c# - WP7 Pivot control and a WebBrowser control

Question

I have a Pivot which contains a WebBrowser control that practically takes up the whole page (appart from the Pivot header of course).

I would like to figure out how to make the WebBrowser control allow for the user to swipe left/right to activate the Pivot control. Currently it just pans the WebBrowser control left/right

Can this be done??

Thank

Answer 1

While I cannot tell you exactly how to pass the swipes to the pivot, I can tell you how to do a part of the job: how to catch/analyze/disable custom gestures over the WebBrowser.

If I remember correctly, in the 7.0:

• the WebBrowser component consisted almost only of an internal TileHost wrapped in some grids/borders
• the TileHost did all the work related to processing touch events
• the TileHost did it completely internally (in the native layer), without the .Net seeing any manipulation-events (I think), or at least it ignored all the attempts to handle/override the manipulation-event on the upper layer. The WebBrowserInterop class was mostly empty in these matters.

Now, in the 7.5 that I have (maybe on 7.1 too, I dont know), it seems that the MS is working really hard on some WebBrowser manipulation problems --- I think they are working towards having the scrolling/swiping fully processed by the .Net layer. They have written a special class PanZoomContainer and injected them into the VisualTree of WebBrowser's internal template. The WebBrowserInterop was greatly enriched with many tunnels for event notifications. The WebBrowserInterop hooks into PanZoomContainer's ManipulationEvents, then passes them to the native layer. Also, it listens to events/commands from the native layer, called for example "ZoomAndScroll" or "ShowSIP" - and mostly passes them back to the PanZoomContainer. The idea is crystal clear right? They have rewired the event handling from completely-internal to a bit of spaghetti, but have achieved passing them through the PanZoomC.

Now, whats in that for me/us?

It is the PanZoomContainer, whose Mani-Events are inspected. The TileHost does not capture them now. In this version of the WebBrowser control, it's VisualTree consists of some borders, grids, a PanZoomContainer and a TileHost (the renderer). It is similar to that:

WebBrowser
  PanZoom
    ContentPresenter
      Border/Name="border"   <- you want this one
        TileHost

I've skipped a few Borders and Grids, they are mostly irrelevant to the problem. Now, if the PanZoomContainer's Mani-Events are listened to, let's block them!

Using VisualTreeHelper, just dig deeper and deeper until you find a FrameworkElement.Name=="border". This is the border that wraps the TileHost that is the "renderer" that takes 99% space of the control. Be warned that there's a ContentPresenter, so you may have to wait until the controltemplate gets instantiated (ie. Loaded/LayoutUpdated).

Once you have your hands on that Border, attach all Mani-Event handlers to it: started, delta and completed. PanZoom is a normal xaml/silverlight/.net/etc control, so it actually obeys e.Handled = true :) Now, if you want to disable ie. vertical scrolling, filter the Delta and Completed events for Translation.Y<>0. If you want to disable tapping but leave srolling/panning - filter X==0&Y==0.

And that was the easy part.

The hard part is to experiment with filtering on different Start/Delta/Stop and adjusting the behaviour to your likes.

Although it might look very nice and tempting, this will NOT get you any real/nice results easily. For example, I wrote "if you want to disable vertical scrolling, then set a filter 'if y==0 then e.handled=true' ". Great? easy? Not!

Assume we want to "disable bouncy horizontal panning" while leaving "vertical scrolling". or vice versa, whatever, it is only an example:

Here's a small rectangular device with a sensitive touchscreen. Please make such a vertical swipe/pan/drag on the screen, that the resulting X-compound will be ZERO. If you set such filter, it will be almost impossible to it properly. Your users will want to kill you for forcing them to retry-that-vertical-scrolling for five or more times, until they make a perfect vertical swipe.

Of course you can make it not ==0, but leave some small margin. ok. But if you make the margin too big, the control will catch the intermediate offaxis movement and make a tiny horizontal pan also.. After a few unlucky vertical swipes, the total horizontal pan may accumulate from those small leftovers will accumulate and the diplacement maybe will be noticeable.

But there's some another vile side effects:

Saying shortly, you have commited e.Handled=true. The event is GONE. Dead. Deased. if you just wanted the WebBrowser to SKIP for example horizontal swipes, so that the outer (Pivot) control notices them and processes..... whoops. The event is GONE. Earlier, the TileHost/PanZoomC have extinguished the events, now you have it done yourself. Sounds like a bad joke, eh?

Fortunatelly:

• since you have attached your handlers to the bottommost "border", they may not only block the events, but may also actually listen&publish them elsewhere. That is, if those handlers detect an interesting movement, they may e.Handled=true on it, but at the same time they can notify your custom objects about that discovery, and ie. start your storyboards.
• mani-events are at hand, but there is also a second layer that listens to the manipulations: the GestureListener/GestureService from the Silverlight Toolkit. It reports events after they are handled by mani-events, but it reports them with no regard to any e.Handled=true that were set on them. It is completely separate gesture-listening mechanism, and you can also use it to detect manipulations that were 'cancelled'

.. and so the fun goes like that and maybe even a little further.