I managed to get all the description of the problem in the subject of the Topic.
Basically I have a game in which the player can zoom in and out.
As there's no such feature, I use layerscale.
But let say I want to spawn something in this layer by mouse clicking.
The coordinate of the mouse gets projected onto the layer which is scaled so the object doesn't appear under the mouse.
I tried something basic like MouseX/layerscale("Main")
I tried by scaling an offset from the center... It worked well with zooming, but when I scroll, it gets off.
Well, I spent my afternoon on it and didn't find any good solution. So I'm asking you guys \o/
Here is a little capix to try things :scaleProj.capx
The red sprite is in the "Main" Layer and is supposed to follow the mouse even if scaled and or scrolled.