[GP]

Hi,

does anyone know why the method removeAllEntities does not remove an EntityBaseDraggable object? The property preventFromRemovalFromEntityManager is set to false.

We are using the BuildEntityButton to drag an EntityBaseDraggable around in our GameScene, but if we want to reset the whole Scene with entityManager.removeAllEntities() the EntityBaseDraggable is still there. This behaviour occurs if the onEntityWasBuilt was not called that means the BuildEntityButton is still in the onEntityPressed handler (scene was changed while the user is still dragging the shape around).

 

Cheers!

[ChristianFelgo Team]

Hi,

please post a complete example with the relevant source code that demonstrates your issue.

Cheers, Chris

[GP]

Hi Chris,

here is a little code example. To find that bug you need to drag some boxes on the platform (they will be removed correctly), then let one box fall on the ground and drag (and hold) a new box into to the scene at once. If you restart the scene now, all entities are removed except the EntityBaseDraggable object.

Here is the source code:

Box.qml

// import QtQuick 1.0 // to target S60 5th Edition or Maemo 5
import QtQuick 1.1
import VPlay 1.0
import Box2D 1.0

EntityBaseDraggable {
    id: box
    entityType: "rectangle"
    entityId: "box"

    colliderComponent: boxCollider
    selectionMouseArea.anchors.fill: rect
    gridSize: 1
    height: 20
    width: 20
    dragOffset: Qt.point(0,0)
    allowedToBuild: true

    property alias sWidth: rect.width
    property alias sHeight: rect.height
    property bool isPlaced:false;

    showRectangleWhenBuildingNotAllowed: false


    Rectangle {
        id: rect
        width: 30
        height: 30
        color: "yellow"
    }


    BoxCollider {
        id: boxCollider
        anchors.fill:rect
        density:100

        friction: 1.6
        restitution: 0

        fixture.onBeginContact: {
            if(!isPlaced) {
                rect.color = "red"; allowedToBuild = false;}}
        fixture.onEndContact:  {
            rect.color = "yellow"; allowedToBuild = true}

    }
}

BoxPreview.qml

import QtQuick 1.1
import VPlay 1.0
import Box2D 1.0


BuildEntityButton {

    id: ballPreview
    toCreateEntityType: "Box.qml"
    width: 20
    height: 20

    property int shapeWidth: 20
    property int shapeHeight: 20

    creationProperties: {

        "sWidth": shapeWidth,
        "sHeight": shapeHeight,
        "isPlaced":true
    }

    onEntityPressed: {

         createdEntity.isPlaced = false;

     }

    Rectangle {
        height: 20
        width: 20
        color: "yellow"
        anchors.fill: parent
    }

}

GameOverScene.qml

// import QtQuick 1.0 // to target S60 5th Edition or Maemo 5
import QtQuick 1.1
import VPlay 1.0
import Box2D 1.0

Scene {
    id: gameOverScene

    Button {
        text: "Restart"
        anchors.centerIn: parent

        onClicked: {
            entityManager.removeAllEntities();
            scene.state = "game"
        }
    }


}

main.qml

import VPlay 1.0
import Box2D 1.0
import QtQuick 1.1

GameWindow {
    id: window
    // the size of the Window can be changed at runtime by pressing the number keys 1-6 with QML window active
    // the content of the logical scene size (480x320) gets scaled to the window size based on the scaleMode
    width: 960
    height: 640

    EntityManager {
        id: entityManager
        entityContainer: scene
    }

    GameOverScene {
        id: gameOverScene
        opacity: 0
    }
    
    Scene {
        id: scene

        opacity: 0

        Row {
            spacing: 5
            anchors {
                top: parent.top
                horizontalCenter: parent.horizontalCenter
            }

            BoxPreview{shapeHeight: 50; shapeWidth: 50}
            BoxPreview{shapeHeight: 50; shapeWidth: 50}
            BoxPreview{shapeHeight: 50; shapeWidth: 50}
        }

        // platform (here you can place shapes)
        Rectangle {
            width: 50
            height: 10

            x: 100
            y: parent.height / 2

            color: "blue"

            BoxCollider {
                anchors.fill: parent
                bodyType: Body.Static
            }
        }



        // ground (if shape falls on ground, game is over)
        Rectangle {
            width: parent.width
            height: 5
            color: "grey"


            anchors.bottom: parent.bottom

            BoxCollider {
                anchors.fill: parent
                bodyType: Body.Static

                fixture.onBeginContact: {
                    scene.state = "gameOver"
                }

            }
        }


        PhysicsWorld {
            id: physicsWorld
            gravity.y: -9.81
            z: 10


            updatesPerSecondForPhysics: 60
            velocityIterations: 5
            positionIterations: 5
        }

        onStateChanged: {
            if (state === "gameOver")
                activeScene = gameOverScene
            else if (state === "game")
                activeScene = scene
        }

        state: "game"

        states: [
            State {
                name: "game"
                PropertyChanges {target: scene; opacity:1}
            },
            State {
                name: "gameOver"
                PropertyChanges {target: gameOverScene; opacity:1}
            }
        ]


    }
}

 

Cheers!

[ChristianFelgo Team]

Ah I got it, thanks to your great example it was easy to find!

The reason why it did not work, is the internal behaviro of the BuildEntityButton: it creates an entity for each button, which gets then dragged around. However, this entity should not be removed when you call entityManager.removeAllEntities, thus it sets its preventFromRemoval flag to true. So what you can do to solve your use-case, is just make the created entity invisible once the game is over, or easier done when the BuildEntityButton gets invisible. So add this code to your BoxPreview and it should work fine:

    // at changing the scene, make the internally created entity from BuildEntityButton invisible at well
    onVisibleChanged: {
      if(!visible) {
        createdEntity.visible = false;
      }
    }

Cheers, Chris

[GP]

Hi Chris,

thank you for your answer. This is a really good approch but the problem is the shape (box) is still there (invisible). I really need to remove the shape completely, so no other shape can collide with it.

Cheers!

[ChristianFelgo Team]

Hi,

just set the collidersActive flag also to false, this should deactivate the collider then.

Cheers, Chris

[GP]

Hi again,

to change the collidersActive flag did not work for me, instead I tried this and this solved my problem:

    onVisibleChanged: {
      if(!visible) {
        createdEntity.visible = false;
        createdEntity.preventFromRemovalFromEntityManager = false;
      }
    }

You have to change the preventFromRemoval flag explicitly again, it is not enough to set that flag only in the box property. However my problem is solved! Thank you very much for your support!

 

Cheers!