[poppler] drawChar(): parameter dy is always 0?

[Ihar `Philips` Filipau]

Hi All!

I'm trying to figure out how to calculate the bounding box of the text
inside the drawChar().

I have noticed that the parameter `dy` is always zero. Also all the
usual ways to calculate the text box always return yMin == yMax. And
the TextOutputDev appears to always use cached fontSize instead.

What is the proper way to calculate text bounding box in case of
beginString()/drawChar()/endString() methods?