Creating-a-collapsable-form


            Title: Creating a "collapsable" form
Question: Have you ever wondered how to make forms in the style of the MacOS? This article shows you how to make forms that collapse to just the caption and then expand again when you doubleclick on the caption bar
Answer:
The answer to this problem involves overriding the WM_NCLBUTTONDBLCLK message and detecting where the message has been sent from. The way to do this (i you want to override other messages as well) is to override the WndProc procedure.
unit Unit1;
interface
uses
 Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs;
type
 TForm1 = class(TForm)
 private
 { Private declarations }
 OldHeight: Integer;
 procedure ZipUpForm;
 public
 { Public declarations }
 { Override the WndProc procedure }
 { If you don't need to override any more messages you can simply
 use 
 procedure CollapseForm(var Message: TMessage); message WM_NCLBUTTONDBLCLK }
 procedure WndProc(var Message: TMessage); override;
 end;
var
 Form1: TForm1;
implementation
{$R *.DFM}
{capture the WM_NCLBUTTONDBLCLK message}
procedure TForm1.WndProc(var Message: TMessage);
begin
if Message.Msg = WM_NCLBUTTONDBLCLK then begin
if Message.wParam = htCaption then 
ZipUpForm;
end else
inherited WndProc(message);
end;
{Procedure for zipping and unzipping the form}
procedure TForm1.ZipUpForm;
begin
if Height = 27 then
 Height := OldHeight
else begin
 OldHeight := Height;
 Height := 27;
end;
end;
{ Use this procedure if you don't need to override any other messages }
{
procedure TForm1.CollapseForm(var Message: TMessage);
begin
if Message.Msg = WM_NCLBUTTONDBLCLK then begin
if Message.wParam = htCaption then 
ZipUpForm;
end else
inherited WndProc(message);
end;
}
end.
You can detect clicks on other non client parts of the form. The values that the wParam can be are:
HTBORDER	
In the border of a window that does not have a sizing border
HTBOTTOM	
In the lower horizontal border of a window
HTBOTTOMLEFT	
In the lower-left corner of a window border
HTBOTTOMRIGHT	
In the lower-right corner of a window border
HTCAPTION	
In a title bar
HTCLIENT	
In a client area
HTERROR	
On the screen background or on a dividing line between windows (same as HTNOWHERE, except that the a beep will be produced for the HTERROR hittest
HTGROWBOX	
In a size box (same as HTSIZE)
HTHSCROLL	
In a horizontal scroll bar
HTLEFT	
In the left border of a window
HTMENU	
In a menu
HTNOWHERE	
On the screen background or on a dividing line between windows
HTREDUCE	
In a Minimize button
HTRIGHT	
In the right border of a window
HTSIZE	
In a size box (same as HTGROWBOX)
HTSYSMENU	
In a System menu or in a Close button in a child window
HTTOP	
In the upper horizontal border of a window
HTTOPLEFT	
In the upper-left corner of a window border
HTTOPRIGHT	
In the upper right corner of a window border
HTTRANSPARENT	
In a window currently covered by another window
HTVSCROLL	
In the vertical scroll bar
HTZOOM	
In a Maximize button
Forms Delphi
