Ring/Lessons/Graphics and 2D Games programming using RingAllegro

Graphics and 2D Games programming using RingAllegro

In this chapter we will learn how to use the allegro game programming library in our Ring applications.

We have the file gamelib.ring that load the DLL library that contains wrappers for the Allegro functions

	Load "allegro.rh"
	Loadlib("ring_allegro.dll")

The file gamelib.ring uses the Load instruction to execute the file allegro.rh which is a ring source code file contains constants to be used in our programs. Then using the function LoadLib() we can load the DLL library "ring_allegro.dll".

To write portable code we can change the gamelib.ring to check the platform before loading the DLL/So file.

Drawing, Animation and Input

The next example uses the Allegro library for drawing, moving objects on the screen and getting input from the keyboard and the mouse.

	Load "gamelib.ring"

	al_init()
	al_init_image_addon()

	display = al_create_display(640,480)

	al_show_native_message_box(display, "Hello", "Welcome",
				"Using Allegro from the Ring programming language", 
				"", 0);

	al_clear_to_color(al_map_rgb(0,0,255))

	BOUNCER_SIZE = 40
	bouncer_x = 10
	bouncer_y = 20
	bouncer = al_create_bitmap(BOUNCER_SIZE, BOUNCER_SIZE)
	al_set_target_bitmap(bouncer)
	al_clear_to_color(al_map_rgb(255,0,255))

	for x = 1 to 30
		bouncer_x += x 
		bouncer_y += x
		al_set_target_bitmap(al_get_backbuffer(display))
		al_clear_to_color(al_map_rgb(0,0,0))
		al_draw_bitmap(bouncer, bouncer_x, bouncer_y, 0)
		al_draw_bitmap(bouncer, 200+bouncer_x,200+ bouncer_y, 0)
		al_flip_display()
		al_rest(0.1)
	next

	al_clear_to_color(al_map_rgb(255,255,255))
	image = al_load_bitmap("man2.jpg")
	al_draw_bitmap(image,200,200,0)
	al_flip_display()
	al_rest(2)

	event_queue = al_create_event_queue()
	al_register_event_source(event_queue, al_get_display_event_source(display))

	ev = al_new_allegro_event()
	timeout = al_new_allegro_timeout()
	al_init_timeout(timeout, 0.06)

	FPS = 60
	timer = al_create_timer(1.0 / FPS)
	al_register_event_source(event_queue, al_get_timer_event_source(timer))
	al_start_timer(timer)
	redraw = true

	SCREEN_W = 640
	SCREEN_H = 480
	BOUNCER_SIZE = 32
	bouncer_x = SCREEN_W / 2.0 - BOUNCER_SIZE / 2.0
	bouncer_y = SCREEN_H / 2.0 - BOUNCER_SIZE / 2.0
	bouncer_dx = -4.0
	bouncer_dy = 4.0

	al_install_mouse()
	al_register_event_source(event_queue, al_get_mouse_event_source())

	al_install_keyboard()
	al_register_event_source(event_queue, al_get_keyboard_event_source())

	KEY_UP = 1
	KEY_DOWN = 2
	KEY_LEFT = 3
	KEY_RIGHT = 4
	Key = [false,false,false,false]

	while true
		al_wait_for_event_until(event_queue, ev, timeout)
		switch al_get_allegro_event_type(ev)
		on ALLEGRO_EVENT_DISPLAY_CLOSE
			exit
		on ALLEGRO_EVENT_TIMER
			
			# Animation
			if bouncer_x < 0 or bouncer_x > SCREEN_W - BOUNCER_SIZE
				bouncer_dx = -bouncer_dx
			ok
	 
			if bouncer_y < 0 or bouncer_y > SCREEN_H - BOUNCER_SIZE
				bouncer_dy = -bouncer_dy
			ok
	 
			bouncer_x += bouncer_dx
			bouncer_y += bouncer_dy
			
			# Keyboard
			if key[KEY_UP] and bouncer_y >= 4.0
				bouncer_y -= 4.0
			ok 
			if key[KEY_DOWN] and bouncer_y <= SCREEN_H - BOUNCER_SIZE - 4.0
				bouncer_y += 4.0
			ok 
			if key[KEY_LEFT] and bouncer_x >= 4.0
				bouncer_x -= 4.0
			ok 
			if key[KEY_RIGHT] and bouncer_x <= SCREEN_W - BOUNCER_SIZE - 4.0
				bouncer_x += 4.0
			ok
	 
			redraw = true
			
		on ALLEGRO_EVENT_MOUSE_AXES
			bouncer_x = al_get_allegro_event_mouse_x(ev)
			bouncer_y = al_get_allegro_event_mouse_y(ev)
		on ALLEGRO_EVENT_MOUSE_ENTER_DISPLAY
			bouncer_x = al_get_allegro_event_mouse_x(ev)
			bouncer_y = al_get_allegro_event_mouse_y(ev)
		on ALLEGRO_EVENT_MOUSE_BUTTON_UP
			exit
		on ALLEGRO_EVENT_KEY_DOWN
			switch al_get_allegro_event_keyboard_keycode(ev)
				on ALLEGRO_KEY_UP
					key[KEY_UP] = true
				on ALLEGRO_KEY_DOWN
					key[KEY_DOWN] = true
				on ALLEGRO_KEY_LEFT
					key[KEY_LEFT] = true
				on ALLEGRO_KEY_RIGHT
					key[KEY_RIGHT] = true
			off
		on ALLEGRO_EVENT_KEY_UP
			switch al_get_allegro_event_keyboard_keycode(ev)
				on ALLEGRO_KEY_UP
					key[KEY_UP] = false
				on ALLEGRO_KEY_DOWN
					key[KEY_DOWN] = false
				on ALLEGRO_KEY_LEFT
					key[KEY_LEFT] = false
				on ALLEGRO_KEY_RIGHT
					key[KEY_RIGHT] = false
				on ALLEGRO_KEY_ESCAPE
					exit
			off
		off
		if redraw and al_is_event_queue_empty(event_queue)
			redraw = false		
			al_clear_to_color(al_map_rgb(0,0,0))
			al_draw_bitmap(bouncer, bouncer_x, bouncer_y, 0)
			al_flip_display()
		ok
		callgc()
	end

	al_destroy_timer(timer)
	al_destroy_allegro_event(ev)
	al_destroy_allegro_timeout(timeout)
	al_destroy_event_queue(event_queue)
	al_destroy_bitmap(bouncer)
	al_destroy_bitmap(image)
	al_destroy_display(display)

.. note:: In the previous example we used the function callgc() which is a Ring function to force calling the Garbage collector inside the While/End loop.

Program Output:

At first the program display a messagebox

Then we see two rectangles are moving on the screen

Then we see an image displayed on the screen

Finally we have one rectangle, and we see it moving all of the time on the screen but we can control it using the Mouse and/or the Keyborad

Using TrueType Fonts

In this example we will see how to use TrueType Fonts *.ttf in our Games using Allegro

	Load "gamelib.ring"

	al_init()
	al_init_font_addon()
	al_init_ttf_addon()

	display = al_create_display(800,600)

	al_clear_to_color(al_map_rgb(0,0,255))
	font = al_load_ttf_font("pirulen.ttf",14,0 )
	al_draw_text(font, al_map_rgb(255,255,255), 10, 10,ALLEGRO_ALIGN_LEFT,
		 "Welcome to the Ring programming language")
	al_flip_display()
	al_rest(2)

	al_destroy_display(display)

Screen Shot:

Playing Sound Files

The next example play a sound file

	Load "gamelib.ring"

	al_init()
	al_install_audio()
	al_init_acodec_addon()
	al_reserve_samples(1) 

	sample = al_load_sample( "footstep.wav" )

	sampleid = al_new_allegro_sample_id()
	al_play_sample(sample, 1.0, 0.0,1.0,ALLEGRO_PLAYMODE_LOOP,sampleid)

	display = al_create_display(640,480)
	al_clear_to_color(al_map_rgb(0,0,255))
	al_flip_display()
	al_rest(10)

	al_destroy_allegro_sample_id(sampleid)
	al_destroy_sample(sample)
	al_destroy_display(display)

	al_exit()

Scaling and Rotating Images

The next example display and rotate an image

	Load "gamelib.ring"

	al_init()
	al_init_image_addon()

	display = al_create_display(640,480)
	al_set_target_bitmap(al_get_backbuffer(display))
	al_clear_to_color(al_map_rgb(255,255,255))

	image = al_load_bitmap("man2.jpg")
	al_draw_rotated_bitmap(image,0,0,250,250,150,0)
	al_draw_scaled_bitmap(image,0,0,250,250,20,20,400,400,0)

	al_flip_display()
	al_rest(2)

	al_destroy_bitmap(image)
	al_destroy_display(display)

Screen Shot:

Display Transparent Image

The next example display image with white background on another image

	Load "gamelib.ring"

	al_init()
	al_init_image_addon()

	display = al_create_display(640,480)	
	imageback = al_load_bitmap("palace.jpg")
	al_draw_bitmap(imageback,0,0,0)

	image = al_load_bitmap("man4.png")
	al_convert_mask_to_alpha(image,al_map_rgb(255,255,255))
	al_draw_bitmap(image,0,0,0)
	al_flip_display()
	al_rest(10)

	al_destroy_bitmap(image)
	al_destroy_display(display)

Screen Shot:

Using Threads

In this example we will learn how to users threads from the Allegro library

	Load "gamelib.ring"

	o1 = new mythreads 

	Func Main
		al_init()
		for k = 1 to 5
			al_create_thread("o1.thread1()")
			al_create_thread("o1.thread2()")
			al_create_thread("o1.thread3()")
		next
		al_rest(2)

	Class Mythreads

		cAppName = "Threads Application"

		Func Thread1
			for x = 1 to 5
				see x + nl	
			next
			See 'Thread(1) : Application Name : '  + cAppName + nl

		Func Thread2
			for x = 1 to 5
				see '*****' + x + nl	
			next
			See 'Thread(2) : Application Name : '  + cAppName + nl

		Func Thread3
			for x = 1 to 5
				see '!!!!' + x + nl	
			next
			See 'Thread(3) : Application Name : '  + cAppName + nl

Output:

	1
	2
	3
	4
	5
	Thread(1) : Application Name : Threads Application
	*****1
	*****2
	*****3
	*****4
	*****5
	Thread(2) : Application Name : Threads Application
	!!!!1
	!!!!2
	!!!!3
	!!!!4
	!!!!5
	Thread(3) : Application Name : Threads Application
	1
	2
	3
	4
	5
	Thread(1) : Application Name : Threads Application
	!!!!1
	!!!!2
	!!!!3
	!!!!4
	!!!!5
	Thread(3) : Application Name : Threads Application
	*****1
	*****2
	*****3
	*****4
	*****5
	Thread(2) : Application Name : Threads Application
	*****1
	*****2
	*****3
	*****4
	*****5
	Thread(2) : Application Name : Threads Application
	!!!!1
	!!!!2
	!!!!3
	!!!!4
	!!!!5
	Thread(3) : Application Name : Threads Application
	1
	2
	3
	4
	5
	Thread(1) : Application Name : Threads Application
	*****1
	*****2
	*****3
	*****1
	*****4
	*****2
	!!!!1
	*****5
	*****3
	1
	!!!!2
	Thread(2) : Application Name : Threads Application
	1
	*****4
	!!!!1
	2
	!!!!3
	!!!!4
	*****5
	!!!!2
	3
	2
	!!!!5
	Thread(2) : Application Name : Threads Application
	!!!!3
	4
	3
	Thread(3) : Application Name : Threads Application
	!!!!4
	5
	4
	!!!!5
	Thread(1) : Application Name : Threads Application
	5
	Thread(3) : Application Name : Threads Application
	Thread(1) : Application Name : Threads Application