Math Input (MathEditor port)

[charlesroddie]

Just as CSharpMath started as a port of iosMath, MathEditor, which builds on iosMath, could be ported to add editing support to CSharpMath.

@verybadcat can you keep us updated about your thoughts on doing this port? Thanks!

[verybadcat]

As we discussed on the phone, it's not likely a priority for me at the moment.

[Happypig375]

I'm targeting this for 0.2.0 for now.

[Happypig375]

I'm afraid that this will take longer than expected. Can you please allow a few more days?

[Happypig375]

0.2.0-alpha has been put on NuGet.
Touch response (navigation) is still being worked on.
The main property is CSharpMath.Forms.EditableMathView.Default.

[charlesroddie]

Great! Is this ready to test? We are a bit overloaded here for the next few days but can test soon.

[Happypig375]

0.2.0-alpha2 is ready!
Still bugfixes to go though.

[Happypig375]

0.2.0-alpha3 brings an editor which left/right buttons are usable.
Please test~

[Happypig375]

I intend to wrap this up very soon. Touch insertion will be pushed to the F# version. Is there an API shape that you would like to be seen?

[charlesroddie]

Gif looks good @Happypig375 . Could we have a normal cursor?

This is the API that I would like:

• A view with Skiasharp dependency only (not Forms).
• Properties and instance methods on the input View for inserts/commands.
• A property for getting latex (perhaps to be replaced with a structural version in the future F# version).
• A method for setting the cursor position based on a coordinate (understood that this is pushed to the F# version).

Inserts/commands needed:

• Left, right, up, down, backspace, clear
• left bracket "(", right bracket ")", 0-9, decimal place, divide, times (cdot), minus, plus
• Characters a-z, A-Z, greek
• Functions including sin, cos, tan ,sin^-1, cos^-1, tan^-1, power, sqrt, nth root, modulus ("| |"), sinh, cosh, tanh, exp ("e^"), ln, log, "!".

Some intelligence will be needed eventually about combining inputs. E.g. if the user types "s" then "i" then "n" it should get combined into the sin function. (To accomodate keyboard usage.) MathQuill is a good reference for good behavior.

Does this conform to what you had in mind?

[Happypig375]

Usage as of 0.2.0-beta1:

1. Having a custom keyboard:

//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);
};

2. Using the default keyboard:

//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);
};

[Happypig375]

To anyone following this thread, please cast a vote on #4 - I'm starting the F# project really soon.

[Happypig375]

@charlesroddie Any suggestions for improvement? I intend this to be the final API of 0.2.0.

[charlesroddie]

Great. We'll take a look today.

[charlesroddie]

The CSharpMath.Editor.MathKeyboardInput enum is clunky to use with all the separate characters. It suggests that consuming code would need to write out all the mapping between a char and the MathKeyboardInput enum.
Perhaps just add a FromChar method? This would just be one line FromChar c = EnumOfValue(int c) but it would make it clearer how to use the keyboard.
In the future F# library it would have a DU where single character a-z, α-ω... input is its own case.

[charlesroddie]

Otherwise the API looks very usable.

[charlesroddie]

Accepting physical keyboard input on Xamarin.Forms depends on xamarin/Xamarin.Forms#3444

[charlesroddie]

To respond to touch/mouseclicks, we need a method to set the current edit/cursor location based on position. This should be doable but any idea how hard it will be @Happypig375 ?

[Happypig375]

There exists such a method in MathKeyboard but its result is awfully wrong. I plan to rewrite it in MathDisplay.NET.

[Happypig375]

For the FromChar method, currently just using keyboard.KeyPress((CSharpMath.Editor.MathKeyboardInput)'x') works just fine, because the enum values are specifically defined as the Unicode codepoints of the characters.

[Happypig375]

@charlesroddie All issues seem to be resolved. Any more issues?

[Happypig375]

If there are no more issues, I'll be releasing 0.2.0 the next few days.

[Happypig375]

Implemented, closing.