You wouldn't expect anyone on this blog to advocate a competitor's technology... but this case is special.
To cut a long story short, a customer found themselves in a situation where a SharePoint 2010 implementation plan collided with the presence of thousands of desktops across the estate still running IE6. Now, for those who may not know – these two products have severe compatibility issues, where SharePoint 2010 pages effectively cannot be viewed in IE6 – or at any rate this is not acceptable user experience.
Upgrading the browser across a massive user base, also having to test a bunch of internal LOB applications is a task the complexity of which I hopefully do not need to explain – which is why the customer resorted to using Google Chrome Frame as an interim solution. GCF is a plug-in to IE that can be fairly easily deployed, and which does a half-decent job rendering SharePoint pages. So, on the surface the solution seemed quite straightforward: deploy the plug-in to all affected workstations, enforce the rendering of the SharePoint 2010 site pages by setting the value of the appropriate registry key with a GPO – job done! However in reality, the following issues made it much easier said than done:
1) For some reasons that we won't mention here, Chrome Frame was also to be deployed to workstations that have IE8 on them – however the requirement was that only IE6 users should have SharePoint pages rendered by Chrome Frame. IE8 users should have them rendered natively – meaning that setting the appropriate registry value would require much more complex Group Policy configuration. A good alternative would be controlling the rendering from the server side using the appropriate HTML metatag or equivalent HTTP header (‘X-UA-Compatible’), the problem being that SharePoint sets the value of it itself – to ‘IE8’, of course.
2) Most SharePoint pages using the default master page (V4.master) have a control embedded in them that causes a warning message to pop up if IE6 is detected:
<SharePoint:WarnOnUnsupportedBrowsers runat="server"/>
This happens every time – irrespective of whether ChromeFrame is present or not, as the latter only adds its signature to the end of the User-Agent string, the browser still identifying itself as IE6:
The solution, after some serious head-scratching, came from the side of SharePoint 2010's wonderful infrastructure of delegate controls. If we look at our default master page again, we may notice a particularly useful little piece in the <head> section:
<SharePoint:DelegateControl runat="server" ControlId="AdditionalPageHead" AllowMultipleControls="true"/>
Now, the AllowMultipleControls property here means that this delegate control can have multiple child candidate controls that will all be added to the page at runtime - which presents us with a really powerful customisation engine indeed! To solve the little problem described above, all I had to do was:
1) Create a custom candidate control and solution as per 'How to: Customize a Delegate Control' (obviously with my own names, etc.);
2) Override the OnInit method as follows:
protected override void OnInit(EventArgs e)
{
base.OnInit(e);
SPWeb contextWeb = SPControl.GetContextWeb(this.Context);
if ((contextWeb != null) && (contextWeb.UIVersion >= 4))
{
HttpBrowserCapabilities browser =
HttpContext.Current.Request.Browser;
//Check if browser is unsupported
if ((browser != null) && (((browser.Browser == "IE") &&
(browser.MajorVersion < 7)) || ((browser.Browser == "Firefox")
&& (browser.MajorVersion < 3))))
{
//Check if Chrome Frame is present
if (HttpContext.Current.Request.UserAgent.Contains
("chromeframe"))
{
foreach (Control c in this.Page.Master.Controls)
{
//Iterate through the collection of controls to
identify the target ones;
foreach (Control childc in c.Controls)
{
//Hide (i.e. disable) the OOB warning control
if (childc is
Microsoft.SharePoint.WebControls.WarnOnUnsupportedBrowsers)
{
childc.Visible = false;
}
//Iterate through the collection of metatags
else if (childc is
System.Web.UI.HtmlControls.HtmlHead)
{
foreach (Control meta in childc.Controls)
{
try
{
//Overwrite the value of the X-UA-
Compatible tag, forcing user's
browser to engage GCF for rendering
if (((HtmlMeta)meta).HttpEquiv ==
"X-UA-Compatible")
{
((HtmlMeta)meta).Content =
"chrome=1";
}
}
catch { }
}
}
}
}
}
}
}
}
Once this solution is deployed, any user hitting any SharePoint page with IE6 with GCF plug-in installed will have that page rendered by GCF and will not see the warning pop-up message. IE8 will render SharePoint pages natively, and IE6 users that do not have Google Chrome Frame will still see the warning...
Simples!