how this operator |= works ?

i have an open source code and i need to understand what this operator " |= " do ?

thanks in advance

It’s also a boolean or-equals operator.

For example:
myBool |= possiblyFalseBool;

is shorthand for:
myBool = myBool | possiblyFalseBool;

The logic here is that if myBool is true, it prevents it from turning false in case possiblyFalseBool actually is false.

The longer way to state it would be:

if (!myBool) {
     myBool = possiblyFalseBool;

This the bitwise or operator. It’s used to compare or set bits.