[RTL UI] GetText/Bidi: wrap untranslated strings in LTR

frontend/gettext.lua

@@ -34,6 +34,15 @@ local GetText_mt = {
     __index = {}
 }
 
+-- wrapUntranslated() will be overriden by bidi.lua when UI language is RTL,
+-- to wrap untranslated english strings as LTR-isolated segments.
+-- It should do nothing when the UI language is LTR.
+GetText.wrapUntranslated_nowrap = function(text) return text end
+GetText.wrapUntranslated = GetText.wrapUntranslated_nowrap
+-- Note: this won't be possible if we switch from our Lua GetText to
+-- GetText through FFI (but hopefully, RTL languages will be fully
+-- translated by then).
+
 --[[--
 Returns a translation.
 
@@ -48,7 +57,7 @@ Returns a translation.
     local translation = _("A meaningful message.")
 --]]
 function GetText_mt.__call(gettext, msgid)
-    return gettext.translation[msgid] or msgid
+    return gettext.translation[msgid] or gettext.wrapUntranslated(msgid)
 end
 
 local function c_escape(what)
@@ -296,9 +305,9 @@ function GetText_mt.__index.ngettext(msgid, msgid_plural, n)
     local plural = GetText.getPlural(n)
 
     if plural == 0 then
-        return GetText.translation[msgid] and GetText.translation[msgid][plural] or msgid
+        return GetText.translation[msgid] and GetText.translation[msgid][plural] or GetText.wrapUntranslated(msgid)
     else
-        return GetText.translation[msgid] and GetText.translation[msgid][plural] or msgid_plural
+        return GetText.translation[msgid] and GetText.translation[msgid][plural] or GetText.wrapUntranslated(msgid_plural)
     end
 end
 
@@ -329,9 +338,9 @@ function GetText_mt.__index.npgettext(msgctxt, msgid, msgid_plural, n)
     local plural = GetText.getPlural(n)
 
     if plural == 0 then
-        return GetText.context[msgctxt] and GetText.context[msgctxt][msgid] and GetText.context[msgctxt][msgid][plural] or msgid
+        return GetText.context[msgctxt] and GetText.context[msgctxt][msgid] and GetText.context[msgctxt][msgid][plural] or GetText.wrapUntranslated(msgid)
     else
-        return GetText.context[msgctxt] and GetText.context[msgctxt][msgid] and GetText.context[msgctxt][msgid][plural] or msgid_plural
+        return GetText.context[msgctxt] and GetText.context[msgctxt][msgid] and GetText.context[msgctxt][msgid][plural] or GetText.wrapUntranslated(msgid_plural)
     end
 end
 
@@ -362,7 +371,7 @@ See [gettext contexts](https://www.gnu.org/software/gettext/manual/html_node/Con
     local copy_text = C_("Text", "Copy")
 --]]
 function GetText_mt.__index.pgettext(msgctxt, msgid)
-    return GetText.context[msgctxt] and GetText.context[msgctxt][msgid] or msgid
+    return GetText.context[msgctxt] and GetText.context[msgctxt][msgid] or GetText.wrapUntranslated(msgid)
 end
 
 setmetatable(GetText, GetText_mt)

frontend/ui/bidi.lua

@@ -99,6 +99,20 @@ function Bidi.setup(lang)
         Bidi.path = Bidi.nowrap
         Bidi.url = Bidi.nowrap
     end
+    -- If RTL UI text, let's have untranslated strings (so english) still rendered LTR
+    if Bidi._rtl_ui_text then
+        _.wrapUntranslated = function(text)
+            -- We need to split by line and wrap each line as LTR (as the
+            -- paragraph direction will still be RTL).
+            local lines = {}
+            for s in text:gmatch("[^\r\n]+") do
+                table.insert(lines, Bidi.ltr(s))
+            end
+            return table.concat(lines, "\n")
+        end
+    else
+        _.wrapUntranslated = _.wrapUntranslated_nowrap
+    end
 end
 
 
@@ -186,9 +200,6 @@ function Bidi.wrap(text)
     return Bidi._rtl_ui_text and Bidi.rtl(text) or text
 end
 
--- See at having GetText_mt.__call() wrap untranslated strings in Bidi.ltr()
--- so they are fully displayed LTR.
-
 -- Use these specific wrappers when the wrapped content type is known
 -- (so we can easily switch to use rtl() if RTL readers prefer filenames
 -- shown as real RTL).