code: function( src, dst ){
      this._dat[ 0|BLEND_FUNC_C_SRC ] = src;
      this._dat[ 0|BLEND_FUNC_C_DST ] = dst;
      this._set = this._set & ~BLEND_FUNC_A_SET | (~~BLEND_FUNC_SET);
      return this;
    }
docs: /*
  enums
  ZERO
  ONE
  SRC_COLOR
  ONE_MINUS_SRC_COLOR
  SRC_ALPHA
  ONE_MINUS_SRC_ALPHA
  DST_ALPHA
  ONE_MINUS_DST_ALPHA
  DST_COLOR
  ONE_MINUS_DST_COLOR
  SRC_ALPHA_SATURATE