Deriving a modified Keybaord.h / Keyboard.cpp that supports modifier-keys Ctrl & Alt problems to understand what the existing code does

[in0]

@StefanL38

it makes use of a function

		k = pgm_read_byte(_asciimap + k);

I have no idea where to lookup this function

Here is the documentation for the avr-libc macro:
https://www.nongnu.org/avr-libc/user-manual/group__avr__pgmspace.html#ga349c2c134daa01aeea62256f1fd7489c

@StefanL38

And I have no idea what mechanism makes it possible to use the function "print" on the level of the users code so the demo-code can be

      Keyboard.print("Hello World");

Here it is:
https://github.com/arduino-libraries/Keyboard/blob/1.0.2/src/Keyboard.h#L95
By inheriting the Arduino core library's Print class, it is only necessary for the Keyboard library to define the application-specific write function and Print provides all the general-purpose print and println overloads:
https://github.com/arduino/ArduinoCore-API/blob/1.2.0/api/Print.cpp