Virtual Joytick (Touch interface) do not use DPI Scaling like UMG

Development Programming & Scripting C++
1

Hi,

I just found that virtual joystick do not use the same scaling as UMG widget.

https://github.com/EpicGames/UnrealEngine/blob/f509bb2d6c62806882d9a10476f3654cf1ee0634/Engine/Source/Runtime/Slate/Private/Widgets/Input/SVirtualJoystick.cpp

in

static FORCEINLINE float GetScaleFactor(const FGeometry& Geometry)

it is hardcoded a **const float DesiredWidth = 1024.0f; **to calculate DPI.

It is hard to place UMG widget properly with Joytick as they don’t follow the same DPI rules.

I’m on a mobile game so the resolution change a lot between devices and I need to be able to control this.

I submit a “bug” request but until then can someone help me on how to fix this?

I already try to do in the GetScaleFactor:


const FVector2D viewportSize = FVector2D(GEngine->GameViewport->Viewport->GetSizeXY());
const float viewportScale = GetDefault<UUserInterfaceSettings>(UUserInterfaceSettings::StaticClass())->GetDPIScaleBasedOnSize(FIntPoint(viewportSize.X, viewportSize.Y));

Sadly, the result are not right. I must miss something in the paint/geometry allocation process in slate but I can get where.

Thanks

@Nick_Darnell I know you build a lot of the UMG Widgets, could you please give me some hint on how to solve this?

2

Little bump in case anyone knows how to fix this.

Thanks,

3

Ran into this as well due to having UI objects in both HUD (not DPI scaled) and HUDWidget (DPI scaled). Use these to translate when needed:



#include "Runtime/UMG/Public/Blueprint/WidgetLayoutLibrary.h"
#include "Runtime/Engine/Classes/Engine/UserInterfaceSettings.h"
#include "Runtime/Engine/Public/SceneView.h"

/**
* Get DPI scale of UMG HUD.
* Used to translate actual pixels to DPI scaled pixels.
*/
float UPrimaryHUDWidget::Get_UMG_DPI_Scale()
{
 // need a variable here to pass to the GetViewportSize function
 FIntPoint viewportSize = GetWorld()->GetGameViewport()->Viewport->GetSizeXY();

 // we need to floor the float values of the viewport size so we can pass those into the GetDPIScaleBasedOnSize function
 int32 X = FGenericPlatformMath::FloorToInt(viewportSize.X);
 int32 Y = FGenericPlatformMath::FloorToInt(viewportSize.Y);

 // the GetDPIScaleBasedOnSize function takes an FIntPoint, so we construct one out of the floored floats of the viewport
 // the fuction returns a float, so we can return the value out of our function here
 return GetDefault<UUserInterfaceSettings>(UUserInterfaceSettings::StaticClass())->GetDPIScaleBasedOnSize(FIntPoint(X, Y));
}

/**
* Get inverse DPI scale of UMG HUD.
* Use to translate DPI scaled pixels to actual pixels.
*/
float UPrimaryHUDWidget::Get_Inverse_UMG_DPI_Scale()
{
 float dpiScale = Get_UMG_DPI_Scale();
 if (dpiScale <= 0.0)
 {
  return 1.0f;
 }
 else
 {
  return 1.0f / dpiScale;
 }
}

An easy test to ensure your DPI scaling works is draw a crosshair in the center of the DPI-scaled HUD based on the actual ViewPort pixel width and height:



    // to get center of screen here we need to invert UMG DPI scaling
    FVector2D iconDrawPosition;
    FIntPoint size = GetWorld()->GetGameViewport()->Viewport->GetSizeXY();
    iconDrawPosition.X = (float)(size.X) * 0.5f *  Get_Inverse_UMG_DPI_Scale();
    iconDrawPosition.Y = (float)(size.Y) * 0.5f *  Get_Inverse_UMG_DPI_Scale();
4

Hi,

thanks for the answer. In fact the joystick is a bit particular.
If you want to apply the DPI as any other, you need to return 1.f in GetScaleFactor(). Otherwise, you apply twice the DPI scale.
I opened a issue case in Unreal and hope they will fix that soon. Otherwise, you need to setup your own class and override a lot of stuff to get this little change working.