Customizable Toolbar: Implementing a toolbar combo button

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Roland Knight
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1 Customizable Toolbar: Implementing a toolbar combo button Problem How do I implement a Combo Button on my toolbar? I'm having trouble getting notifications, filling the list, adding to the list, or handling events. Cause The purpose of this article is to resolve the most common problems that come up when using the SECComboBtn class on the SECCustomToolBar. The combo button is added to the toolbar using a button map and the COMBO_BUTTON macro. For more information regarding adding this and other specialized buttons to the SECCustomToolBar please refer to the customizable toolbar section in the user's guide. Action This article does not go through the mechanics of adding a SECComboBtn, but describe common tasks associated with using a combo in a SECCustomToolBar. These include: Modifying the SECCustomToolBar to route notifications. Getting a pointer to the combo button. Adding a string to the list. Filling the default list for the combo button. Implementing the handler for the combo button events. A sample is available which shows all of the included code in an operating application. Modifying the SECCustomToolBar to route notifications. The first hurdle to be overcome is that the SECCustomToolBar, like most control bars does not participate in message routing as a CView derivative would. This can be easily overcome by implementing a notification mechanism when deriving from the SECCustomToolBar class. For more information about deriving from SECCustomToolBar, please see the article "How can I get the toolbar manager to recognize my SECCustomToolBar derived class?" BOOL CCustomNotifyToolBar::OnCommand(WPARAM wparam, LPARAM lparam) CMainFrame* pframe =((CMainFrame*)AfxGetMainWnd()); CView* pview; SECMDIChildWnd* pchild = (SECMDIChildWnd*) pframe->getactiveframe(); // Get the active view attached to the active MDI child // window. If SDI Returns the frame pview = (CView *) pchild->getactiveview(); if(null!= pview) pview->sendmessage(wmsectoolbarwndnotify,wparam,lparam); else pframe->sendmessage(wmsectoolbarwndnotify,wparam,lparam); return SECControlBar::OnCommand(wParam,lParam); This is the only function that is overridden in this class. This toolbar class is substituted for SECCustomToolBar by setting ptoolbarmgr->m_ptoolbarclass = RUNTIME_CLASS(CCustomNotifyToolBar); in the SECMDIFrameWnd or SECFrameWnd creation code. Getting a pointer to the combo button. To manipulate the SECComboBtn in any way will require that we get a pointer to the combo box object embedded in the SECComboBtn. In the example, GetButtonPointerFromID(int nid) functions by walking the list of control bars looking for SECCustomToolBars. When it finds one, it will walk that bar's list of buttons looking for the button with the ID that is passed in. It returns a pointer to that button in the form of a CWnd*. When this pointer is used, MFC runtime class information must be used to 1

2 verify the type, and the button must be explicitly cast to a CComboBox so that CComboBox method are usable. This method allows the example function to be used with many types of special buttons. If there are multiple embedded controls, it may be necessary to use a different method to obtain the pointer. CWnd* CComboBtnView::GetButtonPointerFromID(int nid) // Iterate the list of control bars. CPtrList &list = ((SECMDIFrameWnd*)AfxGetMainWnd())->m_listControlBars; >POSITION pos = list.getheadposition(); while (pos!= NULL) // Check each to see if it's a SECCustomToolBar derivative. // Note: Menubars will be tested. CControlBar* pcontrolbar = (CControlBar *) list.getnext(pos); if (pcontrolbar->iskindof(runtime_class(seccustomtoolbar))) // The bar being tested is a toolbar. Test the ID of each button // against the ID passed in. SECCustomToolBar* pcustomtoolbar = (>SECCustomToolBar*) pcontrolbar; int inbtns = pcustomtoolbar->getbtncount(); for (int ibtn=0; ibtn >inbtns; ibtn++ ) // Test to see if this is the desired button UINT ntestid=" pcustomtoolbar-">getitemid(ibtn); if (ntestid == nid) // Get the button rect. RECT rect; pcustomtoolbar->getitemrect(ibtn, &rect); // Get the window. POINT p1; p1.x = (rect.left + rect.right) / 2; p1.y = (rect.top + rect.bottom) / 2; CWnd* pwnd = pcustomtoolbar->childwindowfrompoint(p1); return pwnd; return NULL; Adding a string to the list. Adding a string to the list is relatively easy. The method in the following example shows the use of GetButtonPointerFromID() to get the CComboBox pointer, and the use of standard methods to load the string into the list and select it. /////////////////////////////////////////////////////////////////// // AddComboBtnString will add a string to the list after a user // has typed it in. It will also set the selected item to that // string. BOOL CComboBtnView::AddComboBtnString(UINT uibuttonid,cstring stext) CWnd* pwnd = GetButtonPointerFromID(uiButtonID); if (pwnd!= NULL && pwnd->iskindof(runtime_class(ccombobox))) int iindex = ((CComboBox *) pwnd)->addstring(stext); ((CComboBox *) pwnd)->setcursel(iindex); Filling the default list for the combo button. An example function for filling the list uses the ID to get the pointer to the CComboBox, and also passes that ID to a switch statement to determine what information gets loaded. The actual CComboBox code is not shown in this example. 2

3 ////////////////////////////////////////////////// // This loads the combo button from the view. If // you wanted to, you could load in the mainframe so // that you would have the combo loaded even if // there hadn't been an initial view instantiated. BOOL CComboBtnView::LoadComboBtn(UINT uibuttonid) CWnd* pwnd = GetButtonPointerFromID(uiButtonID); InitialComboLoader(uiButtonID, pwnd); Implementing the handler for the combo button events. A registered message is used to call a notification message handler. One source of confusion can be where this registered message is implemented and registered. The toolbar buttons send a wmsectoolbarwndnotify registered message for button notifications. Unfortunately, this value is a const int which can not be mapped properly across the Dll boundary. If using a static library, wmsectoolbarwndnotify can be safely used in the ON_REGISTERED_MESSAGE macro below, but if using Objective Toolkit as a DLL, you must issue the following call to get the appropriate value. Since this mechanism is safe for static libraries as well, it may be prudent to consider registering the message in this fashion for both usages. It is perfectly safe to register the same window message more than once. Only the first registration will be used. In the other cases, the value returned will be that of the previous registration. The following is included at global scope in each of the class implementations for classes that are handling the message. const int wmapptoolbarwndnotify = RegisterWindowMessage(_T("WM_SECTOOLBARWNDNOTIFY")); In each class that will handle the message, we need to add the handler to the message map. ON_REGISTERED_MESSAGE(wmAppToolBarWndNotify, OnToolBarWndNotify) Here is the message handler, like most classic message handlers this is implemented as a switch statement. long CComboBtnView::OnToolBarWndNotify(WPARAM wparam, LPARAM lparam) int nid = LOWORD(wParam); int ievent = HIWORD(wParam); HWND hwnd = (HWND)lParam; switch (nid) case IDR_COMBOBTN: // Note that the ID differs. We are passed the ID of the // object that was mapped to the bar, but we need to use // the ID of the button the object was mapped to in order // to get the window pointer. This can be a source of confusion. CWnd* pwnd = GetButtonPointerFromID(IDB_COMBOBTN); if (!(pwnd!= NULL && pwnd->iskindof(runtime_class(ccombobox)))) return FALSE; switch(ievent) case CBN_EDITCHANGE: // This is the usual code to indicate that something // in the edit portion has changed. m_bbox1dirty = TRUE; case CBN_KILLFOCUS: // If the text has been changed by selection, then // this code will make certain that the new text is // in the edit box. If nothing is selected, then // ((CComboBox*)pWnd)->GetCurSel() will be -1. if(!m_bbox1dirty) 3

4 m_bbox1dirty = FALSE; CString smessage = _T("The new text is: "); ((CComboBox*)pWnd)->GetLBText(((CComboBox*)pWnd)-GetCurSel(),sText); else m_bbox1dirty = FALSE; CString smessage = _T("The new text is: "); char ctext[255]; if(::getwindowtext(hwnd,ctext,255)) smessage += ctext; smessage = ctext; // Notice that the ID is not IDR_COMBOBTN, but is // IDB_COMBOBTN. AddComboBtnString(IDB_COMBOBTN,sMessage); case CBN_SELCHANGE: // Note: I've commented this out in the sample because // it prevents the demo app from showing some important // functionality. But it works, and is included so that // you can test this functionality. CString smessage = _T("The new selection is: "); ((CComboBox*)pWnd)->GetLBText(((CComboBox*)pWnd)-GetCurSel(),sText); case CBN_SELENDOK: // Note: I've commented this out because it prevents the // demo app from showing some important functionality. // But it works, and is included so that you can test this // functionality. CString smessage = _T("The new selection is: "); ((CComboBox*)pWnd)->GetLBText(((CComboBox*)pWnd)->GetCurSel(),sText); case IDR_DIRBOX: // Since this is the same as the previous code, // I've left it out in this example. return FALSE; One issue that has not been addressed in this article is the issue of synchronization. If you copy combo buttons between toolbars, there is a good chance that they will become unsynchronized from each other. If this is a possibility, I recommend that the lists be 4

5 refreshed from an array whenever the list is dropped down, and that the array be refreshed from the list as part of the CBN_KILLFOCUS handler. You may also wish to add keystrokes to each copy of the control in the CBN_EDITCHANGE handler. NB: In addition to the notification codes from the control, the SECComboBtn also sends a notification for when the Return key is pressed. The value of this message is defined as SECComboBtn::Entered(). Likewise, the SECWndBtn base class sends the SECWndBtn::Init() notification code after the button is first created. These are enum integer values, and you check for them the same way you check for CBN_??? values. A sample containing the code in this article is available at Combo Button Sample. Article ID: 736 Last updated: 05 Jan, 2012 Updated by: Meltreger B. Revision: 1 Stingray -> Objective Toolkit -> Customizable Toolbar: Implementing a toolbar combo button 5

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