Add clientside translations.

21 files changed, 629 insertions, 46 deletions

diff --git a/builtin/common/misc_helpers.lua b/builtin/common/misc_helpers.lua
index 776be29d8..67eda11f3 100644
--- a/builtin/common/misc_helpers.lua
+++ b/builtin/common/misc_helpers.lua
@@ -680,6 +680,44 @@ function core.strip_colors(str)
 	return (str:gsub(ESCAPE_CHAR .. "%([bc]@[^)]+%)", ""))
 end
 
+function core.translate(textdomain, str, ...)
+	local start_seq
+	if textdomain == "" then
+		start_seq = ESCAPE_CHAR .. "T"
+	else
+		start_seq = ESCAPE_CHAR .. "(T@" .. textdomain .. ")"
+	end
+	local arg = {n=select('#', ...), ...}
+	local end_seq = ESCAPE_CHAR .. "E"
+	local arg_index = 1
+	local translated = str:gsub("@(.)", function(matched)
+		local c = string.byte(matched)
+		if string.byte("1") <= c and c <= string.byte("9") then
+			local a = c - string.byte("0")
+			if a ~= arg_index then
+				error("Escape sequences in string given to core.translate " ..
+					"are not in the correct order: got @" .. matched ..
+					"but expected @" .. tostring(arg_index))
+			end
+			if a > arg.n then
+				error("Not enough arguments provided to core.translate")
+			end
+			arg_index = arg_index + 1
+			return ESCAPE_CHAR .. "F" .. arg[a] .. ESCAPE_CHAR .. "E"
+		else
+			return matched
+		end
+	end)
+	if arg_index < arg.n + 1 then
+		error("Too many arguments provided to core.translate")
+	end
+	return start_seq .. translated .. end_seq
+end
+
+function core.get_translator(textdomain)
+	return function(str, ...) return core.translate(textdomain or "", str, ...) end
+end
+
 --------------------------------------------------------------------------------
 -- Returns the exact coordinate of a pointed surface
 --------------------------------------------------------------------------------
diff --git a/doc/lua_api.txt b/doc/lua_api.txt
index 32dab9d00..20c3e5a92 100644
--- a/doc/lua_api.txt
+++ b/doc/lua_api.txt
@@ -139,6 +139,7 @@ Mod directory structure
     |   |   `-- modname_something_else.png
     |   |-- sounds
     |   |-- media
+    |   |-- locale
     |   `-- <custom data>
     `-- another
 
@@ -182,6 +183,9 @@ Models for entities or meshnodes.
 Media files (textures, sounds, whatever) that will be transferred to the
 client and will be available for use by the mod.
 
+### `locale`
+Translation files for the clients. (See `Translations`)
+
 Naming convention for registered textual names
 ----------------------------------------------
 Registered names should generally be in this format:
@@ -2152,6 +2156,68 @@ Helper functions
 * `minetest.pointed_thing_to_face_pos(placer, pointed_thing)`: returns a position
     * returns the exact position on the surface of a pointed node
 
+Translations
+------------
+
+Texts can be translated client-side with the help of `minetest.translate` and translation files.
+
+### Translating a string
+Two functions are provided to translate strings: `minetest.translate` and `minetest.get_translator`.
+
+* `minetest.get_translator(textdomain)` is a simple wrapper around `minetest.translate`, and
+  `minetest.get_translator(textdomain)(str, ...)` is equivalent to `minetest.translate(textdomain, str, ...)`.
+  It is intended to be used in the following way, so that it avoids verbose repetitions of `minetest.translate`:
+
+    local S = minetest.get_translator(textdomain)
+    S(str, ...)
+
+  As an extra commodity, if `textdomain` is nil, it is assumed to be "" instead.
+
+* `minetest.translate(textdomain, str, ...)` translates the string `str` with the given `textdomain`
+  for disambiguation. The textdomain must match the textdomain specified in the translation file in order
+  to get the string translated. This can be used so that a string is translated differently in different contexts.
+  It is advised to use the name of the mod as textdomain whenever possible, to avoid clashes with other mods.
+  This function must be given a number of arguments equal to the number of arguments the translated string expects.
+  Arguments are literal strings -- they will not be translated, so if you want them to be, they need to come as
+  outputs of `minetest.translate` as well.
+
+  For instance, suppose we want to translate "@1 Wool" with "@1" being replaced by the translation of "Red".
+  We can do the following:
+
+    local S = minetest.get_translator()
+    S("@1 Wool", S("Red"))
+
+  This will be displayed as "Red Wool" on old clients and on clients that do not have localization enabled.
+  However, if we have for instance a translation file named `wool.fr.tr` containing the following:
+
+    @1 Wool=Laine @1
+    Red=Rouge
+
+  this will be displayed as "Laine Rouge" on clients with a French locale.
+
+### Translation file format
+A translation file has the suffix `.[lang].tr`, where `[lang]` is the language it corresponds to.
+The file should be a text file, with the following format:
+
+* Lines beginning with `# textdomain:` (the space is significant) can be used to specify the text
+  domain of all following translations in the file.
+* All other empty lines or lines beginning with `#` are ignored.
+* Other lines should be in the format `original=translated`. Both `original` and `translated` can
+  contain escape sequences beginning with `@` to insert arguments, literal `@`, `=` or newline
+  (See ### Escapes below). There must be no extraneous whitespace around the `=` or at the beginning
+  or the end of the line.
+
+### Escapes
+Strings that need to be translated can contain several escapes, preceded by `@`.
+* `@@` acts as a literal `@`.
+* `@n`, where `n` is a digit between 1 and 9, is an argument for the translated string that will be inlined
+  when translation. Due to how translations are implemented, the original translation string **must** have
+  its arguments in increasing order, without gaps or repetitions, starting from 1.
+* `@=` acts as a literal `=`. It is not required in strings given to `minetest.translate`, but is in translation
+  files to avoid begin confused with the `=` separating the original from the translation.
+* `@\n` (where the `\n` is a literal newline) acts as a literal newline. As with `@=`, this escape is not required
+  in strings given to `minetest.translate`, but is in translation files.
+
 `minetest` namespace reference
 ------------------------------
 
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 4fc6bca25..cc3d65109 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -450,6 +450,7 @@ set(common_SRCS
 	terminal_chat_console.cpp
 	tileanimation.cpp
 	tool.cpp
+	translation.cpp
 	treegen.cpp
 	version.cpp
 	voxel.cpp
diff --git a/src/camera.cpp b/src/camera.cpp
index 7746b65df..50e18fdd2 100644
--- a/src/camera.cpp
+++ b/src/camera.cpp
@@ -620,10 +620,11 @@ void Camera::drawNametags()
 		f32 transformed_pos[4] = { pos.X, pos.Y, pos.Z, 1.0f };
 		trans.multiplyWith1x4Matrix(transformed_pos);
 		if (transformed_pos[3] > 0) {
-			std::string nametag_colorless = unescape_enriched(nametag->nametag_text);
+			std::wstring nametag_colorless =
+				unescape_translate(utf8_to_wide(nametag->nametag_text));
 			core::dimension2d<u32> textsize =
 				g_fontengine->getFont()->getDimension(
-				utf8_to_wide(nametag_colorless).c_str());
+				nametag_colorless.c_str());
 			f32 zDiv = transformed_pos[3] == 0.0f ? 1.0f :
 				core::reciprocal(transformed_pos[3]);
 			v2u32 screensize = RenderingEngine::get_video_driver()->getScreenSize();
@@ -633,8 +634,9 @@ void Camera::drawNametags()
 			screen_pos.Y = screensize.Y *
 				(0.5 - transformed_pos[1] * zDiv * 0.5) - textsize.Height / 2;
 			core::rect<s32> size(0, 0, textsize.Width, textsize.Height);
-			g_fontengine->getFont()->draw(utf8_to_wide(nametag->nametag_text).c_str(),
-					size + screen_pos, nametag->nametag_color);
+			g_fontengine->getFont()->draw(
+				translate_string(utf8_to_wide(nametag->nametag_text)).c_str(),
+				size + screen_pos, nametag->nametag_color);
 		}
 	}
 }
diff --git a/src/chat.cpp b/src/chat.cpp
index 35c6329c3..fd0718707 100644
--- a/src/chat.cpp
+++ b/src/chat.cpp
@@ -650,6 +650,7 @@ ChatBackend::ChatBackend():
 void ChatBackend::addMessage(std::wstring name, std::wstring text)
 {
 	// Note: A message may consist of multiple lines, for example the MOTD.
+	text = translate_string(text);
 	WStrfnd fnd(text);
 	while (!fnd.at_end())
 	{
diff --git a/src/client.cpp b/src/client.cpp
index 30c1ab4d5..658b10393 100644
--- a/src/client.cpp
+++ b/src/client.cpp
@@ -51,6 +51,7 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 #include "script/scripting_client.h"
 #include "game.h"
 #include "chatmessage.h"
+#include "translation.h"
 
 extern gui::IGUIEnvironment* guienv;
 
@@ -684,8 +685,19 @@ bool Client::loadMedia(const std::string &data, const std::string &filename)
 		return true;
 	}
 
-	errorstream<<"Client: Don't know how to load file \""
-			<<filename<<"\""<<std::endl;
+	const char *translate_ext[] = {
+		".tr", NULL
+	};
+	name = removeStringEnd(filename, translate_ext);
+	if (!name.empty()) {
+		verbosestream << "Client: Loading translation: "
+				<< "\"" << filename << "\"" << std::endl;
+		g_translations->loadTranslation(data);
+		return true;
+	}
+
+	errorstream << "Client: Don't know how to load file \""
+		<< filename << "\"" << std::endl;
 	return false;
 }
 
diff --git a/src/game.cpp b/src/game.cpp
index 68b8e0767..4a26bc844 100644
--- a/src/game.cpp
+++ b/src/game.cpp
@@ -58,6 +58,7 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 #include "sky.h"
 #include "subgame.h"
 #include "tool.h"
+#include "translation.h"
 #include "util/basic_macros.h"
 #include "util/directiontables.h"
 #include "util/pointedthing.h"
@@ -242,7 +243,7 @@ void update_profiler_gui(gui::IGUIStaticText *guitext_profiler, FontEngine *fe,
 
 		std::ostringstream os(std::ios_base::binary);
 		g_profiler->printPage(os, show_profiler, show_profiler_max);
-		std::wstring text = utf8_to_wide(os.str());
+		std::wstring text = translate_string(utf8_to_wide(os.str()));
 		setStaticText(guitext_profiler, text.c_str());
 		guitext_profiler->setVisible(true);
 
@@ -1619,6 +1620,8 @@ bool Game::startup(bool *kill,
 	m_invert_mouse = g_settings->getBool("invert_mouse");
 	m_first_loop_after_window_activation = true;
 
+	g_translations->clear();
+
 	if (!init(map_dir, address, port, gamespec))
 		return false;
 
@@ -3781,7 +3784,7 @@ void Game::handlePointingAtNode(const PointedThing &pointed,
 	NodeMetadata *meta = map.getNodeMetadata(nodepos);
 
 	if (meta) {
-		infotext = unescape_enriched(utf8_to_wide(meta->getString("infotext")));
+		infotext = unescape_translate(utf8_to_wide(meta->getString("infotext")));
 	} else {
 		MapNode n = map.getNodeNoEx(nodepos);
 
@@ -3858,15 +3861,14 @@ void Game::handlePointingAtNode(const PointedThing &pointed,
 void Game::handlePointingAtObject(const PointedThing &pointed, const ItemStack &playeritem,
 		const v3f &player_position, bool show_debug)
 {
-	infotext = unescape_enriched(
+	infotext = unescape_translate(
 		utf8_to_wide(runData.selected_object->infoText()));
 
 	if (show_debug) {
 		if (!infotext.empty()) {
 			infotext += L"\n";
 		}
-		infotext += unescape_enriched(utf8_to_wide(
-			runData.selected_object->debugInfoText()));
+		infotext += utf8_to_wide(runData.selected_object->debugInfoText());
 	}
 
 	if (isLeftPressed()) {
@@ -4399,7 +4401,7 @@ void Game::updateGui(const RunStats &stats, f32 dtime, const CameraOrientation &
 		guitext3->setRelativePosition(rect);
 	}
 
-	setStaticText(guitext_info, infotext.c_str());
+	setStaticText(guitext_info, translate_string(infotext).c_str());
 	guitext_info->setVisible(flags.show_hud && g_menumgr.menuCount() == 0);
 
 	float statustext_time_max = 1.5;
@@ -4413,7 +4415,7 @@ void Game::updateGui(const RunStats &stats, f32 dtime, const CameraOrientation &
 		}
 	}
 
-	setStaticText(guitext_status, m_statustext.c_str());
+	setStaticText(guitext_status, translate_string(m_statustext).c_str());
 	guitext_status->setVisible(!m_statustext.empty());
 
 	if (!m_statustext.empty()) {
diff --git a/src/guiEngine.cpp b/src/guiEngine.cpp
index 07fbd3665..e9b4e54c1 100644
--- a/src/guiEngine.cpp
+++ b/src/guiEngine.cpp
@@ -547,7 +547,7 @@ bool GUIEngine::downloadFile(const std::string &url, const std::string &target)
 /******************************************************************************/
 void GUIEngine::setTopleftText(const std::string &text)
 {
-	m_toplefttext = utf8_to_wide(text);
+	m_toplefttext = translate_string(utf8_to_wide(text));
 
 	updateTopLeftTextSize();
 }
diff --git a/src/guiFormSpecMenu.cpp b/src/guiFormSpecMenu.cpp
index 996eeed53..5ae652601 100644
--- a/src/guiFormSpecMenu.cpp
+++ b/src/guiFormSpecMenu.cpp
@@ -398,7 +398,7 @@ void GUIFormSpecMenu::parseCheckbox(parserData* data, const std::string &element
 		if (selected == "true")
 			fselected = true;
 
-		std::wstring wlabel = utf8_to_wide(unescape_string(label));
+		std::wstring wlabel = translate_string(utf8_to_wide(unescape_string(label)));
 
 		core::rect<s32> rect = core::rect<s32>(
 				pos.X, pos.Y + ((imgsize.Y/2) - m_btn_height),
@@ -594,7 +594,7 @@ void GUIFormSpecMenu::parseButton(parserData* data, const std::string &element,
 		if(!data->explicit_size)
 			warningstream<<"invalid use of button without a size[] element"<<std::endl;
 
-		std::wstring wlabel = utf8_to_wide(unescape_string(label));
+		std::wstring wlabel = translate_string(utf8_to_wide(unescape_string(label)));
 
 		FieldSpec spec(
 			name,
@@ -728,7 +728,7 @@ void GUIFormSpecMenu::parseTable(parserData* data, const std::string &element)
 		spec.ftype = f_Table;
 
 		for (std::string &item : items) {
-			item = unescape_enriched(unescape_string(item));
+			item = wide_to_utf8(unescape_translate(utf8_to_wide(unescape_string(item))));
 		}
 
 		//now really show table
@@ -799,7 +799,7 @@ void GUIFormSpecMenu::parseTextList(parserData* data, const std::string &element
 		spec.ftype = f_Table;
 
 		for (std::string &item : items) {
-			item = unescape_enriched(unescape_string(item));
+			item = wide_to_utf8(unescape_translate(utf8_to_wide(unescape_string(item))));
 		}
 
 		//now really show list
@@ -869,7 +869,7 @@ void GUIFormSpecMenu::parseDropDown(parserData* data, const std::string &element
 		}
 
 		for (const std::string &item : items) {
-			e->addItem(unescape_enriched(unescape_string(
+			e->addItem(unescape_translate(unescape_string(
 				utf8_to_wide(item))).c_str());
 		}
 
@@ -927,7 +927,7 @@ void GUIFormSpecMenu::parsePwdField(parserData* data, const std::string &element
 
 		core::rect<s32> rect = core::rect<s32>(pos.X, pos.Y, pos.X+geom.X, pos.Y+geom.Y);
 
-		std::wstring wlabel = utf8_to_wide(unescape_string(label));
+		std::wstring wlabel = translate_string(utf8_to_wide(unescape_string(label)));
 
 		FieldSpec spec(
 			name,
@@ -999,7 +999,7 @@ void GUIFormSpecMenu::parseSimpleField(parserData* data,
 		default_val = m_form_src->resolveText(default_val);
 
 
-	std::wstring wlabel = utf8_to_wide(unescape_string(label));
+	std::wstring wlabel = translate_string(utf8_to_wide(unescape_string(label)));
 
 	FieldSpec spec(
 		name,
@@ -1099,7 +1099,7 @@ void GUIFormSpecMenu::parseTextArea(parserData* data, std::vector<std::string>&
 		default_val = m_form_src->resolveText(default_val);
 
 
-	std::wstring wlabel = utf8_to_wide(unescape_string(label));
+	std::wstring wlabel = translate_string(utf8_to_wide(unescape_string(label)));
 
 	FieldSpec spec(
 		name,
@@ -1249,7 +1249,7 @@ void GUIFormSpecMenu::parseVertLabel(parserData* data, const std::string &elemen
 		((parts.size() > 2) && (m_formspec_version > FORMSPEC_API_VERSION)))
 	{
 		std::vector<std::string> v_pos = split(parts[0],',');
-		std::wstring text = unescape_enriched(
+		std::wstring text = unescape_translate(
 			unescape_string(utf8_to_wide(parts[1])));
 
 		MY_CHECKPOS("vertlabel",1);
@@ -1436,7 +1436,7 @@ void GUIFormSpecMenu::parseTabHeader(parserData* data, const std::string &elemen
 		e->setNotClipped(true);
 
 		for (const std::string &button : buttons) {
-			e->addTab(unescape_enriched(unescape_string(
+			e->addTab(unescape_translate(unescape_string(
 				utf8_to_wide(button))).c_str(), -1);
 		}
 
@@ -1495,7 +1495,7 @@ void GUIFormSpecMenu::parseItemImageButton(parserData* data, const std::string &
 		item.deSerialize(item_name, idef);
 
 		m_tooltips[name] =
-			TooltipSpec(item.getDefinition(idef).description,
+			TooltipSpec(utf8_to_wide(item.getDefinition(idef).description),
 						m_default_tooltip_bgcolor,
 						m_default_tooltip_color);
 
@@ -1613,7 +1613,7 @@ void GUIFormSpecMenu::parseTooltip(parserData* data, const std::string &element)
 	std::vector<std::string> parts = split(element,';');
 	if (parts.size() == 2) {
 		std::string name = parts[0];
-		m_tooltips[name] = TooltipSpec(unescape_string(parts[1]),
+		m_tooltips[name] = TooltipSpec(utf8_to_wide(unescape_string(parts[1])),
 			m_default_tooltip_bgcolor, m_default_tooltip_color);
 		return;
 	}
@@ -1622,7 +1622,7 @@ void GUIFormSpecMenu::parseTooltip(parserData* data, const std::string &element)
 		std::string name = parts[0];
 		video::SColor tmp_color1, tmp_color2;
 		if ( parseColorString(parts[2], tmp_color1, false) && parseColorString(parts[3], tmp_color2, false) ) {
-			m_tooltips[name] = TooltipSpec(unescape_string(parts[1]),
+			m_tooltips[name] = TooltipSpec(utf8_to_wide(unescape_string(parts[1])),
 				tmp_color1, tmp_color2);
 			return;
 		}
@@ -2632,14 +2632,15 @@ void GUIFormSpecMenu::drawMenu()
 void GUIFormSpecMenu::showTooltip(const std::wstring &text,
 	const irr::video::SColor &color, const irr::video::SColor &bgcolor)
 {
+	const std::wstring ntext = translate_string(text);
 	m_tooltip_element->setOverrideColor(color);
 	m_tooltip_element->setBackgroundColor(bgcolor);
-	setStaticText(m_tooltip_element, text.c_str());
+	setStaticText(m_tooltip_element, ntext.c_str());
 
 	// Tooltip size and offset
 	s32 tooltip_width = m_tooltip_element->getTextWidth() + m_btn_height;
 #if (IRRLICHT_VERSION_MAJOR <= 1 && IRRLICHT_VERSION_MINOR <= 8 && IRRLICHT_VERSION_REVISION < 2) || USE_FREETYPE == 1
-	std::vector<std::wstring> text_rows = str_split(text, L'\n');
+	std::vector<std::wstring> text_rows = str_split(ntext, L'\n');
 	s32 tooltip_height = m_tooltip_element->getTextHeight() * text_rows.size() + 5;
 #else
 	s32 tooltip_height = m_tooltip_element->getTextHeight() + 5;
diff --git a/src/guiFormSpecMenu.h b/src/guiFormSpecMenu.h
index b22d62b13..02f367fbf 100644
--- a/src/guiFormSpecMenu.h
+++ b/src/guiFormSpecMenu.h
@@ -203,7 +203,7 @@ class GUIFormSpecMenu : public GUIModalMenu
 				const std::wstring &default_text, int id) :
 			fname(name),
 			flabel(label),
-			fdefault(unescape_enriched(default_text)),
+			fdefault(unescape_enriched(translate_string(default_text))),
 			fid(id),
 			send(false),
 			ftype(f_Unknown),
@@ -237,10 +237,9 @@ class GUIFormSpecMenu : public GUIModalMenu
 	struct TooltipSpec
 	{
 		TooltipSpec() = default;
-
-		TooltipSpec(const std::string &a_tooltip, irr::video::SColor a_bgcolor,
+		TooltipSpec(const std::wstring &a_tooltip, irr::video::SColor a_bgcolor,
 				irr::video::SColor a_color):
-			tooltip(utf8_to_wide(a_tooltip)),
+			tooltip(translate_string(a_tooltip)),
 			bgcolor(a_bgcolor),
 			color(a_color)
 		{
diff --git a/src/hud.cpp b/src/hud.cpp
index 339f50d4c..7135bc42a 100644
--- a/src/hud.cpp
+++ b/src/hud.cpp
@@ -317,7 +317,7 @@ void Hud::drawLuaElements(const v3s16 &camera_offset)
 										 (e->number >> 8)  & 0xFF,
 										 (e->number >> 0)  & 0xFF);
 				core::rect<s32> size(0, 0, e->scale.X, text_height * e->scale.Y);
-				std::wstring text = unescape_enriched(utf8_to_wide(e->text));
+				std::wstring text = unescape_translate(utf8_to_wide(e->text));
 				core::dimension2d<u32> textsize = font->getDimension(text.c_str());
 				v2s32 offset((e->align.X - 1.0) * (textsize.Width / 2),
 				             (e->align.Y - 1.0) * (textsize.Height / 2));
@@ -354,11 +354,11 @@ void Hud::drawLuaElements(const v3s16 &camera_offset)
 										 (e->number >> 8)  & 0xFF,
 										 (e->number >> 0)  & 0xFF);
 				core::rect<s32> size(0, 0, 200, 2 * text_height);
-				std::wstring text = unescape_enriched(utf8_to_wide(e->name));
+				std::wstring text = unescape_translate(utf8_to_wide(e->name));
 				font->draw(text.c_str(), size + pos, color);
 				std::ostringstream os;
 				os << distance << e->text;
-				text = unescape_enriched(utf8_to_wide(os.str()));
+				text = unescape_translate(utf8_to_wide(os.str()));
 				pos.Y += text_height;
 				font->draw(text.c_str(), size + pos, color);
 				break; }
diff --git a/src/network/clientpackethandler.cpp b/src/network/clientpackethandler.cpp
index 4800ea87c..f42f9219b 100644
--- a/src/network/clientpackethandler.cpp
+++ b/src/network/clientpackethandler.cpp
@@ -36,6 +36,7 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 #include "util/serialize.h"
 #include "util/srp.h"
 #include "tileanimation.h"
+#include "gettext.h"
 
 void Client::handleCommand_Deprecated(NetworkPacket* pkt)
 {
@@ -123,7 +124,12 @@ void Client::handleCommand_AuthAccept(NetworkPacket* pkt)
 					<< m_recommended_send_interval<<std::endl;
 
 	// Reply to server
-	NetworkPacket resp_pkt(TOSERVER_INIT2, 0);
+	std::string lang = gettext("LANG_CODE");
+	if (lang == "LANG_CODE")
+		lang = "";
+
+	NetworkPacket resp_pkt(TOSERVER_INIT2, sizeof(u16) + lang.size());
+	resp_pkt << lang;
 	Send(&resp_pkt);
 
 	m_state = LC_Init;
diff --git a/src/network/serverpackethandler.cpp b/src/network/serverpackethandler.cpp
index 09e04674c..5ed38d6d7 100644
--- a/src/network/serverpackethandler.cpp
+++ b/src/network/serverpackethandler.cpp
@@ -612,6 +612,9 @@ void Server::handleCommand_Init2(NetworkPacket* pkt)
 	m_clients.event(pkt->getPeerId(), CSE_GotInit2);
 	u16 protocol_version = m_clients.getProtocolVersion(pkt->getPeerId());
 
+	std::string lang;
+	if (pkt->getSize() > 0)
+		*pkt >> lang;
 
 	/*
 		Send some initialization data
@@ -632,7 +635,7 @@ void Server::handleCommand_Init2(NetworkPacket* pkt)
 	m_clients.event(pkt->getPeerId(), CSE_SetDefinitionsSent);
 
 	// Send media announcement
-	sendMediaAnnouncement(pkt->getPeerId());
+	sendMediaAnnouncement(pkt->getPeerId(), lang);
 
 	// Send detached inventories
 	sendDetachedInventories(pkt->getPeerId());
diff --git a/src/server.cpp b/src/server.cpp
index 5c09aee4d..e3a26b989 100644
--- a/src/server.cpp
+++ b/src/server.cpp
@@ -2293,6 +2293,7 @@ void Server::fillMediaCache()
 		paths.push_back(mod.path + DIR_DELIM + "sounds");
 		paths.push_back(mod.path + DIR_DELIM + "media");
 		paths.push_back(mod.path + DIR_DELIM + "models");
+		paths.push_back(mod.path + DIR_DELIM + "locale");
 	}
 	paths.push_back(porting::path_user + DIR_DELIM + "textures" + DIR_DELIM + "server");
 
@@ -2315,6 +2316,8 @@ void Server::fillMediaCache()
 				".pcx", ".ppm", ".psd", ".wal", ".rgb",
 				".ogg",
 				".x", ".b3d", ".md2", ".obj",
+				// Custom translation file format
+				".tr",
 				NULL
 			};
 			if (removeStringEnd(filename, supported_ext).empty()){
@@ -2374,7 +2377,7 @@ void Server::fillMediaCache()
 	}
 }
 
-void Server::sendMediaAnnouncement(u16 peer_id)
+void Server::sendMediaAnnouncement(u16 peer_id, const std::string &lang_code)
 {
 	DSTACK(FUNCTION_NAME);
 
@@ -2382,12 +2385,22 @@ void Server::sendMediaAnnouncement(u16 peer_id)
 		<< std::endl;
 
 	// Make packet
-	std::ostringstream os(std::ios_base::binary);
-
 	NetworkPacket pkt(TOCLIENT_ANNOUNCE_MEDIA, 0, peer_id);
-	pkt << (u16) m_media.size();
+
+	u16 media_sent = 0;
+	std::string lang_suffix;
+	lang_suffix.append(".").append(lang_code).append(".tr");
+	for (const auto &i : m_media) {
+		if (str_ends_with(i.first, ".tr") && !str_ends_with(i.first, lang_suffix))
+			continue;
+		media_sent++;
+	}
+
+	pkt << media_sent;
 
 	for (const auto &i : m_media) {
+		if (str_ends_with(i.first, ".tr") && !str_ends_with(i.first, lang_suffix))
+			continue;
 		pkt << i.first << i.second.sha1_digest;
 	}
 
diff --git a/src/server.h b/src/server.h
index ab1660bf2..f14a861fd 100644
--- a/src/server.h
+++ b/src/server.h
@@ -405,7 +405,7 @@ private:
 	void SendBlocks(float dtime);
 
 	void fillMediaCache();
-	void sendMediaAnnouncement(u16 peer_id);
+	void sendMediaAnnouncement(u16 peer_id, const std::string &lang_code);
 	void sendRequestedMedia(u16 peer_id,
 			const std::vector<std::string> &tosend);
 
diff --git a/src/translation.cpp b/src/translation.cpp
new file mode 100644
index 000000000..e8582f328
--- /dev/null
+++ b/src/translation.cpp
@@ -0,0 +1,146 @@
+/*
+Minetest
+Copyright (C) 2017 Nore, Nathanaël Courant <nore@mesecons.net>
+
+This program is free software; you can redistribute it and/or modify
+it under the terms of the GNU Lesser General Public License as published by
+the Free Software Foundation; either version 2.1 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU Lesser General Public License for more details.
+
+You should have received a copy of the GNU Lesser General Public License along
+with this program; if not, write to the Free Software Foundation, Inc.,
+51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+*/
+
+#include "translation.h"
+#include "log.h"
+#include "util/string.h"
+
+static Translations main_translations;
+Translations *g_translations = &main_translations;
+
+Translations::~Translations()
+{
+	clear();
+}
+
+void Translations::clear()
+{
+	m_translations.clear();
+}
+
+const std::wstring &Translations::getTranslation(
+		const std::wstring &textdomain, const std::wstring &s)
+{
+	std::wstring key = textdomain + L"|" + s;
+	try {
+		return m_translations.at(key);
+	} catch (std::out_of_range) {
+		warningstream << "Translations: can't find translation for string \""
+		              << wide_to_utf8(s) << "\" in textdomain \""
+		              << wide_to_utf8(textdomain) << "\"" << std::endl;
+		// Silence that warning in the future
+		m_translations[key] = s;
+		return s;
+	}
+}
+
+void Translations::loadTranslation(const std::string &data)
+{
+	std::istringstream is(data);
+	std::wstring textdomain;
+	std::string line;
+
+	while (is.good()) {
+		std::getline(is, line);
+		if (str_starts_with(line, "# textdomain:")) {
+			textdomain = utf8_to_wide(trim(str_split(line, ':')[1]));
+		}
+		if (line.empty() || line[0] == '#')
+			continue;
+
+		std::wstring wline = utf8_to_wide(line);
+		if (wline.empty())
+			continue;
+
+		// Read line
+		// '=' marks the key-value pair, but may be escaped by an '@'.
+		// '\n' may also be escaped by '@'.
+		// All other escapes are preserved.
+
+		size_t i = 0;
+		std::wostringstream word1, word2;
+		while (i < wline.length() && wline[i] != L'=') {
+			if (wline[i] == L'@') {
+				if (i + 1 < wline.length()) {
+					if (wline[i + 1] == L'=') {
+						word1.put(L'=');
+					} else {
+						word1.put(L'@');
+						word1.put(wline[i + 1]);
+					}
+					i += 2;
+				} else {
+					// End of line, go to the next one.
+					word1.put(L'\n');
+					if (!is.good()) {
+						break;
+					}
+					i = 0;
+					std::getline(is, line);
+					wline = utf8_to_wide(line);
+				}
+			} else {
+				word1.put(wline[i]);
+				i++;
+			}
+		}
+
+		if (i == wline.length()) {
+			errorstream << "Malformed translation line \"" << line << "\""
+			            << std::endl;
+			continue;
+		}
+		i++;
+
+		while (i < wline.length()) {
+			if (wline[i] == L'@') {
+				if (i + 1 < wline.length()) {
+					if (wline[i + 1] == L'=') {
+						word2.put(L'=');
+					} else {
+						word2.put(L'@');
+						word2.put(wline[i + 1]);
+					}
+					i += 2;
+				} else {
+					// End of line, go to the next one.
+					word2.put(L'\n');
+					if (!is.good()) {
+						break;
+					}
+					i = 0;
+					std::getline(is, line);
+					wline = utf8_to_wide(line);
+				}
+			} else {
+				word2.put(wline[i]);
+				i++;
+			}
+		}
+
+		std::wstring oword1 = word1.str(), oword2 = word2.str();
+		if (oword2.empty()) {
+			oword2 = oword1;
+			errorstream << "Ignoring empty translation for \""
+			            << wide_to_utf8(oword1) << "\"" << std::endl;
+		}
+
+		m_translations[textdomain + L"|" + oword1] = oword2;
+	}
+}
\ No newline at end of file
diff --git a/src/translation.h b/src/translation.h
new file mode 100644
index 000000000..18fc6c38f
--- /dev/null
+++ b/src/translation.h
@@ -0,0 +1,42 @@
+/*
+Minetest
+Copyright (C) 2017 Nore, Nathanaël Courant <nore@mesecons.net>
+
+This program is free software; you can redistribute it and/or modify
+it under the terms of the GNU Lesser General Public License as published by
+the Free Software Foundation; either version 2.1 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU Lesser General Public License for more details.
+
+You should have received a copy of the GNU Lesser General Public License along
+with this program; if not, write to the Free Software Foundation, Inc.,
+51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+*/
+
+#pragma once
+
+#include <unordered_map>
+#include <string>
+
+class Translations;
+extern Translations *g_translations;
+
+class Translations
+{
+public:
+	Translations() = default;
+
+	~Translations();
+
+	void loadTranslation(const std::string &data);
+	void clear();
+	const std::wstring &getTranslation(
+			const std::wstring &textdomain, const std::wstring &s);
+
+private:
+	std::unordered_map<std::wstring, std::wstring> m_translations;
+};
diff --git a/src/util/enriched_string.cpp b/src/util/enriched_string.cpp
index f79e77d5a..642188a52 100644
--- a/src/util/enriched_string.cpp
+++ b/src/util/enriched_string.cpp
@@ -36,19 +36,19 @@ EnrichedString::EnrichedString(const std::wstring &string,
 EnrichedString::EnrichedString(const std::wstring &s, const SColor &color)
 {
 	clear();
-	addAtEnd(s, color);
+	addAtEnd(translate_string(s), color);
 }
 
 EnrichedString::EnrichedString(const wchar_t *str, const SColor &color)
 {
 	clear();
-	addAtEnd(std::wstring(str), color);
+	addAtEnd(translate_string(std::wstring(str)), color);
 }
 
 void EnrichedString::operator=(const wchar_t *str)
 {
 	clear();
-	addAtEnd(std::wstring(str), SColor(255, 255, 255, 255));
+	addAtEnd(translate_string(std::wstring(str)), SColor(255, 255, 255, 255));
 }
 
 void EnrichedString::addAtEnd(const std::wstring &s, const SColor &initial_color)
diff --git a/src/util/string.cpp b/src/util/string.cpp
index fc2a2057f..6335aeafe 100644
--- a/src/util/string.cpp
+++ b/src/util/string.cpp
@@ -24,6 +24,7 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 
 #include "hex.h"
 #include "../porting.h"
+#include "../translation.h"
 
 #include <algorithm>
 #include <sstream>
@@ -743,3 +744,196 @@ void str_replace(std::string &str, char from, char to)
 {
 	std::replace(str.begin(), str.end(), from, to);
 }
+
+/* Translated strings have the following format:
+ * \x1bT marks the beginning of a translated string
+ * \x1bE marks its end
+ *
+ * \x1bF marks the beginning of an argument, and \x1bE its end.
+ *
+ * Arguments are *not* translated, as they may contain escape codes.
+ * Thus, if you want a translated argument, it should be inside \x1bT/\x1bE tags as well.
+ *
+ * This representation is chosen so that clients ignoring escape codes will
+ * see untranslated strings.
+ *
+ * For instance, suppose we have a string such as "@1 Wool" with the argument "White"
+ * The string will be sent as "\x1bT\x1bF\x1bTWhite\x1bE\x1bE Wool\x1bE"
+ * To translate this string, we extract what is inside \x1bT/\x1bE tags.
+ * When we notice the \x1bF tag, we recursively extract what is there up to the \x1bE end tag,
+ * translating it as well.
+ * We get the argument "White", translated, and create a template string with "@1" instead of it.
+ * We finally get the template "@1 Wool" that was used in the beginning, which we translate
+ * before filling it again.
+ */
+
+void translate_all(const std::wstring &s, size_t &i, std::wstring &res);
+
+void translate_string(const std::wstring &s, const std::wstring &textdomain,
+		size_t &i, std::wstring &res) {
+	std::wostringstream output;
+	std::vector<std::wstring> args;
+	int arg_number = 1;
+	while (i < s.length()) {
+		// Not an escape sequence: just add the character.
+		if (s[i] != '\x1b') {
+			output.put(s[i]);
+			// The character is a literal '@'; add it twice
+			// so that it is not mistaken for an argument.
+			if (s[i] == L'@')
+				output.put(L'@');
+			++i;
+			continue;
+		}
+
+		// We have an escape sequence: locate it and its data
+		// It is either a single character, or it begins with '('
+		// and extends up to the following ')', with '\' as an escape character.
+		++i;
+		size_t start_index = i;
+		size_t length;
+		if (i == s.length()) {
+			length = 0;
+		} else if (s[i] == L'(') {
+			++i;
+			++start_index;
+			while (i < s.length() && s[i] != L')') {
+				if (s[i] == L'\\')
+					++i;
+				++i;
+			}
+			length = i - start_index;
+			++i;
+			if (i > s.length())
+				i = s.length();
+		} else {
+			++i;
+			length = 1;
+		}
+		std::wstring escape_sequence(s, start_index, length);
+
+		// The escape sequence is now reconstructed.
+		std::vector<std::wstring> parts = split(escape_sequence, L'@');
+		if (parts[0] == L"E") {
+			// "End of translation" escape sequence. We are done locating the string to translate.
+			break;
+		} else if (parts[0] == L"F") {
+			// "Start of argument" escape sequence.
+			// Recursively translate the argument, and add it to the argument list.
+			// Add an "@n" instead of the argument to the template to translate.
+			if (arg_number >= 10) {
+				errorstream << "Ignoring too many arguments to translation" << std::endl;
+				std::wstring arg;
+				translate_all(s, i, arg);
+				args.push_back(arg);
+				continue;
+			}
+			output.put(L'@');
+			output << arg_number;
+			++arg_number;
+			std::wstring arg;
+			translate_all(s, i, arg);
+			args.push_back(arg);
+		} else {
+			// This is an escape sequence *inside* the template string to translate itself.
+			// This should not happen, show an error message.
+			errorstream << "Ignoring escape sequence '" << wide_to_narrow(escape_sequence) << "' in translation" << std::endl;
+		}
+	}
+
+	// Translate the template.
+	std::wstring toutput = g_translations->getTranslation(textdomain, output.str());
+
+	// Put back the arguments in the translated template.
+	std::wostringstream result;
+	size_t j = 0;
+	while (j < toutput.length()) {
+		// Normal character, add it to output and continue.
+		if (toutput[j] != L'@' || j == toutput.length() - 1) {
+			result.put(toutput[j]);
+			++j;
+			continue;
+		}
+
+		++j;
+		// Literal escape for '@'.
+		if (toutput[j] == L'@') {
+			result.put(L'@');
+			++j;
+			continue;
+		}
+
+		// Here we have an argument; get its index and add the translated argument to the output.
+		int arg_index = toutput[j] - L'1';
+		++j;
+		result << args[arg_index];
+	}
+	res = result.str();
+}
+
+void translate_all(const std::wstring &s, size_t &i, std::wstring &res) {
+	std::wostringstream output;
+	while (i < s.length()) {
+		// Not an escape sequence: just add the character.
+		if (s[i] != '\x1b') {
+			output.put(s[i]);
+			++i;
+			continue;
+		}
+
+		// We have an escape sequence: locate it and its data
+		// It is either a single character, or it begins with '('
+		// and extends up to the following ')', with '\' as an escape character.
+		size_t escape_start = i;
+		++i;
+		size_t start_index = i;
+		size_t length;
+		if (i == s.length()) {
+			length = 0;
+		} else if (s[i] == L'(') {
+			++i;
+			++start_index;
+			while (i < s.length() && s[i] != L')') {
+				if (s[i] == L'\\') {
+					++i;
+				}
+				++i;
+			}
+			length = i - start_index;
+			++i;
+			if (i > s.length())
+				i = s.length();
+		} else {
+			++i;
+			length = 1;
+		}
+		std::wstring escape_sequence(s, start_index, length);
+
+		// The escape sequence is now reconstructed.
+		std::vector<std::wstring> parts = split(escape_sequence, L'@');
+		if (parts[0] == L"E") {
+			// "End of argument" escape sequence. Exit.
+			break;
+		} else if (parts[0] == L"T") {
+			// Beginning of translated string.
+			std::wstring textdomain;
+			if (parts.size() > 1)
+				textdomain = parts[1];
+			std::wstring translated;
+			translate_string(s, textdomain, i, translated);
+			output << translated;
+		} else {
+			// Another escape sequence, such as colors. Preserve it.
+			output << std::wstring(s, escape_start, i - escape_start);
+		}
+	}
+
+	res = output.str();
+}
+
+std::wstring translate_string(const std::wstring &s) {
+	size_t i = 0;
+	std::wstring res;
+	translate_all(s, i, res);
+	return res;
+}
diff --git a/src/util/string.h b/src/util/string.h
index 122262af8..2840f1192 100644
--- a/src/util/string.h
+++ b/src/util/string.h
@@ -203,6 +203,56 @@ inline bool str_starts_with(const std::basic_string<T> &str,
 			case_insensitive);
 }
 
+
+/**
+ * Check whether \p str ends with the string suffix. If \p case_insensitive
+ * is true then the check is case insensitve (default is false; i.e. case is
+ * significant).
+ *
+ * @param str
+ * @param suffix
+ * @param case_insensitive
+ * @return true if the str begins with suffix
+ */
+template <typename T>
+inline bool str_ends_with(const std::basic_string<T> &str,
+		const std::basic_string<T> &suffix,
+		bool case_insensitive = false)
+{
+	if (str.size() < suffix.size())
+		return false;
+
+	size_t start = str.size() - suffix.size();
+	if (!case_insensitive)
+		return str.compare(start, suffix.size(), suffix) == 0;
+
+	for (size_t i = 0; i < suffix.size(); ++i)
+		if (tolower(str[start + i]) != tolower(suffix[i]))
+			return false;
+	return true;
+}
+
+
+/**
+ * Check whether \p str ends with the string suffix. If \p case_insensitive
+ * is true then the check is case insensitve (default is false; i.e. case is
+ * significant).
+ *
+ * @param str
+ * @param suffix
+ * @param case_insensitive
+ * @return true if the str begins with suffix
+ */
+template <typename T>
+inline bool str_ends_with(const std::basic_string<T> &str,
+		const T *suffix,
+		bool case_insensitive = false)
+{
+	return str_ends_with(str, std::basic_string<T>(suffix),
+			case_insensitive);
+}
+
+
 /**
  * Splits a string into its component parts separated by the character
  * \p delimiter.
@@ -598,6 +648,12 @@ std::vector<std::basic_string<T> > split(const std::basic_string<T> &s, T delim)
 	return tokens;
 }
 
+std::wstring translate_string(const std::wstring &s);
+
+inline std::wstring unescape_translate(const std::wstring &s) {
+	return unescape_enriched(translate_string(s));
+}
+
 /**
  * Checks that all characters in \p to_check are a decimal digits.
  *
diff --git a/util/travis/clang-format-whitelist.txt b/util/travis/clang-format-whitelist.txt
index f55835656..66341d765 100644
--- a/util/travis/clang-format-whitelist.txt
+++ b/util/travis/clang-format-whitelist.txt
@@ -325,6 +325,7 @@ src/tileanimation.cpp
 src/tool.cpp
 src/tool.h
 src/touchscreengui.cpp
+src/translation.cpp
 src/treegen.cpp
 src/treegen.h
 src/unittest/test_areastore.cpp