Windows Messages? Who,what?!

Problem/Question/Abstract:

How can I use Windows Message and what are they?

Answer:

Hey there manny people are asking what are Windows Messages let's say the Windows Messages are the heart of every Windows.Your application interactionates with other Windows using messages.

You can send or recive messages from the Windows operating systems.

Here is how to send

var
  yopos: Hwnd;
{...}
yopos := FindWindow(nil, 'program Manager');
ShowWindow(yopos, SW_HIDE);
{...}

you can use instead SW_SHOW,SW_MINIMIZE,SW_RESTORE etc;

here is how to close a window

SendMessage(Application.Handle, WM_CLOSE, 0, 0);

There are many examples to give but...

The most popular Windows Messages are:

WM_ACTIVATE: result := 'WM_ACTIVATE             ';
WM_ACTIVATEAPP: result := 'WM_ACTIVATEAPP          ';
WM_ASKCBFORMATNAME: result := 'WM_ASKCBFORMATNAME      ';
WM_CANCELMODE: result := 'WM_CANCELMODE           ';
WM_CHANGECBCHAIN: result := 'WM_CHANGECBCHAIN        ';
WM_CHAR: result := 'WM_CHAR                 ';
WM_CHARTOITEM: result := 'WM_CHARTOITEM           ';
WM_CHILDACTIVATE: result := 'WM_CHILDACTIVATE        ';
WM_CLEAR: result := 'WM_CLEAR                ';
WM_CLOSE: result := 'WM_CLOSE                ';
WM_COMMAND: result := 'WM_COMMAND              ';
WM_COMMNOTIFY: result := 'WM_COMMNOTIFY           ';
WM_COMPACTING: result := 'WM_COMPACTING           ';
WM_COMPAREITEM: result := 'WM_COMPAREITEM          ';
WM_COPY: result := 'WM_COPY                 ';
WM_CREATE: result := 'WM_CREATE               ';
WM_CTLCOLOR: result := 'WM_CTLCOLOR             ';
WM_CUT: result := 'WM_CUT                  ';
WM_DDE_ACK: result := 'WM_DDE_ACK              ';
WM_DDE_ADVISE: result := 'WM_DDE_ADVISE           ';
WM_DDE_DATA: result := 'WM_DDE_DATA             ';
WM_DDE_EXECUTE: result := 'WM_DDE_EXECUTE          ';
WM_DDE_INITIATE: result := 'WM_DDE_INITIATE         ';
WM_DDE_POKE: result := 'WM_DDE_POKE             ';
WM_DDE_REQUEST: result := 'WM_DDE_REQUEST          ';
WM_DDE_TERMINATE: result := 'WM_DDE_TERMINATE        ';
WM_DDE_UNADVISE: result := 'WM_DDE_UNADVISE         ';
WM_DEADCHAR: result := 'WM_DEADCHAR             ';
WM_DELETEITEM: result := 'WM_DELETEITEM           ';
WM_DESTROY: result := 'WM_DESTROY              ';
WM_DESTROYCLIPBOARD: result := 'WM_DESTROYCLIPBOARD     ';
WM_DEVMODECHANGE: result := 'WM_DEVMODECHANGE        ';
WM_DRAWCLIPBOARD: result := 'WM_DRAWCLIPBOARD        ';
WM_DRAWITEM: result := 'WM_DRAWITEM             ';
WM_DROPFILES: result := 'WM_DROPFILES            ';
WM_ENABLE: result := 'WM_ENABLE               ';
WM_ENDSESSION: result := 'WM_ENDSESSION           ';
WM_ENTERIDLE: result := 'WM_ENTERIDLE            ';
WM_ERASEBKGND: result := 'WM_ERASEBKGND           ';
WM_FONTCHANGE: result := 'WM_FONTCHANGE           ';
WM_GETDLGCODE: result := 'WM_GETDLGCODE           ';
WM_GETFONT: result := 'WM_GETFONT              ';
WM_GETMINMAXINFO: result := 'WM_GETMINMAXINFO        ';
WM_GETTEXT: result := 'WM_GETTEXT              ';
WM_GETTEXTLENGTH: result := 'WM_GETTEXTLENGTH        ';
WM_HSCROLL: result := 'WM_HSCROLL              ';
WM_HSCROLLCLIPBOARD: result := 'WM_HSCROLLCLIPBOARD     ';
WM_ICONERASEBKGND: result := 'WM_ICONERASEBKGND       ';
WM_INITDIALOG: result := 'WM_INITDIALOG           ';
WM_INITMENU: result := 'WM_INITMENU             ';
WM_INITMENUPOPUP: result := 'WM_INITMENUPOPUP        ';
WM_KEYDOWN: result := 'WM_KEYDOWN              ';
WM_KEYUP: result := 'WM_KEYUP                ';
WM_KILLFOCUS: result := 'WM_KILLFOCUS            ';
WM_LBUTTONDBLCLK: result := 'WM_LBUTTONDBLCLK        ';
WM_LBUTTONDOWN: result := 'WM_LBUTTONDOWN          ';
WM_LBUTTONUP: result := 'WM_LBUTTONUP            ';
WM_MBUTTONDBLCLK: result := 'WM_MBUTTONDBLCLK        ';
WM_MBUTTONDOWN: result := 'WM_MBUTTONDOWN          ';
WM_MBUTTONUP: result := 'WM_MBUTTONUP            ';
WM_MDIACTIVATE: result := 'WM_MDIACTIVATE          ';
WM_MDICASCADE: result := 'WM_MDICASCADE           ';
WM_MDICREATE: result := 'WM_MDICREATE            ';
WM_MDIDESTROY: result := 'WM_MDIDESTROY           ';
WM_MDIGETACTIVE: result := 'WM_MDIGETACTIVE         ';
WM_MDIICONARRANGE: result := 'WM_MDIICONARRANGE       ';
WM_MDIMAXIMIZE: result := 'WM_MDIMAXIMIZE          ';
WM_MDINEXT: result := 'WM_MDINEXT              ';
WM_MDIRESTORE: result := 'WM_MDIRESTORE           ';
WM_MDISETMENU: result := 'WM_MDISETMENU           ';
WM_MDITILE: result := 'WM_MDITILE              ';
WM_MEASUREITEM: result := 'WM_MEASUREITEM          ';
WM_MENUCHAR: result := 'WM_MENUCHAR             ';
WM_MENUSELECT: result := 'WM_MENUSELECT           ';
WM_MOUSEACTIVATE: result := 'WM_MOUSEACTIVATE        ';
WM_MOUSEMOVE: result := 'WM_MOUSEMOVE            ';
WM_MOVE: result := 'WM_MOVE                 ';
WM_NCACTIVATE: result := 'WM_NCACTIVATE           ';
WM_NCCALCSIZE: result := 'WM_NCCALCSIZE           ';
WM_NCCREATE: result := 'WM_NCCREATE             ';
WM_NCDESTROY: result := 'WM_NCDESTROY            ';
WM_NCHITTEST: result := 'WM_NCHITTEST            ';
WM_NCLBUTTONDBLCLK: result := 'WM_NCLBUTTONDBLCLK      ';
WM_NCLBUTTONDOWN: result := 'WM_NCLBUTTONDOWN        ';
WM_NCLBUTTONUP: result := 'WM_NCLBUTTONUP          ';
WM_NCMBUTTONDBLCLK: result := 'WM_NCMBUTTONDBLCLK      ';
WM_NCMBUTTONDOWN: result := 'WM_NCMBUTTONDOWN        ';
WM_NCMBUTTONUP: result := 'WM_NCMBUTTONUP          ';
WM_NCMOUSEMOVE: result := 'WM_NCMOUSEMOVE          ';
WM_NCPAINT: result := 'WM_NCPAINT              ';
WM_NCRBUTTONDBLCLK: result := 'WM_NCRBUTTONDBLCLK      ';
WM_NCRBUTTONDOWN: result := 'WM_NCRBUTTONDOWN        ';
WM_NCRBUTTONUP: result := 'WM_NCRBUTTONUP          ';
WM_NEXTDLGCTL: result := 'WM_NEXTDLGCTL           ';
WM_PAINT: result := 'WM_PAINT                ';
WM_PAINTCLIPBOARD: result := 'WM_PAINTCLIPBOARD       ';
WM_PALETTECHANGED: result := 'WM_PALETTECHANGED       ';
WM_PALETTEISCHANGING: result := 'WM_PALETTEISCHANGING    ';
WM_PARENTNOTIFY: result := 'WM_PARENTNOTIFY         ';
WM_PASTE: result := 'WM_PASTE                ';
WM_POWER: result := 'WM_POWER                ';
WM_QUERYDRAGICON: result := 'WM_QUERYDRAGICON        ';
WM_QUERYENDSESSION: result := 'WM_QUERYENDSESSION      ';
WM_QUERYNEWPALETTE: result := 'WM_QUERYNEWPALETTE      ';
WM_QUERYOPEN: result := 'WM_QUERYOPEN            ';
WM_QUEUESYNC: result := 'WM_QUEUESYNC            ';
WM_QUIT: result := 'WM_QUIT                 ';
WM_RBUTTONDBLCLK: result := 'WM_RBUTTONDBLCLK        ';
WM_RBUTTONDOWN: result := 'WM_RBUTTONDOWN          ';
WM_RBUTTONUP: result := 'WM_RBUTTONUP            ';
WM_RENDERALLFORMATS: result := 'WM_RENDERALLFORMATS     ';
WM_RENDERFORMAT: result := 'WM_RENDERFORMAT         ';
WM_SETCURSOR: result := 'WM_SETCURSOR            ';
WM_SETFOCUS: result := 'WM_SETFOCUS             ';
WM_SETFONT: result := 'WM_SETFONT              ';
WM_SETREDRAW: result := 'WM_SETREDRAW            ';
WM_SETTEXT: result := 'WM_SETTEXT              ';
WM_SHOWWINDOW: result := 'WM_SHOWWINDOW           ';
WM_SIZE: result := 'WM_SIZE                 ';
WM_SIZECLIPBOARD: result := 'WM_SIZECLIPBOARD        ';
WM_SPOOLERSTATUS: result := 'WM_SPOOLERSTATUS        ';
WM_SYSCHAR: result := 'WM_SYSCHAR              ';
WM_SYSCOLORCHANGE: result := 'WM_SYSCOLORCHANGE       ';
WM_SYSCOMMAND: result := 'WM_SYSCOMMAND           ';
WM_SYSDEADCHAR: result := 'WM_SYSDEADCHAR          ';
WM_SYSKEYDOWN: result := 'WM_SYSKEYDOWN           ';
WM_SYSKEYUP: result := 'WM_SYSKEYUP             ';
WM_SYSTEMERROR: result := 'WM_SYSTEMERROR          ';
WM_TIMECHANGE: result := 'WM_TIMECHANGE           ';
WM_TIMER: result := 'WM_TIMER                ';
WM_UNDO: result := 'WM_UNDO                 ';
WM_USER: result := 'WM_USER                 ';
WM_VKEYTOITEM: result := 'WM_VKEYTOITEM           ';
WM_VSCROLL: result := 'WM_VSCROLL              ';
WM_VSCROLLCLIPBOARD: result := 'WM_VSCROLLCLIPBOARD     ';
WM_WINDOWPOSCHANGED: result := 'WM_WINDOWPOSCHANGED     ';
WM_WINDOWPOSCHANGING: result := 'WM_WINDOWPOSCHANGING    ';
WM_WININICHANGE: result := 'WM_WININICHANGE         ';

You can use these messages using this example:

private

procedure lik(var Msg: TWMNCHITTEST); message WM_NCHITTEST;
public

procedure TForm1.lik(var Msg: TWMNCHITTEST);
begin
  inherited;
  if tx = true then
  begin
    if Msg.Result = Windows.HTMINBUTTON then
      Application.Minimize
    else if Msg.Result = Windows.HTCLOSE then
      Close;
  end;
end;