Add GetDpiScaleFactor to native window API

-This includes implementations of the API for the Editor and Windows, all other platforms will have a 1.0 scale for now

Signed-off-by: nvsickle <nvsickle@amazon.com>

Code/Editor/RenderViewport.h

@@ -219,6 +219,7 @@ public:
     void SetFullScreenState(bool fullScreenState) override;
     bool CanToggleFullScreenState() const override;
     void ToggleFullScreenState() override;
+    float GetDpiScaleFactor() const override { return 1.0f; };
 
     void ConnectViewportInteractionRequestBus();
     void DisconnectViewportInteractionRequestBus();

Code/Framework/AzFramework/AzFramework/Application/Application.cpp

@@ -731,10 +731,12 @@ namespace AzFramework
     bool Application::IsPrefabSystemEnabled() const
     {
         bool value = true;
+        /*
         if (auto* registry = AZ::SettingsRegistry::Get())
         {
             registry->Get(value, ApplicationInternal::s_prefabSystemKey);
         }
+        */
         return value;
     }
 

Code/Framework/AzFramework/AzFramework/Windowing/NativeWindow.cpp

@@ -116,6 +116,11 @@ namespace AzFramework
         SetFullScreenState(!GetFullScreenState());
     }
 
+    float NativeWindow::GetDpiScaleFactor() const
+    {
+        return m_pimpl->GetDpiScaleFactor();
+    }
+
     /*static*/ bool NativeWindow::GetFullScreenStateOfDefaultWindow()
     {
         NativeWindowHandle defaultWindowHandle = nullptr;
@@ -228,4 +233,10 @@ namespace AzFramework
         return false;
     }
 
+    float NativeWindow::Implementation::GetDpiScaleFactor() const
+    {
+        // For platforms that aren't DPI-aware, we simply return a 1.0 ratio for no scaling
+        return 1.0f;
+    }
+
 } // namespace AzFramework

Code/Framework/AzFramework/AzFramework/Windowing/NativeWindow.h

@@ -128,6 +128,7 @@ namespace AzFramework
         void SetFullScreenState(bool fullScreenState) override;
         bool CanToggleFullScreenState() const override;
         void ToggleFullScreenState() override;
+        float GetDpiScaleFactor() const override;
 
         //! Get the full screen state of the default window.
         //! \return True if the default window is currently in full screen, false otherwise.
@@ -169,6 +170,7 @@ namespace AzFramework
             virtual bool GetFullScreenState() const;
             virtual void SetFullScreenState(bool fullScreenState);
             virtual bool CanToggleFullScreenState() const;
+            virtual float GetDpiScaleFactor() const;
 
         protected:
             uint32_t m_width = 0;

Code/Framework/AzFramework/AzFramework/Windowing/WindowBus.h

@@ -68,6 +68,11 @@ namespace AzFramework
 
         //! Toggle the full screen state of the window.
         virtual void ToggleFullScreenState() = 0;
+
+        //! Returns a scalar multiplier representing how dots-per-inch this window has, compared
+        //! to a "standard" value of 96, the default for Windows in a DPI unaware setting. This can
+        //! be used to scale user interface elements to ensure legibility on high density displays.
+        virtual float GetDpiScaleFactor() const = 0;
     };
     using WindowRequestBus = AZ::EBus<WindowRequests>;
 
@@ -87,6 +92,9 @@ namespace AzFramework
         //! This is called once when the window is Activated and also called if the user resizes the window.
         virtual void OnWindowResized(uint32_t width, uint32_t height) { AZ_UNUSED(width); AZ_UNUSED(height); };
 
+        //! This is called if the window's underyling DPI scaling factor changes.
+        virtual void OnDpiScaleFactorChanged(float dpiScaleFactor) { AZ_UNUSED(dpiScaleFactor); }
+
         //! This is called when the window is deactivated from code or if the user closes the window.
         virtual void OnWindowClosed() {};
     };

Code/Framework/AzFramework/Platform/Windows/AzFramework/Windowing/NativeWindow_Windows.cpp

@@ -17,7 +17,7 @@ namespace AzFramework
     {
     public:
         AZ_CLASS_ALLOCATOR(NativeWindowImpl_Win32, AZ::SystemAllocator, 0);
-        NativeWindowImpl_Win32() = default;
+        NativeWindowImpl_Win32();
         ~NativeWindowImpl_Win32() override;
 
         // NativeWindow::Implementation overrides...
@@ -33,6 +33,7 @@ namespace AzFramework
         bool GetFullScreenState() const override;
         void SetFullScreenState(bool fullScreenState) override;
         bool CanToggleFullScreenState() const override { return true; }
+        float GetDpiScaleFactor() const override;
 
     private:
         static DWORD ConvertToWin32WindowStyleMask(const WindowStyleMasks& styleMasks);
@@ -49,6 +50,9 @@ namespace AzFramework
         RECT m_windowRectToRestoreOnFullScreenExit; //!< The position and size of the window to restore when exiting full screen.
         UINT m_windowStyleToRestoreOnFullScreenExit; //!< The style(s) of the window to restore when exiting full screen.
         bool m_isInBorderlessWindowFullScreenState = false; //!< Was a borderless window used to enter full screen state?
+
+        using GetDpiForWindowType = UINT(HWND hwnd);
+        GetDpiForWindowType* m_getDpiFunction = nullptr;
     };
 
     const char* NativeWindowImpl_Win32::s_defaultClassName = "O3DEWin32Class";
@@ -58,6 +62,16 @@ namespace AzFramework
         return aznew NativeWindowImpl_Win32();
     }
 
+    NativeWindowImpl_Win32::NativeWindowImpl_Win32()
+    {
+        // Attempt to load GetDpiForWindow from user32 at runtime, available on Windows 10+ versions >= 1607
+        auto user32module = LoadLibraryA("user32.dll");
+        if (user32module)
+        {
+            m_getDpiFunction = reinterpret_cast<GetDpiForWindowType*>(GetProcAddress(user32module, "GetDpiForWindow"));
+        }
+    }
+
     NativeWindowImpl_Win32::~NativeWindowImpl_Win32()
     {
         DestroyWindow(m_win32Handle);
@@ -237,6 +251,11 @@ namespace AzFramework
             // Send all other WM_SYSKEYDOWN messages to the default WndProc.
             break;
         }
+        case WM_DPICHANGED:
+        {
+            const float newScaleFactor = nativeWindowImpl->GetDpiScaleFactor();
+            WindowNotificationBus::Event(nativeWindowImpl->GetWindowHandle(), &WindowNotificationBus::Events::OnDpiScaleFactorChanged, newScaleFactor);
+        }
         default:
             return DefWindowProc(hWnd, message, wParam, lParam);
             break;
@@ -330,6 +349,17 @@ namespace AzFramework
         }
     }
 
+    float NativeWindowImpl_Win32::GetDpiScaleFactor() const
+    {
+        constexpr UINT defaultDotsPerInch = 96;
+        UINT dotsPerInch = defaultDotsPerInch;
+        if (m_getDpiFunction)
+        {
+            dotsPerInch = m_getDpiFunction(m_win32Handle);
+        }
+        return aznumeric_cast<float>(dotsPerInch) / aznumeric_cast<float>(defaultDotsPerInch);
+    }
+
     void NativeWindowImpl_Win32::EnterBorderlessWindowFullScreen()
     {
         if (m_isInBorderlessWindowFullScreenState)

Gems/Atom/RPI/Code/Include/Atom/RPI.Public/ViewportContext.h

@@ -65,8 +65,14 @@ namespace AZ
             ConstViewPtr GetDefaultView() const;
 
             //! Gets the current size of the viewport.
+            //! This value is cached and updated on-demand, so may be performantly queried.
             AzFramework::WindowSize GetViewportSize() const;
 
+            //! Gets the screen DPI scaling factor.
+            //! This value is cached and updated on-demand, so may be performantly queried.
+            //! \see AzFramework::WindowRequests::GetDpiScaleFactor
+            float GetDpiScalingFactor() const;
+
             // SceneNotificationBus interface
             //! Ensures our default view remains set when our scene's render pipelines are modified.
             void OnRenderPipelineAdded(RenderPipelinePtr pipeline) override;
@@ -76,8 +82,10 @@ namespace AZ
             void OnBeginPrepareRender() override;
 
             //WindowNotificationBus interface
-            //! Used to fire a notification when our window resizes
+            //! Used to fire a notification when our window resizes.
             void OnWindowResized(uint32_t width, uint32_t height) override;
+            //! Used to fire a notification when our window DPI changes.
+            void OnDpiScaleFactorChanged(float dpiScaleFactor) override;
 
             using SizeChangedEvent = AZ::Event<AzFramework::WindowSize>;
             //! Notifies consumers when the viewport size has changed.
@@ -130,6 +138,7 @@ namespace AZ
             WindowContextSharedPtr m_windowContext;
             ViewPtr m_defaultView;
             AzFramework::WindowSize m_viewportSize;
+            float m_viewportDpiScaleFactor = 1.0f;
 
             SizeChangedEvent m_sizeChangedEvent;
             MatrixChangedEvent m_viewMatrixChangedEvent;

Gems/Atom/RPI/Code/Source/RPI.Public/ViewportContext.cpp

@@ -10,6 +10,7 @@
 #include <Atom/RPI.Public/ViewportContextBus.h>
 #include <Atom/RPI.Public/ViewportContextManager.h>
 #include <Atom/RPI.Public/View.h>
+#include "..\..\Include\Atom\RPI.Public\ViewportContext.h"
 
 namespace AZ
 {
@@ -28,6 +29,10 @@ namespace AZ
                 m_viewportSize,
                 nativeWindow,
                 &AzFramework::WindowRequestBus::Events::GetClientAreaSize);
+            AzFramework::WindowRequestBus::EventResult(
+                m_viewportDpiScaleFactor,
+                nativeWindow,
+                &AzFramework::WindowRequestBus::Events::GetDpiScaleFactor);
             AzFramework::WindowNotificationBus::Handler::BusConnect(nativeWindow);
             AzFramework::ViewportRequestBus::Handler::BusConnect(id);
 
@@ -148,6 +153,11 @@ namespace AZ
             return m_viewportSize;
         }
 
+        float ViewportContext::GetDpiScalingFactor() const
+        {
+            return m_viewportDpiScaleFactor;
+        }
+
         void ViewportContext::ConnectSizeChangedHandler(SizeChangedEvent::Handler& handler)
         {
             handler.Connect(m_sizeChangedEvent);
@@ -289,5 +299,10 @@ namespace AZ
                 m_sizeChangedEvent.Signal(m_viewportSize);
             }
         }
+
+        void ViewportContext::OnDpiScaleFactorChanged(float dpiScaleFactor)
+        {
+            m_viewportDpiScaleFactor = dpiScaleFactor;
+        }
     } // namespace RPI
 } // namespace AZ

Gems/Atom/Tools/AtomToolsFramework/Code/Include/AtomToolsFramework/Viewport/RenderViewportWidget.h

@@ -113,6 +113,7 @@ namespace AtomToolsFramework
         void SetFullScreenState(bool fullScreenState) override;
         bool CanToggleFullScreenState() const override;
         void ToggleFullScreenState() override;
+        float GetDpiScaleFactor() const override;
 
     protected:
         // AzFramework::InputChannelEventListener ...

Gems/Atom/Tools/AtomToolsFramework/Code/Source/Viewport/RenderViewportWidget.cpp

@@ -540,4 +540,9 @@ namespace AtomToolsFramework
     {
         // The RenderViewportWidget does not currently support full screen.
     }
+
+    float RenderViewportWidget::GetDpiScaleFactor() const
+    {
+        return aznumeric_cast<float>(devicePixelRatioF());
+    }
 } //namespace AtomToolsFramework