Fixed the y-coordinate to start top-left, not bottom-left

CSharpMath.Forms.Example/CSharpMath.Forms.Example/App.xaml

@@ -17,6 +17,7 @@
             <local:ExamplesPage/>
             <local:MoreExamplesPage/>
             <local:CustomExamplePage/>
+            <local:SlidePage/>
             <local:SettingsPage/>
         </TabbedPage>
     </Application.MainPage>

CSharpMath.Forms.Example/CSharpMath.Forms.Example/CSharpMath.Forms.Example.csproj

@@ -40,5 +40,8 @@
     <EmbeddedResource Update="SettingsPage.xaml">
       <Generator>MSBuild:UpdateDesignTimeXaml</Generator>
     </EmbeddedResource>
+    <EmbeddedResource Update="SlidePage.xaml">
+      <Generator>MSBuild:UpdateDesignTimeXaml</Generator>
+    </EmbeddedResource>
   </ItemGroup>
 </Project>

CSharpMath.Forms.Example/CSharpMath.Forms.Example/IconPage.xaml.cs

@@ -43,15 +43,14 @@ private void PaintSurface(object sender, SKPaintSurfaceEventArgs e) {
       var c = e.Surface.Canvas;
       //draw outer circle
       c.DrawCircle(cx, cy, r + thicknessAdjust, black);
-      painter.TextColor = SKColors.Orange;
+      painter.TextColor = SKColors.White;
       for (int i = 0; i < count; i++) {
         painter.LaTeX = i.ToString();
-        painter.Draw(c, offsetY: -r);
-        c.DrawCircle(cx, cy, 10, new SKPaint { Style = SKPaintStyle.Fill, Color = SKColors.Green });
+        painter.Draw(c, cx, cy - r * 3 / 4);
         c.RotateDegrees(θ, cx, cy);
       }
       //draw inner circle
-      //c.DrawCircle(cx, cy, r - thicknessAdjust, white);
+      c.DrawCircle(cx, cy, r - thicknessAdjust, white);
       painter.TextColor = SKColors.Black;
       painter.LaTeX = @"\raisebox{25mu}{\text{\kern.7222emC\#}\\Math}"; //.7222em is 13/18em
       painter.Draw(c);

CSharpMath.Forms.Example/CSharpMath.Forms.Example/SlidePage.xaml

@@ -0,0 +1,20 @@
+<?xml version="1.0" encoding="utf-8" ?>
+<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
+             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
+             xmlns:skia="clr-namespace:SkiaSharp.Views.Forms;assembly=SkiaSharp.Views.Forms"
+             x:Class="CSharpMath.Forms.Example.SlidePage"
+             Title="Slide">
+    <ContentPage.Content>
+        <StackLayout>
+            <StackLayout Orientation="Horizontal">
+                <Label Text="{x:Binding Value, Source={x:Reference SliderX}}"/>
+                <Slider x:Name="SliderX" HorizontalOptions="FillAndExpand" Minimum="-2" Maximum="{Binding Width, Source={x:Reference Canvas}}" ValueChanged="SliderX_ValueChanged"/>
+            </StackLayout>
+            <StackLayout Orientation="Horizontal">
+                <Label Text="{x:Binding Value, Source={x:Reference SliderY}}"/>
+                <Slider x:Name="SliderY" HorizontalOptions="FillAndExpand" Minimum="-2" Maximum="{Binding Height, Source={x:Reference Canvas}}" ValueChanged="SliderY_ValueChanged"/>
+            </StackLayout>
+            <skia:SKCanvasView x:Name="Canvas" HorizontalOptions="Fill" VerticalOptions="FillAndExpand" EnableTouchEvents="True" PaintSurface="Canvas_PaintSurface" Touch="Canvas_Touch"/>
+        </StackLayout>
+    </ContentPage.Content>
+</ContentPage>

CSharpMath.Forms.Example/CSharpMath.Forms.Example/SlidePage.xaml.cs

@@ -0,0 +1,37 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+using Xamarin.Forms;
+using Xamarin.Forms.Xaml;
+
+using SkiaSharp.Views.Forms;
+
+namespace CSharpMath.Forms.Example
+{
+  [XamlCompilation(XamlCompilationOptions.Compile)]
+  public partial class SlidePage : ContentPage {
+    SkiaSharp.SkiaMathPainter painter = new SkiaSharp.SkiaMathPainter { LaTeX = @"\text{Press to clear}" };
+    bool reset;
+    double x, y;
+
+    public SlidePage() => InitializeComponent();
+
+    private void Canvas_PaintSurface(object sender, SKPaintSurfaceEventArgs e) {
+      if (reset) { e.Surface.Canvas.Clear(); reset = false; }
+      e.Surface.Canvas.DrawCircle(0f, 0f, 100f, new global::SkiaSharp.SKPaint { Color = new global::SkiaSharp.SKColor(255, 0, 0) });
+      painter.Draw(e.Surface.Canvas, (float)x, (float)y);
+      e.Surface.Canvas.DrawCircle(300f, 0f, 100f, new global::SkiaSharp.SKPaint { Color = new global::SkiaSharp.SKColor(255, 255, 0) });
+    }
+
+    private void Canvas_Touch(object sender, SKTouchEventArgs e) {
+      if(e.InContact && e.ActionType == SKTouchAction.Pressed) { reset = true; Canvas.InvalidateSurface(); e.Handled = true; }
+    }
+
+    private void SliderX_ValueChanged(object sender, ValueChangedEventArgs e) { x = e.NewValue; Canvas.InvalidateSurface(); }
+
+    private void SliderY_ValueChanged(object sender, ValueChangedEventArgs e) { y = e.NewValue; Canvas.InvalidateSurface(); }
+  }
+}

CSharpMath.Rendering/MathPainter.cs

@@ -73,8 +73,9 @@ public RectangleF? Measure {
 
     #region Methods
     private static PointF GetDisplayPosition(MathListDisplay<TFonts, Glyph> displayList,
-      TextAlignment alignment, float fontSize,
-      float width, float height, Thickness padding, float offsetX, float offsetY) {
+      float fontSize, bool bottomLeftCoords, 
+      float width, float height,
+      TextAlignment alignment, Thickness padding, float offsetX, float offsetY) {
       float x, y;
       float displayWidth = displayList.Width;
       if ((alignment & TextAlignment.Left) != 0)
@@ -87,16 +88,24 @@ private static PointF GetDisplayPosition(MathListDisplay<TFonts, Glyph> displayL
       if (contentHeight < fontSize / 2) {
         contentHeight = fontSize / 2;
       }
-      //Canvas is inverted!
+      if (!bottomLeftCoords) {
+        //Canvas is inverted!
+        if ((alignment & (TextAlignment.Top | TextAlignment.Bottom)) != 0) {
+          alignment ^= TextAlignment.Top;
+          alignment ^= TextAlignment.Bottom;
+        }
+        //invert y-coordinate as canvas is inverted
+        offsetY *= -1;
+      }
       if ((alignment & TextAlignment.Top) != 0)
-        y = height - padding.Bottom - displayList.Ascent;
-      else if ((alignment & TextAlignment.Bottom) != 0)
         y = padding.Top + displayList.Descent;
+      else if ((alignment & TextAlignment.Bottom) != 0)
+        y = height - padding.Bottom - displayList.Ascent;
       else {
         float availableHeight = height - padding.Top - padding.Bottom;
         y = ((availableHeight - contentHeight) / 2) + padding.Top + displayList.Descent;
       }
-      return new PointF(x + offsetX, y + offsetY);
+      return new PointF(x + offsetX, (y + offsetY) - (bottomLeftCoords ? 0 : height));
     }
 
     public void UpdateDisplay() {
@@ -110,32 +119,30 @@ public void UpdateDisplay() {
 
     public abstract ICanvas WrapCanvas(TCanvas canvas);
 
+    protected abstract bool CoordinatesFromBottomLeftInsteadOfTopLeft { get; }
+
     public void Draw(TCanvas canvas, TextAlignment alignment = TextAlignment.Center, Thickness padding = default, float offsetX = 0, float offsetY = 0) {
       if (MathList == null) return;
       if (_displayChanged) UpdateDisplay();
       var c = WrapCanvas(canvas);
-      //invert y-coordinate as canvas is inverted
-      Draw(c, GetDisplayPosition(_displayList, alignment, FontSize, c.Width, c.Height, padding, offsetX, -offsetY));
+      Draw(c, GetDisplayPosition(_displayList, FontSize, CoordinatesFromBottomLeftInsteadOfTopLeft, c.Width, c.Height, alignment, padding, offsetX, offsetY));
     }
 
     public void Draw(TCanvas canvas, float x, float y) =>
-      //invert y-coordinate as canvas is inverted
-      Draw(WrapCanvas(canvas), new PointF(x, -y));
+      Draw(WrapCanvas(canvas), new PointF(x, CoordinatesFromBottomLeftInsteadOfTopLeft ? y : -y));
 
-    public void Draw(TCanvas canvas, PointF position)
-    {
-      position.Y *= -1;
-      //invert y-coordinate as canvas is inverted
+    public void Draw(TCanvas canvas, PointF position) {
+      if (CoordinatesFromBottomLeftInsteadOfTopLeft) position.Y *= -1;
       Draw(WrapCanvas(canvas), position);
     }
 
     private void Draw(ICanvas canvas, PointF position) {
       if (MathList != null) {
         canvas.Save();
-        //invert the canvas vertically
-        canvas.Scale(1, -1);
-        //canvas is inverted so negate vertical position
-        canvas.Translate(0, -canvas.Height);
+        if (!CoordinatesFromBottomLeftInsteadOfTopLeft) {
+          //invert the canvas vertically
+          canvas.Scale(1, -1);
+        }
         canvas.Scale(Magnification, Magnification);
         canvas.DefaultColor = WrapColor(TextColor);
         canvas.CurrentColor = WrapColor(BackgroundColor);

CSharpMath.SkiaSharp/SkiaMathPainter.cs

@@ -11,6 +11,10 @@ public SkiaMathPainter(float fontSize = 20f, bool antiAlias = true) : base(fontS
     public SKStrokeCap StrokeCap { get; set; }
     public bool AntiAlias { get; set; }
 
+    public void Draw(SKCanvas canvas, SKPoint point) => Draw(canvas, point.X, point.Y);
+
+    protected override bool CoordinatesFromBottomLeftInsteadOfTopLeft => false;
+
     public override SKColor UnwrapColor(Color color) => color.ToNative();
 
     public override Color WrapColor(SKColor color) => color.FromNative();

CSharpMath.Text/TextBuilder.cs

@@ -10,10 +10,16 @@ public static class TextBuilder {
     public static TextAtom Build(string text) {
       var breaker = new CustomBreaker();
       var breakList = new List<BreakAtInfo>();
+      breaker.BreakWords(text);
       breaker.LoadBreakAtList(breakList);
+      bool mathMode = false;
       foreach (var info in breakList) {
-        info.wordKind == WordKind.
+        if (text[info.breakAt] == '$') {
+          mathMode ^= true;
+        }
+
       }
+      return null;
     }
     public static StringBuilder Unbuild(TextAtom atom, StringBuilder b) {
       switch (atom) {

CSharpMath._Extensions/CSharpMath._Extensions.projitems

@@ -0,0 +1,13 @@
+<?xml version="1.0" encoding="utf-8"?>
+<Project xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+  <PropertyGroup>
+    <MSBuildAllProjects>$(MSBuildAllProjects);$(MSBuildThisFileFullPath)</MSBuildAllProjects>
+    <HasSharedItems>true</HasSharedItems>
+    <SharedGUID>4ab068f2-6f09-4b3b-8a81-f89f10cdce18</SharedGUID>
+  </PropertyGroup>
+  <PropertyGroup Label="Configuration">
+    <Import_RootNamespace>CSharpMath._Extensions</Import_RootNamespace>
+  </PropertyGroup>
+  <ItemGroup>
+  </ItemGroup>
+</Project>

CSharpMath._Extensions/CSharpMath._Extensions.shproj

@@ -0,0 +1,13 @@
+<?xml version="1.0" encoding="utf-8"?>
+<Project ToolsVersion="15.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+  <PropertyGroup Label="Globals">
+    <ProjectGuid>4ab068f2-6f09-4b3b-8a81-f89f10cdce18</ProjectGuid>
+    <MinimumVisualStudioVersion>14.0</MinimumVisualStudioVersion>
+  </PropertyGroup>
+  <Import Project="$(MSBuildExtensionsPath)\$(MSBuildToolsVersion)\Microsoft.Common.props" Condition="Exists('$(MSBuildExtensionsPath)\$(MSBuildToolsVersion)\Microsoft.Common.props')" />
+  <Import Project="$(MSBuildExtensionsPath32)\Microsoft\VisualStudio\v$(VisualStudioVersion)\CodeSharing\Microsoft.CodeSharing.Common.Default.props" />
+  <Import Project="$(MSBuildExtensionsPath32)\Microsoft\VisualStudio\v$(VisualStudioVersion)\CodeSharing\Microsoft.CodeSharing.Common.props" />
+  <PropertyGroup />
+  <Import Project="CSharpMath._Extensions.projitems" Label="Shared" />
+  <Import Project="$(MSBuildExtensionsPath32)\Microsoft\VisualStudio\v$(VisualStudioVersion)\CodeSharing\Microsoft.CodeSharing.CSharp.targets" />
+</Project>

CSharpMath.sln

@@ -48,7 +48,7 @@ Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "zDevelopment utilities", "z
 EndProject
 Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "CSharpMath.NuGetPackageTests.CSharp.UWP", "CSharpMath.NuGetPackageTests.CSharp\CSharpMath.NuGetPackageTests.CSharp.UWP\CSharpMath.NuGetPackageTests.CSharp.UWP.csproj", "{DBB121AA-0271-4719-A709-23AB3B464E8F}"
 EndProject
-Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "CSharpMath.NuGetPackageTests.CSharp", "CSharpMath.NuGetPackageTests.CSharp\CSharpMath.NuGetPackageTests.CSharp\CSharpMath.NuGetPackageTests.CSharp.csproj", "{73C44AA1-69ED-4749-BDBA-62A4416F0081}"
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "CSharpMath.NuGetPackageTests.CSharp", "CSharpMath.NuGetPackageTests.CSharp\CSharpMath.NuGetPackageTests.CSharp\CSharpMath.NuGetPackageTests.CSharp.csproj", "{73C44AA1-69ED-4749-BDBA-62A4416F0081}"
 EndProject
 Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "zNuGet package tests", "zNuGet package tests", "{FD179998-539F-43BE-B2A1-89B2B726BC7A}"
 EndProject