Good morning

I'm using kdenlive 17.04.3 with linuxmint cinnamon 18.3.
I'm a newby in video editing and I've been working with kdenlive for a few weeks now.

I just tried to use rotoscoping to rectify some frames in my video but I cannot make it working.
Here is what I've done:
I put two clips on the time line
I put an affine transition between the two of them and a rotoscoping effect on the upper clip.
I tried to left click on the project monitor to draw a matte
The problem is that nothing happens when I click on the monitor (in fact, when I left click, it only makes the video project running of stopping, as it does when I hit space barr on my keyboard)
So I cannot draw any matte at all and cannot see what rotoscoping can do for me

Would somebody have an idea of what went wrong with me????

Thank you for attention

OOOPS...

I solved the problem by myself.
I just discovered that to draw the matte for rotoscoping on the project monitor, we have to put this one in "edit" mode by clicking the small square under the monitor.
Hope this will help somebody latter.