Fix the MOW height calculation in Muttator.

common/content/configbase.js

@@ -104,6 +104,12 @@ const configbase = { //{{{
      */
     name: null,
 
+    /**
+     * @property {number} The height (px) that is available to the output
+     *     window.
+     */
+    get outputHeight() getBrowser().mPanelContainer.boxObject.height,
+
     /**
      * @property {[string]} A list of extra scripts in the liberator or
      *    application namespaces which should be loaded before liberator

common/content/ui.js

@@ -1681,11 +1681,10 @@ function CommandLine() //{{{
 
             let doc = multilineOutputWidget.contentDocument;
 
-            let availableHeight = 250;
+            let availableHeight = 250; // Why? --djk
             try
             {
-                availableHeight = getBrowser().mPanelContainer ?
+                availableHeight = config.outputHeight;
-                    getBrowser().mPanelContainer.boxObject.height : getBrowser().boxObject.height;
                 if (!outputContainer.collapsed)
                     availableHeight += parseFloat(outputContainer.height);
             }

muttator/content/config.js

@@ -142,6 +142,25 @@ const config = { //{{{
         ["COMPOSE"]
     ],
 
+    // NOTE: as I don't use TB I have no idea how robust this is. --djk
+    get outputHeight()
+    {
+        if (!this.isComposeWindow)
+        {
+            let container = document.getElementById("tabpanelcontainer").boxObject;
+            let deck      = document.getElementById("displayDeck");
+            let box       = document.getElementById("messagepanebox");
+            let splitter  = document.getElementById("threadpane-splitter").boxObject;
+
+            if (splitter.width > splitter.height)
+                return container.height - deck.minHeight - box.minHeight- splitter.height;
+            else
+                return container.height - Math.max(deck.minHeight, box.minHeight);
+        }
+        else
+            return document.getElementById("appcontent").boxObject.height;
+    },
+
     scripts: [
         "addressbook.js",
         "mail.js",