There is a windows message that requests the minimum and the maximum value for a
resizable window ('form').
The following code makes sure that a window of type TForm1 is not smaller than
100x100 and not larger than 200x200 pixels:
type
TForm1 = class(TForm)
protected
procedure WMGetMinMaxInfo(var Message: TWMGetMinMaxInfo);
message WM_GETMINMAXINFO;
end;
procedure TForm1.WMGetMinMaxInfo(var Message: TWMGetMinMaxInfo);
begin
with Message.MinMaxInfo^ do
begin
ptMinTrackSize := Point(100, 100);
ptMaxTrackSize := Point(200, 200);
end;
end;