c# - Avoid Scanning EntireRichtextbox Highlighting -

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• richtextbox syntax highlighting in real time--disabling repaint 3 answers

im working on code editor , came set of codes:

public class test2 : form {    richtextbox m_rtb = null;    public static void main() {     application.run(new test2());   }    public test2() {     text = "test2";     clientsize = new size(400, 400);     m_rtb = new richtextbox();     m_rtb.multiline = true;     m_rtb.wordwrap = false;     m_rtb.acceptstab = true;         m_rtb.scrollbars = richtextboxscrollbars.forcedboth;     m_rtb.dock = dockstyle.fill;     m_rtb.selectionfont = new font("courier new", 10, fontstyle.regular);     m_rtb.selectioncolor = color.black;     controls.add(m_rtb);     parse();     m_rtb.textchanged += new eventhandler(this.textchangedevent);   }    void parse() {     string inputlanguage =        "// comment.\n" +       "using system;\n" + "\n" +       "public class stuff : form { \n" +       "  public static void main(string args) {\n" +       "  }\n" +          "}\n" ;       // foreach line in input,     // identify key words , format them when adding rich text box.     regex r = new regex("\\n");     string [] lines = r.split(inputlanguage);     foreach (string l in lines) {       parseline(l);     }       }    void parseline(string line) {     regex r = new regex("([ \\t{}();])");     string [] tokens = r.split(line);      foreach (string token in tokens) {       // set token's default color , font.       m_rtb.selectioncolor = color.black;       m_rtb.selectionfont = new font("courier new", 10, fontstyle.regular);        // check comment.       if (token == "//" || token.startswith("//")) {         // find start of comment , extract whole comment.         int index = line.indexof("//");         string comment = line.substring(index, line.length - index);         m_rtb.selectioncolor = color.lightgreen;         m_rtb.selectionfont = new font("courier new", 10, fontstyle.regular);         m_rtb.selectedtext = comment;         break;       }        // check whether token keyword.        string [] keywords = { "public", "void", "using", "static", "class" };        (int = 0; < keywords.length; i++) {         if (keywords[i] == token) {           // apply alternative color , font highlight keyword.           m_rtb.selectioncolor = color.blue;           m_rtb.selectionfont = new font("courier new", 10, fontstyle.bold);           break;         }       }       m_rtb.selectedtext = token;     }         m_rtb.selectedtext = "\n";   }     private void textchangedevent(object sender, eventargs e) {     // calculate starting position of current line.     int start = 0, end = 0;     (start = m_rtb.selectionstart - 1; start > 0; start--) {       if (m_rtb.text[start] == '\n')  { start++; break; }     }      // calculate end position of current line.     (end = m_rtb.selectionstart; end < m_rtb.text.length; end++) {       if (m_rtb.text[end] == '\n') break;     }      // extract current line being edited.     string line = m_rtb.text.substring(start, end - start);      // backup users current selection point.     int selectionstart = m_rtb.selectionstart;     int selectionlength = m_rtb.selectionlength;      // split line tokens.     regex r = new regex("([ \\t{}();])");     string [] tokens = r.split(line);     int index = start;     foreach (string token in tokens) {        // set token's default color , font.       m_rtb.selectionstart = index;       m_rtb.selectionlength = token.length;       m_rtb.selectioncolor = color.black;       m_rtb.selectionfont = new font("courier new", 10, fontstyle.regular);        // check comment.       if (token == "//" || token.startswith("//")) {         // find start of comment , extract whole comment.         int length = line.length - (index - start);         string commenttext = m_rtb.text.substring(index, length);         m_rtb.selectionstart = index;         m_rtb.selectionlength = length;         m_rtb.selectioncolor = color.lightgreen;         m_rtb.selectionfont = new font("courier new", 10, fontstyle.regular);         break;       }        // check whether token keyword.        string [] keywords = { "public", "void", "using", "static", "class" };        (int = 0; < keywords.length; i++) {         if (keywords[i] == token) {           // apply alternative color , font highlight keyword.                   m_rtb.selectioncolor = color.blue;           m_rtb.selectionfont = new font("courier new", 10, fontstyle.bold);           break;         }       }       index += token.length;     }     // restore users current selection point.         m_rtb.selectionstart = selectionstart;     m_rtb.selectionlength = selectionlength;     }  } 

problem everytime press space keys or type entire code editor keeps on scanning searching on highlight , find bit annoying ...

so want ask possible solution ... avoid highlighting of whole richtextbox scanning highlight next .

thanks lot in advance help! more power!

i answered in recent question, in case else reading , doesn't find it, i'll post here (since performance):

you can use couple of things improve performance:

1) can line user editing getting text range current selection. recommend using wpf's richtextbox contains more features , has useful textpointer class can utilise current line. seems using winforms however, can done these few lines of code (with addition of trivial code):

int start_index = rtb.getfirstcharindexofcurrentline(); int line = rtb.getlinefromcharindex(index); int last_index = rtb.getfirstcharindexfromline(line+1); rtb.select(start_index, last_index); 

you can work current selection.

2) if don't want update frequently, can create timer measures delay since last edit, , reset timer if edit made before timer elapses.