On-the-fly font substitution is awesome! How to turn it off?

stan.m

Is it possible to turn off on-the-fly font substitution? How does it even work?

I'm trying to pick a font that supports a unicode subscript two: ₂ (U+2082). I am putting chemical formulas like H₂O in translatable text and need to find a good looking font that I can embed in my QtQuick application.

My favorite font manager shows an empty box when a font does not support subscript two, but I have to click through the fonts one at a time... I want to go through about 300 fonts. This is tedious.

So I had the bright idea to write a QML font viewer. Amazingly, every font supports subscript two. I look closer and many fonts are using the same glyph for the subscript two.

It seems that QtQuick substitutes a suitable font when a glyph is missing from the requested font. It is amazing that the framework is capable of this on-the-fly without any code on my part. But I still don't know what font to embed in my application to that it will display consistently on another system.

Can anyone tell me how to turn off on-the-fly font substitution in a QtQuick application? If not, can someone point me in the right direction so I can understand this magic?

For reference, here is my font viewer code:

import QtQuick 2.0
import QtQuick.Window 2.0
import QtQuick.Controls 1.0

Window {
    visible: true
    width: 600; height: 800

    TextField {
        id: sampleText
        anchors { left: parent.left; right: parent.right; top: parent.top }
        text: qsTr('H₂O + C₁₂H₂₂O₁₁ = sugar water')
    }
    ListView {
        anchors { left: parent.left; right: parent.right; top: sampleText.bottom; bottom: parent.bottom }
        model: Qt.fontFamilies()
        clip: true

        delegate: Rectangle {
            height: Math.max(output.contentHeight, name.contentHeight)
            width: ListView.view.width
            color: (index % 2) ? '#DEF' : 'white'

            Text {
                id: name
                anchors { left: parent.left; verticalCenter: parent.verticalCenter }
                width: parent.width / 4
                elide: Text.ElideRight
                font.pointSize: 12
                text: modelData
            }
            Text {
                id: output
                anchors { left: name.right; right: parent.right; verticalCenter: parent.verticalCenter }
                elide: Text.ElideRight
                font { pointSize: 24; family: modelData }
                text: sampleText.text
            }
        }
    }
}

Unsolved On-the-fly font substitution is awesome! How to turn it off?