Selecting ltmmPlay Object Renderers for C++

The following example shows how to enumerate and select ltmmPlay object renderers.

#include "ltmm.h" 
#include "resource.h" 
#include "tchar.h" 
#include "stdio.h" 
 
HINSTANCE g_hInstance;  // application instance handle 
IltmmPlay* g_pPlay;  // convert object's interface pointer 
 
// 
// BuildRendererList 
// fills a listbox to match the contents of the collection 
// 
// pRenderers = renderer collection's interface pointer 
// hwndListBox = listbox window handle 
// 
void BuildRendererList(IltmmRenderers* pRenderers, HWND hwndListBox) 
{ 
   long i; 
   long count; 
   int selected = -1; 
   // reset the listbox contents 
   SendMessage(hwndListBox, LB_RESETCONTENT, 0, 0); 
   // get the collection's item count 
   pRenderers->get_Count(&count); 
   for(i = 0; i < count; i++) 
   { 
      IltmmRenderer* pRenderer; 
      BSTR bstr; 
      TCHAR sz[256]; 
      int index; 
      VARIANT_BOOL f; 
      // retrieve collection item 
      pRenderers->Item(i, &pRenderer); 
      // get displayable name 
      pRenderer->get_FriendlyName(&bstr); 
      // convert from unicode 
      _stprintf(sz, _T("%ls"), bstr); 
      // free name 
      SysFreeString(bstr); 
      // add the name to the listbox 
      index = SendMessage(hwndListBox, LB_ADDSTRING, 0, (LPARAM) (LPCTSTR) sz); 
      // associate the listbox item with the collection item index 
      SendMessage(hwndListBox, LB_SETITEMDATA, index, i); 
      // remember this listbox item, if it is selected in the collection 
      pRenderer->get_Selected(&f); 
      if(f) 
         selected = i; 
      // free the collection item 
      pRenderer->Release(); 
   } 
   // select the appropriate listbox item 
   for(i = 0; i < count; i++) 
   { 
      if(selected == (long) SendMessage(hwndListBox, LB_GETITEMDATA, i, 0)) 
      {   
         SendMessage(hwndListBox, LB_SETCURSEL, i, 0); 
         break; 
      } 
   } 
} 
 
// 
// RendererSelectionChanged 
// called to reflect changes in the listbox selection 
// 
// pRenderers = renderer collection's interface pointer 
// hwndListBox = listbox window handle 
// 
void RendererSelectionChanged(IltmmRenderers* pRenderers, HWND hwndListBox) 
{ 
   int index; 
   long item; 
   int i; 
   int count; 
   HRESULT hr; 
   // get the index of current listbox selection 
   index = (int) SendMessage(hwndListBox, LB_GETCURSEL, 0, 0); 
   if(index < 0) 
   {   
      // clear selection 
      pRenderers->put_Selection(-1); 
   } 
   else 
   {   
      // get the collection item index 
      item = (long) SendMessage(hwndListBox, LB_GETITEMDATA, index, 0); 
      // select the item 
#ifdef _DEBUG 
      {   
         IltmmRenderer* pRenderer; 
         pRenderers->Item(item, &pRenderer); 
         hr = pRenderer->put_Selected(VARIANT_TRUE); 
         pRenderer->Release(); 
      } 
#else 
      hr = pRenderers->put_Selection(item); 
#endif 
      // if new selection failed, we need to force the listbox to match the actual selection 
      if(FAILED(hr)) 
      {   
         // get the real selection 
         pRenderers->get_Selection(&item); 
         // find the matching listbox item 
         count = (int) SendMessage(hwndListBox, LB_GETCOUNT, 0, 0); 
         for(i = 0; i < count; i++) 
         {   
            if(item == (long) SendMessage(hwndListBox, LB_GETITEMDATA, i, 0)) 
            {   
               SendMessage(hwndListBox, LB_SETCURSEL, i, 0); 
               break; 
            }   
         }   
      }   
   } 
} 
 
// 
// RefreshRendererList 
// called when to completely rebuild the collection 
// 
// pRenderers = renderer collection's interface pointer 
// hwndListBox = listbox window handle 
// 
void RefreshRendererList(IltmmRenderers* pRenderers, HWND hwndListBox) 
{ 
   IltmmRenderer* pRenderer; 
   long item; 
   BSTR bstr; 
   // get the currently selected item 
   pRenderers->get_Selection(&item); 
   if(item >= 0) 
   {   
      // get it's unique name 
      pRenderers->Item(item, &pRenderer); 
      pRenderer->get_Name(&bstr); 
      pRenderer->Release(); 
   } 
   else 
   {   
      bstr = NULL; 
   } 
   // rebuild the collection 
   pRenderers->Refresh(); 
   if(bstr) 
   {   
      // find the previously selected item 
      pRenderers->Find(bstr, &item); 
      // make it the current selection 
      if(item >= 0) 
         pRenderers->put_Selection(item); 
      SysFreeString(bstr); 
   } 
   // rebuild the listbox 
   BuildRendererList(pRenderers, hwndListBox); 
} 
 
// 
// RendererDlgProc 
// selects object renderers 
// 
BOOL CALLBACK RendererDlgProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam) 
{ 
   IltmmRenderers* pRenderers; 
   switch (msg) 
   { 
   case WM_INITDIALOG: 
      // initialize the audio renderer listbox 
      g_pPlay->get_AudioRenderers(&pRenderers); 
      BuildRendererList(pRenderers, GetDlgItem(hwnd, IDC_AUDIODEVICES)); 
      pRenderers->Release(); 
      return TRUE; 
      break; 
   case WM_COMMAND: 
      switch(LOWORD(wParam)) 
      {   
      case IDC_REFRESHAUDIODEVICES: 
         // refresh the audio renderer listbox 
         g_pPlay->get_AudioRenderers(&pRenderers); 
         RefreshRendererList(pRenderers, GetDlgItem(hwnd, IDC_AUDIODEVICES)); 
         pRenderers->Release(); 
         return TRUE; 
         break; 
      case IDC_AUDIODEVICES: 
         if(HIWORD(wParam) == LBN_SELCHANGE) 
         {   
            // select the audio renderer 
            g_pPlay->get_AudioRenderers(&pRenderers); 
            RendererSelectionChanged(pRenderers, GetDlgItem(hwnd, IDC_AUDIODEVICES)); 
            pRenderers->Release(); 
         }   
         break; 
      case IDOK: 
         EndDialog(hwnd, IDOK); 
         return TRUE; 
         break; 
      }   
      break; 
   }   return FALSE; 
} 
 
int APIENTRY WinMain(HINSTANCE hInstance, 
                     HINSTANCE hPrevInstance, 
                     LPSTR lpCmdLine, 
                     int nCmdShow) 
{ 
   HRESULT hr; 
   g_hInstance = hInstance; 
   // initialize COM library 
   hr = CoInitialize(NULL); 
   if(FAILED(hr)) 
      goto error; 
   // create the convert object 
   hr = CoCreateInstance(CLSID_ltmmPlay, NULL, CLSCTX_INPROC_SERVER, IID_IltmmPlay, (void**) &g_pPlay); 
   if(FAILED(hr)) 
      goto error; 
 
   DialogBox(g_hInstance, (LPCTSTR)IDD_DEVICEDLG, NULL, RendererDlgProc); 
 
error: 
   // cleanup 
   if(g_pPlay) 
      g_pPlay->Release(); 
   CoUninitialize(); 
   return 0; 
} 

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