Add experimental support for RTL languages

This commit permits language plugins to carry the field
“text-direction” with the value “rtl” to trigger right-to-left layout
of the entire page. We also adjust the sidebar layout to work in RTL
mode.

There are still a number of problems to be addressed:

* Brackets and other punctuation incorrectly placed within en-GB UI text
* System tiddler titles are rendered semi-back-to-front (eg
`languages/ca-ES/:$`)

Starting to address #1845 and the discussion in #2523.

core/modules/pluginswitcher.js

@@ -18,12 +18,14 @@ wiki: wiki store to be used
 pluginType: type of plugin to be switched
 controllerTitle: title of tiddler used to control switching of this resource
 defaultPlugins: array of default plugins to be used if nominated plugin isn't found
+onSwitch: callback when plugin is switched (single parameter is array of plugin titles)
 */
 function PluginSwitcher(options) {
 	this.wiki = options.wiki;
 	this.pluginType = options.pluginType;
 	this.controllerTitle = options.controllerTitle;
 	this.defaultPlugins = options.defaultPlugins || [];
+	this.onSwitch = options.onSwitch;
 	// Switch to the current plugin
 	this.switchPlugins();
 	// Listen for changes to the selected plugin
@@ -64,6 +66,10 @@ PluginSwitcher.prototype.switchPlugins = function() {
 	var registeredTiddlers = $tw.wiki.registerPluginTiddlers(this.pluginType,plugins);
 	// Unpack the current theme tiddlers
 	$tw.wiki.unpackPluginTiddlers();
+	// Call the switch handler
+	if(this.onSwitch) {
+		this.onSwitch(plugins);
+	}
 };
 
 exports.PluginSwitcher = PluginSwitcher;

core/modules/startup/startup.js

@@ -63,7 +63,18 @@ exports.startup = function() {
 		controllerTitle: "$:/language",
 		defaultPlugins: [
 			"$:/languages/en-US"
-		]
+		],
+		onSwitch: function(plugins) {
+			if($tw.browser) {
+				console.log("switching language",plugins)
+				var pluginTiddler = $tw.wiki.getTiddler(plugins[0]);
+				if(pluginTiddler) {
+					document.documentElement.setAttribute("dir",pluginTiddler.getFieldString("text-direction") || "auto");
+				} else {
+					document.documentElement.removeAttribute("dir");
+				}
+			}
+		}
 	});
 	// Kick off the theme manager
 	$tw.themeManager = new $tw.PluginSwitcher({

languages/he-IL/plugin.info

@@ -4,5 +4,6 @@
 	"plugin-type": "language",
 	"description": "Hebrew (Israel)",
 	"author": "DoronTzur",
-	"core-version": ">=5.0.0"
+	"core-version": ">=5.0.0",
+	"text-direction": "rtl"
 }

themes/tiddlywiki/vanilla/base.tid

@@ -690,6 +690,11 @@ button.tc-untagged-label {
 		padding: 71px 0 28px 42px;
 	}
 
+	html[dir="rtl"] .tc-sidebar-scrollable {
+		left: auto;
+		right: {{$:/themes/tiddlywiki/vanilla/metrics/storyright}};
+	}
+
 	.tc-story-river {
 		position: relative;
 		left: {{$:/themes/tiddlywiki/vanilla/metrics/storyleft}};