DialASketch

MainPage.xaml

<Page
    x:Class="DialASketch.MainPage"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="using:DialASketch"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    mc:Ignorable="d">
    <Page.TopAppBar>
        <CommandBar>
            <CommandBar.PrimaryCommands>
                <AppBarButton Icon="Clear" Label="Clear" Click="ClearButton_Click"/>
            </CommandBar.PrimaryCommands>
        </CommandBar>
    </Page.TopAppBar>
    <Grid Background="{ThemeResource ApplicationPageBackgroundThemeBrush}">
        <InkCanvas x:Name="SketchCanvas" />
        <Canvas>
            <Ellipse x:Name="Pointer" Width="4" Height="4" Fill="Black"/>
        </Canvas>
    </Grid>
</Page>

MainPage.xaml.cs

using System;
using System.Collections.Generic;
using Windows.Foundation;
using Windows.UI;
using Windows.UI.Input;
using Windows.UI.Input.Inking;
using Windows.UI.Xaml;
using Windows.UI.Xaml.Controls;
using Windows.UI.Xaml.Navigation;

namespace DialASketch
{
    /// <summary>
    /// An empty page that can be used on its own or navigated to within a Frame.
    /// </summary>
    public sealed partial class MainPage : Page
    {
        private RadialController Controller;
        private RadialControllerMenuItem MenuItem;
        
        private bool isHorizontal = true;
        InkStrokeBuilder b = new InkStrokeBuilder();
        private Point lastPoint;

        public MainPage()
        {
            this.InitializeComponent();
            SketchCanvas.SizeChanged += SketchCanvas_SizeChanged;

            Controller = RadialController.CreateForCurrentView();
            Controller.RotationResolutionInDegrees = 2;
            Controller.RotationChanged += Controller_RotationChanged;
            Controller.ButtonClicked += Controller_ButtonClicked;

            MenuItem = RadialControllerMenuItem.CreateFromKnownIcon("DialASketch", RadialControllerMenuKnownIcon.PenType);
            Controller.Menu.Items.Add(MenuItem);
        }

        private void SketchCanvas_SizeChanged(object sender, SizeChangedEventArgs e)
        {
            if (e.NewSize.Width > 0)
            {
                if (lastPoint.X == 0f)
                {
                    lastPoint = new Windows.Foundation.Point { X = SketchCanvas.ActualWidth / 2, Y = SketchCanvas.ActualHeight / 2 };

                    Canvas.SetLeft(Pointer, lastPoint.X - 2);
                    Canvas.SetTop(Pointer, lastPoint.Y - 2);
                }
            }
        }

        protected override void OnNavigatedFrom(NavigationEventArgs e)
        {
            Controller?.Menu.Items.Clear();

            base.OnNavigatedFrom(e);
        }

        private void Controller_ButtonClicked(RadialController sender, RadialControllerButtonClickedEventArgs args)
        {
            // switch direction (since we only have one dial)
            isHorizontal = !isHorizontal;
        }
        
        private void Controller_RotationChanged(RadialController sender, RadialControllerRotationChangedEventArgs args)
        {
            var delta = args.RotationDeltaInDegrees * 4;
            Point newPoint = new Windows.Foundation.Point { X = isHorizontal ? Math.Min(Math.Max(lastPoint.X + delta, 0), SketchCanvas.ActualWidth) : lastPoint.X, Y = !isHorizontal ? Math.Min(Math.Max(lastPoint.Y - delta, 0), SketchCanvas.ActualHeight) : lastPoint.Y };

            Canvas.SetLeft(Pointer, newPoint.X - 2);
            Canvas.SetTop(Pointer, newPoint.Y - 2);

            var stroke = b.CreateStroke(new List<Point> { lastPoint, newPoint });
            lastPoint = newPoint;
            stroke.DrawingAttributes.Color = Colors.Black;
            stroke.DrawingAttributes.PenTip = PenTipShape.Circle;
            SketchCanvas.InkPresenter.StrokeContainer.AddStroke(stroke);
        }

        private void ClearButton_Click(object sender, RoutedEventArgs e)
        {
            SketchCanvas.InkPresenter.StrokeContainer.Clear();

            lastPoint = new Windows.Foundation.Point { X = SketchCanvas.ActualWidth / 2, Y = SketchCanvas.ActualHeight / 2 };

            Canvas.SetLeft(Pointer, lastPoint.X - 2);
            Canvas.SetTop(Pointer, lastPoint.Y - 2);
        }
    }
}