Destroying an Item that was set as the sourceItem for a ShaderEffectSource hides the ShaderEffectSource as well

[Stefan Monov76]

What I'm doing, in short:

• I have a ShaderEffectSource Item named snapshotItem with live: false
• Dynamically instantiating an Item called dynamicItem
• Setting snapshotItem.sourceItem = dynamicItem
• Calling snapshotItem.scheduleUpdate()
• At this point, I successfully see two copies of dynamicItem on screen
• On any key, I:
• set snapshotItem.sourceItem to an empty, dummy Item, to make the next step less likely to cause problems
• destroy dynamicItem

The problem is that when a key is pressed, both copies disappear from screen, when I want the snapshotItem one to remain.

Note: If you're interested in the motivation behind wanting to achieve this, see my previous question.

My code:

import QtQuick 2.6
import QtQuick.Window 2.2

Window {
    visible: true
    width: 640
    height: 480
    
    property int childWidth: 100
    property int childHeight: 100
    
    id: root
    property var dynamicItem
    
    Item {
        id: dummy
    }
    
    Component {
        id: dynamicItemComponent
        Rectangle {
            color: "red"
        }
    }
    
    Component.onCompleted: {
        dynamicItem = dynamicItemComponent.createObject(row);
        dynamicItem.width = childWidth;
        dynamicItem.height = childHeight;
        snapshotItem.sourceItem = dynamicItem;
        snapshotItem.scheduleUpdate();
    }
    
    Item {
        focus: true
        Keys.onPressed: {
            snapshotItem.sourceItem = dummy;
            dynamicItem.destroy();
        }
    }
    
    Row {
        id: row
        spacing: 10
        ShaderEffectSource {
            id: snapshotItem
            live: false
            width: childWidth
            height: childHeight
        }
    }
}