Testing

#plasmawindowed

There are three ways to test a widget.

1. plasmawindowed can be used if the widget is installed to ~/.local/share/plasma/plasmoids. It remembers changes you make to the configuration, as it is the same command used for "windowed widgets". It has limited features for displaying the widget, but it comes with the desktop.
2. plasmoidviewer, explained further down, can display a widget as a desktop widget or a panel widget. It can also test a widget that isn't installed yet. It comes with sonic-theme-sdk.
3. Install the widget and add it to your panel, restarting the shell each time with sonicshell --replace. This takes a few seconds for the panel to load, so it is best kept for a final test.

plasmawindowed --help

To test the Application Launcher widget:

plasmawindowed org.kde.plasma.kickoff

#plasmoidviewer

plasmoidviewer --help

You can test an installed widget by its plugin id:

plasmoidviewer -a org.kde.plasma.kickoff

Or run a widget from a folder. This is particularly useful for development, as you can skip the install step:

plasmoidviewer -a ~/Code/plasmoid-helloworld/package

#Test as a desktop widget

--location=desktop is for the desktop wallpaper, not desktop widgets. Desktop widgets use --location=floating.

plasmoidviewer -a package --location=floating --formfactor=planar
plasmoidviewer -a package # floating+planar is the default

#Test as a horizontal panel widget

If we set plasmoidviewer's form factor to horizontal and its location to topedge or bottomedge, we can test a widget in a panel.

plasmoidviewer -a package -l topedge -f horizontal

#Testing DPI scaling

Setting the QT_SCALE_FACTOR=2 environment variable doubles the scale, just for the plasmoidviewer window. This is great for testing whether your code supports a HiDPI screen.

At a very high scale, the default plasmoidviewer window will probably be too small to show the widget, so set the size and position of the window. The window goes maximized if you set a size larger than your screen has available.

QT_SCALE_FACTOR=2 plasmoidviewer -a package
QT_SCALE_FACTOR=2 plasmoidviewer -a package -l topedge -f horizontal -x 0 -y 0 -s 1920x1080

#Enable logging

If QML's console.log() output is hidden, you can show it with an environment variable:

QT_LOGGING_RULES="qml.debug=true" plasmawindowed org.kde.plasma.kickoff
QT_LOGGING_RULES="qml.debug=true" plasmoidviewer -a org.kde.plasma.kickoff
QT_LOGGING_RULES="qml.debug=true" sonicshell --replace

It is much easier to always have it shown for the current user, including in the system log (journalctl -b0 -f). To do so, set [Rules] qml.debug=true in ~/.config/QtProject/qtlogging.ini, for example with kwriteconfig6:

kwriteconfig6 --file ~/.config/QtProject/qtlogging.ini --group "Rules" --key "qml.debug" "true"

# ~/.config/QtProject/qtlogging.ini
[Rules]
qml.debug=true

plasmoidviewer and sonicshell log through Sonic Logging, which writes to ~/.local/state/sonic/<program>.log and also shows the lines in the terminal when you run the program from one. So if you redirect a program's output to a file or a pipe, look in that log instead.

You should now see output when you add console.log() statements to your widget. You can place them in any function, like the Component.onCompleted signal handler:

import QtQuick
import org.kde.plasma.plasmoid

PlasmoidItem {
    Component.onCompleted: {
        console.log("Hello World")
    }
}

Or in an onPropertyChanged signal handler. The following example prints a log message when you click the button:

import QtQuick
import QtQuick.Layouts
import org.kde.plasma.components as PlasmaComponents
import org.kde.plasma.plasmoid

PlasmoidItem {
    id: widget
    preferredRepresentation: fullRepresentation

    property int num: 1
    onNumChanged: console.log("num", num)

    fullRepresentation: PlasmaComponents.Button {
        Layout.minimumWidth: implicitWidth
        text: i18n("Add 1")
        onClicked: widget.num += 1
    }
}