How to center oversize font inside Text's bounding box? - react-native

Question

I'm trying to create a simple Floating Action Bar button with a plus icon in it, and have had trouble true-centering the "plus" in some edge cases. I was just using '\uFF0B' in a <Text>, but tried to switch to react-native-vector-icons, only to discover that they too were using a font and not an image to back the <Icon> instances, and that my problems seem to persist.
Things are fine on most screens and devices but in some cases users are reporting the plus icon is not perfectly centered. I have a hypothesis that it may involve users' accessibility options increasing the font size in the app beyond size of the parent View. At any rate I can reproduce something like the screenshots folks are sharing with me by setting the fontSize greater than the lineHeight. Assuming that is the issue -
How do you center a single glyph within the view area of a <Text> (or <Icon>, since that derives from <Text>), even when the fontSize may be much larger than the <Text>'s lineHeight or even overall height?
In the below example, the "+" font size is exactly double the line-height, so the plus is centered smack dab on the upper-right corner of the view area, as though it were expecting to be in a box that was 112dp x 112dp; but I want it centered dead-center of the 56dp x 56dp box instead, with the arms of the plus cropped. No combination of style attributes seems to effect it, but rather just controls where the <Icon> positions within its parent.
Currently:
Normally:
For oversized font:
Code:
<View style={s.fabStyle}>
<TouchableOpacity onPress={()=>{this.onPlus()}}>
<Icon name="plus" style={s.fabText} />
</TouchableOpacity>
</View>
...
const s = StyleSheet.create({
fabStyle: {
position: 'absolute',
right: 16,
bottom: 16,
borderRadius: 28,
width: 56,
height: 56,
backgroundColor: styleConstants.color.primary,
display: 'flex',
justifyContent: 'center',
alignItems: 'center',
textAlign: 'center',
},
fabText: {
position: 'relative',
left: 0,
top: 0,
right: 0,
bottom: 0,
fontSize: 112,
color: '#fff',
textAlign: 'center',
lineHeight: 56,
width: 56,
height: 56,
},
});

Answer 1

This isn't an answer to the question itself, which still stands, but an answer to the underlying issue, in case somebody arrives here by Google search with a similar issue. In my case it was indeed the case that accessibility settings were causing font to be bigger than it was designed to be, thus triggering the above scenario. While I still don't know how to center the text adequately in this case, in my case the issue could be circumvented by making sure allowFontScaling=false for relevant Views holding text.