stringWidth method
Implementation
double stringWidth( String str ){
ui.ParagraphBuilder builder = ui.ParagraphBuilder(
ui.ParagraphStyle( textDirection: ui.TextDirection.ltr )
);
builder.pushStyle( ui.TextStyle(
fontSize: _canvasEnv._fontSize,
fontFamily: _canvasEnv._font
) );
builder.addText( str );
ui.Paragraph paragraph = builder.build();
paragraph.layout( const ui.ParagraphConstraints( width: 0 ) );
return paragraph.maxIntrinsicWidth;
}