Added support for curve-based DPI scaling.

CHANGES.md

@@ -5,11 +5,11 @@ Versions marked as 'unofficial' are labelled only for the needs of this changelo
 Change History
 --------------
 
-Version: 1.19 (2020/03-04)
+Version: 1.19 (2020/03-06)
 - 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.
+- Added option for DPI scaling.
 
 Version: 1.18 (2020/01)
 - Updated to engine version 4.24.

Source/ImGui/Private/ImGuiModuleSettings.cpp

@@ -8,6 +8,37 @@
 #include "ImGuiModuleProperties.h"
 
 
+//====================================================================================================
+// FImGuiDPIScaleInfo
+//====================================================================================================
+
+FImGuiDPIScaleInfo::FImGuiDPIScaleInfo()
+{
+	if (FRichCurve* Curve = DPICurve.GetRichCurve())
+	{
+		Curve->AddKey(   0.0f, 1.f);
+
+		Curve->AddKey(2159.5f, 1.f);
+		Curve->AddKey(2160.0f, 2.f);
+
+		Curve->AddKey(4319.5f, 2.f);
+		Curve->AddKey(4320.0f, 4.f);
+	}
+}
+
+float FImGuiDPIScaleInfo::CalculateResolutionBasedScale() const
+{
+	float ResolutionBasedScale = Scale;
+	if (bScaleWithCurve && GEngine && GEngine->GameUserSettings)
+	{
+		if (const FRichCurve* Curve = DPICurve.GetRichCurveConst())
+		{
+			ResolutionBasedScale *= Curve->Eval((float)GEngine->GameUserSettings->GetDesktopResolution().Y, 1.f);
+		}
+	}
+	return ResolutionBasedScale;
+}
+
 //====================================================================================================
 // UImGuiSettings
 //====================================================================================================
@@ -77,10 +108,10 @@ FImGuiModuleSettings::FImGuiModuleSettings(FImGuiModuleProperties& InProperties,
 
 	// Delegate initializer to support settings loaded after this object creation (in stand-alone builds) and potential
 	// reloading of settings.
-	UImGuiSettings::OnSettingsLoaded.AddRaw(this, &FImGuiModuleSettings::UpdateSettings);
+	UImGuiSettings::OnSettingsLoaded.AddRaw(this, &FImGuiModuleSettings::InitializeAllSettings);
 
 	// Call initializer to support settings already loaded (editor).
-	UpdateSettings();
+	InitializeAllSettings();
 }
 
 FImGuiModuleSettings::~FImGuiModuleSettings()
@@ -93,6 +124,12 @@ FImGuiModuleSettings::~FImGuiModuleSettings()
 #endif
 }
 
+void FImGuiModuleSettings::InitializeAllSettings()
+{
+	UpdateSettings();
+	UpdateDPIScaleInfo();
+}
+
 void FImGuiModuleSettings::UpdateSettings()
 {
 	if (UImGuiSettings* SettingsObject = UImGuiSettings::Get())
@@ -104,6 +141,13 @@ void FImGuiModuleSettings::UpdateSettings()
 		SetUseSoftwareCursor(SettingsObject->bUseSoftwareCursor);
 		SetToggleInputKey(SettingsObject->ToggleInput);
 		SetCanvasSizeInfo(SettingsObject->CanvasSize);
+	}
+}
+
+void FImGuiModuleSettings::UpdateDPIScaleInfo()
+{
+	if (UImGuiSettings* SettingsObject = UImGuiSettings::Get())
+	{
 		SetDPIScaleInfo(SettingsObject->DPIScale);
 	}
 }
@@ -172,13 +216,10 @@ void FImGuiModuleSettings::SetCanvasSizeInfo(const FImGuiCanvasSizeInfo& CanvasS
 }
 
 void FImGuiModuleSettings::SetDPIScaleInfo(const FImGuiDPIScaleInfo& ScaleInfo)
-{
-	if (DPIScale != ScaleInfo)
 {
 	DPIScale = ScaleInfo;
 	OnDPIScaleChangedDelegate.Broadcast(DPIScale);
 }
-}
 
 #if WITH_EDITOR
 
@@ -187,6 +228,11 @@ void FImGuiModuleSettings::OnPropertyChanged(class UObject* ObjectBeingModified,
 	if (ObjectBeingModified == UImGuiSettings::Get())
 	{
 		UpdateSettings();
+		if (PropertyChangedEvent.MemberProperty
+			&& (PropertyChangedEvent.MemberProperty->GetFName() == GET_MEMBER_NAME_CHECKED(FImGuiModuleSettings, DPIScale)))
+		{
+			UpdateDPIScaleInfo();
+		}
 	}
 }
 

Source/ImGui/Private/ImGuiModuleSettings.h

@@ -2,6 +2,7 @@
 
 #pragma once
 
+#include <Curves/CurveFloat.h>
 #include <Delegates/Delegate.h>
 #include <UObject/Object.h>
 
@@ -111,24 +112,34 @@ protected:
 	UPROPERTY(EditAnywhere, Category = "DPI Scale")
 	EImGuiDPIScaleMethod ScalingMethod = EImGuiDPIScaleMethod::ImGui;
 
-	// Fixed scale.
+	// An optional scale to apply on top or instead of the curve-based scale.
 	UPROPERTY(EditAnywhere, Category = "DPI Scale", meta = (ClampMin = 0, UIMin = 0))
 	float Scale = 1.f;
 
+	// Curve mapping resolution height to scale.
+	UPROPERTY(config, EditAnywhere, Category = "DPI Scale", meta = (XAxisName = "Resolution Height", YAxisName = "Scale", EditCondition = "bScaleWithCurve"))
+	FRuntimeFloatCurve DPICurve;
+
+	// Whether to use curve-based scaling. If enabled, Scale will be multiplied by a value read from the DPICurve.
+	// If disabled, only the Scale property will be used.
+	UPROPERTY(config, EditAnywhere, Category = "DPI Scale")
+	bool bScaleWithCurve = true;
+
 public:
 
-	float GetImGuiScale() const { return ShouldScaleInSlate() ? 1.f : Scale; }
+	FImGuiDPIScaleInfo();
 
-	float GetSlateScale() const { return ShouldScaleInSlate() ? Scale : 1.f; }
+	float GetImGuiScale() const { return ShouldScaleInSlate() ? 1.f : CalculateScale(); }
+
+	float GetSlateScale() const { return ShouldScaleInSlate() ? CalculateScale() : 1.f; }
 
 	bool ShouldScaleInSlate() const { return ScalingMethod == EImGuiDPIScaleMethod::Slate; }
 
-	bool operator==(const FImGuiDPIScaleInfo& Other) const
+private:
-	{
-		return (Scale == Other.Scale) && (ScalingMethod == Other.ScalingMethod);
-	}
 
-	bool operator!=(const FImGuiDPIScaleInfo& Other) const { return !(*this == Other); }
+	float CalculateScale() const { return Scale * CalculateResolutionBasedScale(); }
+
+	float CalculateResolutionBasedScale() const;
 };
 
 // UObject used for loading and saving ImGui settings. To access actual settings use FImGuiModuleSettings interface.
@@ -262,7 +273,9 @@ public:
 
 private:
 
+	void InitializeAllSettings();
 	void UpdateSettings();
+	void UpdateDPIScaleInfo();
 
 	void SetImGuiInputHandlerClass(const FStringClassReference& ClassReference);
 	void SetShareKeyboardInput(bool bShare);