Devlog #4: Creating Puzzle Slots

Adding Children to C++ UUserWidget

Anyhow, in a past devlog, I talked about adding widgets through C++ using BindWidget. However, this time, I wanted to not only create widget components, but also to add them to my class in a hierarchy (ie; having a UImage be a child of a USizebox). I found useful information on this forum post:

Add child to C++ UUserWidget

I wrote the following code in my NativeConstruct override:

NOTE FROM FUTURE ABYSS: WHILE THIS METHOD DOES INDEED WORK, IT CAUSED ISSUES FOR ME AND WOULDN'T APPEAR VISIBLE AT RUN TIME NO MATTER WHAT. I ENDED UP COMMENTING IT OUT IN THE END.

void UJigsawSlot::NativeConstruct()
{
SizeBox = WidgetTree->ConstructWidget<USizeBox>(USizeBox::StaticClass(), TEXT("RootWidget"));
WidgetTree->RootWidget = SizeBox;
SizeBox->AddChild(Image);
}

And this method did indeed work; when I created the appropriate widgets in the editor, it wouldn't let me add an Image widget component that is a child of the root, it only let me add an image component that is a child of the sizebox:

Creating Event Dispatchers in C++

Afterwards, I needed to add event dispatchers through C++ in a way that they could be run by blueprints. I've done event dispatchers before, but it's been a while so I needed a refresher.

I used the instructions from this forum post:

C++ Event dispatchers: How do we implement them?

And this here is the code I wrote:

JigsawSlot.h

// Fill out your copyright notice in the Description page of Project Settings.
#pragma once
#include "CoreMinimal.h"
#include "Blueprint/UserWidget.h"
#include "JigsawSlot.generated.h"
//delegates must be created outside fo the class declaration
//delegate type declarations must start with F
DECLARE_DYNAMIC_MULTICAST_DELEGATE(FPieceCorrectlyPlacedDelegate);
// We make the class abstract, as we don't want to create
// instances of this, instead we want to create instances
// of our UMG Blueprint subclass.
UCLASS(Abstract)
class PUZZLEGAME_API UJigsawSlot : public UUserWidget
{
GENERATED_BODY()
public:
/* Widgets*/
UPROPERTY(BlueprintReadWrite, Category = "Puzzle", meta = (BindWidget))
class USizeBox* SizeBox;
UPROPERTY(BlueprintReadWrite, Category = "Puzzle", meta = (BindWidget))
class UImage* Image;
/* Variables*/
UPROPERTY(BlueprintReadWrite, Category = "Puzzle", meta = (ExposeOnSpawn = "true"))
FVector2D SlotCoordinate = FVector2D(0, 0);
UPROPERTY(BlueprintReadWrite, Category = "Puzzle", meta = (ExposeOnSpawn = "true"))
UTexture* JigsawImage;
UPROPERTY(BlueprintReadWrite, Category = "Puzzle", meta = (ExposeOnSpawn = "true"))
int NumberOfPieces;
/* Delegates/ Event Dispatchers*/
UPROPERTY(BlueprintAssignable, Category = "Delegate")
FPieceCorrectlyPlacedDelegate OnPieceCorrectlyPlaced;
protected:
// Doing setup in the C++ constructor is not as useful as using NativeConstruct.
virtual void NativeConstruct() override;
};

JigsawSlot.cpp

// Fill out your copyright notice in the Description page of Project Settings.
#include "JigsawSlot.h"
#include "Components/Image.h"
#include "Components/SizeBox.h"
#include "Blueprint/WidgetTree.h"
void UJigsawSlot::NativeConstruct()
{
SizeBox = WidgetTree->ConstructWidget<USizeBox>(USizeBox::StaticClass(), TEXT("RootWidget"));
WidgetTree->RootWidget = SizeBox;
SizeBox->AddChild(Image);
}

And this code worked great! I was able to implement the Event Dispatcher in blueprints: