Added option for DPI scaling. Current implementation scales the widget in Slate and invert-scales the ImGui canvas size to maintain consistent size on the screen.

CHANGES.md

@@ -5,9 +5,11 @@ Versions marked as 'unofficial' are labelled only for the needs of this changelo
 Change History
 --------------
 
-Version: 1.19 WIP (2020/03-04)
+Version: 1.19 (2020/03-04)
 - Integrated fix for issue with ImGui popup/modal windows not being able to be closed in transparent mouse input mode. 
 - Integrated first version of Adaptive Canvas Size.
+- Added different options to define canvas size, with Adaptive Canvas Size being one of the options (viewport).
+- Added option for DPI scaling. Current implementation scales the whole Slate widget and invert-scales the ImGui canvas size to maintain consistent size on the screen.
 
 Version: 1.18 (2020/01)
 - Updated to engine version 4.24.

README.md

@@ -9,7 +9,7 @@ Dear ImGui is an immediate-mode graphical user interface library that is very li
 
 Status
 ------
-Version: 1.19 WIP
+Version: 1.19
 
 ImGui version: 1.74
 
@@ -236,7 +236,7 @@ There is a self-debug functionality build into this plugin. This is hidden by de
 - `ImGui.Debug.Input` - Show debug for input state.
 
 ### Settings
-Plugin settings can be found in *Project Settings/Plugins/ImGui* panel. Right now they amount to a few properties that customize input handling.
+Plugin settings can be found in *Project Settings/Plugins/ImGui* panel. There is a bunch of properties allowing to tweak input handling, keyboard shortcuts (one for now), canvas size and DPI scale.
 
 ##### Extensions
 - `ImGui Input Handler Class` - Path to own implementation of ImGui Input Handler that allows limited customization of the input handling. If not set, then the default implementation is used.

Source/ImGui/Private/ImGuiModuleSettings.cpp

@@ -104,6 +104,7 @@ void FImGuiModuleSettings::UpdateSettings()
 		SetUseSoftwareCursor(SettingsObject->bUseSoftwareCursor);
 		SetToggleInputKey(SettingsObject->ToggleInput);
 		SetCanvasSizeInfo(SettingsObject->CanvasSize);
+		SetDPIScale(SettingsObject->DPIScale);
 	}
 }
 
@@ -170,6 +171,15 @@ void FImGuiModuleSettings::SetCanvasSizeInfo(const FImGuiCanvasSizeInfo& CanvasS
 	}
 }
 
+void FImGuiModuleSettings::SetDPIScale(float Scale)
+{
+	if (DPIScale != Scale)
+	{
+		DPIScale = Scale;
+		OnDPIScaleChangeDelegate.Broadcast(DPIScale);
+	}
+}
+
 #if WITH_EDITOR
 
 void FImGuiModuleSettings::OnPropertyChanged(class UObject* ObjectBeingModified, struct FPropertyChangedEvent& PropertyChangedEvent)

Source/ImGui/Private/ImGuiModuleSettings.h

@@ -148,6 +148,14 @@ protected:
 	UPROPERTY(EditAnywhere, config, Category = "Canvas Size")
 	FImGuiCanvasSizeInfo CanvasSize;
 
+	// DPI scale for the ImGui widgets.
+	//
+	// Note that when this scale is other than 1.0, canvas size will be scaled before it is passed to the ImGui.
+	// It will be scaled to keep the same screen size as defined by the Canvas Size property. If the default
+	// canvas size is 3840x2160 and the DPI scale is 2.0, the size passed to the ImGui will be 1920x1080.
+	UPROPERTY(EditAnywhere, Category = "DPI Scale", meta = (ClampMin = 0, UIMin = 0))
+	float DPIScale = 1.f;
+
 	// Deprecated name for ToggleInput. Kept temporarily to automatically move old configuration.
 	UPROPERTY(config)
 	FImGuiKeyInfo SwitchInputModeKey_DEPRECATED;
@@ -170,6 +178,7 @@ public:
 
 	// Generic delegate used to notify changes of boolean properties.
 	DECLARE_MULTICAST_DELEGATE_OneParam(FBoolChangeDelegate, bool);
+	DECLARE_MULTICAST_DELEGATE_OneParam(FFloatChangeDelegate, float);
 	DECLARE_MULTICAST_DELEGATE_OneParam(FStringClassReferenceChangeDelegate, const FStringClassReference&);
 	DECLARE_MULTICAST_DELEGATE_OneParam(FImGuiCanvasSizeInfoChangeDelegate, const FImGuiCanvasSizeInfo&);
 
@@ -197,6 +206,9 @@ public:
 	// Get the information how to calculate the canvas size.
 	const FImGuiCanvasSizeInfo& GetCanvasSizeInfo() const { return CanvasSize; }
 
+	// Get the DPI Scale.
+	float GetDPIScale() const { return DPIScale; }
+
 	// Delegate raised when ImGui Input Handle is changed.
 	FStringClassReferenceChangeDelegate OnImGuiInputHandlerClassChanged;
 
@@ -206,6 +218,9 @@ public:
 	// Delegate raised when information how to calculate the canvas size is changed.
 	FImGuiCanvasSizeInfoChangeDelegate OnCanvasSizeInfoChangeDelegate;
 
+	// Delegate raised when the DPI scale is changed.
+	FFloatChangeDelegate OnDPIScaleChangeDelegate;
+
 private:
 
 	void UpdateSettings();
@@ -217,6 +232,7 @@ private:
 	void SetUseSoftwareCursor(bool bUse);
 	void SetToggleInputKey(const FImGuiKeyInfo& KeyInfo);
 	void SetCanvasSizeInfo(const FImGuiCanvasSizeInfo& CanvasSizeInfo);
+	void SetDPIScale(float DPIScale);
 
 #if WITH_EDITOR
 	void OnPropertyChanged(class UObject* ObjectBeingModified, struct FPropertyChangedEvent& PropertyChangedEvent);
@@ -228,6 +244,7 @@ private:
 	FStringClassReference ImGuiInputHandlerClass;
 	FImGuiKeyInfo ToggleInputKey;
 	FImGuiCanvasSizeInfo CanvasSize;
+	float DPIScale = 1.f;
 	bool bShareKeyboardInput = false;
 	bool bShareGamepadInput = false;
 	bool bShareMouseInput = false;

Source/ImGui/Private/Widgets/SImGuiLayout.cpp

@@ -5,6 +5,8 @@
 #include "SImGuiLayout.h"
 #include "SImGuiWidget.h"
 
+#include "ImGuiModuleManager.h"
+
 #include <Widgets/Layout/SConstraintCanvas.h>
 #include <Widgets/Layout/SDPIScaler.h>
 #include <Widgets/Layout/SScaleBox.h>
@@ -15,9 +17,18 @@ void SImGuiLayout::Construct(const FArguments& InArgs)
 {
 	checkf(InArgs._GameViewport, TEXT("Null Game Viewport argument"));
 
+	ModuleManager = InArgs._ModuleManager;
 	GameViewport = InArgs._GameViewport;
 
-	// TODO: Remove instantiation of ImGui Widget outside of this class.
+	if (ModuleManager)
+	{
+		auto& Settings = ModuleManager->GetSettings();
+		SetDPIScale(Settings.GetDPIScale());
+		if (!Settings.OnDPIScaleChangeDelegate.IsBoundToObject(this))
+		{
+			Settings.OnDPIScaleChangeDelegate.AddRaw(this, &SImGuiLayout::SetDPIScale);
+		}
+	}
 
 	ChildSlot
 	[
@@ -28,10 +39,9 @@ void SImGuiLayout::Construct(const FArguments& InArgs)
 		.VAlign(VAlign_Fill)
 		.Visibility(EVisibility::SelfHitTestInvisible)
 		[
-			// Apply custom scale if necessary.
-			// TODO: Bind to relevant parameter.
+			// Apply custom scale if needed.
 			SNew(SDPIScaler)
-			.DPIScale(1.f)
+			.DPIScale(TAttribute<float>(this, &SImGuiLayout::GetDPIScale))
 			.Visibility(EVisibility::SelfHitTestInvisible)
 			[
 				SNew(SConstraintCanvas)
@@ -56,4 +66,13 @@ void SImGuiLayout::Construct(const FArguments& InArgs)
 
 	SetVisibility(EVisibility::SelfHitTestInvisible);
 }
+
+SImGuiLayout::~SImGuiLayout()
+{
+	if (ModuleManager)
+	{
+		ModuleManager->GetSettings().OnDPIScaleChangeDelegate.RemoveAll(this);
+	}
+}
+
 END_SLATE_FUNCTION_BUILD_OPTIMIZATION

Source/ImGui/Private/Widgets/SImGuiLayout.h

@@ -24,9 +24,18 @@ public:
 
 	void Construct(const FArguments& InArgs);
 
+	~SImGuiLayout();
+
 	const TWeakObjectPtr<UGameViewportClient>& GetGameViewport() const { return GameViewport; }
 
 private:
 
+	float GetDPIScale() const { return DPIScale; }
+	void SetDPIScale(float Scale) { DPIScale = Scale; }
+
+
+	FImGuiModuleManager* ModuleManager = nullptr;
 	TWeakObjectPtr<UGameViewportClient> GameViewport;
+
+	float DPIScale = 1.f;
 };

Source/ImGui/Private/Widgets/SImGuiWidget.cpp

@@ -84,6 +84,7 @@ void SImGuiWidget::Construct(const FArguments& InArgs)
 	const auto& Settings = ModuleManager->GetSettings();
 	SetHideMouseCursor(Settings.UseSoftwareCursor());
 	CreateInputHandler(Settings.GetImGuiInputHandlerClass());
+	SetDPIScale(Settings.GetDPIScale());
 	SetCanvasSizeInfo(Settings.GetCanvasSizeInfo());
 
 	// Initialize state.
@@ -283,6 +284,10 @@ void SImGuiWidget::RegisterImGuiSettingsDelegates()
 	{
 		Settings.OnUseSoftwareCursorChanged.AddRaw(this, &SImGuiWidget::SetHideMouseCursor);
 	}
+	if (!Settings.OnDPIScaleChangeDelegate.IsBoundToObject(this))
+	{
+		Settings.OnDPIScaleChangeDelegate.AddRaw(this, &SImGuiWidget::SetDPIScale);
+	}
 	if (!Settings.OnCanvasSizeInfoChangeDelegate.IsBoundToObject(this))
 	{
 		Settings.OnCanvasSizeInfoChangeDelegate.AddRaw(this, &SImGuiWidget::SetCanvasSizeInfo);
@@ -295,6 +300,7 @@ void SImGuiWidget::UnregisterImGuiSettingsDelegates()
 
 	Settings.OnImGuiInputHandlerClassChanged.RemoveAll(this);
 	Settings.OnUseSoftwareCursorChanged.RemoveAll(this);
+	Settings.OnDPIScaleChangeDelegate.RemoveAll(this);
 	Settings.OnCanvasSizeInfoChangeDelegate.RemoveAll(this);
 }
 
@@ -503,6 +509,15 @@ void SImGuiWidget::HandleWindowFocusLost()
 	}
 }
 
+void SImGuiWidget::SetDPIScale(float Scale)
+{
+	if (DPIScale != Scale)
+	{
+		DPIScale = Scale;
+		bUpdateCanvasSize = true;
+	}
+}
+
 void SImGuiWidget::SetCanvasSizeInfo(const FImGuiCanvasSizeInfo& CanvasSizeInfo)
 {
 	switch (CanvasSizeInfo.SizeType)
@@ -535,7 +550,6 @@ void SImGuiWidget::SetCanvasSizeInfo(const FImGuiCanvasSizeInfo& CanvasSizeInfo)
 	}
 
 	bUpdateCanvasSize = true;
-	UpdateCanvasSize();
 }
 
 void SImGuiWidget::UpdateCanvasSize()
@@ -557,6 +571,10 @@ void SImGuiWidget::UpdateCanvasSize()
 				bUpdateCanvasSize = false;
 			}
 
+			// Clamping DPI Scale to keep the canvas size from getting too big.
+			CanvasSize /= FMath::Max(DPIScale, 0.01f);
+			CanvasSize = CanvasSize.RoundToVector();
+
 			ContextProxy->SetDisplaySize(CanvasSize);
 		}
 	}
@@ -820,6 +838,7 @@ void SImGuiWidget::OnDebugDraw()
 				TwoColumns::Value("Is Updating", bUpdateCanvasSize);
 				TwoColumns::ValueWidthHeight("Min Canvas Size", MinCanvasSize);
 				TwoColumns::ValueWidthHeight("Canvas Size", CanvasSize);
+				TwoColumns::Value("DPI Scale", DPIScale);
 			});
 
 			TwoColumns::CollapsingGroup("Context", [&]()

Source/ImGui/Private/Widgets/SImGuiWidget.h

@@ -103,6 +103,8 @@ private:
 	void UpdateTransparentMouseInput(const FGeometry& AllottedGeometry);
 	void HandleWindowFocusLost();
 
+	void SetDPIScale(float Scale);
+
 	void SetCanvasSizeInfo(const FImGuiCanvasSizeInfo& CanvasSizeInfo);
 	void UpdateCanvasSize();
 
@@ -137,6 +139,8 @@ private:
 	FVector2D MinCanvasSize = FVector2D::ZeroVector;
 	FVector2D CanvasSize = FVector2D::ZeroVector;
 
+	float DPIScale = 1.f;
+
 	bool bInputEnabled = false;
 	bool bForegroundWindow = false;
 	bool bHideMouseCursor = true;