How to handle chevron button using CToolBarCtrl object?

Article
07/02/2009

Most of the developers work with CToolBarCtrl but they get stuck when it comes to display chevron button. This article is all about how to get chevron button displayed on CToolBarCtrl control while resizing its content window.

There is a good MSDN article on handling chevrons but no good sample implementation on it. I wrote a small sample using CDialog, CToolBarCtrl and CReBarCtrl classes to illustrate the same.

Since the main focus would be on handling chevron button, I am not going to cover tool bar control implementation details. Following are the steps to achieve chevron button on CToolBarCtrl.

1. Using class wizard, create a new class CCustReBarCtrl deriving it from CReBarCtrl MFC class. Add m_wndReBar and m_wndToolBar of type CCustReBarCtrl and CToolBarCtrl respectively in dialog class. Create rebar and tool bar controls in OnInitDialog() dialog method as shown below.

/*Make sure that tool bar resource is loaded here*/

m_wndToolBar.AutoSize();

Rebar control provides chevron control when RBBS_USECHEVRON flag in the fStyle member of the band's REBARBANDINFO structure is set. Before defining the band info, define the following macro in stdafx.h file.

#define REBARBANDINFO_SIZE CCSIZEOF_STRUCT(REBARBANDINFO, cxHeader)

SIZE sizeButtons;

m_wndToolBar.GetMaxSize(&sizeButtons);

REBARBANDINFO rbi;

ZeroMemory((void*)&rbi, sizeof(rbi));

rbi.cbSize = REBARBANDINFO_SIZE; // V5 structure size. Insert fails if the struct is too big

rbi.fMask = RBBIM_CHILD | RBBIM_CHILDSIZE | RBBIM_IDEALSIZE | RBBIM_STYLE;

rbi.fStyle = RBBS_GRIPPERALWAYS | RBBS_USECHEVRON;

rbi.cyMaxChild = rbi.cyMinChild = rbi.cyChild = sizeButtons.cy;

rbi.cxIdeal = rbi.cx = sizeButtons.cx;

rbi.hwndChild = (HWND)m_wndToolBar;

m_wndReBar.InsertBand(-1, &rbi);

RECT rcWindow;

GetClientRect(&rcWindow);

m_wndReBar.MoveWindow(0, 0, rcWindow.right - rcWindow.left, sizeButtons.cy);

2. It’s very important to size the rebar control accordingly when dialog is resized otherwise chevron button will not be displayed. So handle WM_SIZE message (OnSize() method) in the dialog class and add the following code as shown below.

if (m_wndReBar.GetSafeHwnd())

{

RECT rcRebar;

m_wndReBar.GetWindowRect(&rcRebar);

m_wndReBar.MoveWindow(0, 0, cx, rcRebar.bottom - rcRebar.top);

}

3. Now if you run the code and resize the dialog, chevron will be displayed for tools that have been covered. When a user clicks a chevron, the rebar control sends RBN_CHEVRONPUSHED notification. The NMREBARCHEVRON structure that is passed with the notification contains the band's identifier and a RECT structure with the rectangle occupied by the chevron. Your handler must determine which buttons are hidden and display the associated commands on a pop-up menu.

Add RBN_CHEVRONPUSHED notification in CCustReBarCtrl, after adding the message map should look like as shown below

BEGIN_MESSAGE_MAP(CCustRebarCtrl, CReBarCtrl)

ON_NOTIFY_REFLECT(RBN_CHEVRONPUSHED, & CCustRebarCtrl::OnRbnChevronPushed)

END_MESSAGE_MAP()

Following is the code that goes into the chevron handler 'void CCustRebar::OnRbnChevronPushed(NMHDR *pNMHDR, LRESULT *pResult)' method

LPNMREBARCHEVRON pnmrc = reinterpret_cast<LPNMREBARCHEVRON>(pNMHDR);

RECT rcBand;

RECT rcButton;

RECT rcIntersect;

REBARBANDINFO rbi;

TBBUTTON tbb;

UINT cButtons;

UINT iButton;

UINT iMenu;

HMENU hmenuPopup;

MENUITEMINFO mii;

TCHAR szText[200];

HRESULT hr;

CImageList* pimlToolbar;

// Get the child window for this band.

ZeroMemory((void*)&rbi, sizeof(rbi));

rbi.cbSize = REBARBANDINFO_SIZE;

rbi.fMask = RBBIM_CHILD;

GetBandInfo(pnmrc->uBand, &rbi);

CToolBarCtrl *pTBarCtrl = (CToolBarCtrl *)CToolBarCtrl::FromHandle ( rbi.hwndChild );

ASSERT(pTBarCtrl);

ASSERT(pTBarCtrl->IsKindOf(RUNTIME_CLASS(CToolBarCtrl)));

// Get the client rectangle of the child window

pTBarCtrl->GetClientRect(&rcBand);

// Get the number of buttons in the toolbar. This should fail when the

// child window is not a toolbar.

if ((cButtons = pTBarCtrl->GetButtonCount()) == 0)

return;

// Starting from the leftmost button, retrieve each button's bounding

// rectangle until we find a button that is at least partially hidden

for (iButton = 1; iButton < cButtons; iButton++)

{

// Get the button's rectangle

ZeroMemory((void*)&rcButton, sizeof(rcButton));

pTBarCtrl->GetItemRect(iButton, &rcButton);

CRect rtTabButton(rcButton);

CRect rtToolBarCtr(rcBand);

CPoint ptCenter = rtTabButton.CenterPoint();

if(!rtToolBarCtr.PtInRect(ptCenter))

break;

}

// Nothing to do if we didn't find a hidden button

if (iButton == cButtons)

return;

// Allocate an array of bitmaps to hold the images used in menu items. An

// alternate approach is to ownerdraw the menu

UINT cImages = cButtons - iButton;

size_t cb = sizeof(HBITMAP) * cImages;

HBITMAP* ahbmpImages = (HBITMAP*)malloc(cb);

if (!ahbmpImages)

return;

ZeroMemory((void*)ahbmpImages, cb);

// Create a memory DC that we use to render the toolbar images

HDC hdcMem = NULL;

HDC hdcWindow = ::GetDC(m_hWnd);

if (hdcWindow)

{

hdcMem = CreateCompatibleDC(hdcWindow);

}

// Create a popup menu for the hidden toolbar items

hmenuPopup = CreatePopupMenu();

// Get the image list for the toolbar

int cxImage = 0;

int cyImage = 0;

pimlToolbar = pTBarCtrl->GetImageList();

if (pimlToolbar)

{

ImageList_GetIconSize(*pimlToolbar, &cxImage, &cyImage);

}

// Create a menu item for each hidden toolbar item

iMenu = 0;

for ( ; iButton < cButtons; iButton++)

{

ZeroMemory((void*)szText, sizeof(szText));

ZeroMemory((void*)&tbb, sizeof(tbb));

if (pTBarCtrl->GetButton(iButton, &tbb))

{

if(tbb.idCommand != 0)

{

LoadString(GetModuleHandle(NULL), tbb.idCommand, szText, sizeof(szText)-1);

int cch = strlen(szText);

szText[cch+1] = '\0';

}

// Create a bitmap for the toolbar icon and draw the icon into the bitmap

if (hdcMem && pimlToolbar->GetSafeHandle() && ahbmpImages)

{

ahbmpImages[iMenu] = CreateCompatibleBitmap(hdcWindow, cxImage, cyImage);

if (ahbmpImages[iMenu])

{

HBITMAP hbmpOld = (HBITMAP)SelectObject(hdcMem, ahbmpImages[iMenu]);

RECT rcImage = {0, 0, cxImage, cyImage};

// First, fill the background with the menu background

FillRect(hdcMem, &rcImage, GetSysColorBrush(COLOR_MENU));

// Then draw the icon

ImageList_Draw(pimlToolbar->GetSafeHandle(), tbb.iBitmap, hdcMem, 0, 0, ILD_NORMAL);

SelectObject(hdcMem, hbmpOld);

}

// Add a menu item for this toolbar item

ZeroMemory((void*)&mii, sizeof(mii));

mii.cbSize = sizeof(MENUITEMINFO);

mii.fMask = MIIM_STRING;

mii.dwTypeData = szText;

mii.wID = tbb.idCommand;

if (ahbmpImages[iMenu])

{

mii.fMask |= MIIM_BITMAP;

mii.hbmpItem = ahbmpImages[iMenu];

}

InsertMenuItem(hmenuPopup, iMenu++, TRUE, &mii);

}

// Display the popup menu if it has menu items

if (0 < GetMenuItemCount(hmenuPopup))

{

::MapWindowPoints(pnmrc->hdr.hwndFrom, NULL, (LPPOINT)&pnmrc->rc, 2);

TrackPopupMenu(hmenuPopup,

TPM_LEFTALIGN | TPM_TOPALIGN,

pnmrc->rc.left, pnmrc->rc.bottom,

0, m_hWnd, NULL);

}

// Destroy the popup menu

DestroyMenu(hmenuPopup);

// Cleanup the bitmaps

if (ahbmpImages)

{

while (cImages)

{

cImages--;

if (ahbmpImages[cImages])

DeleteObject(ahbmpImages[cImages]);

}

free(ahbmpImages);

}

// Release the DCs used to handle the bitmaps

if (hdcMem)

{

DeleteDC(hdcMem);

}

if (hdcWindow)

{

::ReleaseDC(m_hWnd, hdcWindow);

}

// TODO: Add your control notification handler code here

*pResult = 0;

How to handle chevron button using CToolBarCtrl object?

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