// test double buffering

#include <stdio.h>
#include <grx20.h>
#include <grxkeys.h>

int main(void) {
  GrContext *buffer_one;
  GrContext *buffer_two;
  int i;

  if (!GrSetMode(GR_default_graphics)) {
    fprintf(stderr, "graphic init failed\n");
    getchar();
    exit(0);
  }
  
  buffer_one = GrScreenContext();
  buffer_two = GrCreateContext(GrSizeX(), GrSizeY(), NULL, NULL);
  if(!buffer_two) {
    fprintf(stderr, "creating second buffer failed\n");
    getchar();
    exit(0);
  }
  
  GrClearScreen(GrWhite());
  
  for ( i = 0; i < 10; ++i) {
    
    GrSetContext(buffer_two);
    GrClearContext(GrBlack());
    
    GrLine(i * 40, 0, 400 - i * 40, 400, GrWhite());
    
    GrBitBlt(buffer_one, 0, 0, buffer_two, 0, 0, GrMaxX(), GrMaxY(), GrWRITE);
    GrSetContext(buffer_one);

    GrKeyRead();
  }

  return 0;
}