Adding a Drop Shadow to Panel

Question

WINFORMS C#
Visual Studio 2017

I have a movable panel that will contain other controls. I wanted to add a DropShadow effect to the panel to make it look good, so I used the following code:

private DevExpress.Utils.FormShadow.PopupFormShadow ShadowNew = new DevExpress.Utils.FormShadow.PopupFormShadow();  
//Assigned the panel  
ShadowNew.Form = panelControl1;  

The code to hide the shadow is:

ShadowNew.Form = null;  

This works beautifully, that is until I scroll. Parts of the Panel is not viewable which is normal, but the shadow for that part is still viewable. What I am trying to do now is look for a way to detect when the panel or part of the panel is not viewable when using the scrolling so that I can then hide the shadow, and when the panel is completely viewable show the shadow.

Any suggestion

I am looking for an alternative drop shadow but nothing really looks as good as this.

Sincerely and regards,

Answer 1

I was able to find a solution in VB code here: showthread.php

Partial C# code is:

// This will verify if the right side of the panel is not in the forms viewable area and will hide the shadow, else it will show it.
Rectangle myBounds = this.ClientRectangle;
    if (myBounds.Right < panelControl1.Right)
     {
        ShadowNew.Form = null;
     }
            else
     {
      ShadowNew.Form = panelControl1; 
     }

Thank you for the support.

Answer 2

Hi JoSRM-1861,
You can try to use GraphicsPath to draw a smooth shadow.
Here is a test coed example you can refer to.

public Form1()  
{  
    InitializeComponent();  
    shadowControls.Add(panel1);  
    this.Refresh();  
}  
List<Control> shadowControls = new List<Control>();  
Bitmap shadowBmp = null;  
Point PanelMouseDownLocation;  
private void panel1_MouseDown(object sender, MouseEventArgs e)  
{  
    if (e.Button == MouseButtons.Left) PanelMouseDownLocation = e.Location;     
}  
private void panel1_MouseMove(object sender, MouseEventArgs e)  
{  
    if (e.Button == MouseButtons.Left)  
    {  
        panel1.Left += e.X - PanelMouseDownLocation.X;  
  
        panel1.Top += e.Y - PanelMouseDownLocation.Y;  
        this.Refresh();  
    }     
}  
private void Form1_Paint(object sender, PaintEventArgs e)  
{  
    if (shadowBmp == null || shadowBmp.Size != this.Size)  
    {  
        shadowBmp?.Dispose();  
        shadowBmp = new Bitmap(this.Width, this.Height, PixelFormat.Format32bppArgb);  
    }  
    foreach (Control control in shadowControls)  
    {  
        using (GraphicsPath gp = new GraphicsPath())  
        {  
            gp.AddRectangle(new Rectangle(control.Location.X, control.Location.Y, control.Size.Width, control.Size.Height));  
            DrawShadowSmooth(gp, 100, 60, shadowBmp);  
        }  
        e.Graphics.DrawImage(shadowBmp, new Point(0, 0));  
    }  
}  
  
private static void DrawShadowSmooth(GraphicsPath gp, int intensity, int radius, Bitmap dest)  
{  
    using (Graphics g = Graphics.FromImage(dest))  
    {  
        g.Clear(Color.Transparent);  
        g.CompositingMode = CompositingMode.SourceCopy;  
        double alpha = 0;  
        double astep = 0;  
        double astepstep = (double)intensity / radius / (radius / 2D);  
        for (int thickness = radius; thickness > 0; thickness--)  
        {  
            using (Pen p = new Pen(Color.FromArgb((int)alpha, 0, 0, 0), thickness))  
            {  
                p.LineJoin = LineJoin.Round;  
                g.DrawPath(p, gp);  
            }  
            alpha += astep;  
            astep += astepstep;  
        }  
    }  
}  

The result:

Here is a related thread you can refer to.
Best Regards,
Daniel Zhang

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Answer 3

Hello @Jo SRM

For a movable control (any control) see the following Code Project article. The class also allows remember/restore positions. I didn't address the actual panel as it's DevExpress third party library which I don't have but should work fine.

Example usage

ControlMoverOrResizer.Init(shadowPanel1);