<summary>
Get the font em height where the current position is at.
</summary>
<param name="currentPosition">The current text position.</param>
<param name="fontSize">The current font em height</param>
<param name="textRange">The position range of the current format.</param>
<returns>
Standard HRESULT error code.
</returns>
<summary> Get the font em height where the current position is at. </summary> <param name="currentPosition">The current text position.</param> <param name="fontSize">The current font em height</param> <param name="textRange">The position range of the current format.</param> <returns> Standard HRESULT error code. </returns>