9.11. 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_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:

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 GrЖnlund
 * 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 <gtk/gtk.h>
#include <stdio.h>
#include <string.h>
#include <time.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];
  gchar     *font;
  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
 */

void calendar_date_to_string( CalendarData *data,
			      char         *buffer,
			      gint          buff_len )
{
  struct tm tm;
  time_t time;

  memset (&tm, 0, sizeof (tm));
  gtk_calendar_get_date (GTK_CALENDAR (data->window),
			 &tm.tm_year, &tm.tm_mon, &tm.tm_mday);
  tm.tm_year -= TM_YEAR_BASE;
  time = mktime (&tm);
  strftime (buffer, buff_len-1, "%x", gmtime (&time));
}

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);
}

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);
}

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);
}

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

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

  memset (&tm, 0, sizeof (tm));
  gtk_calendar_get_date (GTK_CALENDAR (data->window),
			 &tm.tm_year, &tm.tm_mon, &tm.tm_mday);
  tm.tm_year -= TM_YEAR_BASE;

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

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);
}

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);
}

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);
}

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);
}


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_display_options (GTK_CALENDAR (calendar->window), options);
}

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);
  
}

void calendar_font_selection_ok( GtkWidget    *button,
                                 CalendarData *calendar )
{
  GtkStyle *style;
  PangoFontDescription *font_desc;

  calendar->font = gtk_font_selection_dialog_get_font_name (
			GTK_FONT_SELECTION_DIALOG (calendar->font_dialog));
  if (calendar->window)
    {
      font_desc = pango_font_description_from_string (calendar->font);
      if (font_desc) 
	{
	  style = gtk_style_copy (gtk_widget_get_style (calendar->window));
	  style->font_desc = font_desc;
	  gtk_widget_set_style (calendar->window, style);
	}
    }
}

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 (G_OBJECT (window), "destroy",
	              G_CALLBACK (gtk_widget_destroyed),
		      &calendar->font_dialog);
    
    g_signal_connect (G_OBJECT (GTK_FONT_SELECTION_DIALOG (window)->ok_button),
		      "clicked", G_CALLBACK (calendar_font_selection_ok),
		      calendar);
    g_signal_connect_swapped (G_OBJECT (GTK_FONT_SELECTION_DIALOG (window)->cancel_button),
			      "clicked",
			      G_CALLBACK (gtk_widget_destroy), 
			      calendar->font_dialog);
  }
  window=calendar->font_dialog;
  if (!GTK_WIDGET_VISIBLE (window))
    gtk_widget_show (window);
  else
    gtk_widget_destroy (window);

}

void create_calendar()
{
  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 = 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 (G_OBJECT (window), "destroy",
		    G_CALLBACK (gtk_main_quit),
		    NULL);
  g_signal_connect (G_OBJECT (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 (G_OBJECT (calendar), "month_changed", 
                    G_CALLBACK (calendar_month_changed),
		    &calendar_data);
  g_signal_connect (G_OBJECT (calendar), "day_selected", 
                    G_CALLBACK (calendar_day_selected),
		    &calendar_data);
  g_signal_connect (G_OBJECT (calendar), "day_selected_double_click", 
                    G_CALLBACK (calendar_day_selected_double_click),
	            &calendar_data);
  g_signal_connect (G_OBJECT (calendar), "prev_month", 
                    G_CALLBACK (calendar_prev_month),
		    &calendar_data);
  g_signal_connect (G_OBJECT (calendar), "next_month", 
                    G_CALLBACK (calendar_next_month),
		    &calendar_data);
  g_signal_connect (G_OBJECT (calendar), "prev_year", 
                    G_CALLBACK (calendar_prev_year),
		    &calendar_data);
  g_signal_connect (G_OBJECT (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 (G_OBJECT (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 (G_OBJECT (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 (G_OBJECT (button), "clicked", 
		    G_CALLBACK (gtk_main_quit), 
		    NULL);
  gtk_container_add (GTK_CONTAINER (bbox), button);
  GTK_WIDGET_SET_FLAGS (button, GTK_CAN_DEFAULT);
  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;
}