二、Windows菜单—浮动弹出式菜单
您还可以在没有顶层菜单列的情况下使用菜单，也就是说，您可以使弹出式菜单出现在屏幕顶层的任何位置。一种方法是使用鼠标右键来启动弹出式菜单。程序10-6所示的POPMENU说明了这种方法。
程序10-6 POPMENU
POPMENU.C
/*----------------------------------------------------------------------
POPMENU.C -- Popup Menu Demonstration
(c) Charles Petzold, 1998
-------------------------------------------------------------------------*/
#include <windows.h>
#include "resource.h"
LRESULT CALLBACK WndProc (HWND, UINT, WPARAM, LPARAM) ;
HINSTANCE hInst ;
TCHAR szAppName[] = TEXT ("PopMenu") ;
int WINAPI WinMain (HINSTANCE hInstance, HINSTANCE hPrevInstance,
PSTR szCmdLine, int iCmdShow)
{
HWND hwnd ;
MSG msg ;
WNDCLASS wndclass ;
wndclass.style = CS_HREDRAW | CS_VREDRAW ;
wndclass.lpfnWndProc = WndProc ;
wndclass.cbClsExtra = 0 ;
wndclass.cbWndExtra = 0 ;
wndclass.hInstance = hInstance ;
wndclass.hIcon = LoadIcon (NULL, szAppName) ;
wndclass.hCursor = LoadCursor (NULL, IDC_ARROW) ;
wndclass.hbrBackground = (HBRUSH) GetStockObject (WHITE_BRUSH) ;
wndclass.lpszMenuName = NULL ;
wndclass.lpszClassName = szAppName ;
if (!RegisterClass (&wndclass))
{
MessageBox ( NULL, TEXT ("This program requires Windows NT!"),
szAppName, MB_ICONERROR) ;
return 0 ;
}
hInst = hInstance ;
hwnd = CreateWindow ( szAppName, TEXT ("Popup Menu Demonstration"),
WS_OVERLAPPEDWINDOW,
CW_USEDEFAULT, CW_USEDEFAULT,
CW_USEDEFAULT, CW_USEDEFAULT,
NULL, NULL, hInstance, NULL) ;
ShowWindow (hwnd, iCmdShow) ;
UpdateWindow (hwnd) ;
while (GetMessage (&msg, NULL, 0, 0))
{
TranslateMessage (&msg) ;
DispatchMessage (&msg) ;
}
return msg.wParam ;
}
LRESULT CALLBACK WndProc ( HWND hwnd, UINT message, WPARAM wParam,LPARAM lParam)
{
static HMENU hMenu ;
static int idColor [5] = {WHITE_BRUSH, LTGRAY_BRUSH, GRAY_BRUSH,
DKGRAY_BRUSH, BLACK_BRUSH } ;
static int iSelection = IDM_BKGND_WHITE ;
POINT point ;
switch (message)
{
case WM_CREATE:
hMenu = LoadMenu (hInst, szAppName) ;
hMenu = GetSubMenu (hMenu, 0) ;
return 0 ;
case WM_RBUTTONUP:
point.x = LOWORD (lParam) ;
point.y = HIWORD (lParam) ;
ClientToScreen (hwnd, &point) ;
TrackPopupMenu (hMenu, TPM_RIGHTBUTTON, point.x, point.y, 0, hwnd, NULL) ;
return 0 ;
case WM_COMMAND:
switch (LOWORD (wParam))
{
case IDM_FILE_NEW:
case IDM_FILE_OPEN:
case IDM_FILE_SAVE:
case IDM_FILE_SAVE_AS:
case IDM_EDIT_UNDO:
case IDM_EDIT_CUT:
case IDM_EDIT_COPY:
case IDM_EDIT_PASTE:
case IDM_EDIT_CLEAR:
MessageBeep (0) ;
return 0 ;
case IDM_BKGND_WHITE: // Note: Logic below
case IDM_BKGND_LTGRAY: // assumes that IDM_WHITE
case IDM_BKGND_GRAY: // through IDM_BLACK are
case IDM_BKGND_DKGRAY: // consecutive numbers in
case IDM_BKGND_BLACK: // the order shown here.
CheckMenuItem (hMenu, iSelection, MF_UNCHECKED) ;
iSelection = LOWORD (wParam) ;
CheckMenuItem (hMenu, iSelection, MF_CHECKED) ;
SetClassLong (hwnd, GCL_HBRBACKGROUND, (LONG)
GetStockObject
(idColor [LOWORD (wParam) - IDM_BKGND_WHITE])) ;
InvalidateRect (hwnd, NULL, TRUE) ;
return 0 ;
case IDM_APP_ABOUT:
MessageBox (hwnd, TEXT ("Popup Menu Demonstration Program\n")
TEXT ("(c) Charles Petzold, 1998"),
szAppName, MB_ICONINFORMATION | MB_OK) ;
return 0 ;
case IDM_APP_EXIT:
SendMessage (hwnd, WM_CLOSE, 0, 0) ;
return 0 ;
case IDM_APP_HELP:
MessageBox (hwnd, TEXT ("Help not yet implemented!"),
szAppName, MB_ICONEXCLAMATION | MB_OK) ;
return 0 ;
}
break ;
case WM_DESTROY:
PostQuitMessage (0) ;
return 0 ;
}
return DefWindowProc (hwnd, message, wParam, lParam) ;
}
POPMENU.RC （摘录）
//Microsoft Developer Studio generated resource script.
#include "resource.h"
#include "afxres.h"
/////////////////////////////////////////////////////////////////////////////
// Menu
POPMENU MENU DISCARDABLE
BEGIN
POPUP "MyMenu"
BEGIN
POPUP "&File"
BEGIN
MENUITEM "&New", IDM_FILE_NEW
MENUITEM "&Open", IDM_FILE_OPEN
MENUITEM "&Save", IDM_FILE_SAVE
MENUITEM "Save &As", IDM_FILE_SAVE_AS
MENUITEM SEPARATOR
MENUITEM "E&xit", IDM_APP_EXIT
END
POPUP "&Edit"
BEGIN
MENUITEM "&Undo", IDM_EDIT_UNDO
MENUITEM SEPARATOR
MENUITEM "Cu&t", IDM_EDIT_CUT
MENUITEM "&Copy", IDM_EDIT_COPY
MENUITEM "&Paste", IDM_EDIT_PASTE
MENUITEM "De&lete", IDM_EDIT_CLEAR
END
POPUP "&Background"
BEGIN
MENUITEM "&White", IDM_BKGND_WHITE, CHECKED
MENUITEM "&Light Gray", IDM_BKGND_LTGRAY
MENUITEM "&Gray", IDM_BKGND_GRAY
MENUITEM "&Dark Gray", IDM_BKGND_DKGRAY
MENUITEM "&Black", IDM_BKGND_BLACK
END
POPUP "&Help"
BEGIN
MENUITEM "&Help...", IDM_APP_HELP
MENUITEM "&About PopMenu...", IDM_APP_ABOUT
END
END
END
RESOURCE.H （摘录）
// Microsoft Developer Studio generated include file.
// Used by PopMenu.rc
#define IDM_FILE_NEW 40001
#define IDM_FILE_OPEN 40002
#define IDM_FILE_SAVE 40003
#define IDM_FILE_SAVE_AS 40004
#define IDM_APP_EXIT 40005
#define IDM_EDIT_UNDO 40006
#define IDM_EDIT_CUT 40007
#define IDM_EDIT_COPY 40008
#define IDM_EDIT_PASTE 40009
#define IDM_EDIT_CLEAR 40010
#define IDM_BKGND_WHITE 40011
#define IDM_BKGND_LTGRAY 40012
#define IDM_BKGND_GRAY 40013
#define IDM_BKGND_DKGRAY 40014
#define IDM_BKGND_BLACK 40015
#define IDM_APP_HELP 40016
#define IDM_APP_ABOUT 40017
资源描述档POPMENU.RC定义的菜单与MENUDEMO.RC中的菜单非常相似。不同的是，在顶层菜单中只包含一项－一个弹出式菜单「MyMenu」，它呼叫「File」、「Edit」、「Background」和「Help」选项。这四个选项垂直一行地出现在弹出式菜单上，而不是水平一列地出现在主菜单上。
在WndProc中的WM_CREATE处理期间，POPMENU取得此弹出式菜单的句柄，就是带有文字「MyMenu」的那个弹出式菜单：
hMenu = LoadMenu (hInst, szAppName) ;
hMenu = GetSubMenu (hMenu, 0) ;
在WM_RBUTTONUP消息处理期间，POPMENU提供了鼠标指针的位置，将此位置转换为屏幕坐标，再将坐标值传递给TrackPopupMenu：
point.x = LOWORD (lParam) ;
point.y = HIWORD (lParam) ;
ClientToScreen (hwnd, &point) ;
TrackPopupMenu (hMenu, TPM_RIGHTBUTTON, point.x, point.y,
0, hwnd, NULL) ;
然后，Windows显示出具有「File」、「Edit」、「Background」和「Help」项的弹出式菜单。选择其中任何一项都可以使嵌套的弹出式菜单显示在右边，菜单函数与一般的菜单一样。
如果要使用与该程序的主菜单相同的菜单并带有TrackPopupMenu，您会遇到一些问题，因为函数需要弹出式菜单句柄。在「Microsoft Knowledge Base」文章ID Q99806有提供一些信息。
