> Before I post this in the bugs forum, I would like to check 
> that I'm not doing anything painfully stupid - although I've 
> programmed for a while I am very new to FLTK..

You are creating your Pictar widget on the stack, and there is
insufficient stack space in your runtime environment to support that.

Either increase you stack space (bad) or create the widget on the heap
by "new"ing it (good)...

See attached:

//----------------------------------------------------------------------
#include <fltk/run.h>
#include <fltk/Window.h>
#include <fltk/Widget.h>
#include <fltk/math.h>
#include <fltk/draw.h>

using namespace fltk;


class Pictar : public Widget
{

public:
	Pictar(int x,int y,int w,int h,const char *l=0) :
Widget(x,y,w,h,l) {};

private:
	double img[600][600];
};


int main(int argc, char **argv)
{
	Window *win;
	Pictar *pic;
	 // create a window
	win = new Window (600, 600);
	win->begin();

	 // add a pictar widget that draws stuff
	pic = new Pictar(0, 0, 600, 600);

	 // display the window
	win->end();
	win->show();

	/*
	 *  do some calculations to make an image..
	 */

	 // tadaa!
	return run();
}
//----------------------------------------------------------------------



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