Modifying Smartphone menu bars in runtime

By Alexander Shargin, June 03, 2002.

Introduction

Menu bars are important part of Smartphone user interface. Smartphone 2002 SDK documentation describes how to create menu bars using SHCreateMenuBar function. But sometimes you need to modify existing menu bar in runtime. The documentation doesn't provide any details on how to do this but samples from Smartphone 2002 SDK give some hints. The main idea is to treat menu bar as a toolbar and use TB_GETBUTTONINFO/TB_SETBUTTONINFO messages to manipulate it.

Note: there are other TB_* messages for toolbars but menu bar seems to ignore them.

In this article I'll show some code examples illustrating how to change different aspects of menu bars. I'll assume that the menu bar was created using the following resource template:

IDR_MAINMENU RCDATA BEGIN IDR_POPUP, 2, I_IMAGENONE, IDM_ACTION, TBSTATE_ENABLED, TBSTYLE_BUTTON | TBSTYLE_AUTOSIZE, IDS_ACTION, 0, NOMENU, I_IMAGENONE, IDM_MENU, TBSTATE_ENABLED, TBSTYLE_DROPDOWN | TBSTYLE_AUTOSIZE, IDS_MENU, 0, 0, END

The first item of this menu acts like button, the second one has popup menu associated with it. Also I'll assume that the HWND of menu bar was stored in hMenuBar variable.

Note: HWND of menu bar is extracted from SHMENUBARINFO::hwndMB member variable after SHCreateMenuBar functions returns. If you don't want to store this HWND permanently you can find it any time using SHFindMenuBar function.

Enabling/disabling menu bar items.

This code disables menu bar item IDM_ACTION:

TBBUTTONINFO tbbi; tbbi.cbSize = sizeof(tbbi); tbbi.dwMask = TBIF_STATE; tbbi.fsState = TBSTATE_INDETERMINATE; ::SendMessage (hMenuBar, TB_SETBUTTONINFO, IDM_ACTION, (LPARAM)&tbbi);

To enable item again similar code is used. The only difference is in fsState variable which is set to TBSTATE_ENABLED instead of TBSTATE_INDETERMINATE.

Changing text of menu bar items

The following code fragment is used to change label of IDM_MENU item to "Tools".

TBBUTTONINFO tbbi; tbbi.cbSize = sizeof(tbbi); tbbi.dwMask = TBIF_TEXT; tbbi.pszText = _T("Tools"); ::SendMessage (hMenuBar, TB_SETBUTTONINFO, IDM_MENU, (LPARAM)&tbbi);

You can also obtain item text from menu bar, e. g.:

TBBUTTONINFO tbbi; TCHAR szBuf[255]; tbbi.cbSize = sizeof(tbbi); tbbi.dwMask = TBIF_TEXT; tbbi.pszText = szBuf; tbbi.cchText = sizeof(szBuf)/sizeof(szBuf[0]); ::SendMessage (hMenuBar, TB_GETBUTTONINFO, IDM_MENU, (LPARAM)&tbbi);

Changing command id associated with menu bar item

SOmetimes you need to change command id associated with menu bar item "on the fly". The following sample changes IDM_ACTION item's command id to 0x1234.

TBBUTTONINFO tbbi; tbbi.cbSize = sizeof(tbbi); tbbi.dwMask = TBIF_COMMAND; tbbi.idCommand = 0x1234; ::SendMessage (hMenuBar, TB_SETBUTTONINFO, IDM_ACTION, (LPARAM)&tbbi);

Note that after command id is changed you must use new command id to manipulate the item.

Manipulating popup menu associated with menu bar item

You may also want to change popup menu associated with menu bar item (add/remove items, enable/disable them etc.). HMENU of this popup menu is obtained through TBBUTTONINFO::lParam member variable:

TBBUTTONINFO tbbi; tbbi.cbSize = sizeof(tbbi); tbbi.dwMask = TBIF_LPARAM; ::SendMessage (hMenuBar, TB_GETBUTTONINFO, IDM_MENU, (LPARAM)&tbbi); HMENU hPopupMenu = (HMENU)tbbi.lParam; // Use hPopupMenu to change popup menu

Note that you can not change popup menu handle associated with menu bar item or remove it completely by setting item style to TBSTYLE_BUTTON.

Conclusion

Smartphone menu bars can be easily updated "on the fly". The documentation is somewhat obscure but with a little experimentation it's not hard to implement required functionality.

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