Use std::function to allow C++ 11 lambda functions

[jacobdekeizer]

Hi,

Thank you for making this library.
I needed to access the this context from a callback in my project, so that I could update a counter in my class.
Having the CallbackFunction use std::function, makes it possible to use the C++11 lambda functions.

My example:

void DevicesScreenActivity::begin()
{
  this->_inputManager->left.setReleasedHandler([&](Button2 &b) {
    Serial.println("test");

    this->selected++;
  });
}

[LennartHennigs]

Hey,
thanks for pointing this out and adding this.
Will merge it!

[ItsFlo]

This breaks compiling for Arduino for me. Compiling for ESP32 and ESP8266 both worked.
I also tried a clean install of the Arduino IDE, only downloaded this library and only added #include "Button2.h" to an empty sketch and it didn´t compile:

fatal error: functional: No such file or directory

I tried to compile for both Uno and Nano.

@jacobdekeizer are you using an Arduino for your project or something else?

[jacobdekeizer]

Hi, I am using an esp32. I didn't know the arduino uno does not support the c++ standard library. I found this example so we can target both esp32/esp8266 and arduino: https://github.com/blynkkk/blynk-library/blob/master/src/Blynk/BlynkConsole.h#L31.

[LennartHennigs]

Hey, I add pre-processor directives to detect ESP8266 & EPS32s and pushed a new released. The code now compiles on Arduino and these two platforms. I will keep it now as it is and maybe revisit it later to find a better solution.

Thanks @ItsFlo for finding the error and thanks @jacobdekeizer for suggesting a fix.
Cheers