//  ================================================================
//
//    graphics.c
//
//  ----------------------------------------------------------------
//
//    (C) 2025 Mitya Selivanov <guattari.tech>
//
//  ================================================================

#ifndef GRAPHICS_HEADER_GUARD_
#define GRAPHICS_HEADER_GUARD_

#ifdef GRAPHICS_HEADER
#define REDUCED_SYSTEM_LAYER_HEADER
#endif

#include "reduced_system_layer.c"

//  ================================================================

#ifndef EPSILON
#define EPSILON (1e-9)
#endif

typedef struct {
  i64       width;
  i64       height;
  vec4_f32 *pixels;
} Pixel_Buffer;

typedef struct {
  Pixel_Buffer buffer;
  vec2         position;
  vec2         scale;
  b8           quick     : 1;
  b8           alpha     : 1;
  b8           xor_color : 1;
  vec4_f32     color;
} Brush;

vec3_f32 gamma_apply (vec3_f32 rgb);
vec3_f32 gamma_revert(vec3_f32 rgb);
vec3_f32 lab_from_rgb(vec3_f32 rgb);
vec3_f32 rgb_from_lab(vec3_f32 lab);
vec3_f32 lab_from_lch(vec3_f32 lch);
vec3_f32 lch_from_lab(vec3_f32 lab);
vec3_f32 rgb_from_lch(vec3_f32 lch);
vec3_f32 lch_from_rgb(vec3_f32 rgb);

vec4_f32 with_alpha(vec3_f32 color, f32 alpha);
vec3_f32 without_alpha(vec4_f32 color);

u32      rgb_u32_from_f32(vec3_f32 color);
vec3_f32 rgb_f32_from_u32(u32 color);
u32      rgba_u32_from_f32(vec4_f32 color);
vec4_f32 rgba_f32_from_u32(u32 color);

#define RGB(...)  ((Brush) { .color = { __VA_ARGS__, 1.f } })
#define RGBA(...) ((Brush) { .color = { __VA_ARGS__ } })
#define LCH(...)  ((Brush) { .color = with_alpha(gamma_apply(rgb_from_lch((vec3_f32) { __VA_ARGS__ })), 1.f) } })
#define LCHA(...) ((Brush) { .color = with_alpha(gamma_apply(rgb_from_lch(without_alpha((vec4_f32) { __VA_ARGS__ }))), ((vec4_f32) { __VA_ARGS__ }).w) } })

b8 rectangle_contains(f64 x0, f64 y0, f64 width, f64 height,          f64 px, f64 py);
b8 triangle_contains (f64 x0, f64 y0, f64 x1, f64 y1, f64 x2, f64 y2, f64 px, f64 py);
b8 ellipse_contains  (f64 x0, f64 y0, f64 width, f64 height,          f64 px, f64 py);
b8 line_contains     (f64 x0, f64 y0, f64 x1, f64 y1, f64 width,      f64 px, f64 py);

void put_pixel            (Brush brush, i64 x, i64 y);
void draw_pixels          (Brush brush, f64 x, f64 y, f64 width, f64 height, Pixel_Buffer src);
void fill_rectangle       (Brush brush, f64 x, f64 y, f64 width, f64 height);
void fill_triangle        (Brush brush, f64 x0, f64 y0, f64 x1, f64 y1, f64 x2, f64 y2);
void fill_ellipse         (Brush brush, f64 x, f64 y, f64 width, f64 height);
void fill_line            (Brush brush, f64 x0, f64 y0, f64 x1, f64 y1, f64 width);
void draw_text_area       (Brush brush, f64 x, f64 y, f64 width, f64 height, f64 max_scale_x, f64 max_scale_y, i64 num_chars, c32 *text);
void draw_selection_cursor(Brush brush, f64 x, f64 y, f64 width, f64 height, f64 max_scale_x, f64 max_scale_y, i64 cursor, i64 selection, i64 num_chars, c32 *text);

#endif // GRAPHICS_HEADER_GUARD_

//  ================================================================

#ifndef GRAPHICS_HEADER
#ifndef GRAPHICS_IMPL_GUARD_
#define GRAPHICS_IMPL_GUARD_

static f64 min3_(f64 a, f64 b, f64 c) {
  if (a < b && a < c)
    return a;
  if (b < c)
    return b;
  return c;
}

static f64 max3_(f64 a, f64 b, f64 c) {
  if (a > b && a > c)
    return a;
  if (b > c)
    return b;
  return c;
}

static b8 same_sign_(f64 a, f64 b) {
  if (a >=  EPSILON && b <= -EPSILON) return 0;
  if (a <= -EPSILON && b >=  EPSILON) return 0;
  return 1;
}

static u64 _bitfont[] = {
  0xbc0000000000, 0xc00300000, 0x5fd5040093f24fc9, 0xa00a2c2a1a280105, 0xc000415e6f, 0x400000020be0000, 0x1c38a8400000007d, 0x40002043e1020215, 0x408102000000010, 0x9800000000020002, 0xf913e00000033, 0x53200000207c8800, 0x3654880000099, 0x54b800000f840e00, 0xe953c000001a, 0x953e000000674080, 0x1e54b800000f, 0x490000000000240, 0x88a08000000, 0x20a220050a142850, 0x6520800000, 0x912f801eab260be, 0x800034952bf0001f, 0xc850bf0000921427, 0xf00010a54afc0003, 0xd29427800002142b, 0x840007e1023f0000, 0x7d09100000217e, 0x3f000188a08fc000, 0xc30c0cfc00000810, 0x27803f101013f00f, 0xc244bf0000f214, 0x4bf0002f21427800, 0xc254a480006c24, 0x407c00102fc08100, 0xf208080f0000fa0, 0x531007d81c607c0, 0xc208288c031141, 0x83fc00046954b10, 0x180e03000000, 0x41040000000ff04, 0x8102040810000404, 0x2a54600000000101, 0x309123e0000e, 0xc912180000a22447, 0x8000062a54700007, 0xe52a4300000029f0, 0xa0000602043e0001, 0x1d48000002074, 0x1f000003610f8000, 0x13e04f800000010, 0x470000780813e00f, 0x184893e0000e224, 0x23e0001f12243000, 0x82a54100000008, 0x40780000009f0200, 0xe208080e0001f20, 0xa22007981860780, 0x82082888022282, 0x16c200004ca95320, 0x7f000004, 0x408200000086d04, 0x8204,
};

#define CHAR_NUM_BITS_X_ 6
#define CHAR_NUM_BITS_Y_ 7
#define CHAR_NUM_BITS_   (CHAR_NUM_BITS_X_ * CHAR_NUM_BITS_Y_)

static i64 char_column_offset_(c32 c, i64 column_index) {
  if (column_index < 0 || column_index >= CHAR_NUM_BITS_X_)
    return -1;
  return (c - 32) * CHAR_NUM_BITS_ + column_index * CHAR_NUM_BITS_Y_;
}

static b8 char_bit_(i64 column_offset, i64 row_index) {
  if (column_offset < 0 || row_index < 0 || row_index >= CHAR_NUM_BITS_Y_)
    return 0;

  i64 bit_index   = column_offset + row_index;
  i64 qword_index = bit_index / 64;
  if (qword_index < 0 || qword_index >= (i64) (sizeof _bitfont / sizeof *_bitfont))
    return 0;
  u64 mask        = 1ull << (bit_index % 64);
  return !!(_bitfont[qword_index] & mask);
}

static u64 char_column_convolved_(c32 c, i64 column_index) {
  if (column_index < 0 || column_index >= CHAR_NUM_BITS_X_)
    return 0;

  u64 column = 0;
  i64 offset = char_column_offset_(c, column_index);

  for (i64 y = 0; y < CHAR_NUM_BITS_Y_; ++y)
    if (char_bit_(offset, y))
      column |= 3ull << y;

  return column;
}

static b8 char_column_empty_(c32 c, i64 column_index) {
  if (column_index < 0 || column_index >= CHAR_NUM_BITS_X_)
    return 1;

  i64 offset = char_column_offset_(c, column_index);

  for (i64 y = 0; y < CHAR_NUM_BITS_Y_; ++y)
    if (char_bit_(offset, y))
      return 0;

  return 1;
}

static i64 char_width_(c32 c) {
  if (c < 32)
    return 0;
  if (c == ' ' || c > 127)
    return 4;

  i64 width = 0;

  for (; width < CHAR_NUM_BITS_X_; ++width)
    if (char_column_empty_(c, width) && char_column_empty_(c, width + 1))
      break;

  return width;
}

static i64 char_spacing_(i64 num_chars, c32 *text, i64 index) {
  if (text == NULL)
    return 0;

  if (index < 0 || index + 1 >= num_chars)
    return 0;

  u64 a = char_column_convolved_(text[index], char_width_(text[index]) - 1);
  u64 b = char_column_convolved_(text[index + 1], 0);

  if (!!(a & b))
    return 1;

  return 0;
}

static i64 text_cursor_(i64 num_chars, c32 *text) {
  if (text == NULL)
    return 0;

  i64 cursor = 0;

  for (i64 i = 0; i < num_chars; ++i) {
    if (text[i] <= ' ') {
      if (text[i] == '\n')
        cursor = 0;
      else if (text[i] == '\b' && i > 0)
        cursor -= char_width_(text[i - 1]) + char_spacing_(num_chars, text, i - 1);
      else if (text[i] == '\r')
        cursor = 0;
      else
        cursor += char_width_(' ') + char_spacing_(num_chars, text, i);
      continue;
    }
    cursor += char_width_(text[i]) + char_spacing_(num_chars, text, i);
  }

  return cursor;
}

static i64 enum_text_columns_(i64 num_chars, c32 *text) {
  if (text == NULL)
    return 0;

  i64 cols = 0;
  i64 n    = 0;

  for (i64 i = 0; i < num_chars; ++i) {
    if (text[i] <= ' ') {
      if (text[i] == '\n') {
        if (cols < n)
          cols = n;
        n = 0;
      } else if (text[i] == '\b' && i > 0) {
        if (cols < n)
          cols = n;
        n -= char_width_(text[i - 1]) + char_spacing_(num_chars, text, i - 1);
      } else if (text[i] == '\r') {
        if (cols < n)
          cols = n;
        n = 0;
      } else
        n += char_width_(' ') + char_spacing_(num_chars, text, i);
      continue;
    }
    n += char_width_(text[i]) + char_spacing_(num_chars, text, i);
  }

  if (cols < n)
    cols = n;

  return cols;
}

static i64 enum_text_rows_(i64 num_chars, c32 *text) {
  if (text == NULL)
    return 0;

  i64 rows = 0;

  for (i64 i = 0; i <= num_chars; ++i)
    if (i == num_chars || text[i] == '\n') {
      if (rows > 0)
        ++rows;
      rows += CHAR_NUM_BITS_Y_;
    }

  return rows;
}

static void brush_defaults_(Brush *b) {
  if (g_platform.frame_width > 0) {
    if (b->scale.x == 0.) b->scale.x = ((f64) g_platform.frame_width)  / g_platform.real_width;
    if (b->scale.y == 0.) b->scale.y = ((f64) g_platform.frame_height) / g_platform.real_height;
  }

  if (b->buffer.pixels == NULL) {
    b->buffer.width  = g_platform.frame_width;
    b->buffer.height = g_platform.frame_height;
    b->buffer.pixels = g_platform.pixels;
  }
}

static void draw_text_(Brush brush, f64 x_, f64 y_, f64 scale_x, f64 scale_y, i64 num_chars, c32 *text) {
  if (text == NULL)
    return;

  brush_defaults_(&brush);

  x_ = brush.position.x + x_ * brush.scale.x;
  y_ = brush.position.y + y_ * brush.scale.y;

  if (brush.scale.x < 0) scale_x *= -brush.scale.x;
  else                   scale_x *=  brush.scale.x;
  if (brush.scale.y < 0) scale_y *= -brush.scale.y;
  else                   scale_y *=  brush.scale.y;

  f64 x = x_;
  f64 y = y_;

  f64 kx = scale_x;
  f64 h  = scale_y * CHAR_NUM_BITS_Y_;

  for (i64 n = 0; n < num_chars; ++n) {
    if (text[n] <= ' ') {
      if (text[n] == '\n') {
        x  = x_;
        y += scale_y * (CHAR_NUM_BITS_Y_ + 1);
      }
      else if (text[n] == '\b' && n > 0)
        x -= kx * (char_width_(text[n - 1]) + char_spacing_(num_chars, text, n - 1));
      else if (text[n] == '\r')
        x  = x_;
      else
        x += kx * (char_width_(' ') + char_spacing_(num_chars, text, n));
      continue;
    }

    i64 num_cols = char_width_(text[n]);
    f64 w        = num_cols * kx;

    i64 i0 = (i64) floor(x);
    i64 i1 = (i64) ceil (x + w);
    i64 j0 = (i64) floor(y);
    i64 j1 = (i64) ceil (y + h);

    for (i64 i = i0; i < i1; ++i) {
      if (i < 0) continue;
      if (i >= g_platform.frame_width) break;

      i64 column = ((i - i0) * num_cols) / (i1 - i0);
      i64 offset = char_column_offset_(text[n], column);

      for (i64 j = j0; j < j1; ++j) {
        if (j < 0) continue;
        if (j >= g_platform.frame_height) break;

        i64 row = ((j - j0) * CHAR_NUM_BITS_Y_) / (j1 - j0);

        if (char_bit_(offset, row))
          put_pixel(brush, i, j);
      }
    }

    x += kx * (num_cols + char_spacing_(num_chars, text, n));
  }
}

static f64 gamma_(f64 x) {
  if (x >= 0.0031308)
    return 1.055 * pow(x, 1.0 / 2.4) - 0.055;
  return 12.92 * x;
}

static f64 gamma_re_(f64 x) {
  if (x >= 0.04045)
    return pow((x + 0.055) / 1.055, 2.4);
  return x / 12.92;
}

//  ================================================================

vec3_f32 gamma_apply(vec3_f32 rgb) {
  return (vec3_f32) {
    .x = (f32) gamma_(rgb.x),
    .y = (f32) gamma_(rgb.y),
    .z = (f32) gamma_(rgb.z),
  };
}

vec3_f32 gamma_revert(vec3_f32 rgb) {
  return (vec3_f32) {
    .x = (f32) gamma_re_(rgb.x),
    .y = (f32) gamma_re_(rgb.y),
    .z = (f32) gamma_re_(rgb.z),
  };
}

vec3_f32 lab_from_rgb(vec3_f32 rgb) {
  f64 l = 0.4122214708 * rgb.x + 0.5363325363 * rgb.y + 0.0514459929 * rgb.z;
  f64 m = 0.2119034982 * rgb.x + 0.6806995451 * rgb.y + 0.1073969566 * rgb.z;
  f64 s = 0.0883024619 * rgb.x + 0.2817188376 * rgb.y + 0.6299787005 * rgb.z;

  f64 l_ = cbrt(l);
  f64 m_ = cbrt(m);
  f64 s_ = cbrt(s);

  return (vec3_f32) {
    .x = (f32) (0.2104542553f * l_ + 0.7936177850f * m_ - 0.0040720468f * s_),
    .y = (f32) (1.9779984951f * l_ - 2.4285922050f * m_ + 0.4505937099f * s_),
    .z = (f32) (0.0259040371f * l_ + 0.7827717662f * m_ - 0.8086757660f * s_),
  };
}

vec3_f32 rgb_from_lab(vec3_f32 lab) {
  f64 l_ = lab.x + 0.3963377774 * lab.y + 0.2158037573 * lab.z;
  f64 m_ = lab.x - 0.1055613458 * lab.y - 0.0638541728 * lab.z;
  f64 s_ = lab.x - 0.0894841775 * lab.y - 1.2914855480 * lab.z;

  f64 l = l_ * l_ * l_;
  f64 m = m_ * m_ * m_;
  f64 s = s_ * s_ * s_;

  return (vec3_f32) {
    .x = (f32) (+4.0767416621 * l - 3.3077115913 * m + 0.2309699292 * s),
    .y = (f32) (-1.2684380046 * l + 2.6097574011 * m - 0.3413193965 * s),
    .z = (f32) (-0.0041960863 * l - 0.7034186147 * m + 1.7076147010 * s),
  };
}

vec3_f32 lch_from_lab(vec3_f32 lab) {
  f64 a = lab.y;
  f64 b = lab.z;

  return (vec3_f32) {
    .x = lab.x,
    .y = (f32) sqrt (a * a + b * b),
    .z = (f32) atan2(b, a),
  };
}

vec3_f32 lab_from_lch(vec3_f32 lch) {
  return (vec3_f32) {
    .x = lch.x,
    .y = (f32) (lch.y * cos(lch.z)),
    .z = (f32) (lch.y * sin(lch.z)),
  };
}

vec3_f32 rgb_from_lch(vec3_f32 lch) {
  return rgb_from_lab(lab_from_lch(lch));
}

vec3_f32 lch_from_rgb(vec3_f32 rgb) {
  return lch_from_lab(lab_from_rgb(rgb));
}

vec4_f32 with_alpha(vec3_f32 color, f32 alpha) {
  return (vec4_f32) {
    .x = color.x,
    .y = color.y,
    .z = color.z,
    .w = alpha,
  };
}

vec3_f32 without_alpha(vec4_f32 color) {
  return (vec3_f32) {
    .x = color.x,
    .y = color.y,
    .z = color.z,
  };
}

u32 rgb_u32_from_f32(vec3_f32 color) {
  i32 ir = (i32) floor(color.x * 255. + .5);
  i32 ig = (i32) floor(color.y * 255. + .5);
  i32 ib = (i32) floor(color.z * 255. + .5);

  u32 r = ir < 0 ? 0u : ir > 255 ? 255u : (u32) ir;
  u32 g = ig < 0 ? 0u : ig > 255 ? 255u : (u32) ig;
  u32 b = ib < 0 ? 0u : ib > 255 ? 255u : (u32) ib;

  return (r << 16) | (g << 8) | b;
}

vec3_f32 rgb_f32_from_u32(u32 color) {
  return (vec3_f32) {
    .x = ((color & 0xff0000) >> 16) / 255.f,
    .y = ((color & 0x00ff00) >>  8) / 255.f,
    .z =  (color & 0x0000ff)        / 255.f,
  };
}

u32 rgba_u32_from_f32(vec4_f32 color) {
  i32 ir = (i32) floor(color.x * 255. + .5);
  i32 ig = (i32) floor(color.y * 255. + .5);
  i32 ib = (i32) floor(color.z * 255. + .5);
  i32 ia = (i32) floor(color.w * 255. + .5);

  u32 r = ir < 0 ? 0u : ir > 255 ? 255u : (u32) ir;
  u32 g = ig < 0 ? 0u : ig > 255 ? 255u : (u32) ig;
  u32 b = ib < 0 ? 0u : ib > 255 ? 255u : (u32) ib;
  u32 a = ia < 0 ? 0u : ia > 255 ? 255u : (u32) ia;

  return (a << 24) | (r << 16) | (g << 8) | b;
}

vec4_f32 rgba_f32_from_u32(u32 color) {
  return (vec4_f32) {
    .x = ((color & 0x00ff0000) >> 16) / 255.f,
    .y = ((color & 0x0000ff00) >>  8) / 255.f,
    .z =  (color & 0x000000ff)        / 255.f,
    .w = ((color & 0xff000000) >> 24) / 255.f,
  };
}

b8 rectangle_contains(f64 x0, f64 y0, f64 width, f64 height, f64 px, f64 py) {
  return px >= x0 && px < x0 + width && py >= y0 && py < y0 + height;
}

b8 triangle_contains(f64 x0, f64 y0, f64 x1, f64 y1, f64 x2, f64 y2, f64 px, f64 py) {
  //  Z-components of cross-products
  //

  f64 z0  = (x1 - x0) * (y2 - y0) - (x2 - x0) * (y1 - y0);
  f64 z1  = (x2 - x1) * (y0 - y1) - (x0 - x1) * (y2 - y1);
  f64 z2  = (x0 - x2) * (y1 - y2) - (x1 - x2) * (y0 - y2);

  f64 pz0 = (px - x0) * (y2 - y0) - (x2 - x0) * (py - y0);
  f64 pz1 = (px - x1) * (y0 - y1) - (x0 - x1) * (py - y1);
  f64 pz2 = (px - x2) * (y1 - y2) - (x1 - x2) * (py - y2);

  return
       same_sign_(z0, pz0)
    && same_sign_(z1, pz1)
    && same_sign_(z2, pz2);
}

b8 ellipse_contains(f64 x0, f64 y0, f64 width, f64 height, f64 px, f64 py) {
  f64 dw = width  / 2;
  f64 dh = height / 2;

  if (dw < EPSILON || dh < EPSILON)
    return 0;

  f64 cx = x0 + dw;
  f64 cy = y0 + dh;
  f64 kx = 1. / dw;
  f64 ky = 1. / dh;

  f64 dx = (px - cx) * kx;
  f64 dy = (py - cy) * ky;

  return dx * dx + dy * dy - 1.0 < EPSILON;
}

b8 line_contains(f64 x0, f64 y0, f64 x1, f64 y1, f64 width, f64 px, f64 py) {
  f64 dx = x1 - x0;
  f64 dy = y1 - y0;

  //  Tangent
  //
  f64 tx = -dy;
  f64 ty = dx;
  f64 tl = sqrt(tx * tx + ty * ty);
  if (tl >= EPSILON) {
    tx /= tl;
    ty /= tl;
  }
  tx *= width * .5;
  ty *= width * .5;

  return
       triangle_contains(x0 - tx, y0 - ty, x0 + tx, y0 + ty, x1 + tx, y1 + ty, px, py)
    || triangle_contains(x0 - tx, y0 - ty, x1 + tx, y1 + ty, x1 - tx, y1 - ty, px, py);
}

void put_pixel(Brush brush, i64 x, i64 y) {
  brush_defaults_(&brush);

  if (x < 0 || x >= brush.buffer.width || y < 0 || y >= brush.buffer.height)
    return;

  i64 n = y * brush.buffer.width + x;

  if (brush.xor_color) {
    u32 dst = rgb_u32_from_f32((vec3_f32) {
      .x = brush.buffer.pixels[n].x,
      .y = brush.buffer.pixels[n].y,
      .z = brush.buffer.pixels[n].z
    });

    u32 src = rgb_u32_from_f32((vec3_f32) {
      .x = brush.color.x,
      .y = brush.color.y,
      .z = brush.color.z
    });

    vec3_f32 c = rgb_f32_from_u32(dst ^ src);

    brush.buffer.pixels[n] = (vec4_f32) {
      .x = c.x,
      .y = c.y,
      .z = c.z,
      .w = 1.f,
    };
  } else if (brush.alpha) {
    vec4_f32 dst = brush.buffer.pixels[n];
    f64      a   = brush.color.w;

    brush.buffer.pixels[n] = (vec4_f32) {
      .x = (f32) (dst.x * (1. - a) + brush.color.x * a),
      .y = (f32) (dst.y * (1. - a) + brush.color.y * a),
      .z = (f32) (dst.z * (1. - a) + brush.color.z * a),
      .w = 1.f,
    };
  } else
    brush.buffer.pixels[n] = brush.color;
}

void draw_pixels(Brush brush, f64 x, f64 y, f64 width, f64 height, Pixel_Buffer src) {
  //  FIXME PERF

  brush_defaults_(&brush);

  f64 x0, y0, x1, y1;

  if (brush.scale.x < 0) {
    x1 = brush.position.x + x * brush.scale.x;
    x0 = x1 + width  * brush.scale.x;
  } else {
    x0 = brush.position.x + x * brush.scale.x;
    x1 = x0 + width  * brush.scale.x;
  }

  if (brush.scale.y < 0) {
    y1 = brush.position.y + y * brush.scale.y;
    y0 = y1 + height * brush.scale.y;
  } else {
    y0 = brush.position.y + y * brush.scale.y;
    y1 = y0 + height * brush.scale.y;
  }

  i64 i0 = (i64) floor(x0);
  i64 i1 = (i64) ceil (x1);
  i64 j0 = (i64) floor(y0);
  i64 j1 = (i64) ceil (y1);

  for (i64 j = j0; j < j1; ++j) {
    i64 src_j = ((j - j0) * src.height) / (j1 - j0);
    for (i64 i = i0; i < i1; ++i) {
      i64 src_i = ((i - i0) * src.width) / (i1 - i0);
      brush.color = src.pixels[src_j * src.width + src_i];
      put_pixel(brush, i, j);
    }
  }
}

void fill_rectangle(Brush brush, f64 x, f64 y, f64 width, f64 height) {
  brush_defaults_(&brush);

  f64 x0, y0, x1, y1;

  if (brush.scale.x < 0) {
    x1 = brush.position.x + x * brush.scale.x;
    x0 = x1 + width * brush.scale.x;
  } else {
    x0 = brush.position.x + x * brush.scale.x;
    x1 = x0 + width * brush.scale.x;
  }

  if (brush.scale.y < 0) {
    y1 = brush.position.y + y * brush.scale.y;
    y0 = y1 + height * brush.scale.y;
  } else {
    y0 = brush.position.y + y * brush.scale.y;
    y1 = y0 + height * brush.scale.y;
  }

  if (!brush.quick) {
    i64 i0 = (i64) ceil (x0);
    i64 i1 = (i64) floor(x1);
    i64 j0 = (i64) ceil (y0);
    i64 j1 = (i64) floor(y1);

    f64 kx0 = i0 - x0;
    f64 kx1 = x1 - i1;
    f64 ky0 = j0 - y0;
    f64 ky1 = y1 - j1;

    for (i64 j = j0; j < j1; ++j)
      for (i64 i = i0; i < i1; ++i)
        put_pixel(brush, i, j);

    if (i0 > i1) {
      kx0 *= kx1;
      kx1 = 0.;
    }

    if (j0 > j1) {
      ky0 *= ky1;
      ky1 = 0.;
    }

    f64 alpha   = brush.alpha ? brush.color.w : 1.;
    brush.alpha = 1;

    brush.color.w = alpha * gamma_(kx0);
    for (i64 j = j0; j < j1; ++j)
      put_pixel(brush, i0 - 1, j);

    brush.color.w = alpha * gamma_(kx1);
    for (i64 j = j0; j < j1; ++j)
      put_pixel(brush, i1, j);

    brush.color.w = alpha * gamma_(ky0);
    for (i64 i = i0; i < i1; ++i)
      put_pixel(brush, i, j0 - 1);

    brush.color.w = alpha * gamma_(ky1);
    for (i64 i = i0; i < i1; ++i)
      put_pixel(brush, i, j1);

    brush.color.w = alpha * gamma_(kx0 * ky0);
    put_pixel(brush, i0 - 1, j0 - 1);

    brush.color.w = alpha * gamma_(kx1 * ky0);
    put_pixel(brush, i1, j0 - 1);

    brush.color.w = alpha * gamma_(kx0 * ky1);
    put_pixel(brush, i0 - 1, j1);

    brush.color.w = alpha * gamma_(kx1 * ky1);
    put_pixel(brush, i1, j1);
  } else {
    i64 i0 = (i64) floor(x0);
    i64 i1 = (i64) ceil (x1);
    i64 j0 = (i64) floor(y0);
    i64 j1 = (i64) ceil (y1);

    for (i64 j = j0; j < j1; ++j)
      for (i64 i = i0; i < i1; ++i)
        put_pixel(brush, i, j);
  }
}

void fill_triangle(Brush brush, f64 x0, f64 y0, f64 x1, f64 y1, f64 x2, f64 y2) {
  //  FIXME PERF:
  //  Implement better algorithm.

  brush_defaults_(&brush);

  x0 = brush.position.x + x0 * brush.scale.x;
  y0 = brush.position.y + y0 * brush.scale.y;

  x1 = brush.position.x + x1 * brush.scale.x;
  y1 = brush.position.y + y1 * brush.scale.y;

  x2 = brush.position.x + x2 * brush.scale.x;
  y2 = brush.position.y + y2 * brush.scale.y;

  i64 min_x = (i64) floor(min3_(x0, x1, x2));
  i64 min_y = (i64) floor(min3_(y0, y1, y2));
  i64 max_x = (i64) ceil (max3_(x0, x1, x2));
  i64 max_y = (i64) ceil (max3_(y0, y1, y2));

  for (i64 j = min_y; j <= max_y; ++j)
    for (i64 i = min_x; i <= max_x; ++i)
      if (triangle_contains(x0, y0, x1, y1, x2, y2, (f64) i, (f64) j))
        put_pixel(brush, i, j);
}

void fill_ellipse(Brush brush, f64 x, f64 y, f64 width, f64 height) {
  //  FIXME PERF:
  //  Implement better algorithm.

  brush_defaults_(&brush);

  f64 x0, y0, x1, y1;

  if (brush.scale.x < 0) {
    x1 = brush.position.x + x * brush.scale.x;
    x0 = x1 + width  * brush.scale.x;
  } else {
    x0 = brush.position.x + x * brush.scale.x;
    x1 = x0 + width  * brush.scale.x;
  }

  if (brush.scale.y < 0) {
    y1 = brush.position.y + y * brush.scale.y;
    y0 = y1 + height * brush.scale.y;
  } else {
    y0 = brush.position.y + y * brush.scale.y;
    y1 = y0 + height * brush.scale.y;
  }

  i64 i0 = (i64) floor(x0);
  i64 i1 = (i64) ceil (x1);
  i64 j0 = (i64) floor(y0);
  i64 j1 = (i64) ceil (y1);

  for (i64 j = j0; j < j1; ++j)
    for (i64 i = i0; i < i1; ++i) {
      if (ellipse_contains(x0, y0, x1 - x0, y1 - y0, (f64) i, (f64) j))
        put_pixel(brush, i, j);
    }
}

void fill_line(Brush brush, f64 x0, f64 y0, f64 x1, f64 y1, f64 width) {
  f64 dx = x1 - x0;
  f64 dy = y1 - y0;

  //  Tangent
  //
  f64 tx = -dy;
  f64 ty = dx;
  f64 tl = sqrt(tx * tx + ty * ty);
  if (tl >= EPSILON) {
    tx /= tl;
    ty /= tl;
  }
  tx *= width * .5;
  ty *= width * .5;

  fill_triangle(brush, x0 - tx, y0 - ty, x0 + tx, y0 + ty, x1 + tx, y1 + ty);
  fill_triangle(brush, x0 - tx, y0 - ty, x1 + tx, y1 + ty, x1 - tx, y1 - ty);
}

void draw_text_area(Brush brush, f64 x, f64 y, f64 width, f64 height, f64 max_scale_x, f64 max_scale_y, i64 num_chars, c32 *text) {
  if (max_scale_x < EPSILON || max_scale_y < EPSILON)
    return;

  i64 num_columns = enum_text_columns_(num_chars, text);
  i64 num_rows    = enum_text_rows_(num_chars, text);

  f64 scale_x = width  / num_columns;
  f64 scale_y = height / num_rows;

  f64 kx = scale_x / max_scale_x;
  f64 ky = scale_y / max_scale_y;

  f64 k = kx < ky ? kx : ky;

  kx = k * max_scale_x;
  ky = k * max_scale_y;

  draw_text_(brush, x, y, kx, ky, num_chars, text);
}

void draw_selection_cursor(Brush brush, f64 x, f64 y, f64 width, f64 height, f64 max_scale_x, f64 max_scale_y, i64 cursor, i64 selection, i64 num_chars, c32 *text) {
  if (max_scale_x < EPSILON || max_scale_y < EPSILON)
    return;

  i64 num_columns = enum_text_columns_(num_chars, text);
  i64 num_rows    = enum_text_rows_(num_chars, text);
  i64 cursor_x    = text_cursor_(cursor, text);
  i64 cursor_y    = enum_text_rows_(cursor, text);

  f64 scale_x = width  / num_columns;
  f64 scale_y = height / num_rows;

  f64 kx = scale_x / max_scale_x;
  f64 ky = scale_y / max_scale_y;

  f64 k = kx < ky ? kx : ky;

  kx = k * max_scale_x;
  ky = k * max_scale_y;

  if (selection != 0) {
    i64 selection_x, selection_y;

    if (selection > 0) {
      selection_x = text_cursor_(cursor + selection, text);
      selection_y = enum_text_rows_(cursor + selection, text);
    } else {
      selection_x = cursor_x;
      selection_y = cursor_y;
      cursor_x    = text_cursor_(cursor + selection, text);
      cursor_y    = enum_text_rows_(cursor + selection, text);
    }

    if (cursor_y == selection_y)
      fill_rectangle(
        brush,
        x + kx * cursor_x,
        y + ky * cursor_y - ky * (CHAR_NUM_BITS_Y_ + 1),
        kx * (selection_x - cursor_x),
        ky * (CHAR_NUM_BITS_Y_ + 1)
      );
    else {
      fill_rectangle(
        brush,
        x + kx * cursor_x,
        y + ky * cursor_y - ky * (CHAR_NUM_BITS_Y_ + 1),
        kx * (num_columns - cursor_x),
        ky * (CHAR_NUM_BITS_Y_ + 1)
      );
      for (i64 j = cursor_y + CHAR_NUM_BITS_Y_ + 1; j < selection_y; j += CHAR_NUM_BITS_Y_ + 1)
        fill_rectangle(
          brush,
          x,
          y + ky * j - ky * (CHAR_NUM_BITS_Y_ + 1),
          kx * num_columns,
          ky * (CHAR_NUM_BITS_Y_ + 1)
        );
      fill_rectangle(
        brush,
        x,
        y + ky * selection_y - ky * (CHAR_NUM_BITS_Y_ + 1),
        kx * selection_x,
        ky * (CHAR_NUM_BITS_Y_ + 1)
      );
    }
  } else
    fill_rectangle(
      brush,
      x + kx * cursor_x,
      y + ky * cursor_y - ky * CHAR_NUM_BITS_Y_,
      kx * .5,
      ky * (CHAR_NUM_BITS_Y_ - 1)
    );
}

#endif // GRAPHICS_IMPL_GUARD_
#endif // GRAPHICS_HEADER