Text rendering problems

[jean jean]

1. Unicode characters break layout in Qml
   

In 1st grid is the text as is should be.

In 2nd grid inserted ⭐ character in text2.

In 3rd grid I created a dummy Text

text: t2.text

and calculated the Test2 pixel size

font.pixelSize: t1.font.pixelSize * t1.height / dummy.height

but text is rendered too small.

EDIT: Example code

import QtQuick 2.7
import QtQuick.Controls 2.0
import QtQuick.Layouts 1.3

ApplicationWindow {
    visible: true
    width: 400
    height: 200
    title: qsTr("Hello World")

    Text {
        id: dummy
        visible: false
        font.bold: true
        text: t2.text
    }

    RowLayout {
        anchors.centerIn: parent
        spacing: 40

        GridLayout {
            columns: 2
            Text {
                text: qsTr("Test1:")
            }
            Text {
                id: t1
                font.bold: true
                text: qsTr("Test2")
            }
            Text {
                text: qsTr("Test3:")
            }
            Text {
                font.bold: true
                text: qsTr("Test4")
            }
        }

        GridLayout {
            columns: 2
            Text {
                text: qsTr("Test1:")
            }
            Text {
                font.bold: true
                text: qsTr("⭐Test2")
            }
            Text {
                text: qsTr("Test3:")
            }
            Text {
                font.bold: true
                text: qsTr("Test4")
            }
        }

        GridLayout {
            columns: 2
            Text {
                text: qsTr("Test1:")
            }
            Text {
                id: t2
                font.bold: true
                text: qsTr("⭐Test2")
                font.pixelSize: t1.font.pixelSize * t1.height / dummy.height
            }
            Text {
                text: qsTr("Test3:")
            }
            Text {
                font.bold: true
                text: qsTr("Test4")
            }
        }
    }
}

2. When using

QCoreApplication::setAttribute(Qt::AA_EnableHighDpiScaling);

and application has to display emoji it will crash but not always on the same character.

Screenshot when typing emoji

This bug is reported here and marked as solved but in Qt 5.9.2 the problem persists.

On that page a user posted a workaround, and most of the time solves the problem, but I could not find a font to cover all emoji and it's still crashing.

I need some solutions to bypass these problems.

Thank you!

[jean jean]

About first problem:

Tested it on windows both qt msvc and qt mingw and working as expected.

Tested it on android:

When used QCoreApplication::setAttribute(Qt::AA_EnableHighDpiScaling) did'nt break the layout but the "star" character was not displayed.

When did not use hdpi scaling worked as expected.