窗口过程 Wndproc

操作系统向应用程序发送一系列消息，如左键按下和左键抬起，应用程序将通过GetMessage等方法 Wndproc应用例子
最终将消息提交到窗口过程（WndProc)指向一个应用程序定义的窗口过程的指针。

每个窗口会有一个称为窗口过程的回调函数(WndProc)，它带有四个参数，分别为：窗口句柄(Window Handle)HWND,消息ID(Message ID)UINT,和两个消息参数(wParam, lParam)WPARAM、LPARAM,
WndProc的第一个参数hWnd就是当前接收消息的窗口句柄，第二个参数就是被传送过来的消息，第三、第四个参数都是附加在消息上的数据，这和MSG结构体是一样的。

1 什么是消息(Message)

消息就是通知和命令。在.NET框架类库中的System.Windows.Forms命名空间中微软采用面对对象的方式重新定义了Message。新的消息(Message)结构的公共部分属性基本与早期的一样，不过它是面对对象的。
公共属性：

HWnd 获取或设定消息的处理函数
Msg 获取或设定消息的ID号
Lparam 指定消息的LParam字段
Wparam 指定消息的WParam字段
Result 指定为响应消息处理函数而向OS系统返回的值

2 消息驱动的过程

所有的外部事件，如键盘输入、鼠标移动、按动鼠标都由OS系统转换成相应的消息发送到应用程序的消息队列。每个应用程序都有一段相应的程序代码来检索、分发这些消息到对应的窗体，然后由窗体的处理函数来处理。

大体的消息说明,如下：

WM_ACTIVATE	0x6	The WM_ACTIVATE message is sent when a window is being activated or deactivated. This message is sent first to the window procedure of the top-level window being deactivated; it is then sent to the window procedure of the top-level window being activated.
WM_ACTIVATEAPP	0x1C	The WM_ACTIVATEAPP message is sent when a window belonging to a different application than the active window is about to be activated. The message is sent to the application whose window is being activated and to the application whose window is being deactivated.
WM_AFXFIRST	0x360	The WM_AFXFIRST specifies the first afx message.
WM_AFXLAST	0x37F	The WM_AFXFIRST specifies the last afx message.
WM_APP	0x8000	The WM_APP constant is used by applications to help define private messages, usually of the form WM_APP+X, where X is an integer value.
WM_ASKCBFORMATNAME	0x30C	The WM_ASKCBFORMATNAME message is sent to the clipboard owner by a clipboard viewer window to request the name of a CF_OWNERDISPLAY clipboard format.
WM_CANCELJOURNAL	0x4B	The WM_CANCELJOURNAL message is posted to an application when a user cancels the application's journaling activities. The message is posted with a NULL window handle.
WM_CANCELMODE	0x1F	The WM_CANCELMODE message is sent to cancel certain modes, such as mouse capture. For example, the system sends this message to the active window when a dialog box or message box is displayed. Certain functions also send this message explicitly to the specified window regardless of whether it is the active window. For example, the EnableWindowfunction sends this message when disabling the specified window.
WM_CAPTURECHANGED	0x215	The WM_CAPTURECHANGED message is sent to the window that is losing the mouse capture.
WM_CHANGECBCHAIN	0x30D	The WM_CHANGECBCHAIN message is sent to the first window in the clipboard viewer chain when a window is being removed from the chain.
WM_CHANGEUISTATE	0x127	An application sends the WM_CHANGEUISTATE message to indicate that the user interface (UI) state should be changed.
WM_CHAR	0x102	The WM_CHAR message is posted to the window with the keyboard focus when a WM_KEYDOWN message is translated by the TranslateMessage function. The WM_CHAR message contains the character code of the key that was pressed.
WM_CHARTOITEM	0x2F	Sent by a list box with the LBS_WANTKEYBOARDINPUT style to its owner in response to a WM_CHAR message.
WM_CHILDACTIVATE	0x22	The WM_CHILDACTIVATE message is sent to a child window when the user clicks the window's title bar or when the window is activated, moved, or sized.
WM_CLEAR	0x303	An application sends a WM_CLEAR message to an edit control or combo box to delete (clear) the current selection, if any, from the edit control.
WM_CLOSE	0x10	The WM_CLOSE message is sent as a signal that a window or an application should terminate.
WM_COMMAND	0x111	The WM_COMMAND message is sent when the user selects a command item from a menu, when a control sends a notification message to its parent window, or when an accelerator keystroke is translated.
WM_COMPACTING	0x41	The WM_COMPACTING message is sent to all top-level windows when the system detects more than 12.5 percent of system time over a 30- to 60-second interval is being spent compacting memory. This indicates that system memory is low.
WM_COMPAREITEM	0x39	The system sends the WM_COMPAREITEM message to determine the relative position of a new item in the sorted list of an owner-drawn combo box or list box. Whenever the application adds a new item, the system sends this message to the owner of a combo box or list box created with the CBS_SORT or LBS_SORT style.
WM_CONTEXTMENU	0x7B	The WM_CONTEXTMENU message notifies a window that the user clicked the right mouse button (right-clicked) in the window.
WM_COPY	0x301	An application sends the WM_COPY message to an edit control or combo box to copy the current selection to the clipboard in CF_TEXT format.
WM_COPYDATA	0x4A	An application sends the WM_COPYDATA message to pass data to another application.
WM_CREATE	0x1	The WM_CREATE message is sent when an application requests that a window be created by calling the CreateWindowEx orCreateWindow function. (The message is sent before the function returns.) The window procedure of the new window receives this message after the window is created, but before the window becomes visible.
WM_CTLCOLORBTN	0x135	The WM_CTLCOLORBTN message is sent to the parent window of a button before drawing the button. The parent window can change the button's text and background colors. However, only owner-drawn buttons respond to the parent window processing this message.
WM_CTLCOLORDLG	0x136	The WM_CTLCOLORDLG message is sent to a dialog box before the system draws the dialog box. By responding to this message, the dialog box can set its text and background colors using the specified display device context handle.
WM_CTLCOLOREDIT	0x133	An edit control that is not read-only or disabled sends the WM_CTLCOLOREDIT message to its parent window when the control is about to be drawn. By responding to this message, the parent window can use the specified device context handle to set the text and background colors of the edit control.
WM_CTLCOLORLISTBOX	0x134	Sent to the parent window of a list box before the system draws the list box. By responding to this message, the parent window can set the text and background colors of the list box by using the specified display device context handle.
WM_CTLCOLORMSGBOX	0x132	The WM_CTLCOLORMSGBOX message is sent to the owner window of a message box before Windows draws the message box. By responding to this message, the owner window can set the text and background colors of the message box by using the given display device context handle.
WM_CTLCOLORSCROLLBAR	0x137	The WM_CTLCOLORSCROLLBAR message is sent to the parent window of a scroll bar control when the control is about to be drawn. By responding to this message, the parent window can use the display context handle to set the background color of the scroll bar control.
WM_CTLCOLORSTATIC	0x138	A static control, or an edit control that is read-only or disabled, sends the WM_CTLCOLORSTATIC message to its parent window when the control is about to be drawn. By responding to this message, the parent window can use the specified device context handle to set the text and background colors of the static control.
WM_CUT	0x300	An application sends a WM_CUT message to an edit control or combo box to delete (cut) the current selection, if any, in the edit control and copy the deleted text to the clipboard in CF_TEXT format.
WM_DEADCHAR	0x103	The WM_DEADCHAR message is posted to the window with the keyboard focus when a WM_KEYUP message is translated by the TranslateMessage function. WM_DEADCHAR specifies a character code generated by a dead key. A dead key is a key that generates a character, such as the umlaut (double-dot), that is combined with another character to form a composite character. For example, the umlaut-O character (Ö) is generated by typing the dead key for the umlaut character, and then typing the O key.
WM_DELETEITEM	0x2D	Sent to the owner of a list box or combo box when the list box or combo box is destroyed or when items are removed by the LB_DELETESTRING, LB_RESETCONTENT, CB_DELETESTRING, or CB_RESETCONTENT message. The system sends a WM_DELETEITEM message for each deleted item. The system sends the WM_DELETEITEM message for any deleted list box or combo box item with nonzero item data.
WM_DESTROY	0x2	The WM_DESTROY message is sent when a window is being destroyed. It is sent to the window procedure of the window being destroyed after the window is removed from the screen. This message is sent first to the window being destroyed and then to the child windows (if any) as they are destroyed. During the processing of the message, it can be assumed that all child windows still exist.
WM_DESTROYCLIPBOARD	0x307	The WM_DESTROYCLIPBOARD message is sent to the clipboard owner when a call to the EmptyClipboard function empties the clipboard.
WM_DEVICECHANGE	0x219	Notifies an application of a change to the hardware configuration of a device or the computer.
WM_DEVMODECHANGE	0x1B	The WM_DEVMODECHANGE message is sent to all top-level windows whenever the user changes device-mode settings.
WM_DISPLAYCHANGE	0x7E	The WM_DISPLAYCHANGE message is sent to all windows when the display resolution has changed.
WM_DRAWCLIPBOARD	0x308	The WM_DRAWCLIPBOARD message is sent to the first window in the clipboard viewer chain when the content of the clipboard changes. This enables a clipboard viewer window to display the new content of the clipboard.
WM_DRAWITEM	0x2B	The WM_DRAWITEM message is sent to the parent window of an owner-drawn button, combo box, list box, or menu when a visual aspect of the button, combo box, list box, or menu has changed.
WM_DROPFILES	0x233	Sent when the user drops a file on the window of an application that has registered itself as a recipient of dropped files.
WM_ENABLE	0xA	The WM_ENABLE message is sent when an application changes the enabled state of a window. It is sent to the window whose enabled state is changing. This message is sent before the EnableWindow function returns, but after the enabled state (WS_DISABLED style bit) of the window has changed.
WM_ENDSESSION	0x16	The WM_ENDSESSION message is sent to an application after the system processes the results of the WM_QUERYENDSESSION message. The WM_ENDSESSION message informs the application whether the session is ending.
WM_ENTERIDLE	0x121	The WM_ENTERIDLE message is sent to the owner window of a modal dialog box or menu that is entering an idle state. A modal dialog box or menu enters an idle state when no messages are waiting in its queue after it has processed one or more previous messages.
WM_ENTERMENULOOP	0x211	The WM_ENTERMENULOOP message informs an application's main window procedure that a menu modal loop has been entered.
WM_ENTERSIZEMOVE	0x231	The WM_ENTERSIZEMOVE message is sent one time to a window after it enters the moving or sizing modal loop. The window enters the moving or sizing modal loop when the user clicks the window's title bar or sizing border, or when the window passes the WM_SYSCOMMAND message to the DefWindowProc function and the wParam parameter of the message specifies the SC_MOVE or SC_SIZE value. The operation is complete when DefWindowProc returns.
WM_ERASEBKGND	0x14	The WM_ERASEBKGND message is sent when the window background must be erased (for example, when a window is resized). The message is sent to prepare an invalidated portion of a window for painting.
WM_EXITMENULOOP	0x212	The WM_EXITMENULOOP message informs an application's main window procedure that a menu modal loop has been exited.
WM_EXITSIZEMOVE	0x232	The WM_EXITSIZEMOVE message is sent one time to a window, after it has exited the moving or sizing modal loop. The window enters the moving or sizing modal loop when the user clicks the window's title bar or sizing border, or when the window passes the WM_SYSCOMMAND message to the DefWindowProc function and the wParam parameter of the message specifies the SC_MOVE or SC_SIZE value. The operation is complete when DefWindowProc returns.
WM_FONTCHANGE	0x1D	An application sends the WM_FONTCHANGE message to all top-level windows in the system after changing the pool of font resources.
WM_GETDLGCODE	0x87	The WM_GETDLGCODE message is sent to the window procedure associated with a control. By default, the system handles all keyboard input to the control; the system interprets certain types of keyboard input as dialog box navigation keys. To override this default behavior, the control can respond to the WM_GETDLGCODE message to indicate the types of input it wants to process itself.
WM_GETFONT	0x31	An application sends a WM_GETFONT message to a control to retrieve the font with which the control is currently drawing its text.
WM_GETHOTKEY	0x33	An application sends a WM_GETHOTKEY message to determine the hot key associated with a window.
WM_GETICON	0x7F	The WM_GETICON message is sent to a window to retrieve a handle to the large or small icon associated with a window. The system displays the large icon in the ALT+TAB dialog, and the small icon in the window caption.
WM_GETMINMAXINFO	0x24	The WM_GETMINMAXINFO message is sent to a window when the size or position of the window is about to change. An application can use this message to override the window's default maximized size and position, or its default minimum or maximum tracking size.
WM_GETOBJECT	0x3D	Active Accessibility sends the WM_GETOBJECT message to obtain information about an accessible object contained in a server application. Applications never send this message directly. It is sent only by Active Accessibility in response to calls toAccessibleObjectFromPoint, AccessibleObjectFromEvent, or AccessibleObjectFromWindow. However, server applications handle this message.
WM_GETTEXT	0xD	An application sends a WM_GETTEXT message to copy the text that corresponds to a window into a buffer provided by the caller.
WM_GETTEXTLENGTH	0xE	An application sends a WM_GETTEXTLENGTH message to determine the length, in characters, of the text associated with a window.
WM_HANDHELDFIRST	0x358	Definition Needed
WM_HANDHELDLAST	0x35F	Definition Needed
WM_HELP	0x53	Indicates that the user pressed the F1 key. If a menu is active when F1 is pressed, WM_HELP is sent to the window associated with the menu; otherwise, WM_HELP is sent to the window that has the keyboard focus. If no window has the keyboard focus, WM_HELP is sent to the currently active window.
WM_HOTKEY	0x312	The WM_HOTKEY message is posted when the user presses a hot key registered by the RegisterHotKey function. The message is placed at the top of the message queue associated with the thread that registered the hot key.
WM_HSCROLL	0x114	This message is sent to a window when a scroll event occurs in the window's standard horizontal scroll bar. This message is also sent to the owner of a horizontal scroll bar control when a scroll event occurs in the control.
WM_HSCROLLCLIPBOARD	0x30E	The WM_HSCROLLCLIPBOARD message is sent to the clipboard owner by a clipboard viewer window. This occurs when the clipboard contains data in the CF_OWNERDISPLAY format and an event occurs in the clipboard viewer's horizontal scroll bar. The owner should scroll the clipboard image and update the scroll bar values.
WM_ICONERASEBKGND	0x27	Windows NT 3.51 and earlier: The WM_ICONERASEBKGND message is sent to a minimized window when the background of the icon must be filled before painting the icon. A window receives this message only if a class icon is defined for the window; otherwise, WM_ERASEBKGND is sent. This message is not sent by newer versions of Windows.
WM_IME_CHAR	0x286	Sent to an application when the IME gets a character of the conversion result. A window receives this message through itsWindowProc function.
WM_IME_COMPOSITION	0x10F	Sent to an application when the IME changes composition status as a result of a keystroke. A window receives this message through its WindowProc function.
WM_IME_COMPOSITIONFULL	0x284	Sent to an application when the IME window finds no space to extend the area for the composition window. A window receives this message through its WindowProc function.
WM_IME_CONTROL	0x283	Sent by an application to direct the IME window to carry out the requested command. The application uses this message to control the IME window that it has created. To send this message, the application calls the SendMessage function with the following parameters.
WM_IME_ENDCOMPOSITION	0x10E	Sent to an application when the IME ends composition. A window receives this message through its WindowProc function.
WM_IME_KEYDOWN	0x290	Sent to an application by the IME to notify the application of a key press and to keep message order. A window receives this message through its WindowProc function.
WM_IME_KEYLAST	0x10F	Definition Needed
WM_IME_KEYUP	0x291	Sent to an application by the IME to notify the application of a key release and to keep message order. A window receives this message through its WindowProc function.
WM_IME_NOTIFY	0x282	Sent to an application to notify it of changes to the IME window. A window receives this message through its WindowProcfunction.
WM_IME_REQUEST	0x288	Sent to an application to provide commands and request information. A window receives this message through itsWindowProc function.
WM_IME_SELECT	0x285	Sent to an application when the operating system is about to change the current IME. A window receives this message through its WindowProc function.
WM_IME_SETCONTEXT	0x281	Sent to an application when a window is activated. A window receives this message through its WindowProc function.
WM_IME_STARTCOMPOSITION	0x10D	Sent immediately before the IME generates the composition string as a result of a keystroke. A window receives this message through its WindowProc function.
WM_INITDIALOG	0x110	The WM_INITDIALOG message is sent to the dialog box procedure immediately before a dialog box is displayed. Dialog box procedures typically use this message to initialize controls and carry out any other initialization tasks that affect the appearance of the dialog box.
WM_INITMENU	0x116	The WM_INITMENU message is sent when a menu is about to become active. It occurs when the user clicks an item on the menu bar or presses a menu key. This allows the application to modify the menu before it is displayed.
WM_INITMENUPOPUP	0x117	The WM_INITMENUPOPUP message is sent when a drop-down menu or submenu is about to become active. This allows an application to modify the menu before it is displayed, without changing the entire menu.
WM_INPUTLANGCHANGE	0x51	The WM_INPUTLANGCHANGE message is sent to the topmost affected window after an application's input language has been changed. You should make any application-specific settings and pass the message to the DefWindowProc function, which passes the message to all first-level child windows. These child windows can pass the message to DefWindowProc to have it pass the message to their child windows, and so on.
WM_INPUTLANGCHANGEREQUEST	0x50	The WM_INPUTLANGCHANGEREQUEST message is posted to the window with the focus when the user chooses a new input language, either with the hotkey (specified in the Keyboard control panel application) or from the indicator on the system taskbar. An application can accept the change by passing the message to the DefWindowProc function or reject the change (and prevent it from taking place) by returning immediately.
WM_KEYDOWN	0x100	The WM_KEYDOWN message is posted to the window with the keyboard focus when a nonsystem key is pressed. A nonsystem key is a key that is pressed when the ALT key is not pressed.
WM_KEYFIRST	0x100	This message filters for keyboard messages.
WM_KEYLAST	0x108	This message filters for keyboard messages.
WM_KEYUP	0x101	The WM_KEYUP message is posted to the window with the keyboard focus when a nonsystem key is released. A nonsystem key is a key that is pressed when the ALT key is not pressed, or a keyboard key that is pressed when a window has the keyboard focus.
WM_KILLFOCUS	0x8	The WM_KILLFOCUS message is sent to a window immediately before it loses the keyboard focus.
WM_LBUTTONDBLCLK	0x203	The WM_LBUTTONDBLCLK message is posted when the user double-clicks the left mouse button while the cursor is in the client area of a window. If the mouse is not captured, the message is posted to the window beneath the cursor. Otherwise, the message is posted to the window that has captured the mouse.
WM_LBUTTONDOWN	0x201	The WM_LBUTTONDOWN message is posted when the user presses the left mouse button while the cursor is in the client area of a window. If the mouse is not captured, the message is posted to the window beneath the cursor. Otherwise, the message is posted to the window that has captured the mouse.
WM_LBUTTONUP	0x202	The WM_LBUTTONUP message is posted when the user releases the left mouse button while the cursor is in the client area of a window. If the mouse is not captured, the message is posted to the window beneath the cursor. Otherwise, the message is posted to the window that has captured the mouse.
WM_MBUTTONDBLCLK	0x209	The WM_MBUTTONDBLCLK message is posted when the user double-clicks the middle mouse button while the cursor is in the client area of a window. If the mouse is not captured, the message is posted to the window beneath the cursor. Otherwise, the message is posted to the window that has captured the mouse.
WM_MBUTTONDOWN	0x207	The WM_MBUTTONDOWN message is posted when the user presses the middle mouse button while the cursor is in the client area of a window. If the mouse is not captured, the message is posted to the window beneath the cursor. Otherwise, the message is posted to the window that has captured the mouse.
WM_MBUTTONUP	0x208	The WM_MBUTTONUP message is posted when the user releases the middle mouse button while the cursor is in the client area of a window. If the mouse is not captured, the message is posted to the window beneath the cursor. Otherwise, the message is posted to the window that has captured the mouse.
WM_MDIACTIVATE	0x222	An application sends the WM_MDIACTIVATE message to a multiple-document interface (MDI) client window to instruct the client window to activate a different MDI child window.
WM_MDICASCADE	0x227	An application sends the WM_MDICASCADE message to a multiple-document interface (MDI) client window to arrange all its child windows in a cascade format.
WM_MDICREATE	0x220	An application sends the WM_MDICREATE message to a multiple-document interface (MDI) client window to create an MDI child window.
WM_MDIDESTROY	0x221	An application sends the WM_MDIDESTROY message to a multiple-document interface (MDI) client window to close an MDI child window.
WM_MDIGETACTIVE	0x229	An application sends the WM_MDIGETACTIVE message to a multiple-document interface (MDI) client window to retrieve the handle to the active MDI child window.
WM_MDIICONARRANGE	0x228	An application sends the WM_MDIICONARRANGE message to a multiple-document interface (MDI) client window to arrange all minimized MDI child windows. It does not affect child windows that are not minimized.
WM_MDIMAXIMIZE	0x225	An application sends the WM_MDIMAXIMIZE message to a multiple-document interface (MDI) client window to maximize an MDI child window. The system resizes the child window to make its client area fill the client window. The system places the child window's window menu icon in the rightmost position of the frame window's menu bar, and places the child window's restore icon in the leftmost position. The system also appends the title bar text of the child window to that of the frame window.
WM_MDINEXT	0x224	An application sends the WM_MDINEXT message to a multiple-document interface (MDI) client window to activate the next or previous child window.
WM_MDIREFRESHMENU	0x234	An application sends the WM_MDIREFRESHMENU message to a multiple-document interface (MDI) client window to refresh the window menu of the MDI frame window.
WM_MDIRESTORE	0x223	An application sends the WM_MDIRESTORE message to a multiple-document interface (MDI) client window to restore an MDI child window from maximized or minimized size.
WM_MDISETMENU	0x230	An application sends the WM_MDISETMENU message to a multiple-document interface (MDI) client window to replace the entire menu of an MDI frame window, to replace the window menu of the frame window, or both.
WM_MDITILE	0x226	An application sends the WM_MDITILE message to a multiple-document interface (MDI) client window to arrange all of its MDI child windows in a tile format.
WM_MEASUREITEM	0x2C	The WM_MEASUREITEM message is sent to the owner window of a combo box, list box, list view control, or menu item when the control or menu is created.
WM_MENUCHAR	0x120	The WM_MENUCHAR message is sent when a menu is active and the user presses a key that does not correspond to any mnemonic or accelerator key. This message is sent to the window that owns the menu.
WM_MENUCOMMAND	0x126	The WM_MENUCOMMAND message is sent when the user makes a selection from a menu.
WM_MENUDRAG	0x123	The WM_MENUDRAG message is sent to the owner of a drag-and-drop menu when the user drags a menu item.
WM_MENUGETOBJECT	0x124	The WM_MENUGETOBJECT message is sent to the owner of a drag-and-drop menu when the mouse cursor enters a menu item or moves from the center of the item to the top or bottom of the item.
WM_MENURBUTTONUP	0x122	The WM_MENURBUTTONUP message is sent when the user releases the right mouse button while the cursor is on a menu item.
WM_MENUSELECT	0x11F	The WM_MENUSELECT message is sent to a menu's owner window when the user selects a menu item.
WM_MOUSEACTIVATE	0x21	The WM_MOUSEACTIVATE message is sent when the cursor is in an inactive window and the user presses a mouse button. The parent window receives this message only if the child window passes it to the DefWindowProc function.
WM_MOUSEFIRST	0x200	Use WM_MOUSEFIRST to specify the first mouse message. Use the PeekMessage() Function.
WM_MOUSEHOVER	0x2A1	The WM_MOUSEHOVER message is posted to a window when the cursor hovers over the client area of the window for the period of time specified in a prior call to TrackMouseEvent.
WM_MOUSELAST	0x20D	Definition Needed
WM_MOUSELEAVE	0x2A3	The WM_MOUSELEAVE message is posted to a window when the cursor leaves the client area of the window specified in a prior call to TrackMouseEvent.
WM_MOUSEMOVE	0x200	The WM_MOUSEMOVE message is posted to a window when the cursor moves. If the mouse is not captured, the message is posted to the window that contains the cursor. Otherwise, the message is posted to the window that has captured the mouse.
WM_MOUSEWHEEL	0x20A	The WM_MOUSEWHEEL message is sent to the focus window when the mouse wheel is rotated. The DefWindowProcfunction propagates the message to the window's parent. There should be no internal forwarding of the message, sinceDefWindowProc propagates it up the parent chain until it finds a window that processes it.
WM_MOUSEHWHEEL	0x20E	The WM_MOUSEHWHEEL message is sent to the focus window when the mouse's horizontal scroll wheel is tilted or rotated. The DefWindowProc function propagates the message to the window's parent. There should be no internal forwarding of the message, since DefWindowProc propagates it up the parent chain until it finds a window that processes it.
WM_MOVE	0x3	The WM_MOVE message is sent after a window has been moved.
WM_MOVING	0x216	The WM_MOVING message is sent to a window that the user is moving. By processing this message, an application can monitor the position of the drag rectangle and, if needed, change its position.
WM_NCACTIVATE	0x86	Non Client Area Activated Caption(Title) of the Form
WM_NCCALCSIZE	0x83	The WM_NCCALCSIZE message is sent when the size and position of a window's client area must be calculated. By processing this message, an application can control the content of the window's client area when the size or position of the window changes.
WM_NCCREATE	0x81	The WM_NCCREATE message is sent prior to the WM_CREATE message when a window is first created.
WM_NCDESTROY	0x82	The WM_NCDESTROY message informs a window that its nonclient area is being destroyed. The DestroyWindow function sends the WM_NCDESTROY message to the window following the WM_DESTROY message. WM_DESTROY is used to free the allocated memory object associated with the window.
WM_NCHITTEST	0x84	The WM_NCHITTEST message is sent to a window when the cursor moves, or when a mouse button is pressed or released. If the mouse is not captured, the message is sent to the window beneath the cursor. Otherwise, the message is sent to the window that has captured the mouse.
WM_NCLBUTTONDBLCLK	0xA3	The WM_NCLBUTTONDBLCLK message is posted when the user double-clicks the left mouse button while the cursor is within the nonclient area of a window. This message is posted to the window that contains the cursor. If a window has captured the mouse, this message is not posted.
WM_NCLBUTTONDOWN	0xA1	The WM_NCLBUTTONDOWN message is posted when the user presses the left mouse button while the cursor is within the nonclient area of a window. This message is posted to the window that contains the cursor. If a window has captured the mouse, this message is not posted.
WM_NCLBUTTONUP	0xA2	The WM_NCLBUTTONUP message is posted when the user releases the left mouse button while the cursor is within the nonclient area of a window. This message is posted to the window that contains the cursor. If a window has captured the mouse, this message is not posted.
WM_NCMBUTTONDBLCLK	0xA9	The WM_NCMBUTTONDBLCLK message is posted when the user double-clicks the middle mouse button while the cursor is within the nonclient area of a window. This message is posted to the window that contains the cursor. If a window has captured the mouse, this message is not posted.
WM_NCMBUTTONDOWN	0xA7	The WM_NCMBUTTONDOWN message is posted when the user presses the middle mouse button while the cursor is within the nonclient area of a window. This message is posted to the window that contains the cursor. If a window has captured the mouse, this message is not posted.
WM_NCMBUTTONUP	0xA8	The WM_NCMBUTTONUP message is posted when the user releases the middle mouse button while the cursor is within the nonclient area of a window. This message is posted to the window that contains the cursor. If a window has captured the mouse, this message is not posted.
WM_NCMOUSEHOVER	0x2A0	The WM_NCMOUSEHOVER message is posted to a window when the cursor hovers over the nonclient area of the window for the period of time specified in a prior call to TrackMouseEvent.
WM_NCMOUSELEAVE	0x2A2	The WM_NCMOUSELEAVE message is posted to a window when the cursor leaves the nonclient area of the window specified in a prior call to TrackMouseEvent.
WM_NCMOUSEMOVE	0xA0	The WM_NCMOUSEMOVE message is posted to a window when the cursor is moved within the nonclient area of the window. This message is posted to the window that contains the cursor. If a window has captured the mouse, this message is not posted.
WM_NCPAINT	0x85	The WM_NCPAINT message is sent to a window when its frame must be painted.
WM_NCRBUTTONDBLCLK	0xA6	The WM_NCRBUTTONDBLCLK message is posted when the user double-clicks the right mouse button while the cursor is within the nonclient area of a window. This message is posted to the window that contains the cursor. If a window has captured the mouse, this message is not posted.
WM_NCRBUTTONDOWN	0xA4	The WM_NCRBUTTONDOWN message is posted when the user presses the right mouse button while the cursor is within the nonclient area of a window. This message is posted to the window that contains the cursor. If a window has captured the mouse, this message is not posted.
WM_NCRBUTTONUP	0xA5	The WM_NCRBUTTONUP message is posted when the user releases the right mouse button while the cursor is within the nonclient area of a window. This message is posted to the window that contains the cursor. If a window has captured the mouse, this message is not posted.
WM_NCXBUTTONDBLCLK	0xAD	The WM_NCXBUTTONDBLCLK message is posted when the user double-clicks the first or second X button while the cursor is within the nonclient area of a window. This message is posted to the window that contains the cursor. If a window has captured the mouse, this message is not posted.
WM_NCXBUTTONDOWN	0xAB	The WM_NCXBUTTONDOWN message is posted when the user presses the first or second X button while the cursor is within the nonclient area of a window. This message is posted to the window that contains the cursor. If a window has captured the mouse, this message is not posted.
WM_NCXBUTTONUP	0xAC	The WM_NCXBUTTONUP message is posted when the user releases the first or second X button while the cursor is within the nonclient area of a window. This message is posted to the window that contains the cursor. If a window has captured the mouse, this message is not posted.
WM_NCUAHDRAWCAPTION	0xAE	The WM_NCUAHDRAWCAPTION message is an undocumented message related to themes. When handling WM_NCPAINT, this message should also be handled.
WM_NCUAHDRAWFRAME	0xAF	The WM_NCUAHDRAWFRAME message is an undocumented message related to themes. When handling WM_NCPAINT, this message should also be handled.
WM_NEXTDLGCTL	0x28	The WM_NEXTDLGCTL message is sent to a dialog box procedure to set the keyboard focus to a different control in the dialog box
WM_NEXTMENU	0x213	The WM_NEXTMENU message is sent to an application when the right or left arrow key is used to switch between the menu bar and the system menu.
WM_NOTIFY	0x4E	Sent by a common control to its parent window when an event has occurred or the control requires some information.
WM_NOTIFYFORMAT	0x55	Determines if a window accepts ANSI or Unicode structures in the WM_NOTIFY notification message. WM_NOTIFYFORMAT messages are sent from a common control to its parent window and from the parent window to the common control.
WM_NULL	0x0	The WM_NULL message performs no operation. An application sends the WM_NULL message if it wants to post a message that the recipient window will ignore.
WM_PAINT	0xF	Occurs when the control needs repainting
WM_PAINTCLIPBOARD	0x309	The WM_PAINTCLIPBOARD message is sent to the clipboard owner by a clipboard viewer window when the clipboard contains data in the CF_OWNERDISPLAY format and the clipboard viewer's client area needs repainting.
WM_PAINTICON	0x26	Windows NT 3.51 and earlier: The WM_PAINTICON message is sent to a minimized window when the icon is to be painted. This message is not sent by newer versions of Microsoft Windows, except in unusual circumstances explained in the Remarks.
WM_PALETTECHANGED	0x311	This message is sent by the OS to all top-level and overlapped windows after the window with the keyboard focus realizes its logical palette. This message enables windows that do not have the keyboard focus to realize their logical palettes and update their client areas.
WM_PALETTEISCHANGING	0x310	The WM_PALETTEISCHANGING message informs applications that an application is going to realize its logical palette.
WM_PARENTNOTIFY	0x210	The WM_PARENTNOTIFY message is sent to the parent of a child window when the child window is created or destroyed, or when the user clicks a mouse button while the cursor is over the child window. When the child window is being created, the system sends WM_PARENTNOTIFY just before the CreateWindow or CreateWindowEx function that creates the window returns. When the child window is being destroyed, the system sends the message before any processing to destroy the window takes place.
WM_PASTE	0x302	An application sends a WM_PASTE message to an edit control or combo box to copy the current content of the clipboard to the edit control at the current caret position. Data is inserted only if the clipboard contains data in CF_TEXT format.
WM_PENWINFIRST	0x380	Definition Needed
WM_PENWINLAST	0x38F	Definition Needed
WM_POWER	0x48	Notifies applications that the system, typically a battery-powered personal computer, is about to enter a suspended mode. Obsolete : use POWERBROADCAST instead
WM_POWERBROADCAST	0x218	Notifies applications that a power-management event has occurred.
WM_PRINT	0x317	The WM_PRINT message is sent to a window to request that it draw itself in the specified device context, most commonly in a printer device context.
WM_PRINTCLIENT	0x318	The WM_PRINTCLIENT message is sent to a window to request that it draw its client area in the specified device context, most commonly in a printer device context.
WM_QUERYDRAGICON	0x37	The WM_QUERYDRAGICON message is sent to a minimized (iconic) window. The window is about to be dragged by the user but does not have an icon defined for its class. An application can return a handle to an icon or cursor. The system displays this cursor or icon while the user drags the icon.
WM_QUERYENDSESSION	0x11	The WM_QUERYENDSESSION message is sent when the user chooses to end the session or when an application calls one of the system shutdown functions. If any application returns zero, the session is not ended. The system stops sending WM_QUERYENDSESSION messages as soon as one application returns zero. After processing this message, the system sends the WM_ENDSESSION message with the wParam parameter set to the results of the WM_QUERYENDSESSION message.
WM_QUERYNEWPALETTE	0x30F	This message informs a window that it is about to receive the keyboard focus, giving the window the opportunity to realize its logical palette when it receives the focus.
WM_QUERYOPEN	0x13	The WM_QUERYOPEN message is sent to an icon when the user requests that the window be restored to its previous size and position.
WM_QUEUESYNC	0x23	The WM_QUEUESYNC message is sent by a computer-based training (CBT) application to separate user-input messages from other messages sent through the WH_JOURNALPLAYBACK Hook procedure.
WM_QUIT	0x12	Once received, it ends the application's Message Loop, signaling the application to end. It can be sent by pressing Alt+F4, Clicking the X in the upper right-hand of the program, or going to File->Exit.
WM_RBUTTONDBLCLK	0x206	he WM_RBUTTONDBLCLK message is posted when the user double-clicks the right mouse button while the cursor is in the client area of a window. If the mouse is not captured, the message is posted to the window beneath the cursor. Otherwise, the message is posted to the window that has captured the mouse.
WM_RBUTTONDOWN	0x204	The WM_RBUTTONDOWN message is posted when the user presses the right mouse button while the cursor is in the client area of a window. If the mouse is not captured, the message is posted to the window beneath the cursor. Otherwise, the message is posted to the window that has captured the mouse.
WM_RBUTTONUP	0x205	The WM_RBUTTONUP message is posted when the user releases the right mouse button while the cursor is in the client area of a window. If the mouse is not captured, the message is posted to the window beneath the cursor. Otherwise, the message is posted to the window that has captured the mouse.
WM_RENDERALLFORMATS	0x306	The WM_RENDERALLFORMATS message is sent to the clipboard owner before it is destroyed, if the clipboard owner has delayed rendering one or more clipboard formats. For the content of the clipboard to remain available to other applications, the clipboard owner must render data in all the formats it is capable of generating, and place the data on the clipboard by calling the SetClipboardData function.
WM_RENDERFORMAT	0x305	The WM_RENDERFORMAT message is sent to the clipboard owner if it has delayed rendering a specific clipboard format and if an application has requested data in that format. The clipboard owner must render data in the specified format and place it on the clipboard by calling the SetClipboardData function.
WM_SETCURSOR	0x20	The WM_SETCURSOR message is sent to a window if the mouse causes the cursor to move within a window and mouse input is not captured.
WM_SETFOCUS	0x7	When the controll got the focus
WM_SETFONT	0x30	An application sends a WM_SETFONT message to specify the font that a control is to use when drawing text.
WM_SETHOTKEY	0x32	An application sends a WM_SETHOTKEY message to a window to associate a hot key with the window. When the user presses the hot key, the system activates the window.
WM_SETICON	0x80	An application sends the WM_SETICON message to associate a new large or small icon with a window. The system displays the large icon in the ALT+TAB dialog box, and the small icon in the window caption.
WM_SETREDRAW	0xB	An application sends the WM_SETREDRAW message to a window to allow changes in that window to be redrawn or to prevent changes in that window from being redrawn.
WM_SETTEXT	0xC	Text / Caption changed on the control. An application sends a WM_SETTEXT message to set the text of a window.
WM_SETTINGCHANGE	0x1A	An application sends the WM_SETTINGCHANGE message to all top-level windows after making a change to the WIN.INI file. The SystemParametersInfo function sends this message after an application uses the function to change a setting in WIN.INI.
WM_SHOWWINDOW	0x18	The WM_SHOWWINDOW message is sent to a window when the window is about to be hidden or shown
WM_SIZE	0x5	The WM_SIZE message is sent to a window after its size has changed.
WM_SIZECLIPBOARD	0x30B	The WM_SIZECLIPBOARD message is sent to the clipboard owner by a clipboard viewer window when the clipboard contains data in the CF_OWNERDISPLAY format and the clipboard viewer's client area has changed size.
WM_SIZING	0x214	The WM_SIZING message is sent to a window that the user is resizing. By processing this message, an application can monitor the size and position of the drag rectangle and, if needed, change its size or position.
WM_SPOOLERSTATUS	0x2A	The WM_SPOOLERSTATUS message is sent from Print Manager whenever a job is added to or removed from the Print Manager queue.
WM_STYLECHANGED	0x7D	The WM_STYLECHANGED message is sent to a window after the SetWindowLong function has changed one or more of the window's styles.
WM_STYLECHANGING	0x7C	The WM_STYLECHANGING message is sent to a window when the SetWindowLong function is about to change one or more of the window's styles.
WM_SYNCPAINT	0x88	The WM_SYNCPAINT message is used to synchronize painting while avoiding linking independent GUI threads.
WM_SYSCHAR	0x106	The WM_SYSCHAR message is posted to the window with the keyboard focus when a WM_SYSKEYDOWN message is translated by the TranslateMessage function. It specifies the character code of a system character key — that is, a character key that is pressed while the ALT key is down.
WM_SYSCOLORCHANGE	0x15	This message is sent to all top-level windows when a change is made to a system color setting.
WM_SYSCOMMAND	0x112	A window receives this message when the user chooses a command from the Window menu (formerly known as the system or control menu) or when the user chooses the maximize button, minimize button, restore button, or close button.
WM_SYSDEADCHAR	0x107	The WM_SYSDEADCHAR message is sent to the window with the keyboard focus when a WM_SYSKEYDOWN message is translated by the TranslateMessage function. WM_SYSDEADCHAR specifies the character code of a system dead key — that is, a dead key that is pressed while holding down the ALT key.
WM_SYSKEYDOWN	0x104	The WM_SYSKEYDOWN message is posted to the window with the keyboard focus when the user presses the F10 key (which activates the menu bar) or holds down the ALT key and then presses another key. It also occurs when no window currently has the keyboard focus; in this case, the WM_SYSKEYDOWN message is sent to the active window. The window that receives the message can distinguish between these two contexts by checking the context code in the lParam parameter.
WM_SYSKEYUP	0x105	The WM_SYSKEYUP message is posted to the window with the keyboard focus when the user releases a key that was pressed while the ALT key was held down. It also occurs when no window currently has the keyboard focus; in this case, the WM_SYSKEYUP message is sent to the active window. The window that receives the message can distinguish between these two contexts by checking the context code in the lParam parameter.
WM_TCARD	0x52	Sent to an application that has initiated a training card with Microsoft Windows Help. The message informs the application when the user clicks an authorable button. An application initiates a training card by specifying the HELP_TCARD command in a call to the WinHelp function.
WM_TIMECHANGE	0x1E	A message that is sent whenever there is a change in the system time.
WM_TIMER	0x113	The WM_TIMER message is posted to the installing thread's message queue when a timer expires. The message is posted by the GetMessage or PeekMessage function.
WM_UNDO	0x304	An application sends a WM_UNDO message to an edit control to undo the last operation. When this message is sent to an edit control, the previously deleted text is restored or the previously added text is deleted.
WM_UNINITMENUPOPUP	0x125	The WM_UNINITMENUPOPUP message is sent when a drop-down menu or submenu has been destroyed.
WM_USER	0x400	The WM_USER constant is used by applications to help define private messages for use by private window classes, usually of the form WM_USER+X, where X is an integer value.
WM_USERCHANGED	0x54	The WM_USERCHANGED message is sent to all windows after the user has logged on or off. When the user logs on or off, the system updates the user-specific settings. The system sends this message immediately after updating the settings.
WM_VKEYTOITEM	0x2E	Sent by a list box with the LBS_WANTKEYBOARDINPUT style to its owner in response to a WM_KEYDOWN message.
WM_VSCROLL	0x115	The WM_VSCROLL message is sent to a window when a scroll event occurs in the window's standard vertical scroll bar. This message is also sent to the owner of a vertical scroll bar control when a scroll event occurs in the control.
WM_VSCROLLCLIPBOARD	0x30A	The WM_VSCROLLCLIPBOARD message is sent to the clipboard owner by a clipboard viewer window when the clipboard contains data in the CF_OWNERDISPLAY format and an event occurs in the clipboard viewer's vertical scroll bar. The owner should scroll the clipboard image and update the scroll bar values.
WM_WINDOWPOSCHANGED	0x47	The WM_WINDOWPOSCHANGED message is sent to a window whose size, position, or place in the Z order has changed as a result of a call to the SetWindowPos function or another window-management function.
WM_WINDOWPOSCHANGING	0x46	The WM_WINDOWPOSCHANGING message is sent to a window whose size, position, or place in the Z order is about to change as a result of a call to the SetWindowPos function or another window-management function.
WM_WININICHANGE	0x1A	An application sends the WM_WININICHANGE message to all top-level windows after making a change to the WIN.INI file. The SystemParametersInfo function sends this message after an application uses the function to change a setting in WIN.INI. Note The WM_WININICHANGE message is provided only for compatibility with earlier versions of the system. Applications should use the WM_SETTINGCHANGE message.
WM_XBUTTONDBLCLK	0x20D	The WM_XBUTTONDBLCLK message is posted when the user double-clicks the first or second X button while the cursor is in the client area of a window. If the mouse is not captured, the message is posted to the window beneath the cursor. Otherwise, the message is posted to the window that has captured the mouse.
WM_XBUTTONDOWN	0x20B	The WM_XBUTTONDOWN message is posted when the user presses the first or second X button while the cursor is in the client area of a window. If the mouse is not captured, the message is posted to the window beneath the cursor. Otherwise, the message is posted to the window that has captured the mouse.
WM_XBUTTONUP	0x20C	The WM_XBUTTONUP message is posted when the user releases the first or second X button while the cursor is in the client area of a window. If the mouse is not captured, the message is posted to the window beneath the cursor. Otherwise, the message is posted to the window that has captured the mouse.

重写 WndProc必须引用DLL并声明：
//返回hWnd参数所指定的窗口的设备环境。
[System.Runtime.InteropServices.DllImport("user32.dll")]
static extern IntPtr GetWindowDC(IntPtr hWnd);
//函数释放设备上下文环境（DC）
[System.Runtime.InteropServices.DllImport("user32.dll")]
static extern int ReleaseDC(IntPtr hWnd, IntPtr hDC);