/// <summary>
/// This is used to perform any additional tasks when showing the drop-down
/// </summary>
public void ShowDropDown()
{
if (!hasInitialized)
{
this.CreateHandle();
}
startIndex = owner.SelectedIndex;
// Let the drop-down perform any initialization prior to display
if (ddControl != null)
{
ddControl.ShowDropDown();
}
}
/// <summary>
/// This is used to size and position the drop-down, perform any additional tasks, and show it
/// </summary>
public void ShowDropDown()
{
int idx;
if (!hasInitialized)
{
this.CreateHandle();
}
startIndex = owner.SelectedIndex;
dragOffset = Point.Empty;
// Let the drop-down perform any initialization prior to display
if (ddControl != null)
{
ddControl.ShowDropDown();
}
if (this.Width < owner.Width)
{
this.Width = owner.Width;
}
// Make sure we are within the screen bounds. Take into account the working area of all screens.
// Note that in certain setups, the leftmost/uppermost screen(s) may have negative coordinates.
Rectangle workingArea, screen = new Rectangle();
foreach (Screen s in Screen.AllScreens)
{
workingArea = s.WorkingArea;
if (workingArea.X < screen.X)
{
screen.X = workingArea.X;
}
if (workingArea.Y < screen.Y)
{
screen.Y = workingArea.Y;
}
if (Math.Abs(workingArea.X) + workingArea.Width > screen.Width)
{
screen.Width = Math.Abs(workingArea.X) + workingArea.Width;
}
if (Math.Abs(workingArea.Y) + workingArea.Height > screen.Height)
{
screen.Height = Math.Abs(workingArea.Y) + workingArea.Height;
}
}
Point pOwner = owner.Parent.PointToScreen(owner.Location);
pOwner.Y += owner.Height;
Point p = pOwner;
if (this.Width > screen.Width)
{
this.Width = screen.Width;
}
if (this.Height > screen.Height)
{
this.Height = screen.Height;
}
if (p.X < screen.X)
{
p.X = screen.X;
}
if (p.Y < screen.Y)
{
p.Y = screen.Y;
}
if (p.X + this.Width > screen.X + screen.Width)
{
p.X = screen.X + screen.Width - this.Width - 1;
}
if (p.Y + this.Height > screen.Y + screen.Height)
{
p.Y = screen.Y + screen.Height - this.Height - 1;
}
// If we are covering the combo box, move the location above the combo box
if (p.Y < pOwner.Y)
{
idx = pOwner.Y - this.Height - owner.Height;
// If we would go off the top of the screen, figure out whether we would have more rows visible
// if we moved the form above the combo box or left it where it is at below the combo box and
// shrink it to fit.
if (idx < screen.Y)
{
if (this.Height + idx > this.Height - (pOwner.Y - p.Y))
{
this.Height += idx;
idx = screen.Y;
}
else
{
this.Height -= (pOwner.Y - p.Y);
idx = pOwner.Y;
}
}
p.Y = idx;
}
// The first time it's shown, the size may change due to auto-scaling
Size sz = this.Size;
this.Location = p;
this.Show();
this.BringToFront();
if (this.Size != sz)
{
this.Size = sz;
}
}
