From 523d70127bb84a5cd46cb6491e263e16c8e0a183 Mon Sep 17 00:00:00 2001
From: Jeremy Ruston <jeremy@osmosoft.com>
Date: Tue, 30 Apr 2013 22:57:10 +0100
Subject: [PATCH] Allow themes to be switched by changing the tiddler
 `$:/theme`

---
 core/modules/themes.js | 64 ++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 62 insertions(+), 2 deletions(-)

diff --git a/core/modules/themes.js b/core/modules/themes.js
index a2df8a535..3059c1214 100644
--- a/core/modules/themes.js
+++ b/core/modules/themes.js
@@ -12,12 +12,72 @@ Manages themes and styling.
 /*global $tw: false */
 "use strict";
 
+var THEME_PLUGIN_TITLE = "$:/theme", // This tiddler contains the title of the current theme plugin
+	DEFAULT_THEME_PLUGIN = "$:/themes/tiddlywiki/snowwhite";
+
 function ThemeManager(wiki) {
 	this.wiki = wiki;
-	// Unpack the current theme tiddlers
-	$tw.wiki.unpackPluginTiddlers("theme");
+	// There's no theme to start with
+	this.currentThemeTitle = undefined;
+	// Switch to the current theme
+	this.switchTheme();
+	// Listen for changes to the theme
+	var self = this;
+	this.wiki.addEventListener("change",function(changes) {
+		if($tw.utils.hop(changes,THEME_PLUGIN_TITLE)) {
+			self.switchTheme();
+		}
+	});
 }
 
+ThemeManager.prototype.switchTheme = function() {
+	// Get the name of the current theme
+	var themePluginTitle = this.wiki.getTiddlerText(THEME_PLUGIN_TITLE,DEFAULT_THEME_PLUGIN);
+	// Get the theme plugin
+	var themePluginTiddler = this.wiki.getTiddler(themePluginTitle);
+	// Complain if we don't have a theme
+	if(!themePluginTiddler || !themePluginTiddler.isPlugin()) {
+		return $tw.utils.error("Cannot load theme " + themePluginTitle);
+	}
+	// Accumulate the titles of the plugins that we need to load
+	var themePlugins = [],
+		self = this,
+		accumulatePlugin = function(title) {
+			var tiddler = self.wiki.getTiddler(title);
+			if(tiddler && tiddler.isPlugin() && themePlugins.indexOf(title) === -1) {
+				themePlugins.push(title);
+				var pluginInfo = JSON.parse(self.wiki.getTiddlerText(title));
+				$tw.utils.each(pluginInfo.dependents,function(title) {
+					accumulatePlugin(title);
+				});
+			}
+		};
+	accumulatePlugin(themePluginTitle);
+	// Unregister any existing theme tiddlers
+	var unregisteredThemeTiddlers = $tw.wiki.unregisterPluginTiddlers("theme");
+	// Accumulate the titles of shadow tiddlers that have changed as a result of this switch
+	var changedTiddlers = {};
+	$tw.utils.each(this.wiki.shadowTiddlers,function(shadowInfo,title) {
+		if(unregisteredThemeTiddlers.indexOf(shadowInfo.source) !== -1) {
+			changedTiddlers[title] = true; // isDeleted?
+		}
+	});
+	// Register any new theme tiddlers
+	var registeredThemeTiddlers = $tw.wiki.registerPluginTiddlers("theme",themePlugins);
+	// Unpack the current theme tiddlers
+	$tw.wiki.unpackPluginTiddlers();
+	// Accumulate the affected shadow tiddlers
+	$tw.utils.each(this.wiki.shadowTiddlers,function(shadowInfo,title) {
+		if(registeredThemeTiddlers.indexOf(shadowInfo.source) !== -1) {
+			changedTiddlers[title] = false; // isDeleted?
+		}
+	});
+	// Issue change events for the modified tiddlers
+	$tw.utils.each(changedTiddlers,function(status,title) {
+		self.wiki.enqueueTiddlerEvent(title,status);
+	});
+};
+
 exports.ThemeManager = ThemeManager;
 
 })();