这些CM消息，居然在Delphi的帮助里是没有任何说明的，真是昏倒。意外在高手的书里找到了所有说明，说明如下：
Message Constant Value Description
cm_Base $B000 Base constant used by all other component messages.
cm_Activate cm_Base + 0; Specific to forms. Sent when form is first displayed and whenever focus changes to a different modeless form within the same application.
cm_Deactivate cm_Base + 1; Specific to forms. Always sent before a cm_Activate message to the form losing the focus.
cm_GotFocus cm_Base + 2; No longer used.
cm_LostFocus cm_Base + 3; No longer used.
cm_CancelMode cm_Base + 4; Sent to a focused control providing opportunity to cancel any internal modes before losing focus, such as capturing mouse input.
cm_DialogKey cm_Base + 5; A key was pressed that has special meaning in a dialogbox. (For example, Tab, Enter, the Arrow keys, and so on.)
cm_DialogChar cm_Base + 6; Sent to the form when characters are pressed and a component that does not accept keyboard input has the focus.
cm_FocusChanged cm_Base + 7; Sent to the form indicating which control now has the focus.
cm_ParentFontChanged cm_Base + 8; The ParentFont property has changed.
cm_ParentColorChanged cm_Base + 9; The ParentColor property has changed.
cm_HitTest cm_Base + 10; Sent when a control needs to determine if a given point is to be considered on the component.
cm_VisibleChanged cm_Base + 11; The Visible property has changed.
cm_EnabledChanged cm_Base + 12; The Enabled property has changed.
cm_ColorChanged cm_Base + 13; The Color property has changed.
cm_FontChanged cm_Base + 14; The Font property has changed.
cm_CursorChanged cm_Base + 15; The Cursor property has changed.
cm_Ctl3dChanged cm_Base + 16; The Ctl3D property has changed.
cm_ParentCtl3dChanged cm_Base + 17; The ParentCtl3D property has changed.
cm_TextChanged cm_Base + 18; The Text or Caption property has changed.
cm_MouseEnter cm_Base + 19; Sent when the mouse pointer becomes positioned over the component.
cm_MouseLeave cm_Base + 20; Sent when the mouse pointer is dragged outside of the bounds of the component.
cm_MenuChanged cm_Base + 21; Sent to the form when a menu item has changed.
cm_AppKeyDown cm_Base + 22; Used to transmit menu shortcut key events trapped by the Application object and forwarded on to the main form.
cm_AppSysCommand cm_Base + 23; Used to transmit wm_SysCommand messages from the Application object to the main form.
cm_ButtonPressed cm_Base + 24; A SpeedButton was pressed.
cm_ShowingChanged cm_Base + 25; The Showing property has changed.
cm_Enter cm_Base + 26; A component receives the input focus.
cm_Exit cm_Base + 27; A component loses the input focus.
cm_DesignHitTest cm_Base + 28; Sent when mouse pointer moved over component while in design-mode.
cm_IconChanged cm_Base + 29; The Icon property has changed.
cm_WantSpecialKey cm_Base + 30; Sent to a component when a special key (for example, Tab, Enter, the Arrow keys, and so on) is pressed. Allows a component to handle special keys in a particular way.
cm_InvokeHelp cm_Base + 31; Sent by a DLL’s Application object to the main Application object using the DLL when on-line help needs to be activated.
cm_WindowHook cm_Base + 32; Sent by a DLL’s Application object to the main Application object using the DLL to establish a window hook.
cm_Release cm_Base + 33; Sent by a form to itself indicating that the form should be destroyed.
cm_ShowHintChanged cm_Base + 34; The ShowHint property has changed.
cm_ParentShowHintChanged cm_Base + 35; The ParentShowHint property has changed.
cm_SysColorChange cm_Base + 36; The system colors have been altered.
cm_WinIniChange cm_Base + 37; A change has been made to the Win.ini file.
cm_FontChange cm_Base + 38; The Font property has changed.
cm_TimeChange cm_Base + 39; The system time has changed.
cm_TabStopChanged cm_Base + 40; The TabStop property has changed.
cm_UIActivate cm_Base + 41; When a form receives the input focus, it sends this message to the active control. TOleControl handles this message in order to activate the OLE Object.
cm_UIDeactivate cm_Base + 42; When a form loses the input focus, it sends this message to the active control. TOleControl handles this message in order to deactivate the OLE Object
cm_DocWindowActivate cm_Base + 43; Sent to the active OLE control when a form is activated or deactivated.
cm_ControlListChange cm_Base + 44; Sent only to window controls (such as descendants of TWinControl) when a component is added to or removed from the Controls list.
cm_GetDataLink cm_Base + 45; Sent by the TDBCtrlGrid component to embedded dataaware components to obtain each control’s data link object.
cm_ChildKey cm_Base + 46; Sent to a component that has the input focus and a key is pressed. The message is then propagated to its parent, and so on.
cm_Drag cm_Base + 47; High-level message sent to a component indicating one of the following drag events: Enter, Leave, Move, Drop, Cancel, or Find Target.
cm_HintShow cm_Base + 48; Sent to a component before displaying its hint.
cm_DialogHandle cm_Base + 49; Sent by a DLL’s Application object to the main Application object using the DLL in order to set the DialogHandle property.
cm_IsToolControl cm_Base + 50; Sent by an OLE container to aligned components giving them the opportunity to remain visible when the embedded OLE object is activated.
cm_RecreateWnd cm_Base + 51; The underlying window control needs to be recreated. Used by TActiveXControl.
cm_Invalidate cm_Base + 52; The underlying window control needs to be invalidated. Used by TActiveXControl.
摘自《Developing Custom Delphi3 Components》 p270
另有：http://blog.csdn.net/linzhengqun/article/details/255363