Sometimes I would like to focus my attention on a specific app,
and not see the desktop underneath the open windows.

Is there a way that I could "hide the desktop"?
Preferably by a keyboard accelerator, but a panel click would be okay too.

An example is I want to watch a movie or something, so I want an effect
that is like Full Screen mode, but it is not in fact full screen.
It's just that there is nothing but my open window(s) over a black background.

Few ways:


1) Stop the plasma-desktop/plasmashell
You could quit the the plasma-desktop (plasma 4) / plasmashell (plasma 5). Plasma objects (desktop/plasmoids) will disappear. Windows will be there and the KRunner ( https://userbase.kde.org/Plasma/Krunner ) will be available.


Plasma 4

Stop (KRunner):

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kquitapp plasma-desktop

Start (KRunner):

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plasma-desktop

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 $ kquitapp --help
Usage: kquitapp [Qt-options] [KDE-options] [options] application

Quit a D-Bus enabled application easily

Generic options:
  --help                    Show help about options
  --help-qt                 Show Qt specific options
  --help-kde                Show KDE specific options
  --help-all                Show all options
  --author                  Show author information
  -v, --version             Show version information
  --license                 Show license information
  --                        End of options

Options:
  --service <service>       Full service name, overrides application name provided
  --path <path>             Path in the D-Bus interface to use [/MainApplication]

Arguments:
  application               The name of the application to quit


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  $ plasma-desktop --help
Usage: plasma-desktop [Qt-options] [KDE-options]

The KDE desktop, panels and widgets workspace application.

Generic options:
  --help                    Show help about options
  --help-qt                 Show Qt specific options
  --help-kde                Show KDE specific options
  --help-all                Show all options
  --author                  Show author information
  -v, --version             Show version information
  --license                 Show license information
  --                        End of options


Plasma 5

Stop (KRunner):

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kquitapp5 plasmashell

Start (KRunner):

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plasmashell

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$ kquitapp5 --help
Usage: kquitapp5 [options] [application]
Quit a D-Bus enabled application easily

Options:
  --service <service>  Full service name, overrides application name provided
  --path <path>        Path in the D-Bus interface to use
  -h, --help           Displays this help.
  -v, --version        Displays version information.

Arguments:
  [application]        The name of the application to quit


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$ plasmashell --help
Usage: plasmashell [options]
Plasma Shell

Options:
  -d, --qmljsdebugger          Enable QML Javascript debugger
  -n, --no-respawn             Do not restart plasma-shell automatically after
                               a crash
  -p, --shell-plugin <plugin>  Force loading the given shell plugin
  -a, --standalone             Load plasmashell as a standalone application,
                               needs the shell-plugin option to be specified
  --test <file>                Enables test mode and specifies the layout
                               javascript file to set up the testing environment
  -h, --help                   Displays this help.
  -v, --version                Displays version information.
  --author                     Show author information.
  --license                    Show license information.
  --desktopfile <file name>    The base file name of the desktop entry for this
                               application.


2) Hide the desktop by starting an application with the fullscreen + keep below + no tittlebar and frame window settings

You could start an application with the settings: fullscreen, keep below, no tittlebar and frame with the window specific settings: https://docs.kde.org/trunk5/en/kde-work ... cific.html. Examples: https://userbase.kde.org/KWin_Rules_Examples

An example

Starting the ImageMagick view application display:

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display /path/to/blackimage.jpg


With the window specific settings:



The Display window will hide the desktop but the windows will be top of the Display window.

The Display window can be quit by right clicking the Display window:



The

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display /path/to/blackimage.jpg


command can be added to the KDE Menu ( https://docs.kde.org/trunk5/en/kde-work ... index.html ) . Then there is an option to add shortcut key.