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GTK+ 2.0 Tutorial
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Calendar

The Calendar widget is an effective way to display and retrieve monthly date related information. It is a very simple widget to create and work with.

Creating a GtkCalendar widget is a simple as: 

GtkWidget *gtk_calendar_new( void );

There might be times where you need to change a lot of information within this widget and the following functions allow you to make multiple change to a Calendar widget without the user seeing multiple on-screen updates.

void gtk_calendar_freeze( GtkCalendar *Calendar );

void gtk_calendar_thaw( GtkCalendar *Calendar );

They work just like the freeze/thaw functions of every other widget.

The Calendar widget has a few options that allow you to change the way the widget both looks and operates by using the function

void gtk_calendar_set_display_options( GtkCalendar               *calendar,
                                       GtkCalendarDisplayOptions  flags );

The flags argument can be formed by combining either of the following five options using the logical bitwise OR (|) operation:

GTK_CALENDAR_SHOW_HEADING

this option specifies that the month and year should be shown when drawing the calendar.

GTK_CALENDAR_SHOW_DAY_NAMES

this option specifies that the three letter descriptions should be displayed for each day (eg Mon,Tue, etc.).

GTK_CALENDAR_NO_MONTH_CHANGE

this option states that the user should not and can not change the currently displayed month. This can be good if you only need to display a particular month such as if you are displaying 12 calendar widgets for every month in a particular year.

GTK_CALENDAR_SHOW_WEEK_NUMBERS

this option specifies that the number for each week should be displayed down the left side of the calendar. (eg. Jan 1 = Week 1,Dec 31 = Week 52).

The following functions are used to set the the currently displayed date:

gint gtk_calendar_select_month( GtkCalendar *calendar, 
                                guint        month,
                                guint        year );

void gtk_calendar_select_day( GtkCalendar *calendar,
                              guint        day );

The return value from gtk_calendar_select_month() is a boolean value indicating whether the selection was successful.

With gtk_calendar_select_day() the specified day number is selected within the current month, if that is possible. A day value of 0 will deselect any current selection.

In addition to having a day selected, any number of days in the month may be "marked". A marked day is highlighted within the calendar display. The following functions are provided to manipulate marked days:

gint gtk_calendar_mark_day( GtkCalendar *calendar,
                            guint        day);

gint gtk_calendar_unmark_day( GtkCalendar *calendar,
                              guint        day);

void gtk_calendar_clear_marks( GtkCalendar *calendar);

The currently marked days are stored within an array within the GtkCalendar structure. This array is 31 elements long so to test whether a particular day is currently marked, you need to access the corresponding element of the array (don't forget in C that array elements are numbered 0 to n-1). For example:

    GtkCalendar *calendar;
    calendar = gtk_calendar_new ();

    ...

    /* Is day 7 marked? */
    if (calendar->marked_date[7-1])
       /* day is marked */

Note that marks are persistent across month and year changes.

The final Calendar widget function is used to retrieve the currently selected date, month and/or year.

void gtk_calendar_get_date( GtkCalendar *calendar, 
                            guint       *year,
                            guint       *month,
                            guint       *day );

This function requires you to pass the addresses of guint variables, into which the result will be placed. Passing NULL as a value will result in the corresponding value not being returned.

The Calendar widget can generate a number of signals indicating date selection and change. The names of these signals are self explanatory, and are:

  • month_changed

  • day_selected

  • day_selected_double_click

  • prev_month

  • next_month

  • prev_year

  • next_year

That just leaves us with the need to put all of this together into example code.

/*
 * Copyright (C) 1998 Cesar Miquel, Shawn T. Amundson, Mattias Gr�nlund
 * Copyright (C) 2000 Tony Gale
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

#include <stdio.h>
#include <string.h>
#include <gtk/gtk.h>

#define DEF_PAD 10
#define DEF_PAD_SMALL 5

#define TM_YEAR_BASE 1900

typedef struct _CalendarData {
  GtkWidget *flag_checkboxes[5];
  gboolean  settings[5];
  GtkWidget *font_dialog;
  GtkWidget *window;
  GtkWidget *prev2_sig;
  GtkWidget *prev_sig;
  GtkWidget *last_sig;
  GtkWidget *month;
} CalendarData;

enum {
  calendar_show_header,
  calendar_show_days,
  calendar_month_change, 
  calendar_show_week,
  calendar_monday_first
};

/*
 * GtkCalendar
 */

static void calendar_date_to_string( CalendarData *data,
                                     char         *buffer,
                                     gint          buff_len )
{
  GDate date;
  guint year, month, day;

  gtk_calendar_get_date (GTK_CALENDAR (data->window),
			 &year, &month, &day);
  g_date_set_dmy (&date, day, month + 1, year);
  g_date_strftime (buffer, buff_len - 1, "%x", &date);

}

static void calendar_set_signal_strings( char         *sig_str,
                                         CalendarData *data )
{
  const gchar *prev_sig;

  prev_sig = gtk_label_get_text (GTK_LABEL (data->prev_sig));
  gtk_label_set_text (GTK_LABEL (data->prev2_sig), prev_sig);

  prev_sig = gtk_label_get_text (GTK_LABEL (data->last_sig));
  gtk_label_set_text (GTK_LABEL (data->prev_sig), prev_sig);
  gtk_label_set_text (GTK_LABEL (data->last_sig), sig_str);
}

static void calendar_month_changed( GtkWidget    *widget,
                                    CalendarData *data )
{
  char buffer[256] = "month_changed: ";

  calendar_date_to_string (data, buffer + 15, 256 - 15);
  calendar_set_signal_strings (buffer, data);
}

static void calendar_day_selected( GtkWidget    *widget,
                                   CalendarData *data )
{
  char buffer[256] = "day_selected: ";

  calendar_date_to_string (data, buffer + 14, 256 - 14);
  calendar_set_signal_strings (buffer, data);
}

static void calendar_day_selected_double_click ( GtkWidget    *widget,
                                                 CalendarData *data )
{
  char buffer[256] = "day_selected_double_click: ";
  guint day;

  calendar_date_to_string (data, buffer + 27, 256 - 27);
  calendar_set_signal_strings (buffer, data);

  gtk_calendar_get_date (GTK_CALENDAR (data->window),
			 NULL, NULL, &day);

  if (GTK_CALENDAR (data->window)->marked_date[day-1] == 0) {
    gtk_calendar_mark_day (GTK_CALENDAR (data->window), day);
  } else { 
    gtk_calendar_unmark_day (GTK_CALENDAR (data->window), day);
  }
}

static void calendar_prev_month( GtkWidget    *widget,
                                 CalendarData *data )
{
  char buffer[256] = "prev_month: ";

  calendar_date_to_string (data, buffer + 12, 256 - 12);
  calendar_set_signal_strings (buffer, data);
}

static void calendar_next_month( GtkWidget    *widget,
                                 CalendarData *data )
{
  char buffer[256] = "next_month: ";

  calendar_date_to_string (data, buffer + 12, 256 - 12);
  calendar_set_signal_strings (buffer, data);
}

static void calendar_prev_year( GtkWidget    *widget,
                                CalendarData *data )
{
  char buffer[256] = "prev_year: ";

  calendar_date_to_string (data, buffer + 11, 256 - 11);
  calendar_set_signal_strings (buffer, data);
}

static void calendar_next_year( GtkWidget    *widget,
                                CalendarData *data )
{
  char buffer[256] = "next_year: ";

  calendar_date_to_string (data, buffer + 11, 256 - 11);
  calendar_set_signal_strings (buffer, data);
}


static void calendar_set_flags( CalendarData *calendar )
{
  gint i;
  gint options = 0;
  for (i = 0;i < 5; i++) 
    if (calendar->settings[i])
      {
	options = options + (1 << i);
      }
  if (calendar->window)
    gtk_calendar_set_display_options (GTK_CALENDAR (calendar->window), options);
}

static void calendar_toggle_flag( GtkWidget    *toggle,
                                  CalendarData *calendar)
{
  gint i;
  gint j;
  j = 0;
  for (i = 0; i < 5; i++)
    if (calendar->flag_checkboxes[i] == toggle)
      j = i;

  calendar->settings[j] = !calendar->settings[j];
  calendar_set_flags (calendar);
  
}

static void calendar_font_selection_ok( GtkWidget    *button,
                                        CalendarData *calendar )
{
  GtkRcStyle *style;
  char *font_name;

  if (calendar->window)
    {
      font_name = gtk_font_selection_dialog_get_font_name (GTK_FONT_SELECTION_DIALOG (calendar->font_dialog));
      if (font_name) 
	{
	  style = gtk_rc_style_new ();
	  pango_font_description_free (style->font_desc);
	  style->font_desc = pango_font_description_from_string (font_name);
	  gtk_widget_modify_style (calendar->window, style);
	  g_free (font_name);
	}
    }

  gtk_widget_destroy (calendar->font_dialog);
}

static void calendar_select_font( GtkWidget    *button,
                                  CalendarData *calendar )
{
  GtkWidget *window;

  if (!calendar->font_dialog) {
    window = gtk_font_selection_dialog_new ("Font Selection Dialog");
    g_return_if_fail (GTK_IS_FONT_SELECTION_DIALOG (window));
    calendar->font_dialog = window;
    
    gtk_window_set_position (GTK_WINDOW (window), GTK_WIN_POS_MOUSE);
    
    g_signal_connect (window, "destroy",
		      G_CALLBACK (gtk_widget_destroyed),
		      &calendar->font_dialog);
    
    g_signal_connect (GTK_FONT_SELECTION_DIALOG (window)->ok_button,
		      "clicked", G_CALLBACK (calendar_font_selection_ok),
		      calendar);
    g_signal_connect_swapped (GTK_FONT_SELECTION_DIALOG (window)->cancel_button,
			     "clicked", G_CALLBACK (gtk_widget_destroy), 
			     calendar->font_dialog);
  }
  window = calendar->font_dialog;
  if (!gtk_widget_get_visible (window))
    gtk_widget_show (window);
  else
    gtk_widget_destroy (window);

}

static void create_calendar( void )
{
  GtkWidget *window;
  GtkWidget *vbox, *vbox2, *vbox3;
  GtkWidget *hbox;
  GtkWidget *hbbox;
  GtkWidget *calendar;
  GtkWidget *toggle;
  GtkWidget *button;
  GtkWidget *frame;
  GtkWidget *separator;
  GtkWidget *label;
  GtkWidget *bbox;
  static CalendarData calendar_data;
  gint i;
  
  struct {
    char *label;
  } flags[] =
    {
      { "Show Heading" },
      { "Show Day Names" },
      { "No Month Change" },
      { "Show Week Numbers" },
      { "Week Start Monday" }
    };

  
  calendar_data.window = NULL;
  calendar_data.font_dialog = NULL;

  for (i = 0; i < 5; i++) {
    calendar_data.settings[i] = 0;
  }

  window = gtk_window_new (GTK_WINDOW_TOPLEVEL);
  gtk_window_set_title (GTK_WINDOW (window), "GtkCalendar Example");
  gtk_container_set_border_width (GTK_CONTAINER (window), 5);
  g_signal_connect (window, "destroy",
		    G_CALLBACK (gtk_main_quit),
		    NULL);
  g_signal_connect (window, "delete-event",
		    G_CALLBACK (gtk_false),
		    NULL);
  gtk_window_set_resizable (GTK_WINDOW (window), FALSE);

  vbox = gtk_vbox_new (FALSE, DEF_PAD);
  gtk_container_add (GTK_CONTAINER (window), vbox);

  /*
   * The top part of the window, Calendar, flags and fontsel.
   */

  hbox = gtk_hbox_new (FALSE, DEF_PAD);
  gtk_box_pack_start (GTK_BOX (vbox), hbox, TRUE, TRUE, DEF_PAD);
  hbbox = gtk_hbutton_box_new ();
  gtk_box_pack_start (GTK_BOX (hbox), hbbox, FALSE, FALSE, DEF_PAD);
  gtk_button_box_set_layout (GTK_BUTTON_BOX (hbbox), GTK_BUTTONBOX_SPREAD);
  gtk_box_set_spacing (GTK_BOX (hbbox), 5);

  /* Calendar widget */
  frame = gtk_frame_new ("Calendar");
  gtk_box_pack_start(GTK_BOX (hbbox), frame, FALSE, TRUE, DEF_PAD);
  calendar=gtk_calendar_new ();
  calendar_data.window = calendar;
  calendar_set_flags (&calendar_data);
  gtk_calendar_mark_day (GTK_CALENDAR (calendar), 19);	
  gtk_container_add (GTK_CONTAINER (frame), calendar);
  g_signal_connect (calendar, "month_changed", 
		    G_CALLBACK (calendar_month_changed),
		    &calendar_data);
  g_signal_connect (calendar, "day_selected", 
		    G_CALLBACK (calendar_day_selected),
		    &calendar_data);
  g_signal_connect (calendar, "day_selected_double_click", 
		    G_CALLBACK (calendar_day_selected_double_click),
		    &calendar_data);
  g_signal_connect (calendar, "prev_month", 
		    G_CALLBACK (calendar_prev_month),
		    &calendar_data);
  g_signal_connect (calendar, "next_month", 
		    G_CALLBACK (calendar_next_month),
		    &calendar_data);
  g_signal_connect (calendar, "prev_year", 
		    G_CALLBACK (calendar_prev_year),
		    &calendar_data);
  g_signal_connect (calendar, "next_year", 
		    G_CALLBACK (calendar_next_year),
		    &calendar_data);


  separator = gtk_vseparator_new ();
  gtk_box_pack_start (GTK_BOX (hbox), separator, FALSE, TRUE, 0);

  vbox2 = gtk_vbox_new (FALSE, DEF_PAD);
  gtk_box_pack_start (GTK_BOX (hbox), vbox2, FALSE, FALSE, DEF_PAD);
  
  /* Build the Right frame with the flags in */ 

  frame = gtk_frame_new ("Flags");
  gtk_box_pack_start (GTK_BOX (vbox2), frame, TRUE, TRUE, DEF_PAD);
  vbox3 = gtk_vbox_new (TRUE, DEF_PAD_SMALL);
  gtk_container_add (GTK_CONTAINER (frame), vbox3);

  for (i = 0; i < 5; i++)
    {
      toggle = gtk_check_button_new_with_label (flags[i].label);
      g_signal_connect (toggle,
			"toggled",
			G_CALLBACK (calendar_toggle_flag),
			&calendar_data);
      gtk_box_pack_start (GTK_BOX (vbox3), toggle, TRUE, TRUE, 0);
      calendar_data.flag_checkboxes[i] = toggle;
    }
  /* Build the right font-button */ 
  button = gtk_button_new_with_label ("Font...");
  g_signal_connect (button,
		    "clicked",
		    G_CALLBACK (calendar_select_font),
		    &calendar_data);
  gtk_box_pack_start (GTK_BOX (vbox2), button, FALSE, FALSE, 0);

  /*
   *  Build the Signal-event part.
   */

  frame = gtk_frame_new ("Signal events");
  gtk_box_pack_start (GTK_BOX (vbox), frame, TRUE, TRUE, DEF_PAD);

  vbox2 = gtk_vbox_new (TRUE, DEF_PAD_SMALL);
  gtk_container_add (GTK_CONTAINER (frame), vbox2);
  
  hbox = gtk_hbox_new (FALSE, 3);
  gtk_box_pack_start (GTK_BOX (vbox2), hbox, FALSE, TRUE, 0);
  label = gtk_label_new ("Signal:");
  gtk_box_pack_start (GTK_BOX (hbox), label, FALSE, TRUE, 0);
  calendar_data.last_sig = gtk_label_new ("");
  gtk_box_pack_start (GTK_BOX (hbox), calendar_data.last_sig, FALSE, TRUE, 0);

  hbox = gtk_hbox_new (FALSE, 3);
  gtk_box_pack_start (GTK_BOX (vbox2), hbox, FALSE, TRUE, 0);
  label = gtk_label_new ("Previous signal:");
  gtk_box_pack_start (GTK_BOX (hbox), label, FALSE, TRUE, 0);
  calendar_data.prev_sig = gtk_label_new ("");
  gtk_box_pack_start (GTK_BOX (hbox), calendar_data.prev_sig, FALSE, TRUE, 0);

  hbox = gtk_hbox_new (FALSE, 3);
  gtk_box_pack_start (GTK_BOX (vbox2), hbox, FALSE, TRUE, 0);
  label = gtk_label_new ("Second previous signal:");
  gtk_box_pack_start (GTK_BOX (hbox), label, FALSE, TRUE, 0);
  calendar_data.prev2_sig = gtk_label_new ("");
  gtk_box_pack_start (GTK_BOX (hbox), calendar_data.prev2_sig, FALSE, TRUE, 0);

  bbox = gtk_hbutton_box_new ();
  gtk_box_pack_start (GTK_BOX (vbox), bbox, FALSE, FALSE, 0);
  gtk_button_box_set_layout (GTK_BUTTON_BOX (bbox), GTK_BUTTONBOX_END);

  button = gtk_button_new_with_label ("Close");
  g_signal_connect (button, "clicked", 
		    G_CALLBACK (gtk_main_quit), 
		    NULL);
  gtk_container_add (GTK_CONTAINER (bbox), button);
  gtk_widget_set_can_default (button, TRUE);
  gtk_widget_grab_default (button);

  gtk_widget_show_all (window);
}


int main (int   argc,
          char *argv[])
{
  gtk_init (&argc, &argv);

  create_calendar ();

  gtk_main ();

  return 0;
}
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