//from XAML
SkiaSharp.Views.Forms.SKCanvasView canvasView = ...;
Xamarin.Forms.Button button = ...;

var painter = new CSharpMath.SkiaSharp.MathPainter
{ /*set all properties aside from LocalTypefaces, FontSize, LineStyle,
    MathList, LaTeX and Source (these are ignored)*/ };
var keyboard = new CSharpMath.Rendering.MathKeyboard(/*optional fontSize*/)
{ /*set Fonts, LineStyle and InsertionIndex here*/ };
button.Pressed += (sender, e) => keyboard.KeyPress(CSharpMath.Editor.MathKeyboardInput.SmallX /*or any key*/);
keyboard.RedrawRequested += (sender, e) => canvasView.InvalidateSurface();
canvasView.PaintSurface += (sender, e) => {
  e.Surface.Canvas.Clear();
  //for any DrawDisplay overload, arguments after canvas are the same as Draw
  CSharpMath.SkiaSharp.MathPainter.DrawDisplay(painter, keyboard.Display, e.Surface.Canvas);
  keyboard.DrawCaret(
    new CSharpMath.SkiaSharp.SkiaCanvas(e.Surface.Canvas, SkiaSharp.SKStrokeCap.Butt, false),
    CSharpMath.Rendering.CaretShape.IBeam);
};

//from XAML
SkiaSharp.Views.Forms.SKCanvasView canvasView = ...;
CSharpMath.Forms.MathKeyboard keyboard = ...;

var painter = new CSharpMath.SkiaSharp.MathPainter
{ /*set all properties aside from LocalTypefaces, FontSize, LineStyle,
    MathList, LaTeX and Source (these are ignored)*/ };
keyboard.RedrawRequested += (sender, e) => canvasView.InvalidateSurface();
canvasView.PaintSurface += (sender, e) => {
  e.Surface.Canvas.Clear();
  //for any DrawDisplay overload, arguments after canvas are the same as Draw
  CSharpMath.SkiaSharp.MathPainter.DrawDisplay(painter, keyboard.Display, e.Surface.Canvas);
  keyboard.DrawCaret(e.Surface.Canvas, CSharpMath.Rendering.CaretShape.IBeam);
};