Now there is no API to get current caret position in TextField.
When we do not have selected test we can use "selection" property for this, but when some text is selected
we could use "start" or "end" of selection, but for some situations (user selects text by moving caret to the right) it is "start", and for others (user selects
text moving the caret to left) it is "end".
So we can not use selection property and need another way to determine caret position.