RichTextBox Line Numbering Font Size Adjustment - VB.NET - vb.net

Question

I'm building a text editor program, and on the left-hand side of the main RichTextBox, is a line numbering scheme that consists of a PictureBox, and a routine uses the Graphics method to draw numbers. As you scroll down the RichTextBox, the line numbers equally adjust.
I found some code online and made a few adjustments, but I'm struggling with one of them.
I have a Zoom In/Out feature so the user can adjust the size of the text in the RichTextBox, this is done by adding/subtracting 0.5 to/from the .ZoomFactor property of the RichTextBox. That part works perfectly and is a great, simple solution. However; If I adjust the zoom on the RichTextBox, the text is now larger than the line numbers, so they don't line up. My idea was to just increase the font size of the line numbering scheme and make small adjustments until they line up perfectly with each other.
Example:
This is it at normal size (the numbers are coloured because I've told the program to do that on purpose)
This is what happens when I adjust the RichTextBox zoom factor, without adjusting font size of line number
The code for drawing the line numbers is:
Private Sub DrawRichTextBoxLineNumbers(ByRef g As Graphics)
With TextEditBox
Dim font_height As Single
font_height = .GetPositionFromCharIndex(.GetFirstCharIndexFromLine(2)).Y _
- .GetPositionFromCharIndex(.GetFirstCharIndexFromLine(1)).Y
If font_height = 0 Then Exit Sub
'Get the first line index and location
Dim first_index As Integer
Dim first_line As Integer
Dim first_line_y As Integer
first_index = .GetCharIndexFromPosition(New _
Point(0, g.VisibleClipBounds.Y + font_height / 3))
first_line = .GetLineFromCharIndex(first_index)
first_line_y = .GetPositionFromCharIndex(first_index).Y
'Print on the PictureBox the visible line numbers of the RichTextBox
g.Clear(Control.DefaultBackColor)
Dim i As Integer = first_line
Dim y As Single
Do While y < g.VisibleClipBounds.Y + g.VisibleClipBounds.Height
y = first_line_y + 2 + font_height * (i - first_line - 1)
g.DrawString((i).ToString, .Font, Brushes.Gray, LineNumber.Width _
- g.MeasureString((i).ToString, .Font).Width, y)
i += 1
Loop
'Debug.WriteLine("Finished: " & firstLine + 1 & " " & i - 1)
End With
End Sub
What adjustment would I make to this section of the code to increase the size?
Dim font_height As Single
font_height = .GetPositionFromCharIndex(.GetFirstCharIndexFromLine(2)).Y _
- .GetPositionFromCharIndex(.GetFirstCharIndexFromLine(1)).Y
If font_height = 0 Then Exit Sub
Any help is greatly appreciated :)

Answer 1

Turns out, the drawing routine already handles this.
I've made it so that when the user moves the mouse on the form, resizes the form or adjusts the zoom, it refreshes.
I simply wrote the following code which immediately solved the problem.
LineNumber.Invalidate()

Answer 2

Also this was a great Line Numbers for RichTextBox with many Features
You can download the Source Code at this Link: https://drive.google.com/file/d/1aMVts_pkok_56DRvCdTkYCGywzjsRqS6/view?usp=sharing