uniform mat4 ModelViewProjectionMatrix;
uniform vec2 ViewportSize = vec2(-1, -1);
uniform float outline_scale = 1.0;

const float line_falloff = 1.0;
const float circle_scale = sqrt(2.0 / 3.1416);
const float square_scale = sqrt(0.5);
const float diagonal_scale = sqrt(0.5);

in vec2 pos;
in float size;
in vec4 color;
in vec4 outlineColor;
in int flags;

flat out vec4 finalColor;
flat out vec4 finalOutlineColor;

flat out int finalFlags;

flat out vec4 radii;
flat out vec4 thresholds;

bool test(int bit)
{
  return (flags & bit) != 0;
}

vec2 line_thresholds(float width)
{
  return vec2(max(0, width - line_falloff), width);
}

void main()
{
  gl_Position = ModelViewProjectionMatrix * vec4(pos, 0.0, 1.0);

  /* Align to pixel grid if the viewport size is known. */
  if (ViewportSize.x > 0) {
    vec2 scale = ViewportSize * 0.5;
    vec2 px_pos = (gl_Position.xy + 1) * scale;
    vec2 adj_pos = round(px_pos - 0.5) + 0.5;
    gl_Position.xy = adj_pos / scale - 1;
  }

  /* Pass through parameters. */
  finalColor = color;
  finalOutlineColor = outlineColor;
  finalFlags = flags;

  if (!test(0xF)) {
    finalFlags |= 1;
  }

  /* Size-dependent line thickness. */
  float half_width = (0.06 + (size - 10) * 0.04);
  float line_width = half_width + line_falloff;

  /* Outline thresholds. */
  thresholds.xy = line_thresholds(line_width * outline_scale);

  /* Inner dot thresholds. */
  thresholds.zw = line_thresholds(line_width * 1.6);

  /* Extend the primitive size by half line width on either side; odd for symmetry. */
  float ext_radius = round(0.5 * size) + thresholds.x;

  gl_PointSize = ceil(ext_radius + thresholds.y) * 2 + 1;

  /* Diamond radius. */
  radii[0] = ext_radius * diagonal_scale;

  /* Circle radius. */
  radii[1] = ext_radius * circle_scale;

  /* Square radius. */
  radii[2] = round(ext_radius * square_scale);

  /* Min/max cutout offset. */
  radii[3] = -line_falloff;

  /* Convert to PointCoord units. */
  radii /= gl_PointSize;
  thresholds /= gl_PointSize;
}