Translations / i18n

Translate your widget

ki18n

Ki18n (KDE internationalization) is the translation library for KDE. It has a programmer’s guide which you can read, but we’ll cover the basics here.

i18n()

Translated strings need to be wrapped in the i18n(...) function. Note that single quotes i18n('Test') will be ignored by the tool that parses your code for all the translation strings. Always use double quotes i18n("Test").
// configGeneral.qml
CheckBox {
    id: showThing
    label: i18n("Show notification")
}

Variables in i18n()

The i18n(...) is an overloaded function which allows you to pass values into the translation i18n(format, variable1, variable2). Just place %1 where you want the first variable to be substitued, and %2 where the second should go.
// main.qml
Item {
    id: showThing
    property int unreadEmailCount: 3
    Plasmoid.toolTipSubText: i18n("%1 unread emails", unreadEmailCount)
}

Plural in i18n()

In English, a translated sentence is different when there’s just 1 item from when there is 2 or more items. i18np(...) can be used in such a situation.

An example from the Ki18n docs is:

i18np("One image in album %2", "%1 images in album %2", numImages, albumName)
i18np("One image in album %2", "More images in album %2", numImages, albumName)

Using i18np(...) can improve our previous example. When unreadEmailCount was 1, the tooltip would have read "1 unread emails".

// main.qml
Item {
    id: showThing
    property int unreadEmailCount: 3
    Plasmoid.toolTipSubText: i18np("%1 unread email", "%1 unread emails", unreadEmailCount)
}

Translation Folder Structure

After we’ve wrapped all the messages in our code with i18n(...) calls, we then need to extract all the messages for our translators into a template.pot file which they can then create a fr.po for their French translations.

We’ll place the template.pot file under a translate folder inside the bundled package so that our users can easily translate our widget when they go poking into our code.

We’ll also create a merge.sh script which will extract the messages from our code into a template.pot, then update the translated fr.po file with any changes.

Lastly, we’ll make a build.sh script to convert the fr.po text files into the binary .mo files which are needed for KDE to recognize the translations.

The latest copy of my merge.sh and build.sh can be found here:

A working example can be seen in the Tiled Menu widget:

└── ~/Code/plasmoid-helloworld/
    └── package
        ├── contents
        │   └── ...
        ├── translate
        │   ├── build.sh
        │   ├── fr.po
        │   ├── template.pot
        │   └── merge.sh
        └── metadata.desktop

After running build.sh we should end up with:

└── ~/Code/plasmoid-helloworld/
    └── package
        ├── contents
        │   └── locale
        │       └── fr
        │           └── LC_MESSAGES
        │               └── plasma_applet_com.github.zren.helloworld.mo
        └── ...

Install GetText

After we’ve wrapped all the messages in our code with i18n(...) calls, we then need to extract all the messages for our translators into a template.pot file.

To do this, we need to install the gettext package.

sudo apt install gettext

Generating template.pot

First thing we need to do in our merge.sh script, is list all files we wish to get translated in our widgets code.

The latest copy of my complete merge.sh script can be found here.

DIR is the directory (absolute path to package/translate/) since we may run the merge script from another directory.

We use kreadconfig5 to grab the widget’s namespace (com.github.zren.helloworld) and store it in plasmoidName. We then remove the beginning of the namespace so we are left with helloworld and store that in widgetName. We also grab the website which a link to the GitHub repo for use as the bugAddress.

After validating that plasmoidName is not an empty string with bash’s [ -z "$plasmoidName" ] operator, we then list all .qml and .js files using find and store the results of the command in a temporary infiles.list file.

Then we generate a template.pot.new using the xgettext command. After generating it, we use sed to replace a few placeholder strings.

In the complete merge.sh, we also parse the widget name in metadata.desktop first with xgettext --language=Desktop and --join-existing in the 2nd xgettext call.

translate/merge.sh

#!/bin/sh

DIR=`cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd`
plasmoidName=`kreadconfig5 --file="$DIR/../metadata.desktop" --group="Desktop Entry" --key="X-KDE-PluginInfo-Name"`
widgetName="${plasmoidName##*.}" # Strip namespace
website=`kreadconfig5 --file="$DIR/../metadata.desktop" --group="Desktop Entry" --key="X-KDE-PluginInfo-Website"`
bugAddress="$website"
packageRoot=".." # Root of translatable sources
projectName="plasma_applet_${plasmoidName}" # project name

#---
if [ -z "$plasmoidName" ]; then
    echo "[merge] Error: Couldn't read plasmoidName."
    exit
fi

#---
echo "[merge] Extracting messages"
find "${packageRoot}" -name '*.cpp' -o -name '*.h' -o -name '*.c' -o -name '*.qml' -o -name '*.js' | sort > "${DIR}/infiles.list"

xgettext \
    --files-from=infiles.list \
    --from-code=UTF-8 \
    --width=400 \
    --add-location=file \
    -C -kde -ci18n -ki18n:1 -ki18nc:1c,2 -ki18np:1,2 -ki18ncp:1c,2,3 -ktr2i18n:1 -kI18N_NOOP:1 \
    -kI18N_NOOP2:1c,2  -kN_:1 -kaliasLocale -kki18n:1 -kki18nc:1c,2 -kki18np:1,2 -kki18ncp:1c,2,3 \
    --package-name="${widgetName}" \
    --msgid-bugs-address="${bugAddress}" \
    -D "${packageRoot}" \
    -D "${DIR}" \
    -o "template.pot.new" \
    || \
    { echo "[merge] error while calling xgettext. aborting."; exit 1; }

sed -i 's/"Content-Type: text\/plain; charset=CHARSET\\n"/"Content-Type: text\/plain; charset=UTF-8\\n"/' "template.pot.new"
sed -i 's/# SOME DESCRIPTIVE TITLE./'"# Translation of ${widgetName} in LANGUAGE"'/' "template.pot.new"
sed -i 's/# Copyright (C) YEAR THE PACKAGE'"'"'S COPYRIGHT HOLDER/'"# Copyright (C) $(date +%Y)"'/' "template.pot.new"

Updating template.pot

Continuing our merge.sh script, we then check to see if an older template.pot file exists.

If it does, we’ll replace the POT-Creation-Date in the new file with the older creation date, then run the diff command to detect if there’s been any changes. If there has been changes, we fix the POT-Creation-Date and overwrite the old template.pot file. To make the changes more noticeable, we also list the added/removed translation messages.

If there hasn’t been any changes, we simply delete the template.pot.new file.

Lastly, we delete the infiles.list to clean things up.

if [ -f "template.pot" ]; then
    newPotDate=`grep "POT-Creation-Date:" template.pot.new | sed 's/.\{3\}$//'`
    oldPotDate=`grep "POT-Creation-Date:" template.pot | sed 's/.\{3\}$//'`
    sed -i 's/'"${newPotDate}"'/'"${oldPotDate}"'/' "template.pot.new"
    changes=`diff "template.pot" "template.pot.new"`
    if [ ! -z "$changes" ]; then
        # There's been changes
        sed -i 's/'"${oldPotDate}"'/'"${newPotDate}"'/' "template.pot.new"
        mv "template.pot.new" "template.pot"

        addedKeys=`echo "$changes" | grep "> msgid" | cut -c 9- | sort`
        removedKeys=`echo "$changes" | grep "< msgid" | cut -c 9- | sort`
        echo ""
        echo "Added Keys:"
        echo "$addedKeys"
        echo ""
        echo "Removed Keys:"
        echo "$removedKeys"
        echo ""

    else
        # No changes
        rm "template.pot.new"
    fi
else
    # template.pot didn't already exist
    mv "template.pot.new" "template.pot"
fi

rm "${DIR}/infiles.list"
echo "[merge] Done extracting messages"

Examining template.pot

Now that we’ve got a template.pot, let’s take a look at it.

The messages we want to translate appear as msgid "Show Thing", with the file it came from appearing in a comment in the line above. Underneath is an empty msgstr "" which is where the translator will place the translated messages.

# Translation of helloworld in LANGUAGE
# Copyright (C) 2018
# This file is distributed under the same license as the helloworld package.
# FIRST AUTHOR <EMAIL@ADDRESS>, YEAR.
#
#, fuzzy
msgid ""
msgstr ""
"Project-Id-Version: helloworld \n"
"Report-Msgid-Bugs-To: https://github.com/Zren/plasmoid-helloworld\n"
"POT-Creation-Date: 2018-12-03 18:47-0500\n"
"PO-Revision-Date: YEAR-MO-DA HO:MI+ZONE\n"
"Last-Translator: FULL NAME <EMAIL@ADDRESS>\n"
"Language-Team: LANGUAGE <LL@li.org>\n"
"Language: \n"
"MIME-Version: 1.0\n"
"Content-Type: text/plain; charset=UTF-8\n"
"Content-Transfer-Encoding: 8bit\n"

#: ../contents/configGeneral.qml
msgid "Show notification"
msgstr ""

#: ../contents/ui/configGeneral.qml
msgid "%1 unread emails"
msgstr ""

#: ../contents/ui/configGeneral.qml
msgid "%1 unread email"
msgid_plural "%1 unread emails"
msgstr[0] ""
msgstr[1] ""

fr.po

Now that we’ve got a template.pot, our translators can copy it and rename it to fr.po.

We use fr since it is the locale code for French, which we’ll be using later.

A full list of locale codes can be found on StackOverflow. Make sure you use underscores (fr_CA) instead of dashes (fr-CA) if the language you are translating is not reusable for the generic fr language.

Translators can then start filling out the empty msgstr "" with translations.

#: ../contents/configGeneral.qml
msgid "Show notification"
msgstr "Montrer les notifications"

Merging updates into fr.po

Our merge.sh currently only extracts messages into template.pot. We should next merge any new messages extracted for translation into our fr.po file.

We’ll first filter the translate directory for .po files.

Then for each .po file, we’ll extract the locale code (fr) from the filename using the basename command then striping out the file extension.

We then use another GetText command msgmerge to generate a new fr.po.new file based on the old fr.po and the current template.pot.

Afterwards, we use sed to replace the LANGUAGE placeholder with our current locale code in case our translator left them as is.

When we’re done, we overwrite the old fr.po with fr.po.new.

translate/merge.sh

#---
echo "[merge] Merging messages"
catalogs=`find . -name '*.po' | sort`
for cat in $catalogs; do
    echo "[merge] $cat"
    catLocale=`basename ${cat%.*}`
    msgmerge \
        --width=400 \
        --add-location=file \
        --no-fuzzy-matching \
        -o "$cat.new" \
        "$cat" "${DIR}/template.pot"
    sed -i 's/# SOME DESCRIPTIVE TITLE./'"# Translation of ${widgetName} in ${catLocale}"'/' "$cat.new"
    sed -i 's/# Translation of '"${widgetName}"' in LANGUAGE/'"# Translation of ${widgetName} in ${catLocale}"'/' "$cat.new"
    sed -i 's/# Copyright (C) YEAR THE PACKAGE'"'"'S COPYRIGHT HOLDER/'"# Copyright (C) $(date +%Y)"'/' "$cat.new"

    mv "$cat.new" "$cat"
done

echo "[merge] Done merging messages"

Building .mo

Once our fr.po has been filled out, we can then convert it to a binary .mo file. So lets get started on our build.sh script.

The latest copy of my complete build.sh script can be found here.

We start with the same code that we used in our merge.sh script to parse our metadata.desktop file and get the widget’s namespace. We also reuse the same code to iterate the .po files.

Then we use another GetText command msgfmt to convert the fr.po file into a fr.mo file.

We then make sure a contents/locale/fr/LC_MESSAGES/ folder exists, creating it if it does not.

Then we copy the fr.mo to the LC_MESSAGES folder, renaming it to plasma_applet_com.github.zren.helloworld.mo. Notice that we put plasma_applet_ in front of the widget’s namespace.

#!/bin/sh

DIR=`cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd`
plasmoidName=`kreadconfig5 --file="$DIR/../metadata.desktop" --group="Desktop Entry" --key="X-KDE-PluginInfo-Name"`
website=`kreadconfig5 --file="$DIR/../metadata.desktop" --group="Desktop Entry" --key="X-KDE-PluginInfo-Website"`
bugAddress="$website"
packageRoot=".." # Root of translatable sources
projectName="plasma_applet_${plasmoidName}" # project name

#---
if [ -z "$plasmoidName" ]; then
    echo "[build] Error: Couldn't read plasmoidName."
    exit
fi

#---
echo "[build] Compiling messages"

catalogs=`find . -name '*.po' | sort`
for cat in $catalogs; do
    echo "$cat"
    catLocale=`basename ${cat%.*}`
    msgfmt -o "${catLocale}.mo" "$cat"

    installPath="$DIR/../contents/locale/${catLocale}/LC_MESSAGES/${projectName}.mo"

    echo "[build] Install to ${installPath}"
    mkdir -p "$(dirname "$installPath")"
    mv "${catLocale}.mo" "${installPath}"
done

echo "[build] Done building messages"

Testing our translations

First make sure you run our build.sh translation script.

Then we need to override the locale environment variables just for our plasmoidviewer instance. If you run the locale command, it should list all the environment variables available to override.

In practice, we only need to override LANG="fr_CA.UTF-8" and another variable it didn’t list LANGUAGE="fr_CA:fr". If your widget is a clock, then you might also need to override LC_TIME="fr_FR.UTF-8".

sh package/translate/build.sh
LANGUAGE="fr_CA:fr" LANG="fr_CA.UTF-8" plasmoidviewer -a package
$ locale
LANG=en_CA.UTF-8
LC_CTYPE="en_CA.UTF-8"
LC_NUMERIC=en_CA.UTF-8
LC_TIME=en_US.UTF-8
LC_COLLATE="en_CA.UTF-8"
LC_MONETARY=en_CA.UTF-8
LC_MESSAGES="en_CA.UTF-8"
LC_PAPER=en_CA.UTF-8
LC_NAME=en_CA.UTF-8
LC_ADDRESS=en_CA.UTF-8
LC_TELEPHONE=en_CA.UTF-8
LC_MEASUREMENT=en_CA.UTF-8
LC_IDENTIFICATION=en_CA.UTF-8
LC_ALL=

Reusing other translations

While it is bad practice to link to private code, if you know another widget has translated a string, you can use i18nd(domain, string, ...) to use translations from that domain. Note that a widget’s domain starts with plasma_applet_, and ends with the widget’s X-KDE-PluginInfo-Name.

Eg: plasma_applet_com.github.zren.helloworld

An example can be found in org.kde.image's main.qml which reuses the same code for the org.kde.slideshow.

CheckBox {
    text: i18nd("plasma_applet_org.kde.plasma.digitalclock", "Show date")
}
CheckBox {
    text: i18nd("plasma_applet_org.kde.plasma.digitalclock", "Show seconds")
}
Button {
    text: i18nd("plasma_wallpaper_org.kde.image", "Open Wallpaper Image")
}