Create Comboboxex Controls
//=============================================================================
//COMMON CONTROLS: COMBOBOXEX - Copyright © 2000,2005 Ken Fitlike
//=============================================================================
//API functions used: CreateWindowEx,DefWindowProc,DestroyIcon,DispatchMessage,
//GetMessage,GetSystemMetrics,GetWindowLongPtr,ImageList_AddIcon,
//ImageList_Create,ImageList_Destroy,InitCommonControlsEx,LoadImage,MessageBox,
//PostQuitMessage,RegisterClassEx,SendMessage,SetWindowLongPtr,ShowWindow,
//UpdateWindow,TranslateMessage,WinMain.
//=============================================================================
//This demonstrates the creation of an comboboxex common control.
//
//BCC55 - Link with comctl32.lib
//MINGW - Link with libcomctl32.a (-lcomctl32)
//MSVC  - Link with comctl32.lib
//=============================================================================
#include <windows.h>  //include all the basics
#include <tchar.h>    //string and other mapping macros

#if defined __MINGW_H
#define _WIN32_IE 0x0400
#endif
#include <commctrl.h>

#include <string>
#include <vector>

//define an unicode string type alias
typedef std::basic_string<TCHAR> ustring;
//=============================================================================
//convenience constant
const UINT CBX_ITEM_MASK=CBEIF_IMAGE|CBEIF_TEXT|CBEIF_SELECTEDIMAGE;

//message processing function declarations
LRESULT CALLBACK WndProc(HWND,UINT,WPARAM,LPARAM);
int OnCreate(const HWND,CREATESTRUCT*);

//non-message function declarations
HWND CreateComboboxex(const HWND,const HINSTANCE,DWORD,const RECT&,const int);
inline int ErrMsg(const ustring&);
int InsertItem(HWND,const ustring&,int,int,INT_PTR index=-1,
               UINT mask=CBX_ITEM_MASK);                     
void StartCommonControls(DWORD flags);

//setup some control id's
enum {
  IDC_COMBOBOXEX=200
};
//=============================================================================
int WINAPI WinMain(HINSTANCE hInst,HINSTANCE,LPSTR pStr,int nCmd)
{
ustring classname=_T("SIMPLEWND");
WNDCLASSEX wcx={0};  //used for storing information about the wnd 'class'

wcx.cbSize         = sizeof(WNDCLASSEX);           
wcx.lpfnWndProc    = WndProc;             //wnd Procedure pointer
wcx.hInstance      = hInst;               //app instance
//use 'LoadImage' to load wnd class icon and cursor as it supersedes the 
//obsolete functions 'LoadIcon' and 'LoadCursor', although these functions will 
//still work. Because the icon and cursor are loaded from system resources ie 
//they are shared, it is not necessary to free the image resources with either 
//'DestroyIcon' or 'DestroyCursor'.
wcx.hIcon         = reinterpret_cast<HICON>(LoadImage(0,IDI_APPLICATION,
                                            IMAGE_ICON,0,0,LR_SHARED));
wcx.hCursor       = reinterpret_cast<HCURSOR>(LoadImage(0,IDC_ARROW,
                                              IMAGE_CURSOR,0,0,LR_SHARED));
wcx.hbrBackground = reinterpret_cast<HBRUSH>(COLOR_BTNFACE+1);   
wcx.lpszClassName = classname.c_str(); 
//the window 'class' (not c++ class) has to be registered with the system
//before windows of that 'class' can be created
if (!RegisterClassEx(&wcx))
  {
  ErrMsg(_T("Failed to register wnd class"));
  return -1;
  }

int desktopwidth=GetSystemMetrics(SM_CXSCREEN);
int desktopheight=GetSystemMetrics(SM_CYSCREEN);

HWND hwnd=CreateWindowEx(0,                     //extended styles
                         classname.c_str(),     //name: wnd 'class'
                         _T("Common Controls - Comboboxex"), //wnd title
                         WS_OVERLAPPEDWINDOW,   //wnd style
                         desktopwidth/4,        //position:left
                         desktopheight/4,       //position: top
                         desktopwidth/2,        //width
                         desktopheight/2,       //height
                         0,                     //parent wnd handle
                         0,                     //menu handle/wnd id
                         hInst,                 //app instance
                         0);                    //user defined info
if (!hwnd)
  {
  ErrMsg(_T("Failed to create wnd"));
  return -1;
  }

ShowWindow(hwnd,nCmd); 
UpdateWindow(hwnd);
//start message loop - windows applications are 'event driven' waiting on user,
//application or system signals to determine what action, if any, to take. Note 
//that an error may cause GetMessage to return a negative value so, ideally,  
//this result should be tested for and appropriate action taken to deal with 
//it(the approach taken here is to simply quit the application).
MSG msg;
while (GetMessage(&msg,0,0,0)>0)
  {
  TranslateMessage(&msg);
  DispatchMessage(&msg);
  }
return static_cast<int>(msg.wParam);
}
//=============================================================================
LRESULT CALLBACK WndProc(HWND hwnd,UINT uMsg,WPARAM wParam,LPARAM lParam)
{
switch (uMsg)
  {
  case WM_CREATE:
    {
    return OnCreate(hwnd,reinterpret_cast<CREATESTRUCT*>(lParam));
    }
  case WM_DESTROY:
    {
    ImageList_Destroy(reinterpret_cast<HIMAGELIST>(static_cast<LONG_PTR>
                      (GetWindowLongPtr(hwnd,GWLP_USERDATA))));
    PostQuitMessage(0);    //signal end of application
    return 0;
    }
  default:
    //let system deal with msg
    return DefWindowProc(hwnd,uMsg,wParam,lParam);  
  }
}
//=============================================================================
int OnCreate(const HWND hwnd,CREATESTRUCT *cs)
{
//handles the WM_CREATE message of the main, parent window; return -1 to fail
//window creation
RECT rc={10,10,300,160};
StartCommonControls(ICC_USEREX_CLASSES);

HWND hwndComboEx=CreateComboboxex(hwnd,cs->hInstance,CBS_DROPDOWN,rc,
                                  IDC_COMBOBOXEX);

//create imagelist to hold icons for use by ComboBoxEx common control
LPCTSTR lpszResID[]={IDI_APPLICATION,IDI_INFORMATION,IDI_QUESTION};
HIMAGELIST hImageList=ImageList_Create(16,16,ILC_MASK|ILC_COLOR32,
                                       sizeof(lpszResID)/sizeof(lpszResID[0]),
                                       0);

//store the image list handle as the user data of the parent window so that
//it can be destroyed when the parent window is destroyed. This will emit a 
//C4244 warning if /wp64 is enabled with ms compilers under win32 due to how 
//SetWindowLongPtr is typedef'd for 32bit and 64bit compatibility. The warning
//in this context can be safely ignored. Despite this being identified as a 
//glitch under msvc.net 2003, it still exists in the later msvc express 2005. 
//A workaround would be to wrap the offending call in #pragma warning 
//directives, or to typedef the fn properly for 32/64 bit compatibility. 
//See http://msdn.microsoft.com/msdnmag/issues/01/08/bugslayer/
//for details.
SetWindowLongPtr(hwnd,GWLP_USERDATA,reinterpret_cast<LONG_PTR>(hImageList));

UINT i;
HICON hIcon;
for (i=0;i<sizeof(lpszResID)/sizeof(lpszResID[0]);++i)
  {
  hIcon=reinterpret_cast<HICON>(LoadImage(0,lpszResID[i],IMAGE_ICON,0,0,
                                          LR_SHARED));
  ImageList_AddIcon(hImageList,hIcon);
  }

//associate the imagelist with the ComboBoxEx common control
SendMessage(hwndComboEx,CBEM_SETIMAGELIST,0,
            reinterpret_cast<LPARAM>(hImageList));

//add some items to the ComboBoxEx common control

InsertItem(hwndComboEx,_T("First Item"),0,0);
InsertItem(hwndComboEx,_T("Second Item"),1,1);
InsertItem(hwndComboEx,_T("Third Item"),2,2);

return 0;
}
//=============================================================================
HWND CreateComboboxex(const HWND hParent,const HINSTANCE hInst,DWORD dwStyle,
                      const RECT& rc,const int id)
{
dwStyle|=WS_CHILD|WS_VISIBLE;
return CreateWindowEx(0,                  //extended styles
                      WC_COMBOBOXEX,      //control 'class' name
                      0,                  //control caption
                      dwStyle,            //wnd style
                      rc.left,            //position: left
                      rc.top,             //position: top
                      rc.right,           //width
                      rc.bottom,          //height
                      hParent,            //parent window handle
                      //control's ID
                      reinterpret_cast<HMENU>(static_cast<INT_PTR>(id)),
                      hInst,              //instance
                      0);                 //user defined info
}
//=============================================================================
inline int ErrMsg(const ustring& s)
{
return MessageBox(0,s.c_str(),_T("ERROR"),MB_OK|MB_ICONEXCLAMATION);
}
//=============================================================================
void StartCommonControls(DWORD flags)
{
//load the common controls dll, specifying the type of control(s) required 
INITCOMMONCONTROLSEX iccx;
iccx.dwSize=sizeof(INITCOMMONCONTROLSEX);
iccx.dwICC=flags;
InitCommonControlsEx(&iccx);
}
//=============================================================================
int InsertItem(HWND hCbx,const ustring& txt,int img_index,
               int selimg_index,INT_PTR index,UINT mask)
{
//insert in item into the comboboxex,'hCbx' with zero-based index of 
//'index'(default value is -1 which adds item to end of list),
//text of 'txt', image index of 'img_index', selected image index of 
//'selimg_index' and mask which defines which of these parameters are actually
//used.

//copy the text into a temporary array (vector) so it's in a suitable form
//for the pszText member of the COMBOBOXEXITEM struct to use. This avoids using
//const_cast on 'txt.c_str()' or variations applied directly to the string that
//break its constant nature.
std::vector<TCHAR> tmp(txt.begin(),txt.end());
tmp.push_back(_T('\0'));

COMBOBOXEXITEM cbei={0};

cbei.mask=mask;
cbei.iItem=index;
cbei.pszText=&tmp[0];
cbei.iImage=img_index;
cbei.iSelectedImage=selimg_index;

return static_cast<int>(SendMessage(hCbx,CBEM_INSERTITEM,0,
                                    reinterpret_cast<LPARAM>(&cbei)));
}
//=============================================================================