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Multiple touch

Multiple touch is an enhancement to the touch screen, which provides the user with the ability to apply elaborate finger gestures onto the display as commands to the device.

Multiple touch is implemented based on the size and type of interfaces. When a finger or an object touches the display causing the light to scatter, the reflection is caught by the sensors. The response for the touch is sent back based on the type of reflection measured.

Only the devices with multiple touch support have 'Pinch Stroke' as a touch stroke.

Pinch Stroke

Pinch stroke is invoked by two separate but simultaneously active touch down events and dragging movements along the line that goes through both touch down points. On release, the pinch in or pinch out state is maintained. Pinch stroke can be utilized, for example, in Photo viewer to zoom in and zoom out.

The following table lists the default touch-events for pinch-stroke:

Table 1. Default touch events for pinch-stroke
User action	State change	Feedback
First touch down	No action.	Tactile: First touch down tactile feedback follows the context-based feedback. Audio feedback is provided with touch down.
Second simultaneous touch down	Activates multiple touch mode for the content defined.	Tactile: When second finger is touched down multiple touch recognition, two sensitive pulses effect is provided. Audio feedback is provided with touch down.
Pinch in	Moving the touch points (directly) closer to each other is recognized as pinch in. Application can use it, for example, for zooming out a picture. The behavior should be in relation to the speed and size of the stroke.	Tactile: Smooth pinch effect is provided while moving the fingers. No audio feedback is provided.
Pinch out	Moving the touch points (directly) away from each other is recognized as pinch out. Application can use it, for example, for zooming in a picture. The behavior should be in relation to the speed and size of the stroke.	Tactile: Smooth pinch effect is provided while moving the fingers. No audio feedback is provided.
Touch release	Releasing one or both fingers stops the pinch.	No tactile or audio feedback given.

Using multiple touch in applications

For multiple touch, use classes TRawEvent and TAdvancedPointerEvent (which extends TPointerEvent ). For more information, see Advanced pointers section.

Parent topic: Touch UI user experience