Add helper for loading Windows system functions

src/app/application.cpp

@@ -64,7 +64,6 @@
 
 #ifndef DISABLE_GUI
 #ifdef Q_OS_WIN
-#include <windows.h>
 #include <QSessionManager>
 #include <QSharedMemory>
 #endif // Q_OS_WIN
@@ -682,7 +681,7 @@ void Application::cleanup()
 
 #ifdef Q_OS_WIN
         typedef BOOL (WINAPI *PSHUTDOWNBRCREATE)(HWND, LPCWSTR);
-        PSHUTDOWNBRCREATE shutdownBRCreate = (PSHUTDOWNBRCREATE)::GetProcAddress(::GetModuleHandleW(L"User32.dll"), "ShutdownBlockReasonCreate");
+        const auto shutdownBRCreate = Utils::Misc::loadWinAPI<PSHUTDOWNBRCREATE>("User32.dll", "ShutdownBlockReasonCreate");
         // Only available on Vista+
         if (shutdownBRCreate)
             shutdownBRCreate((HWND)m_window->effectiveWinId(), tr("Saving torrent progress...").toStdWString().c_str());
@@ -724,7 +723,7 @@ void Application::cleanup()
     if (m_window) {
 #ifdef Q_OS_WIN
         typedef BOOL (WINAPI *PSHUTDOWNBRDESTROY)(HWND);
-        PSHUTDOWNBRDESTROY shutdownBRDestroy = (PSHUTDOWNBRDESTROY)::GetProcAddress(::GetModuleHandleW(L"User32.dll"), "ShutdownBlockReasonDestroy");
+        const auto shutdownBRDestroy = Utils::Misc::loadWinAPI<PSHUTDOWNBRDESTROY>("User32.dll", "ShutdownBlockReasonDestroy");
         // Only available on Vista+
         if (shutdownBRDestroy)
             shutdownBRDestroy((HWND)m_window->effectiveWinId());

src/base/bittorrent/session.cpp

@@ -4543,11 +4543,11 @@ namespace
             return uuid.toString().toUpper(); // Libtorrent expects the GUID in uppercase
 
         using PCONVERTIFACENAMETOLUID = NETIO_STATUS (WINAPI *)(const WCHAR *, PNET_LUID);
-        PCONVERTIFACENAMETOLUID ConvertIfaceNameToLuid = reinterpret_cast<PCONVERTIFACENAMETOLUID>(::GetProcAddress(::GetModuleHandleW(L"Iphlpapi.dll"), "ConvertInterfaceNameToLuidW"));
+        const auto ConvertIfaceNameToLuid = Utils::Misc::loadWinAPI<PCONVERTIFACENAMETOLUID>("Iphlpapi.dll", "ConvertInterfaceNameToLuidW");
         if (!ConvertIfaceNameToLuid) return QString();
 
         using PCONVERTIFACELUIDTOGUID = NETIO_STATUS (WINAPI *)(const NET_LUID *, GUID *);
-        PCONVERTIFACELUIDTOGUID ConvertIfaceLuidToGuid = reinterpret_cast<PCONVERTIFACELUIDTOGUID>(::GetProcAddress(::GetModuleHandleW(L"Iphlpapi.dll"), "ConvertInterfaceLuidToGuid"));
+        const auto ConvertIfaceLuidToGuid = Utils::Misc::loadWinAPI<PCONVERTIFACELUIDTOGUID>("Iphlpapi.dll", "ConvertInterfaceLuidToGuid");
         if (!ConvertIfaceLuidToGuid) return QString();
 
         NET_LUID luid;

src/base/utils/misc.h

@@ -34,6 +34,13 @@
 #include <ctime>
 #include <vector>
 
+#include <QtGlobal>
+
+#ifdef Q_OS_WIN
+#include <memory>
+#include <Windows.h>
+#endif
+
 #include <QDir>
 #include <QFile>
 #include <QPoint>
@@ -109,6 +116,22 @@ namespace Utils
 
 #ifdef Q_OS_WIN
         QString windowsSystemPath();
+
+        template <typename T>
+        T loadWinAPI(const QString &source, const char *funcName)
+        {
+            QString path = windowsSystemPath();
+            if (!path.endsWith('\\'))
+                path += '\\';
+
+            path += source;
+
+            std::unique_ptr<wchar_t[]> pathWchar(new wchar_t[path.length() + 1] {});
+            path.toWCharArray(pathWchar.get());
+
+            return reinterpret_cast<T>(
+                ::GetProcAddress(::LoadLibraryW(pathWchar.get()), funcName));
+        }
 #endif
     }
 }