Add a Howto on setting wallpapers

index.rst

@@ -69,6 +69,7 @@ Core documentation for Qubes users.
    :caption: How-to guides
 
    user/how-to-guides/how-to-organize-your-qubes
+   user/how-to-guides/how-to-set-a-wallpaper
    user/how-to-guides/how-to-update
    user/how-to-guides/how-to-back-up-restore-and-migrate
    user/how-to-guides/how-to-copy-and-paste-text

user/how-to-guides/how-to-set-a-wallpaper.rst

@@ -0,0 +1,49 @@
+===========================================
+How to take screenshots and set a wallpaper
+===========================================
+
+In Qubes OS, :term:`dom0` is strongly isolated from the outside world. It has no direct internet connection (for updates, a dedicated UpdateProxy is used to avoid interacting with untrusted data) and copying files into it is highly discouraged and not supported by tools such as ``qvm-copy``.
+
+:term:`dom0` is also where the desktop environment and Qubes OS GUI tools are running (unless you are using the experimental :doc:`sys-gui</user/advanced-topics/gui-domain>`, thus, if you take a screenshot or want to set a wallpaper, you will be acting within :term:`dom0`.
+
+
+Taking screenshots
+------------------
+
+In default Qubes OS installation, you can use the default XFCE screenshot tool (called Screenshot), either running it from the Qubes OS menu or using the :kbd:`PrintScreen` key.
+
+.. figure:: /attachment/doc/howto-screenshot-1.png
+   :alt: image of Qubes Menu with the page for Other tools open and the Screenshot tool highlighted
+   :align: center
+|
+.. figure:: /attachment/doc/howto-screenshot-2.png
+   :alt: image of the default XFCE screenshot tool
+   :align: center
+
+The file will be saved in :term:`dom0`, so you need to copy it out of :term:`dom0` if you want to use it in any other qube. The easiest way to do it is with the ``qvm-copy-to-vm`` tool in :term:`dom0` terminal:
+
+.. code:: console
+
+    $ qvm-copy-to-vm qube-name Pictures/screenshot_name.jpg
+
+Copying files out of :term:`dom0` is generally safe for your system.
+
+Setting a wallpaper
+-------------------
+
+As mentioned, all desktop environment tools run in :term:`dom0`, and copying files into :term:`dom0` is a big security risk and strongly discouraged. New users often ask: fine, :term:`dom0` needs to be isolated, but how do I then set my own wallpaper in Qubes OS then? The possible solutions are:
+
+- copy a file into :term:`dom0` in a hacky way (not recommended: this breaks isolation of :term:`dom0` and exposes you to risks from a contaminated graphics file)
+
+- use screenshots:
+   - first, display an image you want in **full screen** (you can force full screen by right-clicking on the window title bar, see :doc:`how-to-enter-fullscreen-mode` for more information)
+   - take a screenshot (as above, :ref:`take a screenshot <user/how-to-guides/how-to-set-a-wallpaper:Taking screenshots>`)
+   - use this image as your wallpaper
+
+To set a wallpaper in the default XFCE desktop environment, you can use the Desktop tool.
+
+.. figure:: /attachment/doc/howto-screenshot-3.png
+   :alt: image of Qubes Menu with the page for System Settings tools open and the Desktop application highlighted
+   :align: center
+
+Setting an image as wallpaper **within a normal qube** does not influence :term:`dom0` wallpaper (the one you actually see on the screen) in any way.