Thank you for your answer Uwe,
I understand that for any resize event where [-1.5, 1.5] are to remain fixed proportions should change. But the way that would make sense for me would be if the canvas would change only as possible according to the mainwindow, that is, the canvas would change only with vertical stretching, for example. But I have no idea how to implement this...
Also, the circles are mapped to plot coordinates in the standard fashion, which come with spectrogram definitions (this is a spectrogram plot btw)
Thanks