Silverlight Multi-Touch Control (multitouch)

Multi-point touch input is an input type that relies on the concept of touch-screen input and may also rely on a variety of touches and features that are interpreted as cells (sometimes called frames). Multi-Touch input requires a touch-sensitive hardware and an environment that enables the exposure of touch events to the required infrastructure for each application. This topic discusses the support for multi-touch in Silverlight and introduces several key concepts.

Multi-point Touch hardware

The concept of multi-touch requires the ability to record the hardware on which the pressure is generated on the surface. The surface can be directly a screen (such as a Tablet PC device), or it can be a separate dedicated input device, such as a drawing pad. The tablet PC device, or a similar display, is typically the most associated with Silverlight for touch-sensitive devices.

Platform Requirements

Multi-Touch requires an environment (platform and operating system, host applications such as browsers) that can propagate touch input to an application, such as a Silverlight-based application.

At the operating system level, Windows 7 supports multi-touch input. Part of it is supported by message Wm_touch. The operating system has elevated multi-touch messages to mouse messages at this level. This allows multi-touch users to interact with applications that may not have touch recognition capabilities, but rather use mouse events/messages to perform all their space input processing, using touch and gestures instead of mouse movements or mouse clicks. Windows 7 can also merge these messages when appropriate.

Internet Explorer version 8, as a host, also recognizes Multi-Touch, and it forwards platform multi-touch messages in the same way that plug-ins (such as Silverlight) can interact with multiple-point touches in the host.

Multi-touch input for Silverlight

Sign up for multiple touch controls.

As part of the multi-touch design of the operating system, each application that wishes to receive the multi-touch message independently must register its HWND (for this reason, the Windows 7 touch API contains Registertouchwindow). For the entire Silverlight and all applications that use Silverlight as the runtime, the Silverlight programming environment is responsible for this registration step. Therefore, it is generally not necessary to interact directly with the platform code to handle multi-touch input. However, the unique characteristics of the multi-touch interaction declared by Silverlight for registering multi-touch in its own way are quite specific:

Silverlight registers the original touch input without registering the gesture. If you need to include gestures, you must use your own application code in the context of Silverlight to handle touch input as a gesture. In addition, a larger interoperability design is required so that you can include a separate HWND, which will be used for multi-touch registration from the platform and interoperate with the Silverlight content area.

Typically, Silverlight promotes the raw touch input to mouse events. (However, you can disable elevation based on each touch frame, as described in the following sections of this topic.) ）