How To Suspend Invalidate While I Make Modifications To Bitmap?

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1.00/5 (1 vote)

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We all know how Invalidate works.
1. I create Vector image and draw it on Bitmap.
2. Invalidate redraws Bitmap on Form1 every time regardless me.
3. I make modifications to Bitmap when Invalidate attempts to redraw it.

So, what to do?

Note: I have to use only .Net libraries, not Platform Invoke.

Posted 11-Mar-15 10:08am

Ziya1995

Updated 12-Mar-15 8:43am

v6

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Ziya1995 · Accepted Answer · 2015-03-12T07:27:00

The next way works, but it lags a bit, because Form1 acts like it loses its Focus.

Code:

C#

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)
    {
        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();
    }
}

Using:

C#

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Reflection;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace WindowsFormsApplication1
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();

            this.Paint += Draw;
            (new Thread(Method)).Start();
        }

        Bitmap bitmap = new Bitmap(200, 200);

        private void Draw(object sender, PaintEventArgs e)
        {
            e.Graphics.DrawImage(bitmap, 0, 0);
        }

        private void Method()
        {
            using (Graphics g = Graphics.FromImage(bitmap))
                g.Clear(Color.Red);

            this.Invoke(new Action(delegate
            {
                SuspendUpdate.Suspend(this); // Suspend
            }));

            bitmap = new Bitmap(100, 100); // Modificate while Suspended
            using (Graphics g = Graphics.FromImage(bitmap))
                g.Clear(Color.Yellow);
            this.Invalidate(); // Invalidate does't draw

            this.Invoke(new Action(delegate
            {
                SuspendUpdate.Resume(this); // Resume
                this.Invalidate();
                this.Activate(); // Active Form1 because it loses Focus
            }));
        }
    }

    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)
        {
            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();
        }
    }
}

Ziya1995 · Accepted Answer · 2015-03-15T04:38:00

The next way works 100% sure:

C#

public partial class Form1 : Form
{
    public Form1()
    {
        InitializeComponent();

        this.Paint += Draw;
    }

    Bitmap bitmap = new Bitmap(100, 100);
    bool ok = true;

    Bitmap bitmapSaved = new Bitmap(100, 100);
    bool saved = false;

    private void Draw(object sender, PaintEventArgs e)
    {
        if (ok)
            e.Graphics.DrawImage(bitmap, 0, 0);
        else
        {
            if (!saved)
            {
                using (Graphics g = Graphics.FromImage(bitmapSaved))
                    g.DrawImage(bitmap, 0, 0);
                saved = true;
            }

            e.Graphics.DrawImage(bitmapSaved, 0, 0);
        }
    }

    private void Thread()
    {
        ok = false;
        this.Invoke(new Action(delegate
        {
            this.Refresh();
        }));
        using (Graphics g = Graphics.FromImage(bitmap))
        {
            // Modificate bitmap
        }

        ok = true;
        saved = false;
    }
}

How To Suspend Invalidate While I Make Modifications To Bitmap?

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