So, I'll make my best effort in explaining the behaviour I am seeing in Gimp so you can understand what's what I'm looking for.
Let's say I have a canvas of 800x600 and I create a new layer and paste an image that's 1024x800 ( or if it's smaller I transform its size so it ends up that size ), with the key here being that I end up having a layer whose content is bigger than the Canvas.
Now, I select a circle right in the middle of the layer, then I inverse the selection and I delete the selected part.
I'll end up with a circle of part of the image. The thing is, NOT everything got deleted, the parts of the image that were not visible ( which were "outside" of the canvas ) did not get deleted. If I move the layer down, I can see a border whose thickness is the difference between the image size and the canvas.
Why does this happen and can I avoid it?
Note - I know my description of the issue is convoluted, but I can't really make a GIF about this issue since I don't have the appropriate apps for doing so at work now.
Apologies for that