#version 110

uniform mat4 matrix_in;

attribute vec4 a_position;
attribute vec2 a_texcoord;

varying vec2 ove_texcoord;

uniform vec2 footage_in_resolution;
uniform vec2 ove_resolution;

mat4 scale_mat4(vec3 scale) {
  return mat4(
    scale.x, 0.0, 0.0, 0.0,
    0.0, scale.y, 0.0, 0.0,
    0.0, 0.0, scale.z, 0.0,
    0.0, 0.0, 0.0, 1.0
  );
}

void main() {
  // Create identity matrix
  mat4 transform = mat4(1.0);

  // Scale to square
  transform *= scale_mat4(vec3(1.0/ove_resolution, 1.0));

  // Multiply by received matrix
  transform *= matrix_in;

  // Scale back out to footage size
  transform *= scale_mat4(vec3(footage_in_resolution, 1.0));

  gl_Position = transform * a_position;
  ove_texcoord = a_texcoord;
}