Stirling-PDF/HowToAddNewLanguage.md
Ludy b37457b41d
Add: Configurable UI Language Support with Dynamic Filtering (#2846)
# Description of Changes

### Summary
- Added support for configuring UI languages via `settings.yml`
(`languages` field).
- Modified `LanguageService` to respect the configured languages, while
ensuring British English (`en_GB`) is always enabled.
- Updated Thymeleaf templates to dynamically display only the allowed
languages.
- Improved logging and refactored some list-to-set conversions for
better efficiency.

### Why the Change?
- Allows administrators to limit available UI languages instead of
displaying all detected languages.
- Provides better customization options and simplifies language
management.

### Challenges Encountered
- Ensuring backwards compatibility: If `languages` is empty, all
languages remain enabled.
- Handling `Set<String>` instead of `List<String>` in `LanguageService`
for optimized lookups.

---

## Checklist

### General

- [x] I have read the [Contribution
Guidelines](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/CONTRIBUTING.md)
- [x] I have read the [Stirling-PDF Developer
Guide](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/DeveloperGuide.md)
(if applicable)
- [x] I have read the [How to add new languages to
Stirling-PDF](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/HowToAddNewLanguage.md)
(if applicable)
- [x] I have performed a self-review of my own code
- [x] My changes generate no new warnings

### Documentation

- [ ] I have updated relevant docs on [Stirling-PDF's doc
repo](https://github.com/Stirling-Tools/Stirling-Tools.github.io/blob/main/docs/)
(if functionality has heavily changed)
- [x] I have read the section [Add New Translation
Tags](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/HowToAddNewLanguage.md#add-new-translation-tags)
(for new translation tags only)

### UI Changes (if applicable)

- [ ] Screenshots or videos demonstrating the UI changes are attached
(e.g., as comments or direct attachments in the PR)

### Testing (if applicable)

- [x] I have tested my changes locally. Refer to the [Testing
Guide](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/DeveloperGuide.md#6-testing)
for more details.
2025-02-03 10:52:34 +00:00

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<p align="center">
<img src="https://raw.githubusercontent.com/Stirling-Tools/Stirling-PDF/main/docs/stirling.png" width="80">
<br>
<h1 align="center">Stirling-PDF</h1>
</p>
# How to add new languages to Stirling-PDF
Fork Stirling-PDF and create a new branch out of `main`.
Then add a reference to the language in the navbar by adding a new language entry to the dropdown:
- Edit the file: [languages.html](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/src/main/resources/templates/fragments/languages.html)
- Add a flag SVG file to: [flags directory](https://github.com/Stirling-Tools/Stirling-PDF/tree/main/src/main/resources/static/images/flags)
Any SVG flags are fine; most of the current ones were sourced from [here](https://flagicons.lipis.dev/). If your language isn't represented by a flag, choose a similar one, such as Saudi Arabia's flag for Arabic.
For example, to add Polish, you would add:
```html
<a th:if="${#lists.isEmpty(@languages) or #lists.contains(@languages, 'pl_PL')}" class="dropdown-item lang_dropdown-item" href="" data-bs-language-code="pl_PL"> <img th:src="@{'/images/flags/pl.svg'}" alt="icon" width="20" height="15"> Polski</a>
```
The `data-bs-language-code` is the code used to reference the file in the next step.
### Add Language Property File
Start by copying the existing English property file:
- [messages_en_GB.properties](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/src/main/resources/messages_en_GB.properties)
Copy and rename it to `messages_{your data-bs-language-code here}.properties`. In the Polish example, you would set the name to `messages_pl_PL.properties`.
Then simply translate all property entries within that file and make a Pull Request (PR) into `main` for others to use!
If you do not have a Java IDE, I am happy to verify that the changes work once you raise the PR (but I won't be able to verify the translations themselves).
## Handling Untranslatable Strings
Sometimes, certain strings in the properties file may not require translation because they are the same in the target language or are universal (like names of protocols, certain terminologies, etc.). To ensure accurate statistics for language progress, these strings should be added to the `ignore_translation.toml` file located in the `scripts` directory. This will exclude them from the translation progress calculations.
For example, if the English string `error=Error` does not need translation in Polish, add it to the `ignore_translation.toml` under the Polish section:
```toml
[pl_PL]
ignore = [
"language.direction", # Existing entries
"error" # Add new entries here
]
```
## Add New Translation Tags
> [!IMPORTANT]
> If you add any new translation tags, they must first be added to the `messages_en_GB.properties` file. This ensures consistency across all language files.
- New translation tags **must be added** to the `messages_en_GB.properties` file to maintain a reference for other languages.
- After adding the new tags to `messages_en_GB.properties`, add and translate them in the respective language file (e.g., `messages_pl_PL.properties`).
Make sure to place the entry under the correct language section. This helps maintain the accuracy of translation progress statistics and ensures that the translation tool or scripts do not misinterpret the completion rate.
### Use this code to perform a local check
#### Windows command
```ps
python .github/scripts/check_language_properties.py --reference-file src\main\resources\messages_en_GB.properties --branch "" --files src\main\resources\messages_pl_PL.properties
python .github/scripts/check_language_properties.py --reference-file src\main\resources\messages_en_GB.properties --branch "" --check-file src\main\resources\messages_pl_PL.properties
```