A problem about create a keyword highlighted linkedlabel.

Hello!

I have a bug when paint string in a winforms custom control, and I cannot fix it.

the control is a custom linklabel control and highlight the keyword with a different color.

there are 3 add propertites:

IgnoreCase Keyword and KeywordColor

and rewrite the Paint methord.

here is full code:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Drawing;

namespace WindowsFormsApplication1
{
    class SuperLinkLabel : LinkLabel
    {
        public bool IgnoreCase { get; set; }

        private string keyWord = "";
        public string Keyword
        {
            get { return keyWord; }
            set { keyWord = value; this.Invalidate(); }
        }

        public Color KeywordColor { get; set; }

        public SuperLinkLabel()
        {
            Keyword = "";
            KeywordColor = Color.Red;
        }

        protected override void OnPaint(PaintEventArgs e)
        {
            e.Graphics.FillRectangle(new SolidBrush(SystemColors.Control), e.ClipRectangle);

            StringFormat stringFormat = new StringFormat();
            stringFormat.SetMeasurableCharacterRanges(GetRanges());
            stringFormat.FormatFlags = 0;
            Region[] regions = e.Graphics.MeasureCharacterRanges(Text, 
                Font, 
                new RectangleF(this.ClientRectangle.X, 
                    this.ClientRectangle.Y, 
                    this.ClientRectangle.Width, 
                    this.ClientRectangle.Height), 
                stringFormat);

            int i = 0;
            foreach (var item in GetStringRgn().ToList())
            {
                PointF ptf = new PointF(regions[i].GetBounds(e.Graphics).X,
                    regions[i].GetBounds(e.Graphics).Y);
                bool isKeyword = GetStringRgn().Single(x => x.Item1 == item.Item1).Item3;
                e.Graphics.DrawString(Text.Substring(item.Item1, item.Item2 - item.Item1 + 1), 
                    Font, 
                    isKeyword ? new SolidBrush(KeywordColor) : new SolidBrush(LinkColor), 
                    ptf, 
                    stringFormat);
                i++;
            }
        }

        private CharacterRange[] GetRanges()
        {
            return GetStringRgn().ToList()
                .Select(x => new CharacterRange(x.Item1, x.Item2 - x.Item1 + 1)).ToArray();
        }

        private IEnumerable<Tuple<int, int, bool>> GetStringRgn()
        {
            if (Keyword == "" || Text == "")
            {
                if (Text == "") yield break;
                yield return new Tuple<int, int, bool>(0, Text.Length - 1, false);
                yield break;
            }
            int pre = 0;
            int i = 0;
            while (i <= Text.Length - Keyword.Length)
            {
                //if (i - pre == 30)
                //{
                //    yield return new Tuple<int, int, bool>(pre, i - 1, false);
                //    pre = i;
                //}

                if (Text.Substring(i, Keyword.Length).ToUpper() == Keyword.ToUpper())
                {
                    if (IgnoreCase || Text.Substring(i, Keyword.Length) == Keyword)
                    {
                        if (pre != i) yield return new Tuple<int, int, bool>(pre, i - 1, false);
                        yield return new Tuple<int, int, bool>(i, i + Keyword.Length - 1, true);
                        i += Keyword.Length;
                        pre = i;
                        continue;
                    }
                }
                i++;
            }
            if (pre <= Text.Length - 1)
                yield return new Tuple<int, int, bool>(pre, Text.Length - 1, false);
        }
    }
}

to reproduce the bug, flow these steps:

(1) Create a Windows Forms Application (I'm using VS2012 UP3 + Windows 8, but I think VS2010/VS2013 is also ok)

(2) Create a Class(not a user control) named superlinklabel, and paste the code

(3) Put a superlinklabel Control to form, and set Text property to itself's sourcecode

(4) Set KeyWord property to Color

(5) Build and Run

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Clik here to view.

the bug is shown on the image I attach here.

Thanks a lot.

Zhongyan