Android Question Responsive Font Size?

BCTextEngine actually measures the characters glyphs. You can achieve exact layout.

For a single line measurement, this is also accurate: https://www.b4x.com/android/forum/t...e-text-measurement-and-drawing.92810/#content

Just a note to remind you that perceived font size is not only dependent on physical and pixel screen size,
but also on the distance of the viewer to the screen - think TV, desktop, tablet, phone, watch.

One technique I have experimented with is to use a standard phrase "The quick brown fox jumped over the lazy dog"
Then make sure that phrase can be read from the "usual" distance to the screen of the target device.

Measure the phrase using B4XCanvas.MeasureText and determine the scaling factor for font size.
You'll find that there are some upper and lower limits on readability - so the scaling will need to accommodate that.