exposing FViewport::FOnViewportResized delegate in BlueprintFunctionLibrary to Blueprints

Development Programming & Scripting
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1

Hi everyone,

I’m writing a BlueprintFunctionLibrary as a Plugin and try to expose the delegate of FViewport::FOnViewportResized to bind some custom Blueprint events.

on compile I get

error : Unable to find 'class', 'delegate', 'enum', or 'struct' with name 'FViewport::FOnViewportResized'

I read that this error occurs when the Unreal Reflection system can not find it due to not being declared with UFUCNTION() Or UOBJECT().

Can I somehow work around that?

My current function definition is this:

.h file

#include "UnrealClient.h"

UFUNCTION(BlueprintCallable)
		static void BindToViewportResizeEvent(UPARAM(DisplayName = "Event") FViewport::FOnViewportResized Delegate);

.ccp file

void UMyFuncitonBPLib::BindToViewportResizeEvent(FViewport::FOnViewportResized Delegate)
{
    // theoretically binding like this?
    //FViewport::ViewportResizedEvent.AddUObject(this, &Delegate);
}
2

i would create a new dynamic delegate (not multicast) for my param. and use that.
then bind in a different way. either bind your functionbp, and let your function bp receive the event, then call the delegate (maybe youll need a list for this).
or somehow connect the delegate to the viewport delegate (maybe with a lambda if it allows you).

here’s an example of how i wrap delegates, JUtils/Source/JUtils/Actors/DelegateWrappers.h at master - jerobarraco/JUtils - Codeberg.org
it’s a different use case but can be an example.

3

Thank you for the suggestion.

But I already fail at the definitions :frowning: The Unreal reflection system seem to fail to recognize the existence of the FViewport Class defined in UnrealClient.h. Sorry, I’m still a c++ novice.

#pragma once
#include "UnrealClient.h" // for ViewportResize event bind
#include "ExposedFunctionsBPLibrary.generated.h"

UCLASS()
class UExposedFunctionsBPLibrary : public UBlueprintFunctionLibrary
{
   DECLARE_DYNAMIC_MULTICAST_DELEGATE_TwoParams(FOnViewportResized, FViewport*, 
   Viewport, uint32, ViewportSize);

   UPROPERTY()
   FOnViewportResized OnViewportResize;
}

error : Unable to find 'class', 'delegate', 'enum', or 'struct' with name 'FViewport'
4

skip the viewport then. only declare one param, the size.
though i think you might be importing something wrong.
though, also, i wouldn’t expect that struct to be blueprintable.