Index: plugins/linebreaks.inc
===================================================================
RCS file: plugins/linebreaks.inc
diff -N plugins/linebreaks.inc
--- /dev/null	1 Jan 1970 00:00:00 -0000
+++ plugins/linebreaks.inc	22 Oct 2009 22:49:34 -0000
@@ -0,0 +1,22 @@
+<?php
+// $Id:
+
+/**
+ * @file
+ * Converts p and br tags to linebreaks.
+ */
+
+/**
+ * Implementation of hook_wysiwyg_plugin().
+ */
+function wysiwyg_linebreaks_plugin() {
+  $plugins['linebreaks'] = array(
+    'title' => t('Force linebreaks'),
+    'vendor url' => 'http://drupal.org/project/wysiwyg',
+   # 'icon file' => 'break.gif',
+    'icon title' => t('Converts all p and br tags to linebreaks'),
+    'settings' => array(),
+  );
+  return $plugins;
+}
+
Index: plugins/linebreaks.js
===================================================================
RCS file: plugins/linebreaks.js
diff -N plugins/linebreaks.js
--- /dev/null	1 Jan 1970 00:00:00 -0000
+++ plugins/linebreaks.js	22 Oct 2009 22:49:34 -0000
@@ -0,0 +1,117 @@
+// $Id$
+
+// Adopted from Wordpress 2.8.1-beta editor.js.
+
+Drupal.wysiwyg.plugins.linebreaks = {
+  invoke: function(data, settings, instanceId) {
+    alert('This button does nothing, it belongs to the linebreaks plugin.');
+  },
+  attach: function(content, settings, instanceId) {
+    content = this.wpautop(content);
+    return content;
+  },
+  
+  detach: function(content, settings, instanceId) {
+    content = this.pre_wpautop(content);
+    return content;
+  },
+
+  pre_wpautop : function(content) {
+        var blocklist1, blocklist2;
+
+        // Protect pre|script tags
+        content = content.replace(/<(pre|script)[^>]*>[\s\S]+?<\/\1>/g, function(a) {
+            a = a.replace(/<br ?\/?>[\r\n]*/g, '<wp_temp>');
+            return a.replace(/<\/?p( [^>]*)?>[\r\n]*/g, '<wp_temp>');
+        });
+
+        // Pretty it up for the source editor
+        blocklist1 = 'blockquote|ul|ol|li|table|thead|tbody|tr|th|td|div|h[1-6]|p';
+        content = content.replace(new RegExp('\\s*</('+blocklist1+')>\\s*', 'mg'), '</$1>\n');
+        content = content.replace(new RegExp('\\s*<(('+blocklist1+')[^>]*)>', 'mg'), '\n<$1>');
+
+        // Mark </p> if it has any attributes.
+        content = content.replace(new RegExp('(<p [^>]+>.*?)</p>', 'mg'), '$1</p#>');
+
+        // Sepatate <div> containing <p>
+        content = content.replace(new RegExp('<div([^>]*)>\\s*<p>', 'mgi'), '<div$1>\n\n');
+
+        // Remove <p> and <br />
+        content = content.replace(new RegExp('\\s*<p>', 'mgi'), '');
+        content = content.replace(new RegExp('\\s*</p>\\s*', 'mgi'), '\n\n');
+        content = content.replace(new RegExp('\\n\\s*\\n', 'mgi'), '\n\n');
+        content = content.replace(new RegExp('\\s*<br ?/?>\\s*', 'gi'), '\n');
+
+        // Fix some block element newline issues
+        content = content.replace(new RegExp('\\s*<div', 'mg'), '\n<div');
+        content = content.replace(new RegExp('</div>\\s*', 'mg'), '</div>\n');
+        content = content.replace(new RegExp('\\s*\\[caption([^\\[]+)\\[/caption\\]\\s*', 'gi'), '\n\n[caption$1[/caption]\n\n');
+        content = content.replace(new RegExp('caption\\]\\n\\n+\\[caption', 'g'), 'caption]\n\n[caption');
+
+        blocklist2 = 'blockquote|ul|ol|li|table|thead|tr|th|td|h[1-6]|pre';
+        content = content.replace(new RegExp('\\s*<(('+blocklist2+') ?[^>]*)\\s*>', 'mg'), '\n<$1>');
+        content = content.replace(new RegExp('\\s*</('+blocklist2+')>\\s*', 'mg'), '</$1>\n');
+        content = content.replace(new RegExp('<li([^>]*)>', 'g'), '\t<li$1>');
+
+        if ( content.indexOf('<object') != -1 ) {
+            content = content.replace(/<object[\s\S]+?<\/object>/g, function(a){
+                return a.replace(/[\r\n]+/g, '');
+            });
+        }
+
+        // Unmark special paragraph closing tags
+        content = content.replace(new RegExp('</p#>', 'g'), '</p>\n');
+        content = content.replace(new RegExp('\\s*(<p [^>]+>.*</p>)', 'mg'), '\n$1');
+
+        // Trim whitespace
+        content = content.replace(new RegExp('^\\s*', ''), '');
+        content = content.replace(new RegExp('[\\s\\u00a0]*$', ''), '');
+
+        // put back the line breaks in pre|script
+        content = content.replace(/<wp_temp>/g, '\n');
+
+        // Hope.
+        return content;
+    },
+
+    wpautop : function(pee) {
+        var blocklist = 'table|thead|tfoot|caption|col|colgroup|tbody|tr|td|th|div|dl|dd|dt|ul|ol|li|pre|select|form|blockquote|address|math|p|h[1-6]';
+
+        if ( pee.indexOf('<object') != -1 ) {
+            pee = pee.replace(/<object[\s\S]+?<\/object>/g, function(a){
+                return a.replace(/[\r\n]+/g, '');
+            });
+        }
+
+        pee = pee.replace(/<[^<>]+>/g, function(a){
+            return a.replace(/[\r\n]+/g, ' ');
+        });
+
+        pee = pee + "\n\n";
+        pee = pee.replace(new RegExp('<br />\\s*<br />', 'gi'), "\n\n");
+        pee = pee.replace(new RegExp('(<(?:'+blocklist+')[^>]*>)', 'gi'), "\n$1");
+        pee = pee.replace(new RegExp('(</(?:'+blocklist+')>)', 'gi'), "$1\n\n");
+        pee = pee.replace(new RegExp("\\r\\n|\\r", 'g'), "\n");
+        pee = pee.replace(new RegExp("\\n\\s*\\n+", 'g'), "\n\n");
+        pee = pee.replace(new RegExp('([\\s\\S]+?)\\n\\n', 'mg'), "<p>$1</p>\n");
+        pee = pee.replace(new RegExp('<p>\\s*?</p>', 'gi'), '');
+        pee = pee.replace(new RegExp('<p>\\s*(</?(?:'+blocklist+')[^>]*>)\\s*</p>', 'gi'), "$1");
+        pee = pee.replace(new RegExp("<p>(<li.+?)</p>", 'gi'), "$1");
+        pee = pee.replace(new RegExp('<p>\\s*<blockquote([^>]*)>', 'gi'), "<blockquote$1><p>");
+        pee = pee.replace(new RegExp('</blockquote>\\s*</p>', 'gi'), '</p></blockquote>');
+        pee = pee.replace(new RegExp('<p>\\s*(</?(?:'+blocklist+')[^>]*>)', 'gi'), "$1");
+        pee = pee.replace(new RegExp('(</?(?:'+blocklist+')[^>]*>)\\s*</p>', 'gi'), "$1");
+        pee = pee.replace(new RegExp('\\s*\\n', 'gi'), "<br />\n");
+        pee = pee.replace(new RegExp('(</?(?:'+blocklist+')[^>]*>)\\s*<br />', 'gi'), "$1");
+        pee = pee.replace(new RegExp('<br />(\\s*</?(?:p|li|div|dl|dd|dt|th|pre|td|ul|ol)>)', 'gi'), '$1');
+        pee = pee.replace(new RegExp('(?:<p>|<br ?/?>)*\\s*\\[caption([^\\[]+)\\[/caption\\]\\s*(?:</p>|<br ?/?>)*', 'gi'), '[caption$1[/caption]');
+
+        // Fix the pre|script tags
+        pee = pee.replace(/<(pre|script)[^>]*>[\s\S]+?<\/\1>/g, function(a) {
+            a = a.replace(/<br ?\/?>[\r\n]*/g, '\n');
+            return a.replace(/<\/?p( [^>]*)?>[\r\n]*/g, '\n');
+        });
+
+        return pee;
+    }
+};