I used Qt quite extensively about 10 years ago and we constantly complained about signals. Was working in real-time medical simulations and interfacing with the many io devices we had was painfully slow. Also (at the time) keeping an OpenGL frame (we had multiple at a time) required signal communication that was a high overhead. We ended up replacing all of the signal beside setting up and tearing down the application and handling of system events. Signals are a bad design and I’ll stand on that hill forever.
There are many many things you should never use if you need ultra low latency and/or ultra high bandwidth. That doesn't make them badly designed, simply not suitable for every purpose.
Qt signals are absolutely fine for like 99% of their usage.
Absolutely not, signals and slots make a spaghetti mess of messaging. Often causing a many to one to many dependency hell. In simple cases signals and slots work fine, but quickly become overwhelming as the project grows. I’ve not worked in any large Qt project that wasn’t a dependency mess and a chore to do anything. Signals and slots are a crutch of poor design.
