_connect (drawing_area, "draw", G_CALLBACK (draw), NULL);
+
+  gtk_main ();
+  return 0;
+}

20181112/gtk-6c.c

+#include <gtk/gtk.h>
+
+#define WIDTH 320
+#define HEIGHT 240
+
+gboolean draw (GtkWidget *widget, cairo_t *c, gpointer data)
+{
+  GdkRGBA red = { 1.0, 0.0, 0.0, 0.8 };
+  GdkRGBA yellow = { 1.0, 1.0, 0.0, 0.6 };
+  GdkRGBA blue = { 0.0, 0.5, 1.0, 0.4 };
+
+  gdk_cairo_set_source_rgba (c, &red);
+  cairo_rectangle (c, 10, 10, 60, 40);
+  cairo_fill (c);
+
+  gdk_cairo_set_source_rgba (c, &yellow);
+  cairo_arc (c, 65, 50, 30, 0, 2 * G_PI);
+  cairo_fill (c);
+
+  gdk_cairo_set_source_rgba (c, &blue);
+  cairo_move_to (c, 10, 70);
+  cairo_line_to (c, 70, 70);
+  cairo_line_to (c, 40, 18);
+  cairo_close_path (c);
+  cairo_fill (c);
+
+  return FALSE;  /* TRUE to stop other handlers from being invoked for the event.
+                    FALSE to propagate the event further. */
+}
+
+int main (int argc, char **argv)
+{
+  gtk_init (&argc, &argv);
+
+  GtkWidget *window = gtk_window_new (GTK_WINDOW_TOPLEVEL);
+  gtk_widget_show (window);
+  gtk_window_set_title (GTK_WINDOW (window), "Hello");
+
+  GtkWidget *drawing_area = gtk_drawing_area_new ();
+  gtk_widget_show (drawing_area);
+  gtk_container_add (GTK_CONTAINER (window), drawing_area);
+  gtk_widget_set_size_request (drawing_area, WIDTH, HEIGHT);
+  g_signal_connect (drawing_area, "draw", G_CALLBACK (draw), NULL);
+  g_signal_connect (drawing_area, "clicked", G_CALLBACK (gtk_main_quit), NULL);
+
+  gtk_main ();
+  return 0;
+}

20181112/gtk-6d.c

+#include <stdio.h>
+#include <gtk/gtk.h>
+
+#define WIDTH 320
+#define HEIGHT 240
+
+gboolean draw (GtkWidget *widget, cairo_t *c, gpointer data)
+{
+  GdkRGBA red = { 1.0, 0.0, 0.0, 0.8 };
+  GdkRGBA yellow = { 1.0, 1.0, 0.0, 0.6 };
+  GdkRGBA blue = { 0.0, 0.5, 1.0, 0.4 };
+
+  gdk_cairo_set_source_rgba (c, &red);
+  cairo_rectangle (c, 10, 10, 60, 40);
+  cairo_fill (c);
+
+  gdk_cairo_set_source_rgba (c, &yellow);
+  cairo_arc (c, 65, 50, 30, 0, 2 * G_PI);
+  cairo_fill (c);
+
+  gdk_cairo_set_source_rgba (c, &blue);
+  cairo_move_to (c, 10, 70);
+  cairo_line_to (c, 70, 70);
+  cairo_line_to (c, 40, 18);
+  cairo_close_path (c);
+  cairo_fill (c);
+
+  printf ("draw() wurde aufgerufen.\n");
+
+  return FALSE;  /* TRUE to stop other handlers from being invoked for the event.
+                    FALSE to propagate the event further. */
+}
+
+int main (int argc, char **argv)
+{
+  gtk_init (&argc, &argv);
+
+  GtkWidget *window = gtk_window_new (GTK_WINDOW_TOPLEVEL);
+  gtk_widget_show (window);
+  gtk_window_set_title (GTK_WINDOW (window), "Hello");
+  g_signal_connect (window, "destroy", G_CALLBACK (gtk_main_quit), NULL);
+
+  GtkWidget *drawing_area = gtk_drawing_area_new ();
+  gtk_widget_show (drawing_area);
+  gtk_container_add (GTK_CONTAINER (window), drawing_area);
+  gtk_widget_set_size_request (drawing_area, WIDTH, HEIGHT);
+  g_signal_connect (drawing_area, "draw", G_CALLBACK (draw), NULL);
+
+  gtk_main ();
+  return 0;
+}

20181112/gtk-7.c

+#include <gtk/gtk.h>
+
+#define WIDTH 320
+#define HEIGHT 240
+
+double t = 0.0;
+
+gboolean draw (GtkWidget *widget, cairo_t *c, gpointer data)
+{
+  GdkRGBA red = { 1.0, 0.0, 0.0, 0.8 };
+  GdkRGBA yellow = { 1.0, 1.0, 0.0, 0.6 };
+  GdkRGBA blue = { 0.0, 0.5, 1.0, 0.4 };
+
+  gdk_cairo_set_source_rgba (c, &red);
+  cairo_rectangle (c, 10 + 40 * t, 10 + 30 * t, 60, 40);
+  cairo_fill (c);
+
+  gdk_cairo_set_source_rgba (c, &yellow);
+  cairo_arc (c, 65, 50, 30, 0, 2 * G_PI);
+  cairo_fill (c);
+
+  gdk_cairo_set_source_rgba (c, &blue);
+  cairo_move_to (c, 10, 70);
+  cairo_line_to (c, 70, 70);
+  cairo_line_to (c, 40, 18);
+  cairo_close_path (c);
+  cairo_fill (c);
+
+  return FALSE;  /* TRUE to stop other handlers from being invoked for the event.
+                    FALSE to propagate the event further. */
+}
+
+gboolean timer (GtkWidget *widget)
+{
+  t += 0.05;
+  gtk_widget_queue_draw_area (widget, 0, 0, WIDTH, HEIGHT);
+  g_timeout_add (50, (GSourceFunc) timer, widget);
+  return FALSE;
+}
+
+int main (int argc, char **argv)
+{
+  gtk_init (&argc, &argv);
+  GtkWidget *window = gtk_window_new (GTK_WINDOW_TOPLEVEL);
+  gtk_window_set_title (GTK_WINDOW (window), "Hello");
+  g_signal_connect (window, "destroy", G_CALLBACK (gtk_main_quit), NULL);
+
+  GtkWidget *vbox = gtk_box_new (GTK_ORIENTATION_VERTICAL, 5);
+  gtk_container_add (GTK_CONTAINER (window), vbox);
+
+  GtkWidget *button = gtk_button_new_with_label ("Quit");
+  g_signal_connect (button, "clicked", G_CALLBACK (gtk_main_quit), NULL);
+  gtk_container_add (GTK_CONTAINER (vbox), button);
+
+  GtkWidget *drawing_area = gtk_drawing_area_new ();
+  gtk_container_add (GTK_CONTAINER (vbox), drawing_area);
+  g_signal_connect (drawing_area, "draw", G_CALLBACK (draw), NULL);
+  gtk_widget_set_size_request (drawing_area, WIDTH, HEIGHT);
+
+  g_timeout_add (50, (GSourceFunc) timer, drawing_area);
+
+  gtk_widget_show (drawing_area);
+  gtk_widget_show (button);
+  gtk_widget_show (vbox);
+  gtk_widget_show (window);
+  gtk_main ();
+  return 0;
+}

20181112/gtk-7a.c

+#include <gtk/gtk.h>
+
+#define WIDTH 320
+#define HEIGHT 240
+
+double t = 0.0;
+
+gboolean draw (GtkWidget *widget, cairo_t *c, gpointer data)
+{
+  GdkRGBA red = { 1.0, 0.0, 0.0, 0.8 };
+  GdkRGBA yellow = { 1.0, 1.0, 0.0, 0.6 };
+  GdkRGBA blue = { 0.0, 0.5, 1.0, 0.4 };
+
+  gdk_cairo_set_source_rgba (c, &red);
+  cairo_rectangle (c, 10 + 40 * t, 10 + 30 * t, 60, 40);
+  cairo_fill (c);
+
+  gdk_cairo_set_source_rgba (c, &yellow);
+  cairo_arc (c, 65, 50, 30, 0, 2 * G_PI);
+  cairo_fill (c);
+
+  gdk_cairo_set_source_rgba (c, &blue);
+  cairo_move_to (c, 10, 70);
+  cairo_line_to (c, 70, 70);
+  cairo_line_to (c, 40, 18);
+  cairo_close_path (c);
+  cairo_fill (c);
+
+  return FALSE;  /* TRUE to stop other handlers from being invoked for the event.
+                    FALSE to propagate the event further. */
+}
+
+gboolean timer (GtkWidget *widget)
+{
+  t += 0.05;
+  gtk_widget_queue_draw_area (widget, 0, 0, WIDTH, HEIGHT);
+  g_timeout_add (50, (GSourceFunc) timer, widget);
+  return FALSE;
+}
+
+int main (int argc, char **argv)
+{
+  gtk_init (&argc, &argv);
+
+  GtkWidget *window = gtk_window_new (GTK_WINDOW_TOPLEVEL);
+  gtk_widget_show (window);
+  gtk_window_set_title (GTK_WINDOW (window), "Hello");
+  g_signal_connect (window, "destroy", G_CALLBACK (gtk_main_quit), NULL);
+
+  GtkWidget *drawing_area = gtk_drawing_area_new ();
+  gtk_widget_show (drawing_area);
+  gtk_container_add (GTK_CONTAINER (window), drawing_area);
+  gtk_widget_set_size_request (drawing_area, WIDTH, HEIGHT);
+  g_signal_connect (drawing_area, "draw", G_CALLBACK (draw), NULL);
+
+  g_timeout_add (50, (GSourceFunc) timer, drawing_area);
+
+  gtk_main ();
+  return 0;
+}

20181112/gtk-8.c

+#include <gtk/gtk.h>
+
+#define WIDTH 320
+#define HEIGHT 240
+
+double t = 0.0;
+
+double vx = 40;
+double vy = 30;
+
+gboolean draw (GtkWidget *widget, cairo_t *c, gpointer data)
+{
+  GdkRGBA blue = { 0.0, 0.5, 1.0, 1.0 };
+
+  gdk_cairo_set_source_rgba (c, &blue);
+  cairo_rectangle (c, 10 + vx * t, 10 + vy * t, 10, 10);
+  cairo_fill (c);
+
+  return FALSE;  /* TRUE to stop other handlers from being invoked for the event.
+                    FALSE to propagate the event further. */
+}
+
+gboolean timer (GtkWidget *widget)
+{
+  t += 0.05;
+  gtk_widget_queue_draw_area (widget, 0, 0, WIDTH, HEIGHT);
+  g_timeout_add (50, (GSourceFunc) timer, widget);
+  return FALSE;
+}
+
+int main (int argc, char **argv)
+{
+  gtk_init (&argc, &argv);
+
+  GtkWidget *window = gtk_window_new (GTK_WINDOW_TOPLEVEL);
+  gtk_widget_show (window);
+  gtk_window_set_title (GTK_WINDOW (window), "Hello");
+  g_signal_connect (window, "destroy", G_CALLBACK (gtk_main_quit), NULL);
+
+  GtkWidget *drawing_area = gtk_drawing_area_new ();
+  gtk_widget_show (drawing_area);
+  gtk_container_add (GTK_CONTAINER (window), drawing_area);
+  gtk_widget_set_size_request (drawing_area, WIDTH, HEIGHT);
+  g_signal_connect (drawing_area, "draw", G_CALLBACK (draw), NULL);
+
+  g_timeout_add (50, (GSourceFunc) timer, drawing_area);
+
+  gtk_main ();
+  return 0;
+}

20181112/gtk-9.c

+#include <gtk/gtk.h>
+
+#define WIDTH 320
+#define HEIGHT 240
+
+double t = 0.0;
+
+double x = 10;
+double y = 10;
+double vx = 40;
+double vy = 30;
+double g = 9.81;
+
+gboolean draw (GtkWidget *widget, cairo_t *c, gpointer data)
+{
+  GdkRGBA blue = { 0.0, 0.5, 1.0, 1.0 };
+
+  gdk_cairo_set_source_rgba (c, &blue);
+  cairo_rectangle (c, x + vx * t, y + vy * t - 0.5 * g * t * t, 10, 10);
+  cairo_fill (c);
+
+  return FALSE;  /* TRUE to stop other handlers from being invoked for the event.
+                    FALSE to propagate the event further. */
+}
+
+gboolean timer (GtkWidget *widget)
+{
+  t += 0.05;
+  gtk_widget_queue_draw_area (widget, 0, 0, WIDTH, HEIGHT);
+  g_timeout_add (50, (GSourceFunc) timer, widget);
+  return FALSE;
+}
+
+int main (int argc, char **argv)
+{
+  gtk_init (&argc, &argv);
+
+  GtkWidget *window = gtk_window_new (GTK_WINDOW_TOPLEVEL);
+  gtk_widget_show (window);
+  gtk_window_set_title (GTK_WINDOW (window), "Hello");
+  g_signal_connect (window, "destroy", G_CALLBACK (gtk_main_quit), NULL);
+
+  GtkWidget *drawing_area = gtk_drawing_area_new ();
+  gtk_widget_show (drawing_area);
+  gtk_container_add (GTK_CONTAINER (window), drawing_area);
+  gtk_widget_set_size_request (drawing_area, WIDTH, HEIGHT);
+  g_signal_connect (drawing_area, "draw", G_CALLBACK (draw), NULL);
+
+  g_timeout_add (50, (GSourceFunc) timer, drawing_area);
+
+  gtk_main ();
+  return 0;
+}