How can I put a control and its children on hold while I paint?

Problem

I have a control that I need to make significant changes to. While I’m doing that, I’d like to entirely prohibit it from redrawing – SuspendLayout and ResumeLayout aren’t enough. How can I put a control and its children on hold while I paint?

Asked by Simon

Solution #1

We struggled at my former job to get our complex UI software to paint promptly and seamlessly. We were working with standard. There are three types of controls: net controls, custom controls, and devexpress controls.

I discovered the WM SETREDRAW win32 message after a lot of googling and reflector usage. This effectively disables the rendering of controls while you edit them, and may be applied to the parent/containing panel, IIRC.

This is a very basic class that shows how to use the following message:

class DrawingControl
{
    [DllImport("user32.dll")]
    public static extern int SendMessage(IntPtr hWnd, Int32 wMsg, bool wParam, Int32 lParam);

    private const int WM_SETREDRAW = 11; 

    public static void SuspendDrawing( Control parent )
    {
        SendMessage(parent.Handle, WM_SETREDRAW, false, 0);
    }

    public static void ResumeDrawing( Control parent )
    {
        SendMessage(parent.Handle, WM_SETREDRAW, true, 0);
        parent.Refresh();
    }
}

There are more in-depth talks on this if you search for C# and WM SETREDRAW, for example.

C# Jitter

Suspending Layouts

To whom it may concern, here’s a VB equivalent:

Public Module Extensions
    <DllImport("user32.dll")>
    Private Function SendMessage(ByVal hWnd As IntPtr, ByVal Msg As Integer, ByVal wParam As Boolean, ByVal lParam As IntPtr) As Integer
    End Function

    Private Const WM_SETREDRAW As Integer = 11

    ' Extension methods for Control
    <Extension()>
    Public Sub ResumeDrawing(ByVal Target As Control, ByVal Redraw As Boolean)
        SendMessage(Target.Handle, WM_SETREDRAW, True, IntPtr.Zero)
        If Redraw Then
            Target.Refresh()
        End If
    End Sub

    <Extension()>
    Public Sub SuspendDrawing(ByVal Target As Control)
        SendMessage(Target.Handle, WM_SETREDRAW, False, IntPtr.Zero)
    End Sub

    <Extension()>
    Public Sub ResumeDrawing(ByVal Target As Control)
        ResumeDrawing(Target, True)
    End Sub
End Module

Answered by ng5000

Solution #2

The following approach is similar to ng5000, but it does not require P/Invoke.

public static class SuspendUpdate
{
    private const int WM_SETREDRAW = 0x000B;

    public static void Suspend(Control control)
    {
        Message msgSuspendUpdate = Message.Create(control.Handle, WM_SETREDRAW, IntPtr.Zero,
            IntPtr.Zero);

        NativeWindow window = NativeWindow.FromHandle(control.Handle);
        window.DefWndProc(ref msgSuspendUpdate);
    }

    public static void Resume(Control control)
    {
        // Create a C "true" boolean as an IntPtr
        IntPtr wparam = new IntPtr(1);
        Message msgResumeUpdate = Message.Create(control.Handle, WM_SETREDRAW, wparam,
            IntPtr.Zero);

        NativeWindow window = NativeWindow.FromHandle(control.Handle);
        window.DefWndProc(ref msgResumeUpdate);

        control.Invalidate();
    }
}

Answered by ceztko

Solution #3

I usually use a slightly tweaked version of ngLink’s response.

public class MyControl : Control
{
    private int suspendCounter = 0;

    private void SuspendDrawing()
    {
        if(suspendCounter == 0) 
            SendMessage(this.Handle, WM_SETREDRAW, false, 0);
        suspendCounter++;
    }

    private void ResumeDrawing()
    {
        suspendCounter--; 
        if(suspendCounter == 0) 
        {
            SendMessage(this.Handle, WM_SETREDRAW, true, 0);
            this.Refresh();
        }
    }
}

This enables nested suspend/resume calls. Make sure that each SuspendDrawing is paired with a ResumeDrawing. As a result, making them public is probably not a good idea.

Answered by Ozgur Ozcitak

Solution #4

To help you remember to reenable drawing:

public static void SuspendDrawing(Control control, Action action)
{
    SendMessage(control.Handle, WM_SETREDRAW, false, 0);
    action();
    SendMessage(control.Handle, WM_SETREDRAW, true, 0);
    control.Refresh();
}

usage:

SuspendDrawing(myControl, () =>
{
    somemethod();
});

Answered by Jonathan H

Solution #5

I like this extension based on ng5000’s response:

        #region Suspend
        [DllImport("user32.dll")]
        private static extern int SendMessage(IntPtr hWnd, Int32 wMsg, bool wParam, Int32 lParam);
        private const int WM_SETREDRAW = 11;
        public static IDisposable BeginSuspendlock(this Control ctrl)
        {
            return new suspender(ctrl);
        }
        private class suspender : IDisposable
        {
            private Control _ctrl;
            public suspender(Control ctrl)
            {
                this._ctrl = ctrl;
                SendMessage(this._ctrl.Handle, WM_SETREDRAW, false, 0);
            }
            public void Dispose()
            {
                SendMessage(this._ctrl.Handle, WM_SETREDRAW, true, 0);
                this._ctrl.Refresh();
            }
        }
        #endregion

Use:

using (this.BeginSuspendlock())
{
    //update GUI
}

Answered by Koray

Post is based on https://stackoverflow.com/questions/487661/how-do-i-suspend-painting-for-a-control-and-its-children