[Wayland-bugs] [Bug 99635] It is impossible to screenshot a user selected window.

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=99635

            Bug ID: 99635
           Summary: It is impossible to screenshot a user selected window.
           Product: Wayland
           Version: 1.2.x
          Hardware: Other
                OS: All
            Status: NEW
          Severity: enhancement
          Priority: medium
         Component: wayland
          Assignee: wayland-bugs at lists.freedesktop.org
          Reporter: naelstrof at gmail.com

With the current security of Wayland, it's impossible to allow a user to select
a window to screenshot. A coveted feature of screen shooting in X11.

There's multiple things that'd have to happen for this to work properly:
1. Gnome would have to add a "surface-handle" parameter to their
org.gnome.Shell.Screenshot.ScreenshotWindow function. (other compositors would
have to do something similar)
2. Wayland OR Gnome's compositor would need to publicly expose window
positions, sizes, and "surface-handles".

The reason I put surface-handle in quotes is because that'd be an obviously bad
security flaw, it doesn't have to be a REAL surface handle. Just some sort of
identification number in order to communicate with the compositor which window
needs to be captured. Anytime I refer to "surface-handles" I actually mean an
identification number referring to a specific surface.

So my question is: in order to make screen shooting on Wayland more robust-- is
it the responsibility of the Compositor or Wayland itself to expose surface
information?

As for security, I don't think exposing surface positions or sizes is bad at
all since it's already possible to make global silent screenshots through
gnome's compositor. As for exposing "surface-handles" I can see that reducing
security somewhat, since that'd allow a Wayland application to see even
off-screen windows. Though I don't see the utility of scrying off-screen
windows from the perspective of a malicious application.

The reason I need window positions and sizes is because I'm porting
[slop](https://github.com/naelstrof/slop) to Wayland. The reason I need
"surface-handles" is for [maim](https://github.com/naelstrof/maim).

P.S. Here's some reasons for including this feature:
A user might write a script that screenshots a minimized/off-screen
Counter-Strike game repeatedly to check to see if a match has been found to
send him an email/text/sound.
Time-lapses of specific applications, even if they get minimized or moved
off-screen.
Screen shooting specific locations in games (like a healthbar, dps graph in
path of exile).
Computer-illiterates would appreciate if gnome-screenshot's --interactive
option would easily allow for responsive, automatic window selection.
(Especially if the window is poorly placed or only partially visible.)

Thanks for reading!

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