C# Winform: Build a R script editor using ScintillaNET

In one of my projects, I was required to create an R editor and scripting interface that communicate between winform and R script interpreter. Part of the task is to create an R editor in C# winform. After some search, I found ScintillaNET. The way to use ScintillaNET in C# winform is pretty straightforward, either download its source from github or the binary from nuget. Drag a copy of the Scintilla into the toolbox of VS IDE and drag a copy of it from toolbox to your winform UI.

The next step is to customize ScintillaNET for R syntax highlighting, auto complete and so on. While earlier version of ScintillaNET does not have R Lexer, the current version downloaded (3.3.0) contains a very easy way for R syntax highlighting and auto-complete. Below is the Source codes (Assuming I put the code in a winform named FrmDummy, and my Scintilla editor component I put in the form is named "txtScript"):

    public partial class FrmDummy : Form
    {
 private List<string> Keywords1 = null;
        private List<string> Keywords2 = null;
        private string AutoCompleteKeywords = null;
        
        public FrmDummy()
        {
            InitializeComponent();

            PrepareKeywords();

            ConfigureRScriptSyntaxHighlight();
            ConfigureRScriptAutoFolding();
            ConifugreRScriptAutoComplete();
   
     txtScript.Text=@"#Some dummy R codes
  print('Hello World')
  x <- c('Hello World', 'Hello World2')";
        }
  
        private void PrepareKeywords()
        {
            Keywords1 = @"commandArgs detach length dev.off stop lm library predict lmer 
            plot print display anova read.table read.csv complete.cases dim attach as.numeric seq max 
            min data.frame lines curve as.integer levels nlevels ceiling sqrt ranef order
            AIC summary str head png tryCatch par mfrow interaction.plot qqnorm qqline".Split(new char[] { ' ', '\n', '\r' }, StringSplitOptions.RemoveEmptyEntries).ToList();

            Keywords2 = @"TRUE FALSE if else for while in break continue function".Split(new char[] { ' ', '\n', '\r' }, StringSplitOptions.RemoveEmptyEntries).ToList();

            List<string> keywords = Keywords1.ToList();
            keywords.AddRange(Keywords2);
            keywords.Sort();

            AutoCompleteKeywords = string.Join(" ", keywords);
        }

        private void ConfigureRScriptSyntaxHighlight()
        {

            txtScript.StyleResetDefault();
            txtScript.Styles[Style.Default].Font = "Consolas";
            txtScript.Styles[Style.Default].Size = 10;
            txtScript.StyleClearAll();

            txtScript.Styles[Style.R.Default].ForeColor = Color.Brown;
            txtScript.Styles[Style.R.Comment].ForeColor = Color.FromArgb(0, 128, 0); // Green
            txtScript.Styles[Style.R.Number].ForeColor = Color.Olive;
            txtScript.Styles[Style.R.BaseKWord].ForeColor = Color.Purple;
            txtScript.Styles[Style.R.Identifier].ForeColor = Color.Black;
            txtScript.Styles[Style.R.String].ForeColor = Color.FromArgb(163, 21, 21); // Red
            txtScript.Styles[Style.R.KWord].ForeColor = Color.Blue;
            txtScript.Styles[Style.R.OtherKWord].ForeColor = Color.Blue;
            txtScript.Styles[Style.R.String2].ForeColor = Color.OrangeRed;
            txtScript.Styles[Style.R.Operator].ForeColor = Color.Purple;


            txtScript.Lexer = Lexer.R;

            txtScript.SetKeywords(0, string.Join(" ", Keywords1));
            txtScript.SetKeywords(1, string.Join(" ", Keywords2));
        }

        private void ConifugreRScriptAutoComplete()
        {
            txtScript.CharAdded += scintilla_CharAdded;
        }

        private void scintilla_CharAdded(object sender, CharAddedEventArgs e)
        {
            Scintilla scintilla = txtScript;

            // Find the word start
            var currentPos = scintilla.CurrentPosition;
            var wordStartPos = scintilla.WordStartPosition(currentPos, true);

            // Display the autocompletion list
            var lenEntered = currentPos - wordStartPos;
            if (lenEntered > 0)
            {
                scintilla.AutoCShow(lenEntered, AutoCompleteKeywords);
            }
        }

        private void ConfigureRScriptAutoFolding()
        {
            Scintilla scintilla = txtScript;

            // Instruct the lexer to calculate folding
            scintilla.SetProperty("fold", "1");
            scintilla.SetProperty("fold.compact", "1");

            // Configure a margin to display folding symbols
            scintilla.Margins[2].Type = MarginType.Symbol;
            scintilla.Margins[2].Mask = Marker.MaskFolders;
            scintilla.Margins[2].Sensitive = true;
            scintilla.Margins[2].Width = 20;

            // Set colors for all folding markers
            for (int i = 25; i <= 31; i++)
            {
                scintilla.Markers[i].SetForeColor(SystemColors.ControlLightLight);
                scintilla.Markers[i].SetBackColor(SystemColors.ControlDark);
            }

            // Configure folding markers with respective symbols
            scintilla.Markers[Marker.Folder].Symbol = MarkerSymbol.BoxPlus;
            scintilla.Markers[Marker.FolderOpen].Symbol = MarkerSymbol.BoxMinus;
            scintilla.Markers[Marker.FolderEnd].Symbol = MarkerSymbol.BoxPlusConnected;
            scintilla.Markers[Marker.FolderMidTail].Symbol = MarkerSymbol.TCorner;
            scintilla.Markers[Marker.FolderOpenMid].Symbol = MarkerSymbol.BoxMinusConnected;
            scintilla.Markers[Marker.FolderSub].Symbol = MarkerSymbol.VLine;
            scintilla.Markers[Marker.FolderTail].Symbol = MarkerSymbol.LCorner;

            // Enable automatic folding
            scintilla.AutomaticFold = (AutomaticFold.Show | AutomaticFold.Click | AutomaticFold.Change);
        }
    }

To display the line number, one can set txtScript.Margins[0].Width=30