Mega Code Archive
Creating a collapsable form
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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
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