A few people contacted me after discovering that screenshots should be taken in a 16:9 aspect ratio. The question was basically, how do I do that?
After trying to do this myself for my applications, I too discovered it’s hard. The wmctrl command doesn’t seem to play very nicely with CSD, and certainly won’t work in wayland. So, Owen Taylor (GNOME hacker extraordinaire) to the rescue.
Owen wrote a GNOME Shell extension (which I’ve modified a little) which resizes the current window to a 16:9 size when you press Ctrl+Alt+S. If you press it again, the window will get larger, to the next recommended 16:9 size. Press Ctrl+Alt+Shift+S and the window will get smaller to the previous size. Get the code on github or on extensions.gnome.org. I probably need some more testing as well. Patches very welcome if you’re good at shell extensions :)
With this extension installed I was able to screenshot all my applications that I maintain in no time at all. I’ve been uploading the screenshots into ${projects}/data/appdata and referencing the git.gnome.org URL in the AppData file so anyone can easily update them when the code changes, but this is completely up to you.