Using Libraries


This is an excerpt from an article published in QBXL Magazine, with permission by SJ Zero, the author.


FreeBASIC's greatest strength is it's ability to seamlessly integrate with a number of standard C libraries while maintaining the ease of use that is QB. Even before FB had a built-in graphics library, intrepid coders were using SDL to get graphics and sound routines working. Before the current version included a SDL_net and Winsock, a number of coders, myself included, fought with the headers to get network support into FreeBASIC. Today, I'm just going to cover how to get started with three advanced libraries: SDL, fmod, and tinyPTC. After understanding the fundamentals, you'll see that using C libraries is simple enough that with few exceptions, C libraries are no more difficult to use in FreeBASIC than QB libraries were to use.



What are these Libraries, Anyway?

These libraries are particularly useful because they tend to provide functions for games.

SDL is a library with graphics and input support built in, and a bunch of sub-libraries for network, TrueType font support, and audio. It can be used with OpenGL, but I won't be covering that today.

TinyPTC is primarily a graphics library, the simplest one available. It does little more than give you a pointer to the graphics reigon to draw to.

FMod is a 3d sound and music library. Though its license is strange, it works acceptably for playing sounds, and it nicely encapsulates 3D sound.

Including the Library

The first step in getting any of these libraries to work is including their header files in your project.
For SDL, it's simply
 '$INCLUDE: "SDL\SDL.bi"

For FMOD, it's
 '$Include: 'fmod.bi'

and for tinyPTC, you'll want
 '$INCLUDE: 'tinyptc.bi'

'2. Initilizing the library, loading a file'

Obviously, you can't just include the lib and fire away if it's got to do stuff first.
To initilize SDL and load a bitmap into memory, you must:
CONST SCR_WIDTH = 640
CONST SCR_HEIGHT = 480
DIM MenuScreen AS SDL_Surface ptr 'our bitmap
DIM Shared video AS SDL_Surface ptr 'our screen surface

SDL_Init ( SDL_INIT_VIDEO )
video = SDL_SetVideoMode( SCR_WIDTH, SCR_HEIGHT, 32, 0 ) 'sets the video mode for 640x480x32
MenuScreen = SDL_LoadBMP("bitmap.bmp")

To initilize FMOD and load a sound into memory, you must:
DIM sound AS INTEGER 'it's just a handle, so it's an int!

IF FSOUND_GetVersion <= FMOD_VERSION THEN
ErrorQuit "FMOD version " + STR$(FMOD_VERSION) + " or greater required"
End If

If FSOUND_Init(44100, 32, 0) = FALSE Then
ErrorQuit "Can't initialize FMOD"
End If

sound = FSOUND_Sample_Load(FSOUND_FREE,"sound.wav", FSOUND_HW3D, 0, 0)

Finally, there's no data formats to load with tinyPTC because it's so simple, but you initilize it by going:
const SCR_WIDTH = 320
const SCR_HEIGHT = 200
const SCR_SIZE = SCR_WIDTH*SCR_HEIGHT

if( ptc_open( "tinyPTC test", SCR_WIDTH, SCR_HEIGHT ) = 0 ) then
end -1
end if

Blitting, Playing, or Plotting

The most important step, obviously, is to get whatever you want to do to the screen or speakers. This part is relatively easy, and can be encapsulated further into a wrapper function. For SDL, sending an image to the screen means going:

SUB BlitImage(x as integer,y as integer,image as sdl_surface ptr, dest as sdl_surface ptr) 
DIM Rectangle as SDL_Rect 
DIM Rectangle2 as SDL_Rect 


Rectangle.X = 0 
Rectangle.Y = 0 
rectangle.w = image->w 
rectangle.h = image->h 
Rectangle2.x = x 
Rectangle2.y = y 

SDL_BlitSurface image, @rectangle, dest, @rectangle2

END SUB


For FMOD, the steps to play a sound aren't that difficult either:
FUNCTION fModPlayWave( samp1 as integer ) AS INTEGER 
'where samp1 is the number returned by FSOUND_SampleLoad

DIM position(0 to 2)' as FSound_Vector
DIM vel(0 to 2)' FSound_Vector


fModPlayWave = FSOUND_PlaySoundEx(FSOUND_FREE, samp1, NULL, TRUE)

END FUNCTION

And TinyPTC, which is again, not a high level library like the other two, can plot pixels using the following code:
SUB putd(BYREF buffer(), BYVAL x AS INTEGER, BYVAL y AS INTEGER, BYVAL colr as INTEGER)
		buffer((y * SCR_WIDTH) + x) = colr
		ptc_update @buffer(0) 'This is a pageFlip
END SUB



Shutting Down
So you don't have to manage memory and do all the boring mundane tasks, you must remember to shut down the library before your program exits. Luckily, all three programs allow this with one line. If you can't shut it down, the library no longer cares. It's beautiful.

SDL: SDL_Quit ()

fmod: FSOUND_Close ()

tinyPTC: PTC_Close ()

That's all there is to quitting!
As you can see, there is nothing inherently more difficult in using libraries in FreeBASIC compared to QuickBASIC. In fact, because coders don't need to jump through hoops to get to memory, it's actually much easier, even with the more modern OS and hardware.
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