Manipulating a Running Scene

Loading a scene created in the visual editor creates a visual overlay graphically, but intentionally does nothing else. The objects in view match the scene editor's camera region and the graphics loaded match as well. However, to actually adjust and manipulate a game, add logic, and other ideas, we need computer code.

Because making an application do what we want in code is a complicated topic, we will not go into detail here how everything works and instead will focus on the features that are related to getting items from a scene. Users that want more instruction on coding up parts of an application should reference the various tutorials on the topic on the Quorum site. Here is a template for moving a character in a game:

use Libraries.Game.Game
use Libraries.Game.Scenes.Scene
use Libraries.System.File
use Libraries.Interface.Events.KeyboardListener
use Libraries.Interface.Events.KeyboardEvent
use Libraries.Interface.Item2D
use Libraries.Compute.Vector2
use Libraries.Interface.Events.CollisionListener2D
use Libraries.Interface.Events.CollisionEvent2D
use Libraries.Sound.Speech

/*
    This is a default class for creating a game in Quorum. Note that the Main 
    action begins by calling StartGame(), which loads a window a game can 
    be displayed in. The action CreateGame is where the game should load any 
    assets, like images to be displayed, frames of animation, or sounds to be
    played. 
*/
class Main is Game, KeyboardListener, CollisionListener2D
    
    Speech speech
    Item2D player = undefined

    action Main
        StartGame()
    end

    action CreateGame
        // This code is provided by the Scene template. It automatically loads your scene into the game.
        File file
        file:SetPath("Scenes/Scene2.qs")
        LoadScene(file)
        // End of templated CreateGame code.

        player = FindItem2DByName("1: Boy")

        if player not= undefined
            player:CanRotate(false)
    
            AddKeyboardListener(me)
            AddCollisionListener(me)
            EnablePhysics2D(true)
        end
    end

    action Update(number seconds)
    end

    action PressedKey(KeyboardEvent event)
        if player = undefined
            return now
        end

        Vector2 vector
        if event:keyCode = event:LEFT
            vector:Set(-150, 0)
            player:SetLinearVelocity(vector)
        elseif event:keyCode = event:RIGHT
            vector:Set(150, 0)
            player:SetLinearVelocity(vector)
        elseif event:keyCode = event:UP
            vector:Set(0, 150)
            player:SetLinearVelocity(vector)
        elseif event:keyCode = event:DOWN
            vector:Set(0, -150)
            player:SetLinearVelocity(vector)
        end
    end

    action ReleasedKey(KeyboardEvent event)
        if player = undefined
            return now
        end

        if event:keyCode = event:LEFT or event:keyCode = event:RIGHT or event:keyCode = event:UP or event:keyCode = event:DOWN
            Vector2 vector
            vector:Set(0, 0)
            player:SetLinearVelocity(vector)
        end
    end

    action BeginCollision(CollisionEvent2D event)
        if player = undefined
            return now
        end

        Item2D other = undefined
        if event:GetItemA() = player
            other = event:GetItemB()
        elseif event:GetItemB() = player
            other = event:GetItemA()
        end

        speech:Say(other:GetName())
    end
end

The most crucial point to notice is that when items are given a name, they can be located in a game using the following action:

Item2D player = FindItem2DByName("1: Girl")

This action provides access to items created and loaded in a scene, allowing us to manipulate them with the keyboard, mouse, or however else makes sense for the product we are creating. Note that potentially, we could give all objects in our scene the same name. In such a case, this action would return the first object it finds with the given name, but not all of them. In such a case, we can use other actions to find all items in a scene by looking through the documentation for the Game class or obtaining information from a Layer.

Next Tutorial

In the next tutorial, we will discuss Changing the Scene Palette., which describes changing the scene Palette in Quorum Studio..