JUCE/extras/BLOCKS/doxygen/pages/juce_getting_touch_events.dox

/**
@page getting_touch_events Getting touch events

Touch events are communicated from BLOCKS devices to your application code via TouchSurface objects.

You can obtain a pointer to the %TouchSurface associated with a specific BLOCKS device from its corresponding Block object using the Block::getTouchSurface() method---see the @ref discovering_blocks page for an example of how to obtain %Block objects.
For devices without a touch surface (such as the Control Block) this method will return <code>nullptr</code>, but if the device is capable of sending touch events then the pointer to the %TouchSurface will be valid for the lifetime of the %Block object.

Once you have a %TouchSurface you must register as a TouchSurface::Listener to get touch events.
The process for doing this is to have one of your application's classes inherit from %TouchSurface::Listener and override the pure virtual method TouchSurface::Listener::touchChanged.
Then, when you register your derived class as a listener to a particular %TouchSurface, your overriden method will be called when the corresponding device is touched.

A safe way of registering a class derived from %TouchSurface::Listener with a %TouchSurface is as follows.
@code{.cpp}
class TouchSurfaceListenerExample : public TouchSurface::Listener
{
public:
    TouchSurfaceListenerExample (Block& block)
    {
        if (auto touchSurface = block->getTouchSurface())
            touchSurface->addListener (this);
    }

    virtual void touchChanged (TouchSurface& sourceTouchSurface, const TouchSurface::Touch& touchEvent) override
    {
        // Do something with touchEvent here!
    }
};
@endcode

When your overriden <code>touchChanged</code> method is called you have access to two paramters: a reference to the %TouchSurface that generated this event and a reference to a TouchSurface::Touch.
The %TouchSurface::Touch class contains member variables describing the postion, pressure, velocity, timestamp and more.

You will find multiple examples of using TouchSurfaces in the @ref example_applications pages.
*/