Changing color Of a Characters in Button

Question

public class DualcoloredButton : Button
{
    private string coloredText;
    private Color coloredTextColor = Color.Red;
    private bool coloredTextFound = false;

    public string ColoredText
    {
        get { return coloredText; }
        set
        {
            coloredText = value;
            UpdateColoredText();
        }
    }

    public Color ColoredTextColor
    {
        get { return coloredTextColor; }
        set
        {
            coloredTextColor = value;
            UpdateColoredText();
        }
    }

    public CustomButton()
    {
        // Subscribe to the Paint event to customize the button's appearance
        Paint += CustomButton_Paint;
    }

    private void CustomButton_Paint(object sender, PaintEventArgs e)
    {
        if (!coloredTextFound)
        {
            // Display an error message if the colored text is not found
            MessageBox.Show("Colored text not found on the button.", "Error");
        }
    }

    private void UpdateColoredText()
    {
        if (!string.IsNullOrEmpty(coloredText))
        {
            // Check if the colored text is found on the button's Text property
            int startIndex = Text.IndexOf(coloredText);
            if (startIndex != -1)
            {
                coloredTextFound = true;
                Invalidate(); // Trigger the Paint event to update the button's appearance
            }
            else
            {
                coloredTextFound = false;
            }
        }
    }

    protected override void OnPaint(PaintEventArgs pevent)
    {
        base.OnPaint(pevent);

        if (coloredTextFound)
        {
            // Draw the colored text on the button
            using (Brush brush = new SolidBrush(coloredTextColor))
            {
                pevent.Graphics.DrawString(coloredText, Font, brush, ClientRectangle);
            }
        }
    }
}

The above is the code that i am trying to create a button on which its some characters can have different color from the rest of text color . for example , if "Press me" is the text written on a button , this button would have a property which asks for the characters i want to have different colored . so if i choose "Pr" , both the pr should have the color lets say red but the rest of the "ess me" would have a different color . If not it should just gave a warning message and do nothing . How should i do that in win forms . ? Any expert .

Answer 1

Try using Graphics.MeasureCharacter to find the position of a character and then draw the character in each color.

public class DualcoloredButton : Button
{
    private int index = -1;
    private string textDefault;
    private string coloredText;
    private Color coloredTextColor = Color.Red;

    public DualcoloredButton()
    {
        base.Text = "";
    }

    public override string Text
    {
        get => "";
        set => textDefault = value;
    }

    public string TextDefault
    {
        get => textDefault;
        set
        {
            textDefault = value;
            UpdateColoredText();
            OnTextChanged(EventArgs.Empty);
        }
    }

    public string ColoredText
    {
        get { return coloredText; }
        set
        {
            coloredText = value;
            UpdateColoredText();
        }
    }

    public Color ColoredTextColor
    {
        get { return coloredTextColor; }
        set
        {
            coloredTextColor = value;
            UpdateColoredText();
        }
    }

    private void UpdateColoredText()
    {
        if (!string.IsNullOrEmpty(coloredText) && !string.IsNullOrEmpty(textDefault))
        {
            string displayText = this.TextDefault.Replace("&", "");
            string coloredText = this.coloredText.Replace("&", "");
            index = displayText.IndexOf(coloredText);
        }
        else
        {
            index = -1;
        }
        Invalidate();

    }

    protected override void OnPaint(PaintEventArgs pevent)
    {
        StringFormat sf = new StringFormat();
        sf.Alignment = StringAlignment.Center;
        sf.LineAlignment = StringAlignment.Center;
        sf.Trimming = StringTrimming.None;
        sf.FormatFlags = StringFormatFlags.NoWrap | StringFormatFlags.NoClip;

        base.OnPaint(pevent);


        using (Brush brushColor = new SolidBrush(coloredTextColor))
        using (Brush brushDefault = new SolidBrush(this.ForeColor))
        {
            string displayText = this.TextDefault?.Replace("&", "") ?? "";
            string coloredText = this.coloredText?.Replace("&", "") ?? "";

            if (string.IsNullOrWhiteSpace(displayText))
            {
                return;
            }

            int index = displayText.IndexOf(coloredText);

            Brush[] brushes = new Brush[] { brushDefault, brushColor, brushDefault };

            Part partA = new Part(brushDefault, 0, index);
            Part partB = new Part(brushColor, index, coloredText.Length);
            Part partC = new Part(brushDefault, index + coloredText.Length, displayText.Length - index - coloredText.Length);
            Part[] parts = { partA, partB, partC };

            CharacterRange[] cranges = parts.Select(_ => _.ToCharacterRange()).ToArray();

            sf.SetMeasurableCharacterRanges(cranges);

            var ranges = pevent.Graphics.MeasureCharacterRanges(displayText, this.Font, this.ClientRectangle, sf);

            for (int i = 0; i < ranges.Length; i++)
            {
                RectangleF rect = ranges[i].GetBounds(pevent.Graphics);

                if (rect.Width > 0 && rect.Height > 0)
                {
                    Part part = parts[i];
                    string text = part.SubString(displayText);
                    pevent.Graphics.DrawString(text, Font, part.Brush, rect, sf);
                }

            }

            int indexAmp = this.textDefault.IndexOf("&");
            if (indexAmp < 0 || indexAmp == this.textDefault.Length - 1)
            {
                return;
            }

            if (Control.ModifierKeys == Keys.Alt || IsShowMnemonicUnderLine)
            {
                IsShowMnemonicUnderLine = true;

                cranges = new[] { new CharacterRange(indexAmp, 1) };
                sf.SetMeasurableCharacterRanges(cranges);

                ranges = pevent.Graphics.MeasureCharacterRanges(displayText, this.Font, this.ClientRectangle, sf);
                for (int i = 0; i < ranges.Length; i++)
                {
                    RectangleF rect = ranges[i].GetBounds(pevent.Graphics);

                    if (rect.Width > 0 && rect.Height > 0)
                    {
                        pevent.Graphics.DrawLine(Pens.Black, rect.X, rect.Bottom, rect.Right, rect.Bottom);
                    }

                }
            }
        }

    }

    public bool IsShowMnemonicUnderLine { get; set; }

    protected override bool ProcessMnemonic(char charCode)
    {
        if (textDefault != null)
        {
            int index = textDefault.IndexOf("&");
            if (0 <= index && index < textDefault.Length - 1)
            {
                if (char.ToLower(charCode) == char.ToLower(textDefault[index + 1]))
                {
                    PerformClick();
                    return true;
                }
            }
        }
        return false;
    }

    class Part
    {
        public int Start;
        public int Length;
        public Brush Brush;

        public Part(Brush brush, int start, int length)
        {
            Brush = brush;
            Start = start;
            Length = length;
        }

        public CharacterRange ToCharacterRange()
        {
            return new CharacterRange(Start, Length);
        }

        public string SubString(string text)
        {
            return text.Substring(Start, Length);
        }
    }

}

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Edit: Add Mnemonic logic

Edit: Fix misalignment when TextDefault has Ampersand and coloredText has no Ampersand.

Edit: Add draw underline logic