adapted from https://devblogs.microsoft.com/oldnewthing/20040928-00/?p=37723
| 94 | // https://devblogs.microsoft.com/oldnewthing/20040928-00/?p=37723 |
| 95 | // |
| 96 | HRESULT IContextMenu_GetCommandString(IContextMenu* pcm, UINT_PTR idCmd, UINT uFlags, |
| 97 | UINT* pwReserved, LPWSTR pszName, UINT cchMax) |
| 98 | { |
| 99 | // Callers are expected to be using Unicode. |
| 100 | if (!(uFlags & GCS_UNICODE)) { |
| 101 | return E_INVALIDARG; |
| 102 | } |
| 103 | |
| 104 | // Some context menu handlers have off-by-one bugs and will |
| 105 | // overflow the output buffer. Let�s artificially reduce the |
| 106 | // buffer size so a one-character overflow won�t corrupt memory. |
| 107 | if (cchMax <= 1) { |
| 108 | return E_FAIL; |
| 109 | } |
| 110 | |
| 111 | cchMax--; |
| 112 | |
| 113 | // First try the Unicode message. Preset the output buffer |
| 114 | // with a known value because some handlers return S_OK without |
| 115 | // doing anything. |
| 116 | pszName[0] = L'\0'; |
| 117 | |
| 118 | HRESULT hr = pcm->GetCommandString(idCmd, uFlags, pwReserved, (LPSTR)pszName, cchMax); |
| 119 | |
| 120 | if (SUCCEEDED(hr) && pszName[0] == L'\0') { |
| 121 | // Rats, a buggy IContextMenu handler that returned success |
| 122 | // even though it failed. |
| 123 | hr = E_NOTIMPL; |
| 124 | } |
| 125 | |
| 126 | if (FAILED(hr)) { |
| 127 | // try again with ANSI � pad the buffer with one extra character |
| 128 | // to compensate for context menu handlers that overflow by |
| 129 | // one character. |
| 130 | LPSTR pszAnsi = (LPSTR)LocalAlloc(LMEM_FIXED, (cchMax + 1) * sizeof(CHAR)); |
| 131 | |
| 132 | if (pszAnsi) { |
| 133 | pszAnsi[0] = '\0'; |
| 134 | |
| 135 | hr = pcm->GetCommandString(idCmd, uFlags & ~GCS_UNICODE, pwReserved, pszAnsi, |
| 136 | cchMax); |
| 137 | |
| 138 | if (SUCCEEDED(hr) && pszAnsi[0] == '\0') { |
| 139 | // Rats, a buggy IContextMenu handler that returned success |
| 140 | // even though it failed. |
| 141 | hr = E_NOTIMPL; |
| 142 | } |
| 143 | |
| 144 | if (SUCCEEDED(hr)) { |
| 145 | if (MultiByteToWideChar(CP_ACP, 0, pszAnsi, -1, pszName, cchMax) == 0) { |
| 146 | hr = E_FAIL; |
| 147 | } |
| 148 | } |
| 149 | |
| 150 | LocalFree(pszAnsi); |
| 151 | |
| 152 | } else { |
| 153 | hr = E_OUTOFMEMORY; |