Added bindings to JavascriptEditorViewport

[arthursw]

Added bindings to JavascriptEditorViewport to be able to:

• react to mouse moves and inputs, and keyboard inputs,
• set the viewport type and the view mode,
• project/unproject from screen to world.

Also added a hack to be able to simply draw a selection rectangle on the viewport canvas in FJavascriptEditorViewportClient::Draw(FViewport* Viewport, FCanvas* Canvas), with SelectionBeginPoint and SelectionEndPoint. This should be improved, but it would probably mean exposing FCanvas and FCanvasBoxItem to Blueprint/Javascript.

[nakosung]

This function seems to handle draw behavior for specific use case. I think there should be some functions which exposes FCanvas*Item accessible to BP.

[arthursw]

Yes, I fully agree, I updated my pull request.

I exposed the FCanvas as a UCanvas like in JavascriptEdMode.

For this purpose, I moved GetCanvasByName() from JavascriptEdMode.cpp to JavascriptEditorLibrary.h to be able to access it from JavascriptEdMode.cpp and JavascriptEditorViewport.cpp.

Tell me if there is a better solution.

[arthursw]

I forgot to make some changes... Working on it...

[nakosung]

It is recommended to hold UObject references by FGCObject. Could you transform your code not to call AddToRoot?

[arthursw]

Ok, I did something, I'm not sure that it is a good solution though.

I added

UProperty()
UCanvas *Canvas;

to UJavascriptEditorViewport (I moved GetCanvasByName() back to JavascriptEdMode.cpp).

Instead, I could override FEditorViewportClient::AddReferencedObjects() for the FJavascriptEditorViewportClient (in JavascriptEditorViewport.cpp), maybe it is a better solution?

In JavascriptEditorViewport.cpp:

    virtual void AddReferencedObjects(FReferenceCollector& Collector) override
    {
        FEditorViewportClient::AddReferencedObjects(Collector);
        Collector.AddReferencedObject(CanvasObject);     // Add a reference to the UCanvas object
    }

(In the same way, I could also add Collector.AddReferencedObject(CanvasObject); in FJavascriptEdModeInstance::AddReferencedObjects() in JavascriptEdMode.cpp, and remove CanvasObject->AddToRoot() in GetCanvasByName())

I also fixed some bugs in UJavascriptEditorViewport::DeprojectScreenToWorld()and UJavascriptEditorViewport::ProjectWorldToScreen(), and removed FIntRect ViewRect;and FViewMatrices ViewMatrices; from UJavascriptEditorViewport.

[nakosung]

You may create a private object which inherits from FGCObject and override AddReferencedObjects. In this way, GC ref management can be done in right way. :)

I think uproperty only for gc isn't a good way.

[arthursw]

Ok, but why it is better to create a private object which inherits from FGCObject than to override FEditorViewportClient::AddReferencedObjects()? (FEditorViewportClient is a FGCObject)

[arthursw]

Is it better now?

[nakosung]

Thanks, it is looking good to me!