Make Windows implementation DPI-Aware (+ fix issue with window position) (#322)

* WindowImpl : Fix windows centering on desktop

* WindowImpl : Make nazara DPI aware

* Refactor dpi stuff

* Minor aesthetic stuff

* More minor stuff

Co-authored-by: HardCPP <hardcpp@gmail.com>

src/Nazara/Platform/Win32/WindowImpl.cpp

@@ -5,6 +5,7 @@
 // Un grand merci à Laurent Gomila pour la SFML qui m'aura bien aidé à réaliser cette implémentation
 
 #include <Nazara/Platform/Win32/WindowImpl.hpp>
+#include <Nazara/Core/CallOnExit.hpp>
 #include <Nazara/Core/ConditionVariable.hpp>
 #include <Nazara/Core/Error.hpp>
 #include <Nazara/Core/Mutex.hpp>
@@ -61,7 +62,7 @@ namespace Nz
 		bool async = (style & WindowStyle_Threaded) != 0;
 		bool fullscreen = (style & WindowStyle_Fullscreen) != 0;
 		DWORD win32Style, win32StyleEx;
-		unsigned int x, y;
+		int x, y;
 		unsigned int width = mode.width;
 		unsigned int height = mode.height;
 		if (fullscreen)
@@ -117,8 +118,14 @@ namespace Nz
 			width = rect.right-rect.left;
 			height = rect.bottom-rect.top;
 
-			x = (GetSystemMetrics(SM_CXSCREEN) - width)/2;
-			y = (GetSystemMetrics(SM_CYSCREEN) - height)/2;
+
+			// Grab desktop rect in order to center our window on the main display
+			// TODO: Handle multiple displays
+			RECT desktopRect;
+			GetClientRect(GetDesktopWindow(), &desktopRect);
+
+			x = (desktopRect.right / 2) - (width / 2);
+			y = (desktopRect.bottom / 2) - (height / 2);
 		}
 
 		m_callback = 0;
@@ -939,6 +946,9 @@ namespace Nz
 
 	bool WindowImpl::Initialize()
 	{
+		if (!SetProcessDpiAware())
+			NazaraWarning("failed to make process DPI-aware");
+
 		// Nous devons faire un type Unicode pour que la fenêtre le soit également
 		// http://msdn.microsoft.com/en-us/library/windows/desktop/ms633574(v=vs.85).aspx
 		WNDCLASSW windowClass;
@@ -961,6 +971,50 @@ namespace Nz
 		UnregisterClassW(className, GetModuleHandle(nullptr));
 	}
 
+	bool WindowImpl::SetProcessDpiAware()
+	{
+		// MSDN : https://docs.microsoft.com/en-us/windows/win32/hidpi/setting-the-default-dpi-awareness-for-a-process
+		// This will work only for windows Vista & above
+
+		HINSTANCE shcoreLib = LoadLibraryW(L"SHCore.dll");
+		if (shcoreLib)
+		{
+			CallOnExit closeLibOnExit([&] { FreeLibrary(shcoreLib); });
+
+			/// shellscalingapi.h
+			enum PROCESS_DPI_AWARENESS
+			{
+				PROCESS_DPI_UNAWARE,
+				PROCESS_SYSTEM_DPI_AWARE,
+				PROCESS_PER_MONITOR_DPI_AWARE
+			};
+
+			using SetProcessDpiAwarenessFunc = HRESULT (WINAPI*)(PROCESS_DPI_AWARENESS);
+			auto SetProcessDpiAwareness = reinterpret_cast<SetProcessDpiAwarenessFunc>(GetProcAddress(shcoreLib, "SetProcessDpiAwareness"));
+
+			if (SetProcessDpiAwareness)
+			{
+				HRESULT result = SetProcessDpiAwareness(PROCESS_SYSTEM_DPI_AWARE);
+
+				if (result == S_OK || result == E_ACCESSDENIED) //< E_ACCESSDENIED means it has already been set, probably by the .exe manifest
+					return true;
+			}
+		}
+
+		// If SetProcessDpiAwareness doesn't exist, we call old user32 function
+		HMODULE user32 = GetModuleHandleW(L"user32.dll");
+		if (!user32)
+			return false; //< Shouldn't happen as user32 is linked
+
+		using SetProcessDPIAwareFunc = BOOL (WINAPI*)();
+		auto SetProcessDPIAware = reinterpret_cast<SetProcessDPIAwareFunc>(GetProcAddress(user32, "SetProcessDPIAware"));
+
+		if (!SetProcessDPIAware || !SetProcessDPIAware())
+			return false;
+
+		return true;
+	}
+
 	Keyboard::Key WindowImpl::ConvertVirtualKey(WPARAM key, LPARAM flags)
 	{
 		switch (key)

src/Nazara/Platform/Win32/WindowImpl.hpp

@@ -84,6 +84,8 @@ namespace Nz
 			bool HandleMessage(HWND window, UINT message, WPARAM wParam, LPARAM lParam);
 			void PrepareWindow(bool fullscreen);
 
+			static bool SetProcessDpiAware();
+
 			static Keyboard::Key ConvertVirtualKey(WPARAM key, LPARAM flags);
 			static LRESULT CALLBACK MessageHandler(HWND window, UINT message, WPARAM wParam, LPARAM lParam);
 			static UInt32 RetrieveStyle(HWND window);