Add DPI scaling to IMGUI

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

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

@@ -92,6 +92,11 @@ namespace AZ
             //! Alternatively, connect to ViewportContextNotificationsBus and listen to ViewportContextNotifications::OnViewportSizeChanged.
             void ConnectSizeChangedHandler(SizeChangedEvent::Handler& handler);
 
+            using ScalarChangedEvent = AZ::Event<float>;
+            //! Notifies consumers when the viewport DPI scaling ratio has changed.
+            //! Alternatively, connect to ViewportContextNotificationsBus and listen to ViewportContextNotifications::OnViewportDpiScalingChanged.
+            void ConnectDpiScalingFactorChangedHandler(ScalarChangedEvent::Handler& handler);
+
             using MatrixChangedEvent = AZ::Event<const AZ::Matrix4x4&>;
             //! Notifies consumers when the view matrix has changed.
             void ConnectViewMatrixChangedHandler(MatrixChangedEvent::Handler& handler);
@@ -141,6 +146,7 @@ namespace AZ
             float m_viewportDpiScaleFactor = 1.0f;
 
             SizeChangedEvent m_sizeChangedEvent;
+            ScalarChangedEvent m_dpiScalingFactorChangedEvent;
             MatrixChangedEvent m_viewMatrixChangedEvent;
             MatrixChangedEvent::Handler m_onViewMatrixChangedHandler;
             MatrixChangedEvent m_projectionMatrixChangedEvent;

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

@@ -105,8 +105,10 @@ namespace AZ
         class ViewportContextNotifications
         {
         public:
-            //! Called when the underlying native window size changes for a given viewport context name.
+            //! Called when the underlying native window size changes for a given viewport context.
             virtual void OnViewportSizeChanged(AzFramework::WindowSize size){AZ_UNUSED(size);}
+            //! Called when the window DPI scaling changes for a given viewport context.
+            virtual void OnViewportDpiScalingChanged(float dpiScale){AZ_UNUSED(dpiScale);}
             //! Called when the active view for a given viewport context name changes.
             virtual void OnViewportDefaultViewChanged(AZ::RPI::ViewPtr view){AZ_UNUSED(view);}
             //! Called when the viewport is to be rendered.

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

@@ -51,6 +51,7 @@ namespace AZ
             {
                 AZStd::weak_ptr<ViewportContext> context;
                 ViewportContext::SizeChangedEvent::Handler sizeChangedHandler;
+                ViewportContext::ScalarChangedEvent::Handler dpiScalingChangedHandler;
             };
 
             // ViewportContextManager is a singleton owned solely by RPISystem, which is tagged as a friend

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

@@ -163,6 +163,11 @@ namespace AZ
             handler.Connect(m_sizeChangedEvent);
         }
 
+        void ViewportContext::ConnectDpiScalingFactorChangedHandler(ScalarChangedEvent::Handler& handler)
+        {
+            handler.Connect(m_dpiScalingFactorChangedEvent);
+        }
+
         void ViewportContext::ConnectViewMatrixChangedHandler(MatrixChangedEvent::Handler& handler)
         {
             handler.Connect(m_viewMatrixChangedEvent);
@@ -303,6 +308,7 @@ namespace AZ
         void ViewportContext::OnDpiScaleFactorChanged(float dpiScaleFactor)
         {
             m_viewportDpiScaleFactor = dpiScaleFactor;
+            m_dpiScalingFactorChangedEvent.Signal(dpiScaleFactor);
         }
     } // namespace RPI
 } // namespace AZ

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

@@ -62,9 +62,20 @@ namespace AZ
                     }
                     ViewportContextIdNotificationBus::Event(viewportId, &ViewportContextIdNotificationBus::Events::OnViewportSizeChanged, size);
                 };
+                auto onDpiScalingChanged = [this, viewportId](float dpiScalingFactor)
+                {
+                    // Ensure we emit OnViewportDpiScalingChanged with the correct name.
+                    auto viewportContext = this->GetViewportContextById(viewportId);
+                    if (viewportContext)
+                    {
+                        ViewportContextNotificationBus::Event(viewportContext->GetName(), &ViewportContextNotificationBus::Events::OnViewportDpiScalingChanged, dpiScalingFactor);
+                    }
+                    ViewportContextIdNotificationBus::Event(viewportId, &ViewportContextIdNotificationBus::Events::OnViewportDpiScalingChanged, dpiScalingFactor);
+                };
                 viewportContext->m_name = contextName;
                 viewportData.sizeChangedHandler = ViewportContext::SizeChangedEvent::Handler(onSizeChanged);
                 viewportContext->ConnectSizeChangedHandler(viewportData.sizeChangedHandler);
+                viewportContext->ConnectDpiScalingFactorChangedHandler(viewportData.dpiScalingChangedHandler);
                 ViewPtrStack& associatedViews = GetOrCreateViewStackForContext(contextName);
                 viewportContext->SetDefaultView(associatedViews.back());
                 onSizeChanged(viewportContext->GetViewportSize());
@@ -176,6 +187,7 @@ namespace AZ
             UpdateViewForContext(newContextName);
             // Ensure anyone listening on per-name viewport size updates gets notified.
             ViewportContextNotificationBus::Event(newContextName, &ViewportContextNotificationBus::Events::OnViewportSizeChanged, viewportContext->GetViewportSize());
+            ViewportContextNotificationBus::Event(newContextName, &ViewportContextNotificationBus::Events::OnViewportDpiScalingChanged, viewportContext->GetDpiScalingFactor());
         }
 
         void ViewportContextManager::EnumerateViewportContexts(AZStd::function<void(ViewportContextPtr)> visitorFunction)

Gems/AtomLyIntegration/ImguiAtom/Code/Source/ImguiAtomSystemComponent.cpp

@@ -105,10 +105,20 @@ namespace AZ
                 // Let our ImguiAtomSystemComponent know once we successfully connect and update the viewport size.
                 if (!m_initialized)
                 {
+                    auto atomViewportRequests = AZ::Interface<AZ::RPI::ViewportContextRequestsInterface>::Get();
+                    auto defaultViewportContext = atomViewportRequests->GetDefaultViewportContext();
+                    OnViewportDpiScalingChanged(defaultViewportContext->GetDpiScalingFactor());
                     m_initialized = true;
                 }
             });
-#endif
+#endif //define(IMGUI_ENABLED)
+        }
+
+        void ImguiAtomSystemComponent::OnViewportDpiScalingChanged(float dpiScale)
+        {
+#if defined(IMGUI_ENABLED)
+            ImGui::ImGuiManagerBus::Broadcast(&ImGui::ImGuiManagerBus::Events::SetDpiScalingFactor, dpiScale);
+#endif //define(IMGUI_ENABLED)
         }
     }
 }

Gems/AtomLyIntegration/ImguiAtom/Code/Source/ImguiAtomSystemComponent.h

@@ -51,6 +51,7 @@ namespace AZ
             // ViewportContextNotificationBus overrides...
             void OnRenderTick() override;
             void OnViewportSizeChanged(AzFramework::WindowSize size) override;
+            void OnViewportDpiScalingChanged(float dpiScale) override;
 
             DebugConsole m_debugConsole;
             bool m_initialized = false;

Gems/ImGui/Code/Include/ImGuiBus.h

@@ -86,6 +86,8 @@ namespace ImGui
         virtual void SetImGuiRenderResolution(const ImVec2& res) = 0;
         virtual void OverrideRenderWindowSize(uint32_t width, uint32_t height) = 0;
         virtual void RestoreRenderWindowSizeToDefault() = 0;
+        virtual void SetDpiScalingFactor(float dpiScalingFactor) = 0;
+        virtual float GetDpiScalingFactor() const = 0;
         virtual void Render() = 0;
     };
 

Gems/ImGui/Code/Source/ImGuiManager.cpp

@@ -277,6 +277,20 @@ void ImGui::ImGuiManager::RestoreRenderWindowSizeToDefault()
     InitWindowSize();
 }
 
+void ImGui::ImGuiManager::SetDpiScalingFactor(float dpiScalingFactor)
+{
+    ImGuiIO& io = ImGui::GetIO();
+    // Set the global font scale to size our UI to the scaling factor
+    // Note: Currently we use the default, 13px fixed-size IMGUI font, so this can get somewhat blurry
+    io.FontGlobalScale = dpiScalingFactor;
+}
+
+float ImGui::ImGuiManager::GetDpiScalingFactor() const
+{
+    ImGuiIO& io = ImGui::GetIO();
+    return io.FontGlobalScale;
+}
+
 void ImGuiManager::Render()
 {
     if (m_clientMenuBarState == DisplayState::Hidden && m_editorWindowState == DisplayState::Hidden)

Gems/ImGui/Code/Source/ImGuiManager.h

@@ -57,6 +57,8 @@ namespace ImGui
         void SetImGuiRenderResolution(const ImVec2& res) override { m_renderResolution = res; }
         void OverrideRenderWindowSize(uint32_t width, uint32_t height) override;
         void RestoreRenderWindowSizeToDefault() override;
+        void SetDpiScalingFactor(float dpiScalingFactor) override;
+        float GetDpiScalingFactor() const override;
         void Render() override;
         // -- ImGuiManagerBus Interface -------------------------------------------------------------------