FIX: Resizing CToolbar with Dropdown Arrow Buttons Freezes Apps

RESOLUTION

Because CToolBar::SizeToolBar() is not a virtual function, we need to reimplement this function and override the virtual functions in CToolBar class to call our SizeToolBar() function.

Below are the steps to correct this problem:

1. Derive a class from CToolBar called CMyToolBar.
2. Override virtual functions: CalcFixedLayout() and CalcDynamicLayout() in CMyToolBar class because they both call CalcLayout(), which in turn calls SizeToolBar(). Both CalcLayout() and SizeToolBar are nonvirtual functions in CToolBar class.
   
   The code for all these functions can be copied from the MFC source file Bartool.cpp.
3. Override CalcLayout() in CMyToolBar class. The code in CToolBar::CalcLayout() requires the _AFX_CONTROLPOS structure, which should be copied from the Bartool.cpp file as well.
   
   The code in CToolBar::CalcLayout() also calls the _GetButton() and _SetButton() functions. These functions have internal linkage, so we need to override those to avoid the LNK2001 error.
   
   NOTE: The first statement of _GetButton() casts the "this" pointer to CToolBar*, we have to cast it to CMyToolBar* in order to call the protected CWnd::DefWindowProc() function. For example:

         void CMyToolBar::_GetButton(int nIndex, TBBUTTON* pButton) const
         {
            CMyToolBar* pBar = (CMyToolBar*) this;
            VERIFY(pBar->DefWindowProc(TB_GETBUTTON, nIndex,
              (LPARAM)pButton));
            // TBSTATE_ENABLED == TBBS_DISABLED so invert it.
            pButton->fsState ^= TBSTATE_ENABLED;
         }
   						

4. Override SizeToolBar() in CMyToolBar class. Replace the while-loop with the following fix-up code:

         while (sizeMin.cx < sizeMax.cx)
         {
            sizeMid.cx = (sizeMin.cx + sizeMax.cx) / 2;
            WrapToolBar(pData, nCount, sizeMid.cx);
            sizeMid = CalcSize(pData, nCount);
   
            if (nLength < sizeMid.cy)
            {
               if (sizeMin == sizeMid)
               {
                  WrapToolBar(pData, nCount, sizeMax.cx);
                  return;
               }
               sizeMin = sizeMid;
            }
            else if (nLength > sizeMid.cy && sizeMax != sizeMid)
               sizeMax = sizeMid;
            else
               return;
         }
   						

5. Finally, use CMyToolBar when declaring the toolbar object in the header file of the CMainFrame class.

   while (sizeMin.cx < sizeMax.cx)
   {
      sizeMid.cx = (sizeMin.cx + sizeMax.cx) / 2;
      WrapToolBar(pData, nCount, sizeMid.cx);
      sizeMid = CalcSize(pData, nCount);

      if (nLength < sizeMid.cy)
      {
         if (sizeMin == sizeMid)
         {
            WrapToolBar(pData, nCount, sizeMax.cx);
            return;
         }
         sizeMin = sizeMid;
      }
      else if (nLength > sizeMid.cy)
         sizeMax = sizeMid;
      else
         return;
   }