Qwt: Is it possible to perform GUI operations from a separate QProcess?

[seanj]

First of all, I am thinking the answer is no, but I cannot say for sure, so a confirmation would be nice.

I am new to Qt and Qwt (and GUI programming in general), and I am relatively new to C++.
I know you should not perform any GUI operations from a separate thread, but I was wondering if I could make something work using QProcess (or fork() obviously) and QSharedMemory, while still making it "feel" like one application.

My goal is to build a GUI to display large amounts of data in real-time with Qt and Qwt. The GUI needs to contain 2 plots: the first plot needs to replot a completely new set of 1e6 samples for every update (needs to be done very quickly, minimum 10FPS), the second plot is a waterfall display (Google "fft waterfall display" if unfamiliar) based on the data of the first plot. My biggest concern is the speed of painting.

If I only create the first plot, my GUI updates at about 17FPS.

I am running my program on CentOS 7 with Qt 5.9.7 and Qwt 6.1.5.