Bee Eee Blog

I’m developing a component that is like the sidebar in the Visual C# Express (c). To get it to appear when the mouse is over the control isn’t a problem, however I soon discovered that using the MouseEnter and MouseLeave didn’t work. When I went over child controls the MouseLeave would be called and cause my sidebar to collapse.

Instead I had to create a global mouse hook so that no matter what control the mouse was over I could get a mouse event.

First was the code to import the hook function:

// create a mouse over eventstatic int WH_MOUSE_LL = 14;
[System.Runtime.InteropServices.DllImport("kernel32.dll")]
static extern IntPtr GetModuleHandle(string moduleName);

[System.Runtime.InteropServices.DllImport("user32.dll")]
static extern IntPtr SetWindowsHookEx(int idHook, HookProc lpfn, IntPtr hMod, uint dwThreadId);

[System.Runtime.InteropServices.DllImport("user32.dll")]
public static extern int UnhookWindowsHookEx(IntPtr hhook);

[System.Runtime.InteropServices.DllImport("user32.dll")]
static extern IntPtr CallNextHookEx(IntPtr hhk, int nCode, uint wParam, IntPtr lParam);
delegate IntPtr HookProc(int nCode, uint wParam, IntPtr lParam);

private HookProc hookProc;
private IntPtr hook;

Here is the event handler

IntPtr LowLevelMouseProc(int nCode, uint wParam, IntPtr lParam)
{
    // get the current mouse position
    Point p = Cursor.Position;

    // convert to client rectangle to screen position
    Rectangle r = RectangleToScreen(ClientRectangle);

    // check to see if mouse is within control bounds
    bool exp = (p.Y > r.Top && p.Y < r.Bottom && p.X > r.Left && p.X < r.Right);

    // adjust the expansion
    if (exp != Expanded)
         Expanded = exp;

    // Finished with this
    return CallNextHookEx(IntPtr.Zero, nCode, wParam, lParam);
}

Then the initialization code I put in the OnLoad event handler:

if (!DesignMode)
{
    hookProc = new HookProc(LowLevelMouseProc);
    hook = SetWindowsHookEx(WH_MOUSE_LL, hookProc, GetModuleHandle(null), 0);
}

And then code for closing in the OnHandleDestroyed event handler:

protected override void OnHandleDestroyed(EventArgs e)
{
        UnhookWindowsHookEx(hook);
        base.OnHandleDestroyed(e);
}

That should just about do it then. Now the UserControl can sense whether the mouse is overhead whether or not the mouse is over a child control.

It turns out that a user control can fairly easily become a container control during design time. In other words being able to put other controls within your user control is fairly straight forward.

The steps are as follows.

add the following to your usings section:

using System.ComponentModel.Design;

and then add the following attribute just above your declared class.

[Designer("System.Windows.Forms.Design.ParentControlDesigner, System.Design", typeof(IDesigner))]

public class UserControl1 : System.Windows.Forms.UserControl

{
...
}

Then recompile the project and there it is.

Here is an example of a thread-safe call into a form.

delegate void logCallback(string strLog);
private void log(string log)
{
  if (this.InvokeRequired)
  {
    logCallBack d = new logCallback(log);
    this.Invoke(d, log);
  }
  else
  {
     this.log( strLog );
  }
}

First we determine whether the overhead of an invoke can be dismissed. Then if we must invoke we first create an instance of the delegate. Then we call invoke. That’s it. Not too hard.

Finally found how this way online to hide the tabs on a tab control. Works pretty good. This will quite simplify my GUI coding and mean I won’t need to import a component. Thanks jeeftan

Rectangle rect = new RectangleF(
                        tabPage1.Left,
                        tabPage1.Top,
                        tabPage1.Width,
                        tabPage1.Height );
tabControl1.Region = new Region(rect);

Ran across a simple how-to to enable double buffering for a form. Just put the code snippet in the form’s constructor after the InializeComponents

this.SetStyle(
            ControlStyles.AllPaintingInWmPaint |
            ControlStyles.UserPaint |
            ControlStyles.DoubleBuffer,true);

This gets rid of flicker, it also makes draw a tad slower.

Found the code at: http://www.bobpowell.net/doublebuffer.htm Thanks Bob Powell!