CODEWITHSUNDEEP
c#winformsbuffer
ManjuVijayan
ManjuVijayan

Reputation: 348

Avoid Flickering in Windows Forms?

Double buffering not working with combo-box. is there any another methods to avoid flickering in windows forms?

i have one windows form with number of panels in it. I'm showing only one panel at a time based on my menu selection.

i have one icon panel,one header panel and the combo box. based on the selected item of that combo-box the gridview1 and 2 are filling. when I'm rapidly selecting the combo-box item using my keyboard down arrow the icon panel and the header panel are always repainting. i need to keep that both without any change. this two panels producing some flashing effect(ie,they are blinking or flashing) while I'm changing the combo box selected index. is there any way to avoid this flashing.? i tried double-buffered enabled in form constructor and form load event.

Please Help.

InitializeComponent();

this.SetStyle(ControlStyles.DoubleBuffer, true);
this.SetStyle(ControlStyles.AllPaintingInWmPaint, true);
this.SetStyle(ControlStyles.UserPaint, true);
this.SetStyle(ControlStyles.SupportsTransparentBackColor, false);
this.SetStyle(ControlStyles.Opaque, false);
this.SetStyle(ControlStyles.OptimizedDoubleBuffer, true);
this.SetStyle(ControlStyles.ResizeRedraw, true);

I've tried this code in form constructor and form load event.

Upvotes: 9

Views: 20619

Answers (3)

user3541403
user3541403

Reputation: 247

    protected override CreateParams CreateParams
    {
        get
        {
            CreateParams handleParam = base.CreateParams;
            handleParam.ExStyle |= 0x02000000;   // WS_EX_COMPOSITED       
            return handleParam;
        }
    }

Upvotes: 4

Nick Hill
Nick Hill

Reputation: 4917

Yet another solution:

//TODO: Don't forget to include using System.Runtime.InteropServices.

internal static class NativeWinAPI
{
    internal static readonly int GWL_EXSTYLE = -20;
    internal static readonly int WS_EX_COMPOSITED = 0x02000000;

    [DllImport("user32")]
    internal static extern int GetWindowLong(IntPtr hWnd, int nIndex);

    [DllImport("user32")]
    internal static extern int SetWindowLong(IntPtr hWnd, int nIndex, int dwNewLong);
}

And your form constructor should look as follows:

public MyForm()
{
    InitializeComponent();

    int style = NativeWinAPI.GetWindowLong(this.Handle, NativeWinAPI.GWL_EXSTYLE);
    style |= NativeWinAPI.WS_EX_COMPOSITED;
    NativeWinAPI.SetWindowLong(this.Handle, NativeWinAPI.GWL_EXSTYLE, style);
}

In the code above, you might change this.Handle to something like MyFlickeringPanel.Handle

You can read a bit more about it here: Extended Window Styles and here: CreateWindowEx.

With WS_EX_COMPOSITED set, all descendants of a window get bottom-to-top painting order using double-buffering. Bottom-to-top painting order allows a descendent window to have translucency (alpha) and transparency (color-key) effects, but only if the descendent window also has the WS_EX_TRANSPARENT bit set. Double-buffering allows the window and its descendents to be painted without flicker.

Upvotes: 36

varg
varg

Reputation: 3636

Solution #1:
Use ComboxBox.BeginUpdate() before you add items. This will prevent the Control from repainting the ComboBox each time an item is added to the list. After adding the items, you can use ComboBox.EndUpdate() to repaint.

Solution #2 

private void EnableDoubleBuffering()
{
    this.SetStyle(ControlStyles.OptimizedDoubleBuffer | ControlStyles.UserPaint | ControlStyles.AllPaintingInWmPaint, true);
}

Upvotes: 2

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