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Readme.md
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@ -76,3 +76,4 @@ There is a documentation \("[How to build Gtk4 Tutorial](gfm/Readme_for_develope
1. [GtkGridView and activate signal](gfm/sec26.md)
1. [GtkExpression](gfm/sec27.md)
1. [GtkColumnView](gfm/sec28.md)
1. [Periodic Events](gfm/sec29.md)

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Up: [Readme.md](../Readme.md), Prev: [Section 28](sec28.md)
# Periodic Events
## How do we create an animation?
In this section we will build on previous sections, and with the addition of a
function which periodically redraws a GtkDrawingArea, will create an analog
clock application.
The application uses a compiled in 'resource' file, so if the GTK4 libraries and
their dependencies are installed and available, the application will run.
The program also makes use of some mathematical and time handling functions.
The complete code is at the end.
## Drawing the clock face and hands
~~~C
1 static void
2 draw_clock (GtkDrawingArea *area, cairo_t *cr, int width, int height, gpointer user_data) {
3
4 // Scale to unit square and translate (0, 0) to be (0.5, 0.5), i.e.
5 // the center of the window
6 cairo_scale(cr, width, height);
7
8 cairo_translate(cr, 0.5, 0.5);
9 cairo_set_line_width(cr, m_line_width);
10
11 cairo_save(cr);
12 cairo_set_source_rgba(cr, 0.337, 0.612, 0.117, 0.9); // green
13 cairo_paint(cr);
14 cairo_restore(cr);
15 cairo_arc(cr, 0.0, 0.0, m_radius, 0.0, 2.0 * M_PI);
16 cairo_save(cr);
17 cairo_set_source_rgba(cr, 1.0, 1.0, 1.0, 0.8);
18 cairo_fill_preserve(cr);
19 cairo_restore(cr);
20 cairo_stroke_preserve(cr);
21 cairo_clip(cr);
22
23 // Clock ticks
24 for (int i = 0; i < 12; i++)
25 {
26 double inset = 0.05;
27
28 cairo_save(cr);
29 cairo_set_line_cap(cr, CAIRO_LINE_CAP_ROUND);
30
31 if(i % 3 != 0)
32 {
33 inset *= 0.8;
34 cairo_set_line_width(cr, 0.03);
35 }
36
37 cairo_move_to(
38 cr,
39 (m_radius - inset) * cos (i * M_PI / 6.0),
40 (m_radius - inset) * sin (i * M_PI / 6.0));
41 cairo_line_to(
42 cr,
43 m_radius * cos (i * M_PI / 6.0),
44 m_radius * sin (i * M_PI / 6.0));
45 cairo_stroke(cr);
46 cairo_restore(cr); /* stack-pen-size */
47 }
48
49 // store the current time
50 time_t rawtime;
51 time(&rawtime);
52 struct tm * timeinfo = localtime (&rawtime);
53
54 // compute the angles of the indicators of our clock
55 double minutes = timeinfo->tm_min * M_PI / 30.0;
56 double hours = timeinfo->tm_hour * M_PI / 6.0;
57 double seconds = timeinfo->tm_sec * M_PI / 30.0;
58
59 cairo_save(cr);
60 cairo_set_line_cap(cr, CAIRO_LINE_CAP_ROUND);
61
62 // draw the seconds hand
63 cairo_save(cr);
64 cairo_set_line_width(cr, m_line_width / 3.0);
65 cairo_set_source_rgba(cr, 0.7, 0.7, 0.7, 0.8); // gray
66 cairo_move_to(cr, 0.0, 0.0);
67 cairo_line_to(cr,
68 sin(seconds) * (m_radius * 0.9),
69 -cos(seconds) * (m_radius * 0.9));
70 cairo_stroke(cr);
71 cairo_restore(cr);
72
73 // draw the minutes hand
74 cairo_set_source_rgba(cr, 0.117, 0.337, 0.612, 0.9); // blue
75 cairo_move_to(cr, 0, 0);
76 cairo_line_to(cr,
77 sin(minutes + seconds / 60) * (m_radius * 0.8),
78 -cos(minutes + seconds / 60) * (m_radius * 0.8));
79 cairo_stroke(cr);
80
81 // draw the hours hand
82 cairo_set_source_rgba(cr, 0.337, 0.612, 0.117, 0.9); // green
83 cairo_move_to(cr, 0.0, 0.0);
84 cairo_line_to(cr,
85 sin(hours + minutes / 12.0) * (m_radius * 0.5),
86 -cos(hours + minutes / 12.0) * (m_radius * 0.5));
87 cairo_stroke(cr);
88 cairo_restore(cr);
89
90 // draw a little dot in the middle
91 cairo_arc(cr, 0.0, 0.0, m_line_width / 3.0, 0.0, 2.0 * M_PI);
92 cairo_fill(cr);
93 }
~~~
~~~C
1 #include <gtk/gtk.h>
2 #include <math.h>
3 #include <time.h>
4
5 float m_radius = 0.42;
6 float m_line_width = 0.05;
7
8 static void
9 draw_clock (GtkDrawingArea *area, cairo_t *cr, int width, int height, gpointer user_data) {
10
11 // Scale to unit square and translate (0, 0) to be (0.5, 0.5), i.e.
12 // the center of the window
13 cairo_scale(cr, width, height);
14
15 cairo_translate(cr, 0.5, 0.5);
16 cairo_set_line_width(cr, m_line_width);
17
18 cairo_save(cr);
19 cairo_set_source_rgba(cr, 0.337, 0.612, 0.117, 0.9); // green
20 cairo_paint(cr);
21 cairo_restore(cr);
22 cairo_arc(cr, 0.0, 0.0, m_radius, 0.0, 2.0 * M_PI);
23 cairo_save(cr);
24 cairo_set_source_rgba(cr, 1.0, 1.0, 1.0, 0.8);
25 cairo_fill_preserve(cr);
26 cairo_restore(cr);
27 cairo_stroke_preserve(cr);
28 cairo_clip(cr);
29
30 // Clock ticks
31 for (int i = 0; i < 12; i++)
32 {
33 double inset = 0.05;
34
35 cairo_save(cr);
36 cairo_set_line_cap(cr, CAIRO_LINE_CAP_ROUND);
37
38 if(i % 3 != 0)
39 {
40 inset *= 0.8;
41 cairo_set_line_width(cr, 0.03);
42 }
43
44 cairo_move_to(
45 cr,
46 (m_radius - inset) * cos (i * M_PI / 6.0),
47 (m_radius - inset) * sin (i * M_PI / 6.0));
48 cairo_line_to(
49 cr,
50 m_radius * cos (i * M_PI / 6.0),
51 m_radius * sin (i * M_PI / 6.0));
52 cairo_stroke(cr);
53 cairo_restore(cr); /* stack-pen-size */
54 }
55
56 // store the current time
57 time_t rawtime;
58 time(&rawtime);
59 struct tm * timeinfo = localtime (&rawtime);
60
61 // compute the angles of the indicators of our clock
62 double minutes = timeinfo->tm_min * M_PI / 30.0;
63 double hours = timeinfo->tm_hour * M_PI / 6.0;
64 double seconds = timeinfo->tm_sec * M_PI / 30.0;
65
66 cairo_save(cr);
67 cairo_set_line_cap(cr, CAIRO_LINE_CAP_ROUND);
68
69 // draw the seconds hand
70 cairo_save(cr);
71 cairo_set_line_width(cr, m_line_width / 3.0);
72 cairo_set_source_rgba(cr, 0.7, 0.7, 0.7, 0.8); // gray
73 cairo_move_to(cr, 0.0, 0.0);
74 cairo_line_to(cr,
75 sin(seconds) * (m_radius * 0.9),
76 -cos(seconds) * (m_radius * 0.9));
77 cairo_stroke(cr);
78 cairo_restore(cr);
79
80 // draw the minutes hand
81 cairo_set_source_rgba(cr, 0.117, 0.337, 0.612, 0.9); // blue
82 cairo_move_to(cr, 0, 0);
83 cairo_line_to(cr,
84 sin(minutes + seconds / 60) * (m_radius * 0.8),
85 -cos(minutes + seconds / 60) * (m_radius * 0.8));
86 cairo_stroke(cr);
87
88 // draw the hours hand
89 cairo_set_source_rgba(cr, 0.337, 0.612, 0.117, 0.9); // green
90 cairo_move_to(cr, 0.0, 0.0);
91 cairo_line_to(cr,
92 sin(hours + minutes / 12.0) * (m_radius * 0.5),
93 -cos(hours + minutes / 12.0) * (m_radius * 0.5));
94 cairo_stroke(cr);
95 cairo_restore(cr);
96
97 // draw a little dot in the middle
98 cairo_arc(cr, 0.0, 0.0, m_line_width / 3.0, 0.0, 2.0 * M_PI);
99 cairo_fill(cr);
100 }
101
102
103 gboolean time_handler(GtkWidget* widget) {
104 gtk_widget_queue_draw(widget);
105
106 return TRUE;
107 }
108
109
110 static void
111 app_activate (GApplication *app, gpointer user_data) {
112 GtkWidget *win;
113 GtkWidget *clock;
114 GtkBuilder *build;
115
116 build = gtk_builder_new_from_resource ("/com/github/ToshioCP/tfc/tfc.ui");
117 win = GTK_WIDGET (gtk_builder_get_object (build, "win"));
118 gtk_window_set_application (GTK_WINDOW (win), GTK_APPLICATION (app));
119
120 clock = GTK_WIDGET (gtk_builder_get_object (build, "clock"));
121 g_object_unref(build);
122
123 gtk_drawing_area_set_draw_func(GTK_DRAWING_AREA (clock), draw_clock, NULL, NULL);
124 g_timeout_add(1000, (GSourceFunc) time_handler, (gpointer) clock);
125 gtk_widget_show(win);
126
127 }
128
129 static void
130 app_open (GApplication *app, GFile **files, gint n_files, gchar *hint, gpointer user_data) {
131
132 app_activate(app,user_data);
133
134 }
135
136 int
137 main (int argc, char **argv) {
138 GtkApplication *app;
139 int stat;
140
141 app = gtk_application_new ("com.github.ToshioCP.tfc", G_APPLICATION_HANDLES_OPEN);
142 g_signal_connect (app, "activate", G_CALLBACK (app_activate), NULL);
143 g_signal_connect (app, "open", G_CALLBACK (app_open), NULL);
144 stat = g_application_run (G_APPLICATION (app), argc, argv);
145 g_object_unref (app);
146 return stat;
147 }
~~~
`tfc.c`
~~~C
1 #include <gtk/gtk.h>
2 #include <math.h>
3 #include <time.h>
4
5 float m_radius = 0.42;
6 float m_line_width = 0.05;
7
8 static void
9 draw_clock (GtkDrawingArea *area, cairo_t *cr, int width, int height, gpointer user_data) {
10
11 // Scale to unit square and translate (0, 0) to be (0.5, 0.5), i.e.
12 // the center of the window
13 cairo_scale(cr, width, height);
14
15 cairo_translate(cr, 0.5, 0.5);
16 cairo_set_line_width(cr, m_line_width);
17
18 cairo_save(cr);
19 cairo_set_source_rgba(cr, 0.337, 0.612, 0.117, 0.9); // green
20 cairo_paint(cr);
21 cairo_restore(cr);
22 cairo_arc(cr, 0.0, 0.0, m_radius, 0.0, 2.0 * M_PI);
23 cairo_save(cr);
24 cairo_set_source_rgba(cr, 1.0, 1.0, 1.0, 0.8);
25 cairo_fill_preserve(cr);
26 cairo_restore(cr);
27 cairo_stroke_preserve(cr);
28 cairo_clip(cr);
29
30 // Clock ticks
31 for (int i = 0; i < 12; i++)
32 {
33 double inset = 0.05;
34
35 cairo_save(cr);
36 cairo_set_line_cap(cr, CAIRO_LINE_CAP_ROUND);
37
38 if(i % 3 != 0)
39 {
40 inset *= 0.8;
41 cairo_set_line_width(cr, 0.03);
42 }
43
44 cairo_move_to(
45 cr,
46 (m_radius - inset) * cos (i * M_PI / 6.0),
47 (m_radius - inset) * sin (i * M_PI / 6.0));
48 cairo_line_to(
49 cr,
50 m_radius * cos (i * M_PI / 6.0),
51 m_radius * sin (i * M_PI / 6.0));
52 cairo_stroke(cr);
53 cairo_restore(cr); /* stack-pen-size */
54 }
55
56 // store the current time
57 time_t rawtime;
58 time(&rawtime);
59 struct tm * timeinfo = localtime (&rawtime);
60
61 // compute the angles of the indicators of our clock
62 double minutes = timeinfo->tm_min * M_PI / 30.0;
63 double hours = timeinfo->tm_hour * M_PI / 6.0;
64 double seconds = timeinfo->tm_sec * M_PI / 30.0;
65
66 cairo_save(cr);
67 cairo_set_line_cap(cr, CAIRO_LINE_CAP_ROUND);
68
69 // draw the seconds hand
70 cairo_save(cr);
71 cairo_set_line_width(cr, m_line_width / 3.0);
72 cairo_set_source_rgba(cr, 0.7, 0.7, 0.7, 0.8); // gray
73 cairo_move_to(cr, 0.0, 0.0);
74 cairo_line_to(cr,
75 sin(seconds) * (m_radius * 0.9),
76 -cos(seconds) * (m_radius * 0.9));
77 cairo_stroke(cr);
78 cairo_restore(cr);
79
80 // draw the minutes hand
81 cairo_set_source_rgba(cr, 0.117, 0.337, 0.612, 0.9); // blue
82 cairo_move_to(cr, 0, 0);
83 cairo_line_to(cr,
84 sin(minutes + seconds / 60) * (m_radius * 0.8),
85 -cos(minutes + seconds / 60) * (m_radius * 0.8));
86 cairo_stroke(cr);
87
88 // draw the hours hand
89 cairo_set_source_rgba(cr, 0.337, 0.612, 0.117, 0.9); // green
90 cairo_move_to(cr, 0.0, 0.0);
91 cairo_line_to(cr,
92 sin(hours + minutes / 12.0) * (m_radius * 0.5),
93 -cos(hours + minutes / 12.0) * (m_radius * 0.5));
94 cairo_stroke(cr);
95 cairo_restore(cr);
96
97 // draw a little dot in the middle
98 cairo_arc(cr, 0.0, 0.0, m_line_width / 3.0, 0.0, 2.0 * M_PI);
99 cairo_fill(cr);
100 }
101
102
103 gboolean time_handler(GtkWidget* widget) {
104 gtk_widget_queue_draw(widget);
105
106 return TRUE;
107 }
108
109
110 static void
111 app_activate (GApplication *app, gpointer user_data) {
112 GtkWidget *win;
113 GtkWidget *clock;
114 GtkBuilder *build;
115
116 build = gtk_builder_new_from_resource ("/com/github/ToshioCP/tfc/tfc.ui");
117 win = GTK_WIDGET (gtk_builder_get_object (build, "win"));
118 gtk_window_set_application (GTK_WINDOW (win), GTK_APPLICATION (app));
119
120 clock = GTK_WIDGET (gtk_builder_get_object (build, "clock"));
121 g_object_unref(build);
122
123 gtk_drawing_area_set_draw_func(GTK_DRAWING_AREA (clock), draw_clock, NULL, NULL);
124 g_timeout_add(1000, (GSourceFunc) time_handler, (gpointer) clock);
125 gtk_widget_show(win);
126
127 }
128
129 static void
130 app_open (GApplication *app, GFile **files, gint n_files, gchar *hint, gpointer user_data) {
131
132 app_activate(app,user_data);
133
134 }
135
136 int
137 main (int argc, char **argv) {
138 GtkApplication *app;
139 int stat;
140
141 app = gtk_application_new ("com.github.ToshioCP.tfc", G_APPLICATION_HANDLES_OPEN);
142 g_signal_connect (app, "activate", G_CALLBACK (app_activate), NULL);
143 g_signal_connect (app, "open", G_CALLBACK (app_open), NULL);
144 stat = g_application_run (G_APPLICATION (app), argc, argv);
145 g_object_unref (app);
146 return stat;
147 }
~~~
`tfc.ui`
~~~xml
1 <?xml version="1.0" encoding="UTF-8"?>
2 <interface>
3 <object class="GtkApplicationWindow" id="win">
4 <property name="title">Clock</property>
5 <property name="default-width">200</property>
6 <property name="default-height">200</property>
7 <child>
8 <object class="GtkDrawingArea" id="clock">
9 <property name="hexpand">TRUE</property>
10 <property name="vexpand">TRUE</property>
11 </object>
12 </child>
13 </object>
14 </interface>
~~~
~~~xml
1 <?xml version="1.0" encoding="UTF-8"?>
2 <gresources>
3 <gresource prefix="/com/github/ToshioCP/tfc">
4 <file>tfc.ui</file>
5 </gresource>
6 </gresources>
~~~
Up: [Readme.md](../Readme.md), Prev: [Section 28](sec28.md)