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May

17

Shorter, more useful links with SDRV.MS

If you’re like most people, when you share files via SkyDrive you typically do so directly via email. This is one reason we built the connected address book, bringing together your friends’ addresses across Facebook, Google, and LinkedIn. Another benefit: when you share photos via email, your friends get a beautiful email with thumbnail previews.

Back in December, we added another way to share. You can get a link to any file or folder on SkyDrive and send that link to friends. You can choose to let friends edit or add files, or choose to make the link read-only. Since then, SkyDrive users have created over 13 million links—copying and pasting them into their favorite apps or services.

While this feature has been popular, we’ve also gotten a lot of feedback that our links are too long and too ugly. We agree!

Sharing with links just got a bit friendlier:

We’ve shortened our regular URLs by 40%. Our previous URLs didn’t even fit inside a Tweet! Oh the shame!
You can shorten them even further thanks to our new partnership with bitly and the new domain for shortened SkyDrive URLs: http://sdrv.ms
We’ve added OpenGraph support to our URLs so that when you paste them into places like Facebook, a nice thumbnail preview gets generated

Shorter links

As you can see in the Share dialog, there is a Shorten button

Screenshot of Share dialog box showing the Shorten button

Shortening using our own custom domain

Clicking the button will result in a very short URL using the SDRV.MS domain

Screenshot of Share dialog box showing the shortened URL

Support for OpenGraph for link previews

If you copy that URL to Facebook you’ll see a nicer preview

Screenshot of Facebook preview, including file icon and sample of content

Stats on your short links

Since bitly powers the shortener, you also get great power features. For example, you can add a ‘+’ to the end of any short URL to see statistics. You can also generate a QR code for that URL by appending ’.qrcode’ to that URL.

Screenshot of bitly stats, including clicks over time, referers, locations and QR code

We hope you enjoy these changes, and thanks for using SkyDrive!

Omar Shahine
Group Program Manager, SkyDrive.com

May

16

Listbox, Why Art Thou Blanking?

Category: Vista News | Leave a Comment

One of the biggest performance changes for developers using Silverlight in Mango (WP 7.5) is off-thread input for ListBox. In a nutshell this basically means that all any flick or pan a user makes on a ListBox is handled by a dedicated thread, the Direct Manipulation (DM) thread, instead of the UI thread. By connecting the DM thread to the Compositor thread (that’s the one that does all the drawing to the screen independent of the UI thread) we have a ListBox that moves smoothly even when the UI thread is completely blocked.

Unfortunately this also comes with a price – the ListBox is now so responsive and moves so fast that the Listbox can run out of content to display to the user as the user is flicking, and blank – basically drawing nothing except for an updated ScrollBar (so the user knows he’s still moving in the ListBox, but it doesn’t help much) and the background while the UI thread scrambles to bring in new items to fill up the holes.

My ListBox isn’t blanking, why do I care about this blog post?

You care because you care about your users. You’re the kind of dev who knows that even though he’s got a great, powerful phone, not everyone does. You care because you are proud to call yourself a developer. You care because… ok, back to reality.

With the release of Tango, Windows Phone is now supported on lower powered machines which often have slower hardware and less memory, so even though your device shows no blanking, others may see blanking, especially if they’re rocking a new, lower powered, Tango phone. This post will help give you the tools that let your app run smooth, with hardly any blanks, even on those phones.

My ListBox is not blanking, but it’s really jerky during scroll

Holy Smokes Batman! Jerky scrolling is all but eliminated in the new ListBox, even for WP7 apps – are you sure you’re using it? There’s a good chance you’re using the original LongListSelector (LLS) from the toolkit, which doesn’t auto-update when you move your project to Mango. To take full advantage of the new ListBox improvements you need to download the latest toolkit from http://silverlight.codeplex.com and update to the new LLS which is based on the platform’s ListBox.

Why does blanking occur: the nitty gritty

There are a couple of common code / design reasons that cause a ListBox to blank, but in general it all boils down to the amount of time it takes to bring in a new item. The ListBox maintains a one screen buffer of items in each direction which moves with the user’s viewport as they scroll around. If the ListBox can’t fill that buffer in the direction of the scroll fast enough, you get blanking.

Diagram 1: In a stationary world, when there is no scrolling going on, the user will be looking at the center screen and there will be buffered items waiting to be shown in both directions

Filling the buffer takes a few steps, namely creating an Item Container (if a suitable one from the excess buffer in the other direction doesn’t already exist) and Data Binding the new item’s content (which kicks off the Measure pass). All of these updates occur on the UI thread and they all happen at once (not item by item) so if a flick is fast and the ListBox realizes that it needs to draw a full screen worth’s of items it will block the UI thread while it does just that.

Diagram 2: As the user moves downwards we balance the buffers by transferring the excess buffer from the top buffer (red) to the bottom buffer and re-databind it to the new data, maintaining 1 screen of buffer in each direction.

But if the user flicks again while the UI thread is blocked bringing in buffer items, we’ll get even more out of sync and move completely out of our buffer space – since there is nothing in the Control to draw (remember, the ListBox is still scrambling on the UI thread to bring the new items in, it’s just too slow) you just get the background, i.e blankness.

If there’s nothing to draw, why is the ListBox still moving? Or, look at it from another angle:

As we mentioned earlier, scrolling is now off-thread, so from the Compositor’s point of view it’s moving the ListBox and everything in it, the problem is that the UI thread hasn’t stuck anything in it (at that position) yet, so we blank.

Diagram 3: Fast flicking a few times get you into this situation, where we have excess buffer above which we are trying to move downwards, but because there is so much of it and the UI thread is blocked trying to bring these items in we don’t finish in time and the user sees blankness (black) until the items are ready, at which time they simply appear.

So why is *my* ListBox blanking? And how do I fix it?

Let’s run through a couple of common reasons why ListBoxes blank, with some proposed solutions to each one.

1. Using ValueConverters in your template

ValueConverters are great – they allow you to transform your data on the fly as they are being DataBound into your items. Unfortunately they incur a UI thread cost – we need to transition from Silverlight into User Code, run your converter and then return. If your converter is heavy or you’re using lots of them in your template, then this will introduce blanking.

Question to ask yourself: does this code look like it can run in a trivial amount of time across all of the elements being brought in for a given frame? If not, you probably should explore a different way of doing the DataBinding. For example,you can have the object translate the values on population / property get time instead of using a converter - even though this may break your Data Model this can significantly reduce the DataBinding cost (and you could always wrap your object in a ViewModel).

2. Complex DataTemplates

When an item is moved from one buffer to another during a scroll, ListBox is usually smart enough to determine that this is the same kind of item and just update the data in the item. While this might sound cheap this dirties the item causing it to be remeasured. If your template is complex you will find that a lot of your time is wasted in Measure – remeasuring the layout of the control now that the data has been updated.

Fixing this is very per-scenario. Some general guidelines are to make sure to only use a container if you really need the options it provides – do you have a Grid within a Grid? Could you replace all of your Grids with a simple Canvas or maybe a StackPanel?

3. Decoding images on the UI thread

By default all images are decoded synchronously on the UI thread, so if you have something like this:

you’re going to block the UI thread for however long it takes to decode your image. Luckily there’s an easy fix for this, change your template to read as follows:

Note that this does come with some caveats – older images will still show up until the new ones are loaded and the user may see a visual pop-in of the image when it is done loading, but these can all be worked around and massaged into a nice user experience that is not harmed by excessive image decode.

For further details see this blog post.

4. Using PrepareItemForContainerOverride to dynamically select a template

A simple list item is often times just not good enough – your app has an image item, a text item, a video item, a link item etc. etc. and you have a different template for each one of them. A common pattern is to use the ListBox’s PrepareItemForContainerOverride callback to dynamically change the container’s template based on what item is being databound.

Unfortunately, doing this can completely throw off the ListBox’s buffering technique – the ListBox sees that the container that it had in its buffer is not the type that you need and junks it, wasting even more time on the march to blankness.

So how do I solve this? Surprisingly enough, it is often cheaper to have all of your template parts in one large template (yes, yes, I know about point 2 above – keep reading!) with each mini-template collapsed if it does not apply. Since collapsed template items incur next to no cost during layout, they have next to no impact on run time (though there is a slightly larger memory cost).

And how do I get my different items to display on the different templates? Simple – databind to a new property on your classes which either has a type enumeration that runs through a value converter (ItemTypeToVisibility), these kinds of converters are often cheap, or wrap your class in a UI view model so that it has a property that returns the Visibility type directly.

5. Pulling data from [favorite heavy source] as part of your binding

The properties you bind to should have simple getters (setters is a different story) – always. If you have logic like this:

public int Rating
{
get
{
    <read from database>
    - or -
    <read from IsoStore>
    - or -
    <parse out some XML>
    - etc -
}
}

then you’re doing something wrong. This kind of logic is fine for a property that you know is only read very rarely, if at all, but if it’s in a ListBox then it most likely is going to be seen and you should be initializing the data up front.

Don’t get me wrong – you don’t need to load everything as you are pulling in 1000 items to your list, but you can certainly do it on a background thread as a deferred task kicked off in the constructor of your object. If your objects are really heavy and memory is becoming an issue then you have a few possible routes:

Implement a completely delayed load by hooking into the ListBox’s scroll amount or compression states and only loading more items when you get to the end of the list
Implement a DoubleLinkedObservableCollection, where each item in the collection knows about the next node (in each direction) and when it gets databound (based on one of the properties) it notifies X number of nodes on each side to make sure they all have their data ready to go. This should be done on a background thread, just don’t forget to Dispatch back to update any properties that raise a PropertyChanged event.

6. Cut down background work

With only one core any background thread can interfere with the smoothness of the UI thread. Although background threads get a much smaller time slice compared to the UI thread, enough of them vying for time will effectively starve the UI thread.

Diagram 4: Fictional time slice showing the effects of more background threads (not to scale)

Across any given slice of time, the UI thread will be allowed to run longer than any other thread, but is effectively running at the same priority, hence it is forced to yield to the background threads when its time is up. The more background threads, the longer it is before you get back to the UI thread so that it can complete its task.

Moral of the story? Be wise about the number of active background, especially in high stress scenarios. Stick to using a thread pool so that you can queue up your work without it all trying to run at the same time.

I’ve tried all the above, it’s still blanking and I only have a couple of screens of data – help!

If you find yourself blanking on a relative small set of data (approximately 3-5 screens), then it might be time for drastic measures. As mentioned above the cause for blanking is the amount of time it takes to bring in new items with new data as the user is scrolling, i.e. the virtualization overhead is the culprit. If you disable virtualization on your list, you’ll generate of all your items up front and scrolling will be blankless. To do this, add the following to your XAML:

<ListBox.ItemsPanel>  <ItemsPanelTemplate>    <StackPanel>    </StackPanel>  </ItemsPanelTemplate></ListBox.ItemsPanel>

While making this change is relatively simple, the impact can be drastic – no more blanking, but it comes at a cost:

Startup time for the Page increases – we now have to realize more items, so it’s going to take longer
Memory – same as above, more items hanging around, larger memory cost

If you give it a try on a low end device and startup and memory look acceptable – then this is your magic bullet!

So what are we left with?

Hopefully at this point you have a non to minimally blanking list, which scrolls smoothly and generally delights your users! Have you run into any other pitfalls that you think others should be warned of? Let us know below!

Running into other, unrelated performance issues? Drop us a line and we’ll see if we can focus on them in a future blog post (stay tuned for a "memory" series coming soon).

May

16

Windows Phone designer is named one of country’s most creative

Category: Vista News | Leave a Comment

The June issue of Fast Company carries the magazine’s latest picks for its annual 100 Most Creative People in Business, which celebrates “innovators who dare to think differently.” This year one of our own made the coveted list: Windows Phone designer Jeff Fong. Check out his write-up.

Fong, 43, joined the Windows Phone design team three years ago and has been one of the leading thinkers behind Windows Phone’s signature look and the set of underlying design principles known as “Metro.”

Trained as an illustrator at the Art Center College of Design in Pasadena, Calif., Fong says he always had an interest in combining traditional media with technology. In 1993 he won an internship at Microsoft and was assigned to work on two of the company’s early multimedia efforts aimed at kids—Creative Writer and Fine Artist. He hasn’t looked back since.

Over the years Fong has worked on everything from an interactive gardening guide to Windows Media Center and the Zune music player, two other Microsoft products often praised for their fresh and distinctive designs. After the company made the decision to reboot its smartphone effort, Fong was tapped to help lead a team to define the look and feel of what would become Windows Phone, turning to airport and subway signage as one source of inspiration.

I caught up with Fong last week for a quick Q&A on Windows Phone and design.

###

The design of Windows Phone—and its influence on other high-profile Microsoft products like Windows 8—has been getting a lot of attention lately, including stories in Bloomberg Businessweek and the New York Times. Apple co-founder Steve Wozniak also recently gushed about his “beautiful” new Windows Phone. Some folks seem genuinely surprised that Microsoft could design something like this. Are you?

A lot of people come with preconceived notions about Microsoft. There’s always been good design here. But I think the stuff that we’ve done previously has been mostly expected. The thing we did with Windows Phone is we came out with a design that is unexpected. It’s not like anything else you see out there. That change in direction is the thing that’s bringing the attention I think.

What is the “Metro” design philosophy? Can you boil it down into a sentence or two?

Without going deep into the principles, we wanted to find a way to present content in the most clear, direct, and honest way possible. Really that’s the heart of it.

It’s certainly a big break from the look and design of other smartphones I see out there.

There’s a tendency to make things look kind of pretty. And the way you make things look pretty is by adding decorative elements like drop shadows, reflections, glassy surfaces, and things like that. To me, it’s a distraction. One of my favorite examples is when you go to a museum, a lot of times the frame of the painting actually feels more important than the painting itself. It’s the same idea here: When you start adding other things on top of the content, it’s actually taking your attention away from it. Stripping away complexity is really relevant today in our very busy lives. I want information to be presented in a way that’s really easy for you to consume.

You spent a bunch of time working on Windows Media Center, a popular Windows desktop feature designed for connecting PCs to TVs. Was it difficult going from a big screen to a small one?

The thing I like about what we’re doing now is having touch surfaces for direct interaction, versus TV and a remote control. There’s a lot more nuance in that interaction, and we spend a lot of time thinking about the gestures and how the UI [user interface] responds. There’s something kind of magical when you touch something and it just responds.

Speaking of responding, people often mention how much they like the subtle animations found throughout Windows Phone. Are those just for decoration?

It’s storytelling. We’re taking you on a journey from Start. Motion brings a sense of depth and life and makes you feel like the phone is responding to you. We also use motion to enhance your perception of speed. For example, we often start with an initial fast motion and then we slow it down, so what you notice more, mentally, is that initial burst of speed. It makes our software feel really responsive to our customers, and I think that’s delightful.

I saw a report last week arguing smartphones may be the fastest spreading technology in history. How will the Windows Phone I carry in my pocket 10 years from now be different?

I don’t know, and I think that’s what makes it so fun. [laughs] But I think the biggest shift that’s happened over the last few years is how connected everything is and I don’t think we’ve pushed the limits of that connectedness, whether it’s technology-to-technology or person-to-person. I think there’s a lot of really interesting opportunities to explore.

Where do you draw inspiration from when you get stuck on a design problem?

Right now the thing that really fascinates me is architecture. I see a lot of parallels between what we do and how an architect thinks about a space. And the other thing that’s really an inspiration is the great designers we have in this studio. We have just awesome designers here. When all else fails, we have a brainstorming session. There’s nothing like just talking to other really smart, amazing people to get past a mental block.

What will you be doing in 10 years?

The great things about Microsoft is there’s always some new technology to work on. Since I’ve been here, I went from floppy disks to CD-ROMs to the web to TV to devices to phones. There’s no way 10 years ago I would’ve been able to say I’m going to be working on smartphones. To me the fun part is just combining technology with design to bring really amazing consumer experiences.

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