Download the project: sliders.zip

Coding a simple GTK+ board game

Tutorial By: Ishan Chattopadhyaya
Example originally written for A Journey through GTK+, a book by Muttiah Annamalai

Introduction

In this small little example program, we'll be creating a small board game, i.e. the 15-puzzle (which was popularised by the great Sam Lloyd). We'll call this game Sliders. This example is based almost entirely upon the GtkTable widget. The rules of the game are simple. There are 15 jumbled up bricks placed in a 4x4 square matrix. One slot is left empty & only bricks that are adjacent to the empty slot can be moved in to the slot (by clicking on the brick). Object is to rearrange the bricks in ascending order with the bottom-most slot as empty. Achieving the objective in lesser no. of moves is more creditable. [Note for puzzle solvers: Due to lack of time, and my laziness of course ;-), checks for 14-15-problem (i.e. 14 & 15 reversed) are not done while randomising the bricks. If you are in modifying the prog. so as to include this, pls. mail me]

Coding the app

The program consists of 5 major sections/functions:

• create_main_window ( .. ): This function, as the function name suggests, creates the interface of the window that'll act as the board. It creates a 4x4 table and places a numbered button in its each of its cells, leaving the last. Each buttons are set (using the gtk_object_get_data function) with a data item "current_pos" which contains the absolute current position of the button. Remember, the buttons are free to move about anywhere as desired by the user, so its important to retain its position in a variable.
• on_button_clicked ( .. ):This is the signal handler attached to the 'clicked' signal of any button of the table. It first calls is_legal_slide () function to acertain whether the button clicked is adjacent to the empty slot or not. It then "slides" the button to the empty square and subsequently a counter, move_no, logging the no. of moves taken, is incremented. Also, the function has_player_won () is called to ensure whether winning position has been reached or not, and if yes, shows a picture smiley.xpm.
• is_legal_slide ( .. ): This function acertains validity of the "slide" by checking whether the button clicked is adjacent to the empty slot or not. It returns TRUE or FALSE.
• has_player_won( .. ): It checks whether the "current_pos" value of the button matches the button's index (i.e. the no. written on the button). Returns TRUE or FALSE.
• on_new_activate ( .. )&swap_buttons ( .. ): When on_new_activate () is called, it randomly de-arranges the bricks by calling swap_buttons () function.

Here's the code listing: [for downloading this proj, click here]

/* Sliders.h */ GtkWidget *main_window, *vbox1; GtkWidget *table1; GtkWidget *buttons[15]; GtkWidget *statusbar1; GtkWidget *alignment1; GtkWidget *image; gint move_no; gint vacant_pos; GtkWidget* create_main_window (void); void swap_buttons (int p, int q); void on_new_activate (GtkMenuItem *menuitem, gpointer user_data); void on_open1_activate (GtkMenuItem *menuitem, gpointer user_data); void on_save1_activate (GtkMenuItem *menuitem, gpointer user_data); void on_save_as1_activate (GtkMenuItem *menuitem, gpointer user_data); void on_quit1_activate (GtkMenuItem *menuitem, gpointer user_data); void on_cut1_activate (GtkMenuItem *menuitem, gpointer user_data); void on_copy1_activate (GtkMenuItem *menuitem, gpointer user_data); void on_paste1_activate (GtkMenuItem *menuitem, gpointer user_data); void on_delete1_activate (GtkMenuItem *menuitem, gpointer user_data); void on_about1_activate (GtkMenuItem *menuitem, gpointer user_data);

/* Sliders.c */ #include <math.h> #include <gtk/gtk.h> #include "sliders.h" int main (int argc, char *argv[]) { gtk_init (&argc, &argv); main_window = create_main_window (); gtk_widget_show_all (main_window); gtk_main (); return 0; } gboolean is_legal_slide (gint current_pos, gint vacant_pos) { int current_x_pos, current_y_pos, vacant_x_pos, vacant_y_pos; int a, b; vacant_x_pos=vacant_pos%4 ; vacant_y_pos=(int)(vacant_pos/4); current_x_pos=current_pos%4 ; current_y_pos=(int)(current_pos/4); a=abs(vacant_x_pos - current_x_pos); b=abs(vacant_y_pos - current_y_pos); if ( ( (a==1 && b==0) || (a==0 && b==1) ) && !(a==1 && b==1) ) // a XOR b return TRUE; else return FALSE; } gboolean has_player_won (void) { int x; for (x=0; x<15; x++) if (x!= (gint) gtk_object_get_data(GTK_OBJECT(buttons[x]),"current_pos")) return FALSE; return TRUE; } void on_button_clicked (GtkWidget *button, gpointer user_data) { int x_pos, y_pos; int current_pos; current_pos = (gint) gtk_object_get_data (GTK_OBJECT(button), "current_pos"); if ( is_legal_slide(current_pos, vacant_pos) ) { x_pos = vacant_pos%4; y_pos = (int)(vacant_pos/4); gtk_container_remove (GTK_CONTAINER(table1), button); gtk_table_attach (GTK_TABLE (table1), button, x_pos, x_pos + 1, y_pos, y_pos + 1, (GtkAttachOptions) (GTK_FILL), (GtkAttachOptions) (0), 0, 0); gtk_object_set_data (GTK_OBJECT(button), "current_pos", (gpointer) vacant_pos); vacant_pos = current_pos; move_no++; if ( has_player_won() ) { gtk_statusbar_push (GTK_STATUSBAR(statusbar1), 0, "Win!"); gtk_widget_hide (table1); image = gtk_image_new (); gtk_image_set_from_file (GTK_IMAGE(image), "smiley.xpm"); gtk_object_ref(GTK_OBJECT(table1)); gtk_container_remove (GTK_CONTAINER(alignment1), table1); gtk_container_add (GTK_CONTAINER(alignment1), image); gtk_widget_show (image); } else gtk_statusbar_push (GTK_STATUSBAR(statusbar1), 0, g_strdup_printf("Move no.: %i", move_no)); } else gtk_statusbar_push (GTK_STATUSBAR(statusbar1), 0, "\aIllegal move!"); } GtkWidget *create_main_window (void) { GtkWidget *main_window, *menubar1,*menuitem1,*menuitem1_menu,*new; GtkWidget *separatormenuitem1,*quit1,*menuitem4; GtkWidget *menuitem4_menu,*about1,*toolbar1; GtkWidget *new_button,*toolbutton5,*toolbutton6; gint tmp_toolbar_icon_size, x, y, c=0; GtkAccelGroup *accel_group = gtk_accel_group_new (); vacant_pos = 15; move_no=0; main_window = gtk_window_new (GTK_WINDOW_TOPLEVEL); gtk_window_set_title (GTK_WINDOW (main_window), "Sliders"); vbox1 = gtk_vbox_new (FALSE, 0); gtk_container_add (GTK_CONTAINER (main_window), vbox1); menubar1 = gtk_menu_bar_new (); menuitem1 = gtk_menu_item_new_with_mnemonic ("_File"); menuitem1_menu = gtk_menu_new (); gtk_menu_item_set_submenu (GTK_MENU_ITEM (menuitem1), menuitem1_menu); new = gtk_image_menu_item_new_from_stock ("gtk-new", accel_group); separatormenuitem1 = gtk_separator_menu_item_new (); gtk_widget_set_sensitive (separatormenuitem1, FALSE); quit1 = gtk_image_menu_item_new_from_stock ("gtk-quit", accel_group); menuitem4 = gtk_menu_item_new_with_mnemonic ("_Help"); menuitem4_menu = gtk_menu_new (); gtk_menu_item_set_submenu (GTK_MENU_ITEM (menuitem4), menuitem4_menu); about1 = gtk_menu_item_new_with_mnemonic ("_About"); gtk_box_pack_start (GTK_BOX (vbox1), menubar1, FALSE, FALSE, 0); gtk_container_add (GTK_CONTAINER (menubar1), menuitem1); gtk_container_add (GTK_CONTAINER (menuitem1_menu), new); gtk_container_add (GTK_CONTAINER (menuitem1_menu), separatormenuitem1); gtk_container_add (GTK_CONTAINER (menuitem1_menu), quit1); gtk_container_add (GTK_CONTAINER (menubar1), menuitem4); gtk_container_add (GTK_CONTAINER (menuitem4_menu), about1); toolbar1 = gtk_toolbar_new (); gtk_box_pack_start (GTK_BOX (vbox1), toolbar1, FALSE, FALSE, 0); gtk_toolbar_set_style (GTK_TOOLBAR (toolbar1), GTK_TOOLBAR_BOTH); tmp_toolbar_icon_size = gtk_toolbar_get_icon_size (GTK_TOOLBAR (toolbar1)); new_button = (GtkWidget*) gtk_tool_button_new_from_stock ("gtk-new"); gtk_container_add (GTK_CONTAINER (toolbar1), new_button); toolbutton5 = (GtkWidget*) gtk_tool_button_new_from_stock ("gtk-open"); gtk_container_add (GTK_CONTAINER (toolbar1), toolbutton5); toolbutton6 = (GtkWidget*) gtk_tool_button_new_from_stock ("gtk-save"); gtk_container_add (GTK_CONTAINER (toolbar1), toolbutton6); alignment1 = gtk_alignment_new (0.5, 0.5, 1, 1); gtk_box_pack_start (GTK_BOX (vbox1), alignment1, TRUE, TRUE, 0); gtk_alignment_set_padding (GTK_ALIGNMENT (alignment1), 20, 20, 40, 40); table1 = gtk_table_new (4, 4, TRUE); gtk_container_add (GTK_CONTAINER (alignment1), table1); for (x=0; x<15; x++) { gchar *temp = g_strdup_printf ("%i", x+1); buttons[x] = gtk_button_new_with_mnemonic (temp); gtk_object_set_data (GTK_OBJECT(buttons[x]), "current_pos", (gpointer) x); g_free (temp); } for (x=0; x<4; x++) for (y=0; y<4; y++) if (!(x==3 && y==3)) gtk_table_attach (GTK_TABLE (table1), buttons[c++], y,y+1,x,x+1, (GtkAttachOptions) (GTK_FILL), (GtkAttachOptions) (0), 0, 0); for (x=0; x<15; x++) gtk_signal_connect(GTK_OBJECT(buttons[x]), "clicked", GTK_SIGNAL_FUNC(on_button_clicked), (gpointer)x); statusbar1 = gtk_statusbar_new (); gtk_statusbar_set_has_resize_grip (GTK_STATUSBAR(statusbar1), FALSE); gtk_statusbar_push (GTK_STATUSBAR(statusbar1), 0, "Welcome to Sliders"); gtk_box_pack_start (GTK_BOX (vbox1), statusbar1, FALSE, FALSE, 0); g_signal_connect ((gpointer) main_window, "delete_event", G_CALLBACK (gtk_main_quit), NULL); g_signal_connect ((gpointer) new, "activate", G_CALLBACK (on_new_activate), NULL); g_signal_connect ((gpointer) new_button, "clicked", G_CALLBACK (on_new_activate), NULL); g_signal_connect ((gpointer) quit1, "activate", G_CALLBACK (gtk_main_quit), NULL); g_signal_connect ((gpointer) about1, "activate", G_CALLBACK (on_about1_activate), NULL); gtk_window_add_accel_group (GTK_WINDOW (main_window), accel_group); return main_window; } void swap_buttons (int p, int q) { gint p_pos = (gint) gtk_object_get_data (GTK_OBJECT(buttons[p]), "current_pos"); gint q_pos = (gint) gtk_object_get_data (GTK_OBJECT(buttons[q]), "current_pos"); int p_x_pos = p_pos%4; int p_y_pos = (int)(p_pos/4); int q_x_pos = q_pos%4; int q_y_pos = (int)(q_pos/4); gtk_object_ref (GTK_OBJECT(buttons[p])); gtk_object_ref (GTK_OBJECT(buttons[q])); gtk_container_remove (GTK_CONTAINER(table1), buttons[p]); gtk_container_remove (GTK_CONTAINER(table1), buttons[q]); gtk_table_attach (GTK_TABLE (table1), buttons[p], q_x_pos, q_x_pos + 1, q_y_pos, q_y_pos + 1, (GtkAttachOptions) (GTK_FILL), (GtkAttachOptions) (0), 0, 0); gtk_table_attach (GTK_TABLE (table1), buttons[q], p_x_pos, p_x_pos + 1, p_y_pos, p_y_pos + 1, (GtkAttachOptions) (GTK_FILL), (GtkAttachOptions) (0), 0, 0); gtk_object_set_data (GTK_OBJECT(buttons[p]), "current_pos", (gpointer) q_pos); gtk_object_set_data (GTK_OBJECT(buttons[q]), "current_pos", (gpointer) p_pos); } void on_new_activate (GtkMenuItem *menuitem, gpointer user_data) { int rand, x; gtk_statusbar_push (GTK_STATUSBAR(statusbar1), 0, "Welcome to sliders"); move_no=0; if (GTK_IS_WIDGET(image) && GTK_IS_WIDGET(image->parent)) { gtk_object_ref (GTK_OBJECT(image)); gtk_container_remove (GTK_CONTAINER(alignment1), image); gtk_container_add (GTK_CONTAINER(alignment1), table1); gtk_widget_show (table1); } for (x=0; x<=14; x++) { rand = abs(g_rand_int ( g_rand_new () )) % 15; if (x!=rand) swap_buttons (x, rand); } } void on_about1_activate (GtkMenuItem *menuitem, gpointer user_data) { GtkWidget *dialog; dialog = gtk_message_dialog_new_with_markup (GTK_WINDOW(main_window), GTK_DIALOG_MODAL, GTK_MESSAGE_INFO, GTK_BUTTONS_OK, "<b>Sliders</b>\n\nExample program by:\nIshan Chattopadhyaya and Muthiah Annamalai\nfor\n<i>A Journey through GTK+</i>"); gtk_dialog_run (GTK_DIALOG (dialog)); gtk_widget_destroy (dialog); }

The save and open features are not implemented. Maybe saving could involve saving the current board position and move no. to an external XML file. Another feature that could be added is a Hall of Fame sort of a scores dialog, whose data could be stored in XML.

Conclusion

This small program can hopefully be helpful for someone out there who's new to GTK+ and is learning. Comments at: ichattopadhyaya@gmail.com