Use wine_get_dos_file_name rather than relying on GetFullPathNameW

dlls/shell32/shellpath.c

@@ -1265,12 +1265,19 @@ static HRESULT _SHGetDefaultValue(BYTE folder, LPWSTR pszPath)
             /* special case for "My Documents", map to $HOME */
             if (home)
             {
-                WCHAR homeW[MAX_PATH];
+                LPWSTR homeW = wine_get_dos_file_name(home);
 
-                MultiByteToWideChar(CP_UNIXCP, 0, home, -1, homeW, MAX_PATH);
-                if (GetFullPathNameW(homeW, MAX_PATH, pszPath, NULL) != 0 &&
-                 PathIsDirectoryW(pszPath))
-                    hr = S_OK;
+                if (homeW)
+                {
+                    if (PathIsDirectoryW(homeW))
+                    {
+                        lstrcpynW(pszPath, homeW, MAX_PATH);
+                        hr = S_OK;
+                    }
+                    HeapFree(GetProcessHeap(), 0, homeW);
+                }
+                else
+                    hr = HRESULT_FROM_WIN32(GetLastError());
             }
             break;
         }
@@ -1282,13 +1289,22 @@ static HRESULT _SHGetDefaultValue(BYTE folder, LPWSTR pszPath)
             /* special case for Desktop, map to $HOME/Desktop if it exists */
             if (home)
             {
-                WCHAR desktopW[MAX_PATH];
+                LPWSTR homeW = wine_get_dos_file_name(home);
 
-                MultiByteToWideChar(CP_UNIXCP, 0, home, -1, desktopW, MAX_PATH);
-                PathAppendW(desktopW, DesktopW);
-                if (GetFullPathNameW(desktopW, MAX_PATH, pszPath, NULL) != 0 &&
-                 PathIsDirectoryW(pszPath))
-                    hr = S_OK;
+                if (homeW)
+                {
+                    lstrcpynW(pszPath, homeW, MAX_PATH);
+                    if (PathAppendW(pszPath, DesktopW))
+                    {
+                        if (PathIsDirectoryW(pszPath))
+                            hr = S_OK;
+                    }
+                    else
+                        hr = HRESULT_FROM_WIN32(GetLastError());
+                    HeapFree(GetProcessHeap(), 0, homeW);
+                }
+                else
+                    hr = HRESULT_FROM_WIN32(GetLastError());
             }
             break;
         }