Disable Painting of the VScrollbar in a System.Windows.Forms.RichTextBox
- by SchlaWiener
I have a custom control inherited from RichTextBox.
This control has the ability to "disable" rich text editing.
I achive this by just setting the Rtf property to the text property during the TextChanged event.
this is how my code looks like:
private bool lockTextChanged;
void RichTextBox_TextChanged(object sender, EventArgs e)
{
// prevent StackOverflowException
if (lockTextChanged) return;
// remember current position
int rtbstart = rtb.SelectionStart;
int len = rtb.SelectionLength;
// prevent painting
rtb.SuspendLayout();
// set the text property to remove the entire formatting.
lockTextChanged = true;
rtb.Text = rtb.Text;
rtb.Select(rtbstart, len);
lockTextChanged = false;
rtb.ResumeLayout(true);
}
That worked well. However in a large text with like 200 lines the controls jitters (you see the first lines of text for the wink).
To prevent that from happening I filter the WM_PAINT between SuspendLayout() and ResumeLayout()
private bool layoutSuspended;
public new void SuspendLayout()
{
layoutSuspended = true;
base.SuspendLayout();
}
public new void ResumeLayout()
{
layoutSuspended = false;
base.ResumeLayout();
}
public new void ResumeLayout(bool performLayout)
{
layoutSuspended = false;
base.ResumeLayout(performLayout);
}
private const int WM_PAINT = 0x000F;
protected override void WndProc(ref System.Windows.Forms.Message m)
{
if (!(m.Msg == WM_PAINT && layoutSuspended))
base.WndProc(ref m);
}
that did the trick, the RichTextBox isn't jittering anymoe.
That's what I wanted to achive, except one thing:
The scrollbar is still jittering everytime I type text to my control.
Now my question:
Does anyone have a clue for me how to prevent the scrollbar from redrawing during Suspend/Resume Layout?
