convert an array of NSValues / CGPoints to a CGPoint struct for use with glDrawArrays in cocos2d

Question

Hi there,

I'm pretty new to Objective-C and even C in general here, so please bear with me. My main goal is to display my NSMutableArray of CGPoints (via NSValue) with glDrawArrays(GL_LINE_STRIP, 0, points);

I noticed that cocos2d requires an array(?) pointer *poli like so:

void ccDrawPoly( CGPoint *poli, int points, BOOL closePolygon ) { ... }

So I tried to convert my NSMutableArray to a C array and I can access/debug the CGPoints just fine:

NSUInteger count = [points count];
id *buffer = malloc(sizeof(NSValue) * count);
[points getObjects: buffer];
for(uint i = 0; i < count; i++) {
  NSValue *val = buffer[i];
  CGPoint p = [val CGPointValue];
  NSLog(@"points x %i: %f", i, p.x);
  /* shows up in the console as:
  -----------points at 0: 42.000000
  -----------points at 1: 44.000000
  ... etc
  */
}
free(buffer);

But I guess where I'm stuck is getting them into a data type that either ccDrawPoly or glDrawArrays(GL_LINE_STRIP, 0, points) will accept. Which is apparently a struct or something, but I'm not sure how to get them into a struct.

Any help would be greatly appreciated! Thanks!

Answer 1

Here's the new code I'm using in case it helps someone else:

@interface Blah : CCLayer
{
  CGPoint *parr;
  NSUInteger parr_count;
  NSUInteger parr_max;
}
@end

@implementation Blah

-(id) init
{
  if((self = [super init])) {
    parr_count = 0;
    parr_max = 64;
    parr = malloc(parr_max * 2 * sizeof(CGPoint));
  }
  return self;
}

...

-(void) ccTouchMoved:(UITouch *)touch withEvent:(UIEvent *)event
{
  CGPoint prev_loc = [touch previousLocationInView: [touch view]];
  CGPoint prev_glloc = [[CCDirector sharedDirector] convertToGL:prev_loc];

  CGPoint loc = [touch locationInView: [touch view]];
  CGPoint glloc = [[CCDirector sharedDirector] convertToGL:loc];

  if(parr_count >= 2048) { // hard limit of 2048
    return;
  } else if(parr_count == parr_max) {
    parr_max = 2 * parr_max;
    parr = realloc(parr, parr_max * 2 * sizeof(GLfloat));
  }

  parr[parr_count] = prev_glloc;
  parr_count += 1;
  parr[parr_count] = glloc;
  parr_count += 1;
}

...

-(void) draw
{
  if(parr_count < 2048)
    ccDrawPoly(parr, parr_count, NO);
}

- (void) dealloc
{
  free(parr);
  [super dealloc];
}

@end

It seems to work fine! If anyone has any optimizations or comments I'd be grateful, thanks.