一、delphi发送消息的函数主要有以下三个：
（一）、SendMessage函数，其原型如下：
function SendMessage(
hWnd: HWND; {目标句柄}
Msg: UINT; {要发送的消息(编号)}
wParam: WPARAM; {消息参数}
lParam: LPARAM {消息参数}
): LRESULT; stdcall; {返回处理结果}
（二）、PostMessage函数
function PostMessage(
hWnd: HWND; {目标句柄}
Msg: UINT; {要发送的消息(编号)}
wParam: WPARAM; {消息参数}
lParam: LPARAM {消息参数}
): BOOL; stdcall; {是否发送成功}
（三）、Perform 函数
function Perform(
Msg: Cardinal; {要发送的消息(编号)}
WParam: WPARAM; {消息参数}
LParam: LPARAM {消息参数}
): LRESULT; {返回处理结果}
SendMessage和PostMessage是API函数，Perform是delphi从TControl类开始定义的方法，所有从TControl继承的子类对象都可以使用。SendMessage和Perform方法，发送消息后，要等系统回馈结果后才执行下一步操作，而PostMessage函数则只管发送消息，发送消息后程序会马上执行下一步代码。
二、delphi 消息编号（Msg）规则及参数结构理解
（一）、消息编号
消息编号是window或者用户为各种不同消息定义唯一编号，他其实就是无符号整数（Cardinal）,为了便于理解， delphi以常量形式对每一个数字进行定义，主要有以下几种形式：
1、windows消息，以WM_为前缀，如WM_CLOSE为窗口关闭消息；
2、delphi自定义消息，以CM_、CN为前缀；
3、用户自定义消息 以WM_USER基数，如 Const MyMessage=WM_USER+1；
定义消息编号主要作用是定位消息处理函数，作为message关键字的识别码，例如以下函数头的定义：
procedure WMKeyDown(var Message: TWMKeyDown); message WM_KEYDOWN;
以上函数头定义了WM_KEYDOWN消息编号，其常量数值为 WM_KEYDOWN= $0100，其作用就是当窗口接受到编号为$100的消息就执行WMKeyDown这个函数。
（二）、消息结构体
消息结构体一般作为消息函数的参数类型出现，如上例中的TWMKeyDown就是一个消息结构体。消息结构体的标准定义如下：
PMsg = ^TMsg;
tagMSG = packed record
hwnd: HWND;
message: UINT;
wParam: WPARAM;
lParam: LPARAM;
time: DWORD;
pt: TPoint;
end;
TMsg = tagMSG;
MSG = tagMSG;
这种标准结构体与delphi VCL消息结构体并不兼容，所以delphi定义了自己的消息结构体。
PMessage = ^TMessage;
TMessage = packed record
Msg: Cardinal; {消息编号}
case Integer of
0: (
WParam: WPARAM;
LParam: LPARAM;
Result: LRESULT);
1: (
WParamLo: Word;
WParamHi: Word;
LParamLo: Word;
LParamHi: Word;
ResultLo: Word;
ResultHi: Word);
end;
在我们实际使用中，虽然标准的结构体可以满足我们的使用，但由于使用过程中我们还要进行数据转换，为了更加便捷和易于理解，delphi在message单元文件中为我们定义大量的消息结构体，供我们直接调用。
TWMNoParams
TWMCancelMode = TWMNoParams;
TWMChildActivate = TWMNoParams;
TWMClear = TWMNoParams;
TWMClose = TWMNoParams;
TWMCopy = TWMNoParams;
TWMCut = TWMNoParams;
TWMDestroy = TWMNoParams;
TWMDestroyClipboard = TWMNoParams;
TWMDrawClipboard = TWMNoParams;
TWMFontChange = TWMNoParams;
TWMGetDlgCode = TWMNoParams;
TWMGetFont = TWMNoParams;
TWMGetHotKey = TWMNoParams;
TWMGetTextLength = TWMNoParams;
TWMMDIGetActive = TWMNoParams;
TWMMDIIconArrange = TWMNoParams;
TWMMDIRefreshMenu = TWMNoParams;
TWMNCDestroy = TWMNoParams;
TWMPaintIcon = TWMNoParams;
TWMPaste = TWMNoParams;
TWMQueryDragIcon = TWMNoParams;
TWMQueryNewPalette = TWMNoParams;
TWMQueryOpen = TWMNoParams;
TWMQueueSync = TWMNoParams;
TWMRenderAllFormats = TWMNoParams;
TWMSysColorChange = TWMNoParams;
TWMTimeChange = TWMNoParams;
TWMQueryUIState = TWMNoParams;
TWMUndo = TWMNoParams;
TWMKey
TWMChar = TWMKey;
TWMKeyDown = TWMKey;
TWMKeyUp = TWMKey;
TWMDeadChar = TWMChar;
TWMSysChar = TWMKey;
TWMSysKeyDown = TWMKey;
TWMSysKeyUp = TWMKey;
TWMMouse
TWMLButtonDblClk = TWMMouse;
TWMLButtonDown = TWMMouse;
TWMLButtonUp = TWMMouse;
TWMMButtonDblClk = TWMMouse;
TWMMButtonDown = TWMMouse;
TWMMButtonUp = TWMMouse;
TWMMouseMove = TWMMouse;
TWMRButtonDblClk = TWMMouse;
TWMRButtonDown = TWMMouse;
TWMRButtonUp = TWMMouse;
TWMMouseWheel
TMSHMouseWheel
TWMWindowPosMsg
TWMWindowPosChanged = TWMWindowPosMsg;
TWMWindowPosChanging = TWMWindowPosMsg;
TWMScroll
TWMHScroll = TWMScroll;
TWMVScroll = TWMScroll;
TWMActivate
TWMActivateApp
TWMAskCBFormatName
TWMChangeCBChain
TWMCharToItem
TWMVKeyToItem = TWMCharToItem;
TWMChooseFont_GetLogFont
TWMCommand
TWMCompacting
TWMCompareItem
TWMCopyData
TWMCreate
TWMCtlColor
TWMCtlColorBtn = TWMCtlColor;
TWMCtlColorDlg = TWMCtlColor;
TWMCtlColorEdit = TWMCtlColor;
TWMCtlColorListbox = TWMCtlColor;
TWMCtlColorMsgbox = TWMCtlColor;
TWMCtlColorScrollbar = TWMCtlColor;
TWMCtlColorStatic = TWMCtlColor;
TWMDDE_Ack
TWMDDE_Advise
TWMDDE_Data
TWMDDE_Execute
TWMDDE_Initiate
TWMDDE_Poke
TWMDDE_Request
TWMDDE_Terminate
TWMDDE_Unadvise
TWMDeleteItem
TWMDevModeChange
TWMDrawItem
TWMDropFiles
TWMEnable
TWMEndSession
TWMEnterIdle
TWMEnterMenuLoop
TWMExitMenuLoop = TWMEnterMenuLoop;
TWMEraseBkgnd
TWMGetIcon
TWMGetMinMaxInfo
TWMGetText
TWMHotKey
TWMHScrollClipboard
TWMIconEraseBkgnd = TWMEraseBkgnd;
TWMInitDialog
TWMInitMenu
TWMInitMenuPopup
TWMKillFocus
TWMMDIActivate
TWMMDICascade
TWMMDICreate
TWMMDIDestroy
TWMMDIMaximize
TWMMDINext
TWMMDIRestore
TWMMDISetMenu
TWMMDITile
TWMMeasureItem
TWMMenuChar
TWMMenuSelect
TWMMouseActivate
TWMMove
TWMMoving
TWMNCActivate
TWMNCCalcSize
TWMNCCreate
TWMNCHitTest
TWMNCHitMessage
TWMNCLButtonDblClk = TWMNCHitMessage;
TWMNCLButtonDown = TWMNCHitMessage;
TWMNCLButtonUp = TWMNCHitMessage;
TWMNCMButtonDblClk = TWMNCHitMessage;
TWMNCMButtonDown = TWMNCHitMessage;
TWMNCMButtonUp = TWMNCHitMessage;
TWMNCMouseMove = TWMNCHitMessage;
TWMNCRButtonDblClk = TWMNCHitMessage;
TWMNCRButtonDown = TWMNCHitMessage;
TWMNCRButtonUp = TWMNCHitMessage;
TWMNCPaint
TWMNextDlgCtl
TWMNotify
TWMNotifyFormat
TWMPaint
TWMPaintClipboard
TWMPaletteChanged
TWMPaletteIsChanging
TWMParentNotify
TWMPower
TWMQueryEndSession
TWMQuit
TWMRenderFormat
TWMSetCursor
TWMSetFocus
TWMSetFont
TWMSetHotKey
TWMSetIcon
TWMSetRedraw
TWMSetText
TWMShowWindow
TWMSize
TWMSizeClipboard
TWMSpoolerStatus
TWMStyleChange
TWMStyleChanged = TWMStyleChange;
TWMStyleChanging = TWMStyleChange;
TWMSysCommand
TWMSysDeadChar
TWMSystemError
TWMTimer
TWMUIState
TWMChangeUIState = TWMUIState;
TWMUpdateUIState = TWMUIState;
TWMVScrollClipboard
TWMWinIniChange
TWMSettingChange
TWMHelp
TWMDisplayChange
TWMContextMenu
TWMPrint
TWMPrintClient = TWMPrint;