The correct way:
is to declare the widget in C++ using the UPROPERTY meta specifier “BindWidget” as I do in my framework:
Look for “BindWidget”
Direct example:
UPROPERTY(BlueprintReadOnly, Category = "Widgets", meta = (BindWidget))
UTextBlock* TitleTextWidget = nullptr;
You then create a UserWidget based on this C++ UserWidget and open that in the widget editor. The widget designer will be notified that an inner widget is either optional or required (by name and widget type).
During runtime the C++ widget pointer will automatically be set to the inner widget the designer placed on the widget editor.
This makes it possible to write all the core logic in C++ while not yet having the design. The designer still has complete freedom to implement the widget tree’s layout.
I don’t know if the widget editor (or the UAsset) allows this, or should.
Of these only NativePreConstruct would run inside the editor window, and it could run multiple times conditionally as well. Afaik it runs every time the widget tree changes.
Something else:
Your header has a flaw:
public:
UCanvasPanel* CanvasPanel;
problem 1:
UCanvasPanel is a UObject so it should be marked as UPROPERTY, as it is a property of your class. Not marking it UPROPERTY will cause it to be garbage collected incorrectly (nulling your pointer when it should not).
The garbage collector system builds a chain of UObjects referencing UObjects. If a UObject is not part of the main chain (not referenced properly (or not marked UPROPERTY when should)), it is garbage collected.
problem 2:
The pointer is not initialized as nullptr. This can lead to undefined behavior.
problem 3:
A category is missing for a blueprint accessible property. Afaik I’ve only seen FAB complain when you don’t add the category specifier to a UPROPERTY.
A best practice recommendation:
Mark the property as private or protected when possible. If required to directly access the property (either within that space or pubicly), write a getter method.
Fix:
protected:
UPROPERTY(BlueprintReadOnly, Category = "Widgets", meta = (BindWidget))
UCanvasPanel* MyCanvasPanel = nullptr;
Epic’s recommendation:
Since UE5 EPIC started to recommend using TObjectPtr over raw pointers, but it’s not a requirement. Not required by the engine, not by FAB, really just optional.