Testing and debugging Plasmoid for Plasma with Qt Creator — Syncthing Tray 2026-06-05 documentation

# Testing and debugging Plasmoid for Plasma with Qt Creator

The following instructions allow to test the Plasmoid by installing it in a test directory rather than the regular home to separate testing from production.

1. Build as usual, ensure `NO_PLASMOID` is turned off.

2. Add a build step to execute the custom target `init_plasmoid_testing` which will install the Plasmoid in a test directory which is `$CMAKE_BUILD_DIR/plasmoid-testing` by default (configurable via cache variable `PLASMOID_TESTDIR`, the sub directory `plasmoid-testing` is not part of the variable).

3. Add new config for “run” in Qt Creator and set `bash` as executable.

4. Set `%{sourceDir}/../../syncthingtray/plasmoid/scripts/starttesting.sh plasmoidviewer --applet martchus.syncthingplasmoid-devel` as CLI argument.

   - Remove the `-devel` suffix if not building with a CMake development preset.

   - It is also possible to use `plasmawindowed` or `plasmashell`, see sections below.

   - It is also possible to specify `org.kde.plasma.systemtray` as applet to test how the Plasmoid looks like within the system tray plasmoid.

   - This usage of `%{sourceDir}` assumes one used the “Building this straight” instructions from the main README.md.

   - When using a suffix (e.g. development build via CMake presets), this suffix needs to be appended to the applet name.

5. Keep `%{buildDir}` as working directory.

6. In the execution environment there’s nothing mandatory to be set because `starttesting.sh` should already take care of setting the environment.

   - The home directory is set in accordance with the directory used in step 2. but can be overridden by setting `TEST_HOME`; make sure that `TEST_HOME` and the CMake variable `PLASMOID_TESTDIR` are set in accordance.

   - If not already set, `QT_PLUGIN_PATH` is set to `$CMAKE_CURRENT_BINARY_DIR/plasmoid/lib` which should contain the plugin for the Plasmoid under `plasma/applets/*syncthingplasmoid*.so`.

   - Set `QT_DEBUG_PLUGINS` to 1 for verbose plugin detection (the verbose output might be suppressed when starting via Qt Creator so it may be worthwhile to start this from a terminal).

7. Ignore warning that executable is no debug build, it is sufficient when the plugin is a debug build (see next section for QML debugging).

## Saving/restoring settings

Be aware that `plasmoidviewer` will revert Plasmoid-specific settings to the defaults on startup. So it is not possible to test restoring/saving settings using it. For this use case, `plasmawindowed` can be used instead.

## Testing within the real Plasma shell

Some issues are only reproducible within the actual Plasma shell. It is possible to test with the real Plasma shell in the same way as described above by setting `plasmashell` as executable.

It is only possible to run one `plasmashell` at a time so you have to stop your regular `plasmashell` first. While developing you can start e.g. `tint2` to be not without a shell. It works quite well within an X11 Plasma session when both shells are placed on different screen edges.

## Enable QML debugging

It is not clear whether the following instructions are still valid for Plasma 6. It seems that QML debugging can be enabled under Plasma 6 by setting the environment variable `PLASMA_ENABLE_QML_DEBUG` but this has not been tested yet.

To enable QML debugging, it is required to rebuild `plasmoidviewer` with QML debugging enabled.

For Arch Linux, I created the package `plasmoidviewer-debug` for that purpose. Installing this package and using `plasmoidviewer-debug` instead of `plasmoidviewer` should make enabling QML debugging in the Run section of Qt Creator work.

To create a debug build of `plasmoidviewer` manually:

1. Get `plasma-sdk`: `git clone https://anongit.kde.org/plasma-sdk.git`

2. Create a debug build of `plasmoidviewer` and ensure `QT_QML_DEBUG` is defined when compiling `plasmoidviewer`, e.g. by applying [PATCH] Enable QML debugging.

3. Prepend the build directory containing the `plasmoidviewer` binary to the path variable in the build environment of Syncthing Tray.

4. Enable QML debugging in the Run section.

# Testing against a development build of Plasma

1. Build the whole dependency chain up to `plasma-desktop` installing it under some custom prefix. Note that `plasma-sdk` alone is not sufficient.

2. Then follow the usual steps but make sure you build Syncthing Tray against the custom KDE builds. This is achieved the easiest by using the ``debug-kde-custom`CMake preset. This preset uses the environment variable`KDE_INSTALL_DIR` which must point to the custom prefix used in step 1.

3. Source the `prefix.sh` script that should be present in the build directory of any KDE library you built in step 1, e.g. `source kde/plasma-sdk/prefix.sh`.

4. When setting the environment one needs to be more careful to not override variables set in step 3. It is the easiest to just start e.g. `plasmawindowed` from the shell:

       QT_PLUGIN_PATH=$BUILD_DIR/syncthingtray/`debug-kde-custom/syncthingtray/plasmoid/lib:$QT_PLUGIN_PATH HOME=$BUILD_DIR/syncthingtray/`debug-kde-custom/plasmoid-testing kdeinstall/bin/plasmawindowed martchus.syncthingplasmoid-devel

   - It would make sense to tweak `starttesting.sh` to be able to do the sourcing automatically.