QML TextArea emoji width measure error

[hobbe]

From image you can see,the selected emoji char should be a little more wide than double x-width,but the selection width acturally are 4 times than the emoji should be.
And,When I measure width of this emoji(combined with multi QChar) via QFontMetrics,the result is emojiLen2x-width not 2*x-width
How can I fix this problem?