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

In message <001401c73cf5$f73a0fa0$9601a8c0@PC01>, John Grogan <johngrogan@xxxxxxxxxxxx> writes 
When using relative leading between lines of differing sizes, I note that (for
Homerton Medium font) the actual leading is the given percentage of the size
of the line above the leading plus approximately 0.225 * ( size of line below -
size of line above ).  Is this how the leading is calculated?  If so, is the 
0.225
(a) correct, (b) universal for all fonts and sizes and (c) arbitrary - or does 
it
have some deep mystical significance? 
It doesn't work in the way you suggest. There is no magic constant. The leading is given by the fraction of the maximum point size used in the line.
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)


PS: I couldn't find any reference to the subject in the manual but I did notice 
a
couple of typos in the section about relative leading.  In the first paragraph, 
it
says that the line spacing is 45pt + 20% of 54pt (instead of 45pt) and in Fig
5.7 it shows the results of this calculation as 54.09pt (instead of 54pt).


Thanks.
What is the more damning "I never read the manual" or "I wrote that"? People with pocket calculators eh? 


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David Pilling
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