Types of user input in UWP:

• touch
• mouse
• pen / stylus
• keyboard

User input events can be grouped into three categories:

• pointers - the low-level raw events
• gestures - higher-level events calculated from the pointer events such as press and hold
• manipulations - the highest-level events for complex gestures such as swipe, rotate, and pinch to zoom

In UWP the UIElement class is a base class for most of the objects that have visual appearance and that can process user input. This is a list of events defined by UIElement:

• Input from touch, the mouse, and the pen:
  • PointerCanceled
  • PointerCaptureLost
  • PointerEntered
  • PointerExited
  • PointerMoved
  • PointerPressed
  • PointerReleased
  • PointerWheelChanged

• Input from multiple fingers:
  • ManipulationCompleted
  • ManipulationDelta
  • ManipulationInertiaStarting
  • ManipulationStarted
  • ManipulationStarting

• Keyboard input:
  • KeyDown
  • KeyUp

• Higher level events:
  • Tapped - a mouse click, a tap with a pen, or a tap with a finger
  • DoubleTapped
  • RightTapped - a mouse right-button click or holding a finger down for a moment and then lifting (this gesture also generates Holding events)
  • Holding

• Signalling when an element is the target of keyboard input:
  • GotFocus
  • LostFocus

• Drap-and-drop events:
  • DragEnter
  • DragOver
  • DragLeave
  • Drop

The pointer events abstract touch, mouse, and pen input. They are:

• low-level raw events
• routed events i.e. they bubble up the visual tree
• exposed by UIElement

Pointer events:

• PointerPressed
• PointerMoved
• PointerReleased - raised when a previously pressed pointer releases contact while within the UIElement; note that PointerCanceled or PointerCaptureLost can be invoked instead of this event
• PointerEntered
• PointerExited - raised when a pointer leaves a UIElement's bounds, but only if the pointer was initially within this element's bounds
• PointerCanceled - raised when the pointer that was previously in contact with the UIElement is lost due to an abnormal reason
• PointerCaptureLost - raised when the pointer is lost from the UIElement while the user is carrying out an action
• PointerWheelChanged

Properties and methods of the pointer event argument (PointerRoutedEventArgs):

• GetCurrentPoint - returns the PointerPoint relative to the window or to a specified UIElement
• Pointer - the pointer that raised the event
• GetIntermediatePoints - a collection of accumulated PointerPoint objects (used with high-resolution input such as pen or touch digitizers)
• Handled - used to stop bubbling
• KeyModifiers

The pointer abstraction involves the following classes:

• Windows.Devices.Input.PointerDevice - The physical device: touch digitizer, mouse, pen digitizer.
  • Hardware details such as MaxContacts and PointerDeviceType.
  • The PointerDevice.GetPointerDevices method returns a list of all the PointerDevices attached to the system

• Windows.UI.Xaml.Input.Pointer - A single, unique input contact: a finger for the touch digitizer, the mouse pointer for the mouse, a pen for the pen digitizer.
  • PointerId uniquely identifies an input contact

• Windows.UI.Input.PointerPoint - The input data from each pointer.
  • Position represents adjusted client coordinates of the pointer
  • IsInContact indicates if the pointer is touching the screen
  • Properties is an instance of the PointerPointProperties containing extra information about the input
  • The PointerPoint.GetCurrentPoint method returns the current PointerPoint for a specific pointer ID
  • The PointerPoint.GetIntermediatePoints method returns a collection of PointerPoints for a Pointer as the input device moves around the screen

• Windows.UI.Input.PointerPointProperties - Extended information about each point.
  • ContactRect represents adjusted bounding rectangle of the contact area in client window coordinates
  • IsInRange indicates whether the pointer device is within close proximity to a sensor in the device or a digitizer
  • IsPrimary indicates whether the input is from the primary pointer - the first one that made contact

Example: Draw on Canvas by handling its PointerPressed, PointerMoved, and PointerReleased events:

<Page
    x:Class="WBS.MainPage"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
 
    <Grid Background="White">
        <Grid.RowDefinitions>
            <RowDefinition Height="0.1*" />
            <RowDefinition />
        </Grid.RowDefinitions>
        <TextBlock Text="Drawing on a Canvas by handling its PointerPressed, PointerMoved, 
                         and PointerReleased events." 
                   Foreground="Black" FontSize="25" Margin="20" />
        <Canvas x:Name="Canvas1" Grid.Row="1" Background="Beige" 
                PointerPressed="Canvas1_PointerPressed" 
                PointerMoved="Canvas1_PointerMoved" 
                PointerReleased="Canvas1_PointerReleased" />
    </Grid>
</Page>

using Windows.Foundation;
using Windows.UI;
using Windows.UI.Input;
using Windows.UI.Xaml.Controls;
using Windows.UI.Xaml.Input;
using Windows.UI.Xaml.Media;
using Windows.UI.Xaml.Shapes;
 
namespace WBS
{
    public sealed partial class MainPage : Page
    {
        private bool isDrawing = false;
 
        public MainPage4()
        {
            this.InitializeComponent();
        }
 
        private void Canvas1_PointerPressed(object sender, PointerRoutedEventArgs args)
        {
            PointerPoint point = args.GetCurrentPoint(Canvas1);
            DrawEllipse(point.Position, Colors.Red);
            isDrawing = true;
            args.Handled = true;
        }
 
        private void Canvas1_PointerMoved(object sender, PointerRoutedEventArgs args)
        {
            if (isDrawing)
            {
                PointerPoint point = args.GetCurrentPoint(Canvas1);
                DrawEllipse(point.Position, Colors.Green);
            }
 
            args.Handled = true;
        }
 
        private void Canvas1_PointerReleased(object sender, PointerRoutedEventArgs args)
        {
            PointerPoint point = args.GetCurrentPoint(Canvas1);
            DrawEllipse(point.Position, Colors.Blue);
            isDrawing = false;
            args.Handled = true;
        }
 
        private void DrawEllipse(Point pos, Color col)
        {
            const double radius = 20.0;
 
            Ellipse circle = new Ellipse
            {
                Width = radius * 2,
                Height = radius * 2,
                Fill = new SolidColorBrush(col)
            };
 
            Canvas.SetLeft(circle, pos.X - radius);
            Canvas.SetTop(circle, pos.Y - radius);
            Canvas1.Children.Add(circle);
        }
    }
}