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C# - How to create a semi transparent or blurred backcolor on windows form

I am creating a Speed Meter to measure my internet speed and stays at top of every app, then I how do I make Its background semi transparent or blurred something like this.

C#

DwmExtendFrameIntoClientArea()

DwmEnableBlurBehindWindow()

DWMNCRENDERINGPOLICY

DwmSetWindowAttribute()

DWMWINDOWATTRIBUTE.NCRenderingPolicy

WndProc

1 Answer
1

Since I really needed to verify whether what I said in the comments actually made sense, here is a WinForms Form with a Blur effect applied to it.

WinForms

Form

This procedure is quite simple.
You need to override the class WndProc; when a WM_DWMCOMPOSITIONCHANGED message (informing of the Aero composition state) is received, the Window needs to register the rendering policy with DwmSetWindowAttribute(), setting the DWMWINDOWATTRIBUTE enumerator to NCRenderingPolicy and enable it setting the DWMNCRENDERINGPOLICY enumerator to Enabled.

WndProc

NCRenderingPolicy

Enabled

Then, before showing the interface, call DwmEnableBlurBehindWindow(), setting its DWM_BLURBEHIND structure relevant fields (dwFlags and fEnable) to 1.
Here, I'm calling it from the Form.Load() event.

dwFlags

fEnable

1

Form.Load()

It's more clear in code:
(As a note, the BlurBehind effect does not work if the Form has a white background color)

BlurBehind

All the Windows API declarations, structure and enums are already available in another question here.
Insert all the code in a class and add a refence to this class in the using statement section of the Form.

using

public partial class frmBlurBehind : Form
{
public frmBlurBehind() => InitializeComponent();

private void frmBlurBehind_Load(object sender, EventArgs e)
{
if (CheckAeroEnabled()) { WinApi.Dwm.WindowEnableBlurBehind(this.Handle); }
}

private bool CheckAeroEnabled() => (Environment.OSVersion.Version.Major >= 6)
? WinApi.Dwm.IsCompositionEnabled()
: false;

protected override void WndProc(ref Message m)
{
switch (m.Msg)
{
case (int)WinApi.WinMessage.WM_DWMCOMPOSITIONCHANGED:
{
WinApi.Dwm.DWMNCRENDERINGPOLICY Policy = WinApi.Dwm.DWMNCRENDERINGPOLICY.Enabled;
WinApi.Dwm.WindowSetAttribute(this.Handle, WinApi.Dwm.DWMWINDOWATTRIBUTE.NCRenderingPolicy, (int)Policy);
m.Result = (IntPtr)0;
}
break;
default:
break;
}
base.WndProc(ref m);
}
}


This is a sample result with a Form.BackColor set to (64, 64, 64):

Form.BackColor

64, 64, 64

Window Selected Windows Unselected


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