I am writing a status bar that should take as little resources as possible i.e. should save power and does not steal cpu-/io-/gpu-time from more important processes and keep memory usage at an acceptable level. I expect the bar to mainly render simple shapes, icons, text, but also transparency effects or rainbow effects should be possible. The status bar is always visible, but most of the time it is less important than what the user is actually looking at.
Does Vulkan (or any other gpu-api) fit my requirements better than a software renderer?
If I understand correctly, a software renderer must upload its frames to the gpu to display them. The data copy could be eliminated by just rendering directly with the gpu. Also some rendering techniques (e.g. transparency, blur) are clearly more efficient on a gpu. Is there a reason other than implementation simplicity for which gui programs commonly prefer software rendering? I could imagine that APIs like Vulkan that are mostly designed for game engines that want to benefit from as much computer resources as possible may produce too much overhead in my use case.
I wanna say "no". GPUs are typically for processing at bulk, not for background tasks.
Real answer is you have to measure. And you have to be aware that there are HW differences, so even if it is beneficial on your PC, it might be annoying on someone else's PC (draining battery, causing noise, etc).