One of the more limiting issues of writing client side script in the browser is the same origin limitations of XMLHttpRequest. The latest version of all browsers support a subset of CORS to allow servers to opt-in particular resources for cross-domain access. Since IE8 there's XDomainRequest and in all other browsers (including IE10) there's XHR L2's cross-origin request features. But the vast majority of resources out on the web do not opt-in using CORS headers and so client side only web apps like a podcast player or a feed reader aren't doable.
One hack-y way around this I've found is to use YQL as a CORS proxy. YQL applies the CORS header to all its responses and among its features it allows a caller to request an arbitrary XML, HTML, or JSON resource. So my network helper script first attempts to access a URI directly using XDomainRequest if that exists and XMLHttpRequest otherwise. If that fails it then tries to use XDR or XHR to access the URI via YQL. I wrap my URIs in the following manner, where type is either "html", "xml", or "json":
yqlRequest = function(uri, method, type, onComplete, onError) {
var yqlUri = "http://query.yahooapis.com/v1/public/yql?q=" +
encodeURIComponent("SELECT * FROM " + type + ' where url="' + encodeURIComponent(uri) + '"');
if (type == "html") {
yqlUri += encodeURIComponent(" and xpath='/*'");
}
else if (type == "json") {
yqlUri += "&callback=&format=json";
}
...
Working on GeolocMock it took me a bit to realize why my HTML could use the W3C Geolocation API in IE9 but not in my WebBrowser control in my .NET application. Eventually I realized that I was getting the wrong IE doc mode. Reading this old More IE8 Extensibility Improvements IE blog post from the IE blog I found the issue is that for app compat the WebOC picks older doc modes but an app hosting the WebOC can set a regkey to get different doc modes. The IE9 mode isn't listed in that article but I took a guess based on the values there and the decimal value 9999 gets my app IE9 mode. The following is the code I run in my application to set its regkey so that my app can get the IE9 doc mode and use the geolocation API.
static private void UseIE9DocMode()
{
RegistryKey key = null;
try
{
key = Registry.CurrentUser.OpenSubKey("Software\\Microsoft\\Internet Explorer\\Main\\FeatureControl\\FEATURE_BROWSER_EMULATION", true);
}
catch (Exception)
{
key = Registry.CurrentUser.CreateSubKey("Software\\Microsoft\\Internet Explorer\\Main\\FeatureControl\\FEATURE_BROWSER_EMULATION");
}
key.SetValue(System.Diagnostics.Process.GetCurrentProcess().MainModule.ModuleName, 9999, RegistryValueKind.DWord);
key.Close();
}
I've made a WPAD server Fiddler extension and in a fit of creativity I've named it: WPAD Server Fiddler Extension.
Of course you know about Fiddler, Eric's awesome HTTP debugger tool, the HTTP proxy that lets you inspect, visualize and modify the HTTP traffic that flows through it. And on the subject you've probably definitely heard of WPAD, the Web Proxy Auto Discovery protocol that allows web browsers like IE to use DHCP or DNS to automatically discover HTTP proxies on their network. While working on a particularly nasty WPAD bug towards the end of IE8 I really wished I had a way to see the WPAD requests and responses and modify PAC responses in Fiddler. Well the wishes of me of the past are now fulfilled by present day me as this Fiddler extension will respond to WPAD DHCP requests telling those clients (by default) that Fiddler is their proxy.
When I started working on this project I didn't really understand how DHCP worked especially with respect to WPAD. I won't bore you with my misconceptions: it works by having your one DHCP server on your network respond to regular DHCP requests as well as WPAD DHCP requests. And Windows I've found runs a DHCP client service (you can start/stop it via Start|Run|'services.msc', scroll to DHCP Client or via the command line with "net start/stop 'DHCP Client'") that caches DHCP server responses making it just slightly more difficult to test and debug my extension. If a Windows app uses the DHCP client APIs to ask for the WPAD option, this service will send out a DHCP request and take the first DHCP server response it gets. That means that if you're on a network with a DHCP server, my extension will be racing to respond to the client. If the DHCP server wins then the client ignores the WPAD response from my extension.
Various documents and tools I found useful while working on this:
I built timestamp.exe, a Windows command line tool to convert between computer and human readable date/time formats mostly for working on the first run wizard for IE8. We commonly write out our dates in binary form to the registry and in order to test and debug my work it became useful to be able to determine to what date the binary value of a FILETIME or SYSTEMTIME corresponded or to produce my own binary value of a FILETIME and insert it into the registry.
For instance, to convert to a binary value:
[PS C:\] timestamp -inString 2009/08/28:10:18 -outHexValue -convert filetime
2009/08/28:10:18 as FILETIME: 00 7c c8 d1 c8 27 ca 01Converting in the other direction, if you don't know what format the bytes are in, just feed them in and timestamp will try all conversions and list only the valid ones:
[PS C:\] timestamp -inHexValue "40 52 1c 3b"
40 52 1c 3b as FILETIME: 1601-01-01:00:01:39.171
40 52 1c 3b as Unix Time: 2001-06-05:03:30:08.000
40 52 1c 3b as DOS Time: 2009-08-28:10:18:00.000[PS C:\] timestamp -inHexValue "40 52 1c 3b" -convert guess
40 52 1c 3b as DOS Time: 2009-08-28:10:18:00.000When I first wrote this I had a bug in my function that parses the date-time value string in which I could parse 2009-07-02:10:18 just fine, but I wouldn't be able to parse 2009-09-02:10:18 correctly. This was my code:
success = swscanf_s(timeString, L"%hi%*[\\/- ,]%hi%*[\\/- ,]%hi%*[\\/- ,Tt:.]%hi%*[:.]%hi%*[:.]%hi%*[:.]%hi",
&systemTime->wYear,
&systemTime->wMonth,
&systemTime->wDay,
&systemTime->wHour,
&systemTime->wMinute,
&systemTime->wSecond,
&systemTime->wMilliseconds) > 1;
To convert between these various forms yourself read The Old New Thing date conversion article or Josh Poley's date time article. I previously wrote about date formats I like and dislike.
Before we shipped IE8 there were no Accelerators, so we had some fun making our own for our favorite web services. I've got a small set of tips for creating Accelerators for other people's web services. I was planning on writing this up as an IE blog post, but Jon wrote a post covering a similar area so rather than write a full and coherent blog post I'll just list a few points:
There's no easy way to use local applications on a PC as the result of an accelerator or a search provider in IE8 but there is a hack-y/obvious way, that I'll describe here. Both accelerators and search providers in IE8 fill in URL templates and navigate to the resulting URL when an accelerator or search provider is executed by the user. These URLs are limited in scheme to http and https but those pages may do anything any other webpage may do. If your local application has an ActiveX control you could use that, or (as I will provide examples for) if the local application has registered for an application protocol you can redirect to that URL. In any case, unfortunately this means that you must put a webpage on the Internet in order to get an accelerator or search provider to use a local application.
For examples of the app protocol case, I've created a callto accelerator that uses whatever application is registered for the callto scheme on your system, and a Windows Search search provider that opens Explorer's search with your search query. The callto accelerator navigates to my redirection page with 'callto:' followed by the selected text in the fragment and the redirection page redirects to that callto URL. In the Windows Search search provider case the same thing happens except the fragment contains 'search-ms:query=' followed by the selected text, which starts Windows Search on your system with the selected text as the query. I've looked into app protocols previously.
I've redone my blog's layout to remind myself how terrible CSS is -- err I mean to play
with the more advanced features of CSS 2.1 which are all now available in IE8. As part of the new layout I've included my Delicious links by default but at a smaller size and I've replaced the
navigation list options with Technical, Personal and Everything as I've heard from folks that that would actually be useful. Besides the layout I've also updated the back-end, switching from my
handmade PHP+XSLT+RSS/Atom monster to a slightly less horrible PHP+DB solution. As a result everything should be much much faster including search which, incidentally, is so much easier to
implement outside of XSLT.
I've made a QR Encode accelerator around Google Chart's QR code generator. QR codes are 2D bar-codes that can store (among other things) URLs and have good support on mobile
phones. The accelerator I've written lets you generate a QR code for a selected link and view it in the preview window. In combination with the ZXing
bar-code scanner app for my Android cellphone, its easy for me to right click on a link in IE8 on my desktop PC, hover over the QR Encode accelerator to have the link's associated QR code
displayed, and then with my phone read that QR code to open my phone's browser to the URL contained inside. Its much easier to browse around in the comfort of my desktop and only send particular
URLs to my cellphone as necessary.
A while ago I promised to say how an xsltproc Meddler script would be useful and the general answer is
its useful for hooking up a client application that wants data from the web in a particular XML format and the data is available on the web but in another XML format. The specific case for this
post is a Flickr Search service that includes IE8 Visual Search Suggestions. IE8
wants the Visual Search Suggestions XML format and Flickr gives out search data in their Flickr web API XML format.
So I wrote an XSLT to convert from Flickr Search XML to Visual Suggestions XML and used my xsltproc Meddler script to actually apply this xslt.
After getting this all working I've placed the result in two places: (1) I've updated the xsltproc Meddler script to include this XSLT and an XML file to install it as a search provider - although you'll need to edit the XML to include your own Flickr API key. (2) I've created a service for this so you can just install the Flickr search provider if you're interested in having the functionality and don't care about the implementation. Additionally, to the search provider I've added accelerator preview support to show the Flickr slideshow which I think looks snazzy.
Doing a quick search for this it looks like there's at least one other such implementation, but mine has the distinction of being done through XSLT which I provide, updated XML namespaces to work with the released version of IE8, and I made it so you know its good.
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