windows提供的鼠标移出消息有时候很有用，但是vb6中没有把这个事件封装给我们。
但是我们仍然可以使用子类化技术实现他，下面的代码就是一个简单的例子来处理windows的
wm_mouseleave消息的，我演示的是鼠标移出一个button时的情形。
1.加入一个模块，专门用来处理子类函数：
option explicit
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'copyright 2002 40star, all rights reserved.
'
'e-mail ：40star@163.com
'distribution：你可以完全自由随便的使用这段代码，不管你用于任何目的
' 程序在于交流和学习
' 如有任何bug请和我联系
'
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private declare function sendmessage lib "user32" alias "sendmessagea" _
(byval hwnd as long, byval wmsg as long, _
byval wparam as long, lparam as string) as long
private declare function getwindowlong lib "user32" alias _
"getwindowlonga" (byval hwnd as long, _
byval nindex as long) as long
private declare function setwindowlong lib "user32" alias _
"setwindowlonga" (byval hwnd as long, byval nindex _
as long, byval dwnewlong as long) as long
private declare function callwindowproc lib "user32" alias _
"callwindowproca" (byval lpprevwndfunc as long, byval _
hwnd as long, byval msg as long, byval wparam as _
long, byval lparam as long) as long
const gwl_wndproc = (-4&)
dim prevwndproc&
private const wm_destroy = &h2
public declare function trackmouseevent lib "user32" (lpeventtrack as trackmouseeventtype) as long
public const tme_cancel = &h80000000
public const tme_hover = &h1&
public const tme_leave = &h2&
public const tme_nonclient = &h10&
public const tme_query = &h40000000
private const wm_mouseleave = &h2a3&
public type trackmouseeventtype
cbsize as long
dwflags as long
hwndtrack as long
dwhovertime as long
end type
public btracking as boolean
dim evttrack as trackmouseeventtype
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private function subwndproc(byval hwnd as long, byval msg as long, _
byval wparam as long, byval lparam as long) _
as long
if msg = wm_destroy then terminate (hwnd)
'处理鼠标移出消息
if msg = wm_mouseleave then
btracking = false
form1.print "the mouse left the form!"
end if
subwndproc = callwindowproc(prevwndproc, hwnd, msg, wparam, lparam)
end function
public sub init(hwnd as long)
prevwndproc = setwindowlong(hwnd, gwl_wndproc, addressof subwndproc)
end sub
public sub terminate(hwnd as long)
call setwindowlong(hwnd, gwl_wndproc, prevwndproc)
end sub
' -- 模块结束 -- '
2. 窗体中处理需要加入的代码：
option explicit
private sub command1_mousemove(button as integer, shift as integer, x as single, y as single)
if btracking = false then
btracking = true
dim et as trackmouseeventtype
'initialize structure
et.cbsize = len(et)
et.hwndtrack = command1.hwnd
et.dwflags = tme_leave
'start the tracking
trackmouseevent et
end if
end sub
private sub form_load()
call init(command1.hwnd)
end sub
private sub form_unload(cancel as integer)
call terminate(command1.hwnd)
end sub
此例程在win2000 + vb6中调试通过
