rest-in-dust/assets/shaders/canvas_fragment.glsl

#version 130

in vec4 _color;
in vec2 _tex_coord;

out vec4 frag_color;
uniform sampler2D sampler;
uniform int has_texture;

void main() {
  if (has_texture == 1)
    {
      frag_color = _color * texture(sampler, _tex_coord);
    }
  else
    {
      frag_color = _color;
    }
}