🔒 Locked

SDL_Surface into script

Started by Gibbon_99 Dec 18, 2005 at 10:37 PM 2 replies 1.6k views

Original Post

Dec 18, 2005 at 10:37 PM

Hi I've got AngelScript up and working; and am happily passing global variables and functions for the scripts to access. I'm starting SDL from within my script - and have passed in SDL_Init - no problems, it runs. But to setup a screen in SDL, you call a function that returns a 'SDL_Surface'. I have declared this in my C code - SDL_Surface *mainScreen. How do I pass this into my script so it can pass on the pointer from the SDL_CreateSurface function. At the moment I have:


      result = scriptEngine->RegisterObjectType("SDL_Surface", sizeof(SDL_Surface), asOBJ_CLASS);
      if (result < 0)
      {
              conPrint(GL_TRUE, "Script: Error: Couldn't register object type");
              return false;
      }

and then later I pass 'mainScreen' as a global variable. But I get a seg fault when calling 'RegisterObjectType' - how do I go about passing in this structure? Thanks

Deyja

Dec 19, 2005 at 5:01 AM

Since you work with pointers to SDL_Surface when doing SDL normally, it would be best to not register it as a full fledged type. If you register it with a size of zero, and give it proper addref/release behaviors, you could use handles. Or you can register a smartpointer type.

Eitherway, you're going to have to register more than just the type. It won't work right without the proper behaviors.

WitchLord

Dec 19, 2005 at 9:57 AM

Instead of allowing the scripts handle the SDL_Surface pointer directly, you may want to wrap it in a slightly safer type, e.g:

class ScriptSDLSurface{public:  ScriptSDLSurface() { refCount = 1; surface = ... }  ~ScriptSDLSurface() { if( surface ) ... }  void Addref() {refCount++;}  void Release() {if(--refCount == 0) delete this;}    SDL_Surface *surface;  int refCount;};

Using this the scripts won't have to worry about freeing surfaces as they will be released when no longer referenced by any variable. Of course it would require extra work on your part, as you would have to write wrapper functions where the SDL_Surface pointer is used.

Or if you prefer a lighter type, but that requires manual management, you could represent the SDL_Surface * with an integer type, or perhaps a registered type that has the size of a pointer. In this case there would not be any need for wrapper functions.

Gibbon_99

Dec 19, 2005 at 3:37 PM

Thanks - I ended up doing it a different way. After a bit more thought - the scripts never really need to touch the allocated SDL_Surface. So, the script just calls a host application function that manages the SDL_Surface, and returns a value telling the script the result.

My next challenge is how to expose an array of structs to the scripts.

struct{   char levelName[];   int enemysAlive;   int *tiles;} _level;_level alllevels[NUM_LEVELS];

So that I can write the level loading code in AngelScript.

cheers

Topic Locked

This topic has been locked by a moderator. New replies are not allowed.