[softwarelist] Re: Leading calculation for lines of differing sizes

----- Original Message ----- From: "David Pilling" <flist@xxxxxxxxxxxxxxxxxxx> 
To: <davidpilling@xxxxxxxxxxxxx>
Sent: Sunday, January 21, 2007 6:17 PM
Subject: [softwarelist] Re: Leading calculation for lines of differing sizes
Lets say that y is the coordinate of the top of the bounding box of a line of text. Then y' the coordinate of the next line bounding box is at 

y'=y+max_point_size_of_first_line*leading

(I think - it is a complicated business)


Hello, David,
Thanks for your reply. I had been taking [incremental] leading to be the size of the space between the bounding boxes (equivalent to the lead strips that used to separate lines) so that total leading would be that value plus the height of the bounding box of the first line which I think is a long-winded way of expressing the same as your analysis above.
This, however, didn't match my observations. Take for example a 10 pt line with 400% leading (or 50pt absolute leading - it doesn't actually matter) followed by a 200 pt line with any leading - each with a capital X. The second line overlaps the first. Using your formula this shouldn't be possible. However, I recalled then that fonts have an "origin" which is not necessarily either the top or the bottom of the bounding box. If leading is defined as the spacing between the /origins/ of the two lines then indeed all is explained.
As you suggest, this does make the calculation of the amount of space taken up by several lines of differing sizes a bit more complicated but I think I can now see how it should be done. 

Many thanks for your help (again!).

Regards
John Grogan

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