The name displayed in the KCM header needs to match the name displayed
in the sidebar list item.

The settings are now read via KConfigXT, with a trick to follow the config
scheme of SDDM. One KConfig object is used to read the defaults and another one
to read the actual config values, see SddmSettingsBase.h for details.
The UI is now entirely in Qml and follows the GridviewKCM style. The preview pane
has been moved into a Dialog. The "Advanced" has been moved into a page called
"Behavior" and the sync options live now in a OverlaySheet accessible from the main
page as does the background configuration.
BUG:403530
BUG:407689
BUG:411004
BUG:411504
BUG:419327
BUG:424639

- Choose better QString overloads
- Remove unused variables
- Add missing emit keywords
- Avoid multi-arg method call
- Avoid detaching in loop
- Do not show empty error messages, for exmple when the user clicks the
  cancel button

BUG: 407686
FIXED-IN: 5.20

Summary: Make it compile against qt5.15

Reviewers: davidedmundson, apol

Reviewed By: apol

Subscribers: plasma-devel

Tags: #plasma

Differential Revision: https://phabricator.kde.org/D27866

Summary:
Suggested for D26813. Prerequiste if user-manager is to not send any SDDM config file path on its own.

The config file paths are now defined in the authhelper as opposed to being sent in a variant map from the main kcm file.

I also edited paths in that main file because they were wrong.

This does not yet solve bug 414396.

CC-BUG: 342722

Test Plan: Testing with D26813 I managed to write to the config file without user-manager defining the path.

Reviewers: #plasma, davidedmundson

Reviewed By: #plasma, davidedmundson

Subscribers: plasma-devel

Tags: #plasma

Differential Revision: https://phabricator.kde.org/D27142

"AdvanceConfig" doesn't make sense.

1. header files
2. Qt
3. KDE

- alphabetically organized
- no spacing after copyright info
- one line of spacing after last include

NOTE: xcursor.cpp differs because it won't compile with a standardized ordering of includes.

Summary:
As of SDDM release 0.16.0 it advised to use /etc/sddm.conf.d/ as the directory for user settings.

This patch aims to achieve it by saving in that very same directory under the filename "kde_settings.conf".

It must also remove identical entries from the old "sddm.conf" file because SDDM will simply load them instead of new user set values.

BUG: 386241
FIXED-IN: 5.17

Test Plan:
- compiles
- writes to new config file
- reads from new config file
- deletes identical entries from old config file when writing them to new one

Reviewers: davidedmundson, ngraham, #plasma

Reviewed By: davidedmundson, ngraham, #plasma

Subscribers: GB_2, plasma-devel

Tags: #plasma

Differential Revision: https://phabricator.kde.org/D21832

Summary:
The lambda returns a QStringBuilder which contains dangling references.
Work around that by converting to QString inside the lambda's context.

Test Plan: Does not crash anymore.

Reviewers: #plasma, davidedmundson

Reviewed By: #plasma, davidedmundson

Subscribers: plasma-devel

Tags: #plasma

Differential Revision: https://phabricator.kde.org/D15498

Summary:
The lambda returns a QStringBuilder which contains dangling references.
Work around that by converting to QString inside the lambda's context.

Test Plan: Does not crash anymore.

Reviewers: #plasma

Subscribers: plasma-devel

Tags: #plasma

Differential Revision: https://phabricator.kde.org/D15498

Summary:
SDDM reads files in alphabetical order from /usr/lib/sddm/sddm.conf.d/,
then /etc/sddm.conf.d/ and /etc/sddm.conf. The latest occurence takes
precedence.
The paths in CMakeLists are copied from sddm.

Test Plan: kcmshell5 kcm_sddm now shows the right preselected values.

Reviewers: #plasma, davidedmundson

Reviewed By: #plasma, davidedmundson

Subscribers: plasma-devel

Tags: #plasma

Differential Revision: https://phabricator.kde.org/D12359

Summary:
Add SDDM theme install/uninstall with Get Hot New Stuff to the SDDM KCM.
Button arrangement is copied from the colour KCM. We can install from either a
local .zip file or the KDE store.

It assumes a zip file containing a folder/folders of themes to be installed
into the SDDM directory. metadata is very loosely checked.

As it needs to be root to install, this is added into the helper.

An additional executable is needed to make KNS work properly. We need to keep track of which
KNS packages contain which themes, which is done in a local config file.

Test Plan:
Installed a theme via GHNS
Uninstalled it
Installed a theme manually
Uninstalled it

Reviewers: #plasma, mart

Reviewed By: mart

Subscribers: plasma-devel

Tags: #plasma

Differential Revision: https://phabricator.kde.org/D3685

Reviewed-by: David Edmundson

There are some FIXMEs which probably break translations for now.

implemented halt and reboot command strings.