adventskalender-2009/src/draw.c

#include "SDL.h"
#include <math.h>
#include <stdbool.h>
#include "draw.h"
#include "config.h"


void drawPixel(int x, int y, int color) {
  unsigned int *p = (unsigned int*)screen->pixels;

  int lineOffset = y * (screen->pitch/4);
  p[lineOffset+x] = color;
}

int _sign(float a) {
  return a > 0 ? 1 : (a < 0 ? -1 : 0);
}

void drawLine(int x1, int y1, int x2, int y2, int color) {
  float u, s, v, d1x, d1y, d2x, d2y, m, n;
  int x = x1, y = y1;

  u = x2-x1;
  v = y2-y1;

  d1x = d2x = _sign(u);
  d1y = _sign(v);
  d2y = 0;
  m = abs(u);
  n = abs(v);

  if (m <= n) {
    d2x = 0;
    d2y = _sign(v);
    m = abs(v);
    n = abs(u);
  }

  s = (int)(m/2);

  for (int i=0; i<round(m); i++) {
    drawPixel(x, y, color);
    s += n;
    if (s >= m) {
      s -= m;
      x += d1x;
      y += d1y;
    } else {
      x += d2x;
      y += d2y;
    }
  }
}

void drawRect(int x1, int y1, int x2, int y2, int color, bool filled) {
  int tmp;

  if (x1 > x2) { tmp = x1; x2 = x1; x1 = tmp; }
  if (y1 > y2) { tmp = y1; y2 = y1; y1 = tmp; }
  
  if (filled) {
    for (int i=y1; i<=y2; i++) drawLine(x1, i, x2, i, color);
  } else {
    drawLine(x1, y1, x2, y1, color);
    drawLine(x1, y1, x1, y2, color);
    drawLine(x2, y1, x2, y2, color);
    drawLine(x1, y2, x2, y2, color);
  }
}

// TODO: Write some code in here!
void drawCircle(int x, int y, int radius, int color, bool filled) {
}

void drawScreen() {
  Uint32 white = SDL_MapRGB(screen->format, 255, 255, 255);
  drawPixel(SCREEN_WIDTH/2, SCREEN_HEIGHT/2, white);
  for (int i=0; i<250; i+=1)
    drawLine(200, 300-i, 600, 300+i, SDL_MapRGB(screen->format, 0, 0, i));

  drawRect(0, 50, 200, 300, white, true);
  drawRect(600, 300, 799, 550, white, false);

  // Random dots
  for (int i=0; i<100; i++)
    drawPixel(rand()%200+600, rand()%250+300, white);

  drawCircle(SCREEN_WIDTH/2, SCREEN_HEIGHT/2, 100, white, true);
  drawCircle(SCREEN_WIDTH/2, SCREEN_HEIGHT/2, 104, white, false);

  for (int i=0; i<=600; i++) drawLine(0, i, 799, i, white);
}