The following example shows a simple clipboard viewer application.
HINSTANCE hinst;
UINT uFormat = (UINT)(-1);
BOOL fAuto = TRUE;
LRESULT APIENTRY MainWndProc(hwnd, uMsg, wParam, lParam)
HWND hwnd;
UINT uMsg;
WPARAM wParam;
LPARAM lParam;
{
static HWND hwndNextViewer;
HDC hdc;
HDC hdcMem;
PAINTSTRUCT ps;
LPPAINTSTRUCT lpps;
RECT rc;
LPRECT lprc;
HGLOBAL hglb;
LPSTR lpstr;
HBITMAP hbm;
HENHMETAFILE hemf;
HWND hwndOwner;
switch (uMsg)
{
case WM_PAINT:
hdc = BeginPaint(hwnd, &ps);
// Branch depending on the clipboard format.
switch (uFormat)
{
case CF_OWNERDISPLAY:
hwndOwner = GetClipboardOwner();
hglb = GlobalAlloc(GMEM_DDESHARE,
sizeof(PAINTSTRUCT));
lpps = GlobalLock(hglb);
memcpy(lpps, &ps, sizeof(PAINTSTRUCT));
GlobalUnlock(hglb);
SendMessage(hwndOwner, WM_PAINTCLIPBOARD,
(WPARAM) hwnd, (LPARAM) hglb);
GlobalFree(hglb);
break;
case CF_BITMAP:
hdcMem = CreateCompatibleDC(hdc);
if (hdcMem != NULL)
{
if (OpenClipboard(hwnd))
{
hbm = (HBITMAP)
GetClipboardData(uFormat);
SelectObject(hdcMem, hbm);
GetClientRect(hwnd, &rc);
BitBlt(hdc, 0, 0, rc.right, rc.bottom,
hdcMem, 0, 0, SRCCOPY);
CloseClipboard();
}
DeleteDC(hdcMem);
}
break;
case CF_TEXT:
if (OpenClipboard(hwnd))
{
hglb = GetClipboardData(uFormat);
lpstr = GlobalLock(hglb);
GetClientRect(hwnd, &rc);
DrawText(hdc, lpstr, -1, &rc, DT_LEFT);
GlobalUnlock(hglb);
CloseClipboard();
}
break;
case CF_ENHMETAFILE:
if (OpenClipboard(hwnd))
{
hemf = GetClipboardData(uFormat);
GetClientRect(hwnd, &rc);
PlayEnhMetaFile(hdc, hemf, &rc);
CloseClipboard();
}
break;
case 0:
GetClientRect(hwnd, &rc);
DrawText(hdc, "The clipboard is empty.", -1,
&rc, DT_CENTER | DT_SINGLELINE |
DT_VCENTER);
break;
default:
GetClientRect(hwnd, &rc);
DrawText(hdc, "Unable to display format.", -1,
&rc, DT_CENTER | DT_SINGLELINE |
DT_VCENTER);
}
EndPaint(hwnd, &ps);
break;
case WM_SIZE:
if (uFormat == CF_OWNERDISPLAY)
{
hwndOwner = GetClipboardOwner();
hglb = GlobalAlloc(GMEM_DDESHARE, sizeof(RECT));
lprc = GlobalLock(hglb);
GetClientRect(hwnd, lprc);
GlobalUnlock(hglb);
SendMessage(hwndOwner, WM_SIZECLIPBOARD,
(WPARAM) hwnd, (LPARAM) hglb);
GlobalFree(hglb);
}
break;
case WM_CREATE:
// Add the window to the clipboard viewer chain.
hwndNextViewer = SetClipboardViewer(hwnd);
break;
case WM_CHANGECBCHAIN:
// If the next window is closing, repair the chain.
if ((HWND) wParam == hwndNextViewer)
hwndNextViewer = (HWND) lParam;
// Otherwise, pass the message to the next link.
else if (hwndNextViewer != NULL)
SendMessage(hwndNextViewer, uMsg, wParam, lParam);
break;
case WM_DESTROY:
ChangeClipboardChain(hwnd, hwndNextViewer);
PostQuitMessage(0);
break;
case WM_DRAWCLIPBOARD: // clipboard contents changed.
// Update the window by using Auto clipboard format.
SetAutoView(hwnd);
// Pass the message to the next window in clipboard
// viewer chain.
SendMessage(hwndNextViewer, uMsg, wParam, lParam);
break;
case WM_INITMENUPOPUP:
if (!HIWORD(lParam))
InitMenu(hwnd, (HMENU) wParam);
break;
case WM_COMMAND:
switch (LOWORD(wParam))
{
case IDM_EXIT:
DestroyWindow(hwnd);
break;
case IDM_AUTO:
SetAutoView(hwnd);
break;
default:
fAuto = FALSE;
uFormat = LOWORD(wParam);
InvalidateRect(hwnd, NULL, TRUE);
}
break;
default:
return DefWindowProc(hwnd, uMsg, wParam, lParam);
}
return (LRESULT) NULL;
}
void WINAPI SetAutoView(HWND hwnd)
{
static UINT auPriorityList[] = {
CF_OWNERDISPLAY,
CF_TEXT,
CF_ENHMETAFILE,
CF_BITMAP
};
uFormat = GetPriorityClipboardFormat(auPriorityList, 4);
fAuto = TRUE;
InvalidateRect(hwnd, NULL, TRUE);
UpdateWindow(hwnd);
}
void WINAPI InitMenu(HWND hwnd, HMENU hmenu)
{
UINT uFormat;
char szFormatName[80];
LPCSTR lpFormatName;
UINT fuFlags;
UINT idMenuItem;
// If a menu is not the display menu, no initialization is necessary.
if (GetMenuItemID(hmenu, 0) != IDM_AUTO)
return;
// Delete all menu items except the first.
while (GetMenuItemCount(hmenu) > 1)
DeleteMenu(hmenu, 1, MF_BYPOSITION);
// Check or uncheck the Auto menu item.
fuFlags = fAuto ? MF_BYCOMMAND | MF_CHECKED :
MF_BYCOMMAND | MF_UNCHECKED;
CheckMenuItem(hmenu, IDM_AUTO, fuFlags);
// If there are no clipboard formats, return.
if (CountClipboardFormats() == 0)
return;
// Open the clipboard.
if (!OpenClipboard(hwnd))
return;
// Add a separator and then a menu item for each format.
AppendMenu(hmenu, MF_SEPARATOR, 0, NULL);
uFormat = EnumClipboardFormats(0);
while (uFormat)
{
// Call an application-defined function to get the name
// of the clipboard format.
lpFormatName = GetPredefinedClipboardFormatName(uFormat);
// For registered formats, get the registered name.
if (lpFormatName == NULL)
{
if (GetClipboardFormatName(uFormat, szFormatName,
sizeof(szFormatName)))
lpFormatName = szFormatName;
else
lpFormatName = "(unknown)";
}
// Add a menu item for the format. For displayable
// formats, use the format ID for the menu ID.
if (IsDisplayableFormat(uFormat))
{
fuFlags = MF_STRING;
idMenuItem = uFormat;
}
else
{
fuFlags = MF_STRING | MF_GRAYED;
idMenuItem = 0;
}
AppendMenu(hmenu, fuFlags, idMenuItem, lpFormatName);
uFormat = EnumClipboardFormats(uFormat);
}
CloseClipboard();
}
BOOL WINAPI IsDisplayableFormat(UINT uFormat)
{
switch (uFormat)
{
case CF_OWNERDISPLAY:
case CF_TEXT:
case CF_ENHMETAFILE:
case CF_BITMAP:
return TRUE;
}
return FALSE;
}