show tooltip for href (links), src (images) and name (named anchors) in Composer; b=47519, fix by glazman@netscape.com and neil@parkwaycc.co.uk, r=brade, r=glazman for kin's changes, sr=kin

editor/ui/composer/content/editor.js

@@ -3073,8 +3073,11 @@ function GetSelectionContainer()
   var editor = GetCurrentEditor();
   if (!editor) return null;
 
-  var selection = editor.selection;
-  if (!selection) return null;
+  try {
+    var selection = editor.selection;
+    if (!selection) return null;
+  }
+  catch (e) { return null; }
 
   var result = { oneElementSelected:false };
 
@@ -3139,3 +3142,20 @@ function GetSelectionContainer()
 
   return result;
 }
+
+function FillInHTMLTooltip(tooltip)
+{
+  var tooltipText = null;
+  for (var node = document.tooltipNode; node; node = node.parentNode) {
+    if (node instanceof Components.interfaces.nsIDOMHTMLImageElement ||
+        node instanceof Components.interfaces.nsIDOMHTMLInputElement)
+      tooltipText = node.getAttribute("src");
+    else if (node instanceof Components.interfaces.nsIDOMHTMLAnchorElement)
+      tooltipText = node.getAttribute("href") || node.name;
+    if (tooltipText) {
+      tooltip.setAttribute("label", tooltipText);
+      return true;
+    }
+  }
+  return false;
+}

editor/ui/composer/content/editor.xul

@@ -97,6 +97,8 @@
     <command id="toggleSidebar"/>
   </commandset>
 
+  <tooltip id="aHTMLTooltip" onpopupshowing="return FillInHTMLTooltip(this);"/>
+
   <broadcaster id="args" value="about:blank"/>
   <broadcaster id="canPrint"/>
   
@@ -245,7 +247,8 @@
            which breaks deck frame-hiding mechanism 
        -->
       <stack>
-        <editor type="content-primary" id="content-frame" src="about:blank" context="editorContentContext" flex="1"/>
+        <editor type="content-primary" id="content-frame" src="about:blank"
+                context="editorContentContext" flex="1" tooltip="aHTMLTooltip"/>
       </stack>
       <vbox>
         <label id="doctype-text" crop="right"/>