/*
   framebuffer_demo1 ARM9 Code 
   Chris Double (chris.double@double.co.nz)
   http://www.double.co.nz/nintendo_ds
*/

#include <nds.h>

static int old_x = 0;
static int old_y = 0;
static int shape_x = 0;
static int shape_y = 0;
static int shape_width = 10;
static int shape_height = 10;

void draw_shape(int x, int y, uint16* buffer, uint16 color)
{
  buffer += y * SCREEN_WIDTH + x;
  for(int i = 0; i < shape_height; ++i) {
    uint16* line = buffer + (SCREEN_WIDTH * i);
    for(int j = 0; j < shape_width; ++j) {
      *line++ = color;
    }
  }
}

void on_irq() 
{	
  if(REG_IF & IRQ_VBLANK) {
    draw_shape(old_x, old_y, VRAM_A, RGB15(0, 0, 0));
    draw_shape(shape_x, shape_y, VRAM_A, RGB15(31, 0, 0));

    // Tell the DS we handled the VBLANK interrupt
    VBLANK_INTR_WAIT_FLAGS |= IRQ_VBLANK;
    REG_IF |= IRQ_VBLANK;
  }
  else {
    // Ignore all other interrupts
    REG_IF = REG_IF;
  }
}

void InitInterruptHandler()
{
  REG_IME = 0;
  IRQ_HANDLER = on_irq;
  REG_IE = IRQ_VBLANK;
  REG_IF = ~0;
  DISP_SR = DISP_VBLANK_IRQ;
  REG_IME = 1;
}

int main(void)
{
  powerON(POWER_ALL);
  videoSetMode(MODE_FB0);
  vramSetBankA(VRAM_A_LCD);

  // Initialize and enable interrupts
  InitInterruptHandler();

  //  lcdSwap();
  while(1) {
    old_x = shape_x;
    old_y = shape_y;
    shape_x++;
    if(shape_x + shape_width >= SCREEN_WIDTH) {
      shape_x = 0;
      shape_y += shape_height;
      if(shape_y + shape_height >= SCREEN_HEIGHT) {
	shape_y = 0;
      }
    }      
    swiWaitForVBlank();
  }

  return 0;
}