When copying click vectors and appending, the resize will be overkill

[bernardosulzbach]

Assume that the standard implementation copies into a vector which is exactly as large as required. So copying 3 clicks gets a vector for 3 Position objects. Now, after pushing a new click into it, it grows to 6 Position objects.

Possibly defining an iterator that gets a vector and an object and returns all elements in the vector and then the provided object would allow for proper vector initialization.

[bernardosulzbach]

Not sure this is valid. In the way the code is currently implemented, the derived state will have a vector as long as ever needed (the copy operator does not seem to shrink it), so this reallocation does not seem to happen. An example test is shown below.

#include <iostream>
#include <vector>

void *operator new(size_t size) {
  std::cout << "Allocating " << size << " bytes." << '\n';
  return malloc(size);
}

void operator delete(void *pointer) {
  std::cout << "Freeing memory." << '\n';
  free(pointer);
}

int main() {
  std::vector<int> v;
  for (int i = 1; i <= 9; i++)
    v.push_back(i);
  auto v_copy = v;
  v.pop_back();
  v_copy = v;
  v.pop_back();
  v_copy = v;
  return 0;
}