woboq / property_bindings Goto Github PK

Hi.
Can you please explain what's the motivation of this connection? Especially I have trouble to understand the destination method index "methodCount()". Does this suppress the signal (because it points to a not existing method)?
Thank you.

I noticed that dependent properties only seem to update when dependent on independent properties, or when queried. Unfortunately, that breaks hooks with grandparents.

Hooks need to be triggered regardless of whether the new value is queried or not. Typically they exist because we need to break out of the property system and indirectly trigger a query. e.g. GraphicsRectObject::color -> GraphicsRectObject::update -> GraphicsRectObject::paint.

Example:

#include <iostream>
#include "property.h"

struct Rectangle {
  property<double> width;
  property<double> height;
  property<double> area {
    [&](){ return width * height; }
  };
};

void printA() { std::cout << "A"; }
void printB() { std::cout << "B"; }

int main() {
  Rectangle r;

  property_hook<double> hookA(
    printA, [&]{ return r.width * r.height; });

  property_hook<double> hookB(
    printB, [&]{ return r.area; });

  r.width = 5;

  std::cout << std::endl;
}

Actual Output:
A

Expected Output:
AB