i18n: Add support for translating the class reference

- Parse `.po` files from `doc/translations/*.po` like already done
  with `editor/translations/*.po`.
- Add logic to register a doc translation mapping in `TranslationServer`
  and `EditorSettings`.
- Add `DTR()` to lookup the doc translation mapping (similar to `TTR()`).
  Strings are automatically dedented and stripped of whitespace to ensure
  that they would match the translation catalog.
- Use `DTR()` to translate relevant strings in `EditorHelp`,
  `EditorInspector`, `CreateDialog`, `ConnectionsDialog`.
- Small simplification to `TranslationLoaderPO`, the path argument was
  not really meaningful.

1 files changed, 9 insertions, 2 deletions

diff --git a/core/ustring.cpp b/core/ustring.cpp
index da089dce40..8027ae29b5 100644
--- a/core/ustring.cpp
+++ b/core/ustring.cpp
@@ -4412,7 +4412,6 @@ String String::unquote() const {
 
 #ifdef TOOLS_ENABLED
 String TTR(const String &p_text) {
-
 	if (TranslationServer::get_singleton()) {
 		return TranslationServer::get_singleton()->tool_translate(p_text);
 	}
@@ -4420,10 +4419,18 @@ String TTR(const String &p_text) {
 	return p_text;
 }
 
+String DTR(const String &p_text) {
+	if (TranslationServer::get_singleton()) {
+		// Comes straight from the XML, so remove indentation and any trailing whitespace.
+		const String text = p_text.dedent().strip_edges();
+		return TranslationServer::get_singleton()->doc_translate(text);
+	}
+
+	return p_text;
+}
 #endif
 
 String RTR(const String &p_text) {
-
 	if (TranslationServer::get_singleton()) {
 		String rtr = TranslationServer::get_singleton()->tool_translate(p_text);
 		if (rtr == String() || rtr == p_text) {