Curve without SHIFT and touch Raspbian

Hi.

I’m using MyPaint with a raspberry pi (ARM dist version by raspbian) and it’s awesome!
The only problem is that I have to use a keyboard to do curves (pressing SHIFT).
I’m using a touch screen on my raspberry pi with a capacitive pen (no pressure content), and the auto generated end lines (etc) for fake pressure works fine but, i want to do curves without a keyboard

Like Paint on Windows that we just click two times on the line to make curves

I don’t find any settings to change this (at least I’M not finding)

Can you Dev guys think about it, please? If yes, u guys will make a true touch screen drawer for raspbians users!

Thanks!

obs.:> sry for my english