Imagine this, you have a window open, e.g. firefox and want to capture a rectangular region from it, e.g. from coords 100,100 to 400,400, because that's where the content you're interested in appears on the screen. You fire up Spectacle, start a rectangular region screen capture, and at that moment the entire window with the contents you wanted to capture SHIFTS by a considerable amount. Mind you, this shift only happens in the "preview"/frame freeze created by spectacle for allowing you to draw your region. The window does not really move from a window manager perspective. This means that: - capturing the area you intended to becomes a guess work - as soon as the selection is captured, what you see goes back to normal This is a recent regression, but I don't know exactly since which version (I think it must've happened within the past month, not more). I have a dual screen setup, will test if I can reproduce also with just the internal screen enabled.
Created attachment 175766 [details] capturing the region you want requires a lot of luck now
FYI, the window you see in the preview mode which is "pushing in" from the right, is the OBS Studio window I had entirely on my other screen and that I was using to record the bug. It seems like when entering "rectangular region" selection mode, the view gets offset/shifted by a certain amount I also just confirmed that this doesn't happen when working with a single screen.
*** This bug has been marked as a duplicate of bug 496057 ***