You are not the first wanting that... You might find related posts in the forum.

In any case, you won't have a simple path (eg. a straight line for "l") but a more or less complex curve outlining the shape of the letter.

A good advice seen in one of these older threads is to draw the text in an image buffer, then read the pixels to see if a coordinate is above the text.

Or, like others, just define the paths yourself!