A few times I have by accident when resizing a image in the comp-window resized the comp- window.
Well not the window itself but I have dragged the corners and resized the view of the project/comp.
Its like a mask and outside the mask its black and inside you see the comp.
Dont know what to call this so I havent found anything on the net.
Just want to know what it is and what to use if for.
a screenshot would help dymistify what just happened, but if I had to guess by your description, you probably activated to region of interest switch:
just click on it again to disable it.
more about this feature here:
Thanks, that was exact the thing I was looking for.