[cairo] Showing my ignorance about text rendering again

Peter Clifton pcjc2 at cam.ac.uk
Tue Feb 23 16:26:00 PST 2010

Hi guys,

I figured someone might know the answer to this - as it will take me
ages to figure out from the source code...

When rending text with pango-cairo, where does the inter-line spacing
metric come from?

Lets say I have a 13pt sans-serif font, lets say family "Arial". My
estimation (from looking at the rendering), that "something" is giving
about 12% leading. IE.. inter-baseline spacing is 1.12 times 13 points.
(When converted to appropriate world coordinates).

Is the "height line" coming from the font metrics, freetype, ...?

I know the answer to this question is probably "no", but should I expect
text rendered in a 13pt font to measure 13 points anywhere? (I had
previously believed this was the nominal designed inter-baseline
spacing, but that only seems true for zero leading).

Would one normally expect the ascent + descent of a "13 pt" font to
measure 13 points?

Best regards,

Peter Clifton

Electrical Engineering Division,
Engineering Department,
University of Cambridge,
9, JJ Thomson Avenue,

Tel: +44 (0)7729 980173 - (No signal in the lab!)

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