Change the StartPosition
property on the child form:
StartPosition = FormStartPosition.Manual
The default value is WindowsDefaultLocation
, which causes each instance of the child form to drift down and to the right each time.
The following block of code from the Form
class is called when the form is an MdiChild
form, and the form is initially being displayed. (I trimmed out some unrelated parts.)
For all other StartPosition
values beside Manual
, there's some calculation going on regarding the location of the form, but it does nothing for StartPosition.Manual
.
// Adjusts the CreateParams to reflect the window bounds and start position.
private void FillInCreateParamsStartPosition(CreateParams cp) {
switch ((FormStartPosition)formState[FormStateStartPos]) {
case FormStartPosition.WindowsDefaultBounds:
cp.Width = NativeMethods.CW_USEDEFAULT;
cp.Height = NativeMethods.CW_USEDEFAULT;
...
case FormStartPosition.WindowsDefaultLocation:
case FormStartPosition.CenterParent:
...
cp.X = NativeMethods.CW_USEDEFAULT;
cp.Y = NativeMethods.CW_USEDEFAULT;
break;
case FormStartPosition.CenterScreen:
if (IsMdiChild) {
...
cp.X = Math.Max(clientRect.X,clientRect.X + (clientRect.Width - cp.Width)/2);
cp.Y = Math.Max(clientRect.Y,clientRect.Y + (clientRect.Height - cp.Height)/2);
}
else {
...
if (WindowState != FormWindowState.Maximized) {
cp.X = Math.Max(screenRect.X,screenRect.X + (screenRect.Width - cp.Width)/2);
cp.Y = Math.Max(screenRect.Y,screenRect.Y + (screenRect.Height - cp.Height)/2);
}
}
break;
}
}