isp page 4 - Dave's Blog

Send URL to Cellphone - QR Encode Accelerator

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.

Outline View Internet Explorer Extension

I've made another extension for IE8, Outline View, which gives you a side bar in IE that displays an outline of the current page and lets you make intrapage bookmarks.

The outline is generated based on the heading tags in the document (e.g. h1, h2, etc), kind of like what W3C's Semantic data extractor tool displays for an outline. So if the page doesn't use heading tags the way the HTML spec intended or just sticks img tags in them, then the outline doesn't look so hot. On a page that does use headings as intended though it looks really good. For instance a section from the HTML 4 spec shows up quite nicely and I find its actually useful to be able to jump around to the different sections. Actually, I've been surprised going to various blogs how well the outline view is actually working -- I thought a lot more webdevs would be abusing their heading tags.

I've also added intrapage bookmarks. When you make a text selection and clear it, that selected text is added as a temporary intrapage bookmark which shows up in the correct place in the outline. You can navigate to the bookmark or right click to make it permanent. Right now I'm storing the permanent intrapage bookmarks in IE8's new per-domain DOM storage because I wanted to avoid writing code to synchronize a cross process store of bookmarks, it allowed me to play with the DOM storage a bit, and the bookmarks will get cleared appropriately when the user clears their history via the control panel.

Notes on Creating Internet Explorer Extensions in C++ and COM

Working on Internet Explorer extensions in C++ & COM, I had to relearn or rediscover how to do several totally basic and important things. To save myself and possibly others trouble in the future, here's some pertinent links and tips.

First you must choose your IE extensibility point. Here's a very short list of the few I've used:

• Explorer Bars and IE Toolbars
• IE Tools, IE Help, and IE Context Menu menu items
• IE Toolbar Buttons

Once you've created your COM object that implements IObjectWithSite and whatever other interfaces your extensibility point requires as described in the above links you'll see your SetSite method get called by IE. You might want to know how to get the top level browser object from the IUnknown site object passed in via that method.

After that you may also want to listen for some events from the browser. To do this you'll need to:

1. Implement the dispinterface that has the event you want. For instance DWebBrowserEvents2, or HTMLDocumentEvents, or HTMLWindowEvents2. You'll have to search around in that area of the documentation to find the event you're looking for.
2. Register for events using AtlAdvise. The object you need to subscribe to depends on the events you want. For example, DWebBrowserEvents2 come from the webbrowser object, HTMLDocumentEvents come from the document object assuming its an HTML document (I obtained via get_Document method on the webbrowser), and HTMLWindowEvents2 come from the window object (which oddly I obtained via calling the get_script method on the document object). Note that depending on when your SetSite method is called the document may not exist yet. For my extension I signed up for browser events immediately and then listened for events like NavigateComplete before signing up for document and window events.
3. Implement IDispatch. The Invoke method will get called with event notifications from the dispinterfaces you sign up for in AtlAdvise. Implementing Invoke manually is a slight pain as all the parameters come in as VARIANTs and are in reverse order. There's some ATL macros that may make this easier but I didn't bother.
4. Call AtlUnadvise at some point -- at the latest when SetSite is called again and your site object changes.

If you want to check if an IHTMLElement is not visible on screen due how the page is scrolled, try comparing the Body or Document Element's client height and width, which appears to be the dimensions of the visible document area, to the element's bounding client rect which appears to be its position relative to the upper left corner of the visible document area. I've found this to be working for me so far, but I'm not positive that frames, iframes, zooming, editable document areas, etc won't mess this up.

Be sure to use pointers you get from the IWebBrowser/IHTMLDocument/etc. only on the thread on which you obtained the pointer or correctly marshal the pointers to other threads to avoid weird crashes and hangs.

Obtaining the HTML document of a subframe is slightly more complicated then you might hope. On the other hand this might be resolved by the new to IE8 method IHTMLFrameElement3::get_contentDocument

Check out Eric's IE blog post on IE extensibility which has some great links on this topic as well.

Subst Allows Non-Letter Drive Letters

I knew that the command line tool subst would create virtual drives that map to existing directories but I didn't know that subst lets you name the virtual drives with characters that aren't US-ASCII letters. For instance you can run 'subst 4: C:\windows' and then 'more 4:\win.ini' to dump C:\windows\win.ini. This also works for non-US-ASCII characters like, "Ｃ" (aka U+FF23, Fullwidth Latin Capital Letter C), which when displayed by cmd.exe via some best fit style character conversions looks just like the regular US-ASCII 'C'. None of Explorer, IE, or the common file dialogs allow the use of these odd virtual drives -- just cmd.exe, so I'm not sure how this would ever be useful but I thought it was odd and I wanted to share.

Phone Replacement For Grocery Card

Another use for my new phone is as a replacement for my grocery card, those little plastic cards with a bar code on them that the grocery store gives you to track your purchasing habits. I've previously gone to great lengths to increase space in my pockets by removing infrequently used keys and reducing my wallet to the essentials. So I was glad to get rid of the QFC card and replace it with a photo of its bar code on my phone. Since the important part of the QFC card is the bar code which is just an image of black lines, if your phone has a camera and a screen with a reasonable resolution you can take a photo of the bar code and later display it to a reader. I've so far been able to try it once and successfully at a normal checkout line, but the reaction from the checkout lady was enough that I may in the future just keep a card in my car. She was very excited, asked me what kind of phone I had, called over another checkout person and generally made a large fuss. Also the checkout people generally don't mind giving me a new card if I don't have one with me.

Signs of Fall Tree

sequelguy posted a photo:

Immediately after Sarah took this photo, a truck pulled into the empty parking spot and the driver jumped out to apologize for messing up the photo. The driver was a zombie.

Failing Electronics

Electronic devices shouldn't fail, they should just sit wherever I place them and work forever. A while back my home web server started failing so I moved over to a real web hosting service. And this was the home web server I built from pieces Eric gave me after my previous one died during the big power failure the year before. The power socket on my old laptop has come undone from the motherboard so that it can no longer be powered. Just a week or two ago my Xbox 360 stopped displaying video. The CPU fan on my media center died. I also want to put my camera and GPS in this list, but the camera died due to accidentally turning on in my pocket and the GPS was stolen so those aren't the devices just arbitrarily failing.

QuickBase Formula Pretty Printer and Syntax Highlighter

Sarah asked me if I knew of a syntax highlighter for the QuickBase formula language which she uses at work. I couldn't find one but thought it might be fun to make a QuickBase Formula syntax highlighter based on the QuickBase help's description of the formula syntax. Thankfully the language is relatively simple since my skills with ANTLR, the parser generator, are rusty now and I've only used it previously for personal projects (like Javaish, the ridiculous Java based shell idea I had).

With the help of some great ANTLR examples and an ANTLR cheat sheet I was able to come up with the grammar that parses the QuickBase Formula syntax and prints out the same formula marked up with HTML SPAN tags and various CSS classes. ANTLR produces the parser in Java which I wrapped up in an applet, put in a jar, and embedded in an HTML page. The script in that page runs user input through the applet's parser and sticks the output at the bottom of the page with appropriate CSS rules to highlight and print the formula in a pretty fashion.

What I learned:

• I didn't realize that Java applets are easy to use via script in an HTML page. In the JavaScript I can simply refer to publicly exposed methods on the applet and run JavaScript strings through them. It makes for a great combination: do the heavy coding in Java and do the UI in HTML. I may end up doing this again in the future.
• I love ANTLRWorks, the ANTLR IDE, that didn't exist the last time I used ANTLR. It tells you about issues with your grammar as you create it, lets you easily debug the grammar running it forwards and backwards, display parse trees, and other useful things.

Xbox Achievements for Everyday Life

I just upgraded to the Zune 3.0 software which includes games and purchasing music on the Zune via WiFi and once again I'm thrilled that the new firmware is available for old Zunes like mine. Rooting around looking at the new features I noticed Zune Badges for the first time. They're like Xbox Achievements, for example I have a Pixies Silver Artist Power Listener award for listening to the Pixies over 1000 times. I know its ridiculous but I like it, and now I want achievements for everything.

Achievements everywhere would require more developments in self-tracking. Self-trackers, folks who keep statistics on exactly when and what they eat, when and how much they exercise, anything one may track about one's self, were the topic of a Kevin Kelly Quantified Self blog post (also check out Cory Doctorow's SF short story The Things that Make Me Weak and Strange Get Engineered Away featuring a colony of self-trackers). For someone like me with a medium length attention span the data collection needs to be completely automatic or I will lose interest and stop collecting within a week. For instance, Nike iPod shoes that keep track of how many steps the wearer takes. I'll also need software to analyze, display, and share this data on a website like Mycrocosm. I don't want to have to spend extreme amounts of time to create something as wonderful as the Feltron Report (check out his statistic on how many daily measurements he takes for the report). Once we have the data we can give out achievements for everything!

Achievements for Everyday Life

	Carnivore Eat at least ten different kinds of animals.
	Make Friends Meet at least 10% of the residents in your home town.
	Globetrotter Visit a city in every country.
	You're Old Survive at least 80 years of life.

Of course none of the above is practical yet, but how about Delicious achievements based on the public Delicious feeds? That should be doable...

Facebook Profile Views Application - Failed Idea

I had an idea for a Facebook app the other day. I wondered who actually looked at my profile and thought I could create a Facebook app that would record this information and display it. When I talked to Vishu though he said that this wasn't something that Facebook would be too happy with. Indeed the Platform Policy explicitly disallows this in section 2.8. This explained why the app didn't already exist. Its probably for the best since everyone assumes they can anonymously view Facebook profiles and would be irritated if that weren't the case.

On the topic of assumed anonymity, check out this article on the aggregation and selling off of your cell phone data including your physical location.

Deriving a Non-Recursive Fibonacci Function Using Linear Algebra

In my Intro to Algorithms course in college the Fibonacci sequence was used as the example algorithm to which various types of algorithm creation methods were applied. As the course went on we made better and better performing algorithms to find the nth Fibonacci number. In another course we were told about a matrix that when multiplied successively produced Fibonacci numbers. In my linear algebra courses I realized I could diagonalize the matrix to find a non-recursive Fibonacci function. To my surprise this worked and I found a function.

Looking online I found that of course this same function was already well known. Mostly I was irritated that after all the algorithms we created for faster and faster Fibonacci functions we were never told about a constant time function like this.

I recently found my paper depicting this and thought it would be a good thing to use to try out MathML, a markup language for displaying math. I went to the MathML implementations page and installed a plugin for IE to display MathML and then began writing up my paper in MathML. I wrote the MathML by hand and must say that's not how its intended to be created. The language is very verbose and it took me a long time to get the page of equations transcribed.

MathML has presentation elements and content elements that can be used separately or together. I stuck to content elements and while it looked great in IE with my extension when I tried it in FireFox which has builtin MathML support it didn't render. As it turns out FireFox doesn't support MathML content elements. I had already finished creating this page by hand and wasn't about to switch to content elements. Also, in order to get IE to render a MathML document, the document needs directives at the top for specific IE extensions which is a pain. Thankfully, the W3C has a MathML cross platform stylesheet. You just include this XSL at the top of your XHTML page and it turns content elements into appropriate presentation elements, and inserts all the known IE extension goo required for you. So now my page can look lovely and all the ickiness to get it to render is contained in the W3C's XSL.