Windows: during Setup, and if VeraCrypt already installed, open online help only if PC connected to Internet

src/Common/Dlgcode.c

@@ -18,6 +18,7 @@
 #include <dbt.h>
 #include <Setupapi.h>
 #include <aclapi.h>
+#include <Netlistmgr.h>
 #include <fcntl.h>
 #include <io.h>
 #include <math.h>
@@ -11223,10 +11224,18 @@ void Applink (const char *dest)
 	
 	if (buildUrl)
 	{
-		// in case of setup, always open the online documentation because existing documentation may be outdated
+		// in case of setup, open the online documentation if we are connected to Internet because existing documentation may be outdated
 #ifdef SETUP
+		if (IsInternetConnected())
+		{
 			StringCbPrintfW (url, sizeof (url), L"https://www.veracrypt.fr/en/%s", page);
 			buildUrl = FALSE;
+		}
+		else
+		{
+			StringCbPrintfW (url, sizeof (url), L"file:///%sdocs/html/en/%s", installDir, page);
+			CorrectURL (url);
+		}
 #else
 		StringCbPrintfW (url, sizeof (url), L"file:///%sdocs/html/en/%s", installDir, page);
 		CorrectURL (url);
@@ -15233,6 +15242,33 @@ void PasswordEditDropTarget::GotDrop(CLIPFORMAT format)
 }
 
 
+// check if the PC is connected to the internet using INetworkListManager interface
+BOOL IsInternetConnected()
+{
+    HRESULT hr;
+    BOOL isConnected = FALSE;
+    INetworkListManager* pNetworkListManager = nullptr;
+
+    hr = CoInitializeEx(NULL, COINIT_APARTMENTTHREADED | COINIT_DISABLE_OLE1DDE);
+    if (SUCCEEDED(hr))
+    {
+        hr = CoCreateInstance(CLSID_NetworkListManager, NULL, CLSCTX_ALL, IID_PPV_ARGS(&pNetworkListManager));
+        if (SUCCEEDED(hr))
+        {
+            VARIANT_BOOL isConnectedVariant;
+            hr = pNetworkListManager->get_IsConnectedToInternet(&isConnectedVariant);
+            if (SUCCEEDED(hr))
+            {
+                isConnected = isConnectedVariant == VARIANT_TRUE;
+            }
+            pNetworkListManager->Release();
+        }
+        CoUninitialize();
+    }
+
+    return isConnected;
+}
+
 /*
  * Query the status of Hibernate and Fast Startup
  */

src/Common/Dlgcode.h

@@ -597,6 +597,7 @@ DWORD FastResizeFile (const wchar_t* filePath, __int64 fileSize);
 #ifdef _WIN64
 void GetAppRandomSeed (unsigned char* pbRandSeed, size_t cbRandSeed);
 #endif
+BOOL IsInternetConnected();
 #ifdef __cplusplus
 }