MICROSOFT_PRESS_EBOOK_PROGRAMMING_WINDOWS_8_APPS_WITH_HTML_CSS_AND_JAVASCRIPT_PDF

Method
msSetPointerCapture
Description
Captures the pointerId for the element so that pointer events come to it and are not
raised for other elements (even if you move outside the first element and into another).
MSGotPointerCapture will be fired on the element as well.
msReleasePointerCapture
Ends capture, triggering an MSLostPointerCapture event.
msGetPointerCapture
Returns the element with the capture, if any (otherwise null).
We see this in the Input DOM pointer event handling sample, where it sets capture within its
MSPointerDown handler and releases it in MSPointerUp:
this.MSPointerDown = function (evt) {
canvas.msSetPointerCapture(evt.pointerId);
// ...
};
this.MSPointerUp = function (evt) {
canvas.msReleasePointerCapture(evt.pointerId);
// ...
};
Gesture Events
The first thing to know about all MSGesture* events is that they don’t just fire automatically like click
and MSPointer* events, and you don’t just add a listener and be done with it (that’s what click is for!).
Instead, you need to do a little bit of configuration first to tell the system how exactly you want gestures
to occur, and you need to use MSPointerDown to associate the gesture configurations with a particular
pointerId. This small added bit of complexity makes it possible for apps to work with multiple
concurrent gestures and keep them all independent just as you can do with pointer events. Imagine, for
example, a jigsaw puzzle app (as presented in a small way in one of the samples in “The Gesture
Samples” below) that allows multiple people sitting around a table-size touch screen to work with
individual pieces as they will. Using gestures, each person can be manipu-lating an individual piece (or
two!), moving it around, rotating it, perhaps zooming in to see a larger view, and, of course, testing out
placement. For Windows Store apps written in JavaScript, it’s also helpful that manipulation deltas for
configured elements—which include translation, rotation, and scaling—are given in the coordinate
space of the parent element, meaning that it’s fairly straightforward to translate the manipulation into
CSS transforms and such to make the manipulation visible. In short, there is a great deal of flexibility
here when you need it; if you don’t, you can use gestures in a simple manner as well. Let’s see how it all
works.
Tip If you’re observant, you’ll notice that everything in this section has no dependency on WinRT APIs.
As a result, the gesture events described here work in both the local and web contexts.
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