Text height/overlapping bug

Question

We are having a problem where part of a previous textline is
overlapping the next line. The tails of letters like "j" and "g"
and "y" are overlapping the next line when we have different font
sizes. From our text metrics debugging, the line height seems to be
off by the descent amount. I am using build 5011. Here is sample
code to recreate the problem.

Answer 1

I think this is not a bug, but a byproduct of the fact that
TLF is doing baseline leading. TLF is placing the first line based
on the largest ascent on the line. You can alter the placement of
this line down by changing the value of the firstBaselineOffset
property. The second line is placed according to its lineHeight
propery (also sometimes called the leading). In this case, the
lineHeight is the default value, 120% of the largest fontSize,
which with the fontSize=12 will be 14.4 pixels. So the second line
is placed so that its baseline is 14.4 pixels below the baseline of
the first line. In this case, that's too tight.
There are a couple of things you could do to space the
paragraphs out further. You could assign a larger lineHeight to the
second line, either a larger percentage or absolute pixel value. Or
you could add space between the two paragraphs by assigning a
positive value to the first paragraph's marginBottom. Or you could
set the marginTop of the second paragraph.
Baseline leading is a different model from that used by most
word processors, including Microsoft Word. It is used in
applications such as Adobe InDesign and Illustrator. The advantage
is that it gives the user more control over how the lines are
placed. The disadvantage is cases like these where it doesn't do
the right thing by default.
I hope that one of these proposals is a viable solution to
your problem.
Thanks!