Better Justification in 1.3.4

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In 1.3.4 we implemented some ideas which come via pdfTeX (long read: [Micro-typographic extensions to the TeX typesetting system]) from the famous [hz-program].

The first improvement does not have such noble origin but is a straight-forward change on the normal linebreaking algorithm: instead of always enlarging spaces to justify a line, Scribus now also considers shrinking spaces and takes the option which looks better for the current line. This has a tremendous effect on the justification quality if you set the minimal wordspacing to a value between 50% and 66%.

If wordspacing is not enough to justify a line, other programs resort to automatic letter spacing to fill the line. I abhor that idea, but I borrowed something similar from pdfTeX: glyph extension. This is just a horizontal scaling of characters. The advantage of glyph extension (compared to letter spacing) is that it doesn't change the text color (that is the proportion of black/white in a line). The disadvantage is that glyph extension changes the shape of letters. Therefore you should restrict yourself to values between 95%-105% for glyph extension.

The third improvement in Scribus 1.3.4 are optical margins. With justified text, if the last letter of each line is aligned geometrically, the right margin still looks ragged to the human eye. That's because characters like 'r' or 'y' leave more white space at the end than eg. 'o' or 'k'. One of the worst characters in that respect is at the same time a very common character at the end of a line: the hyphen. An older concept called Hanging Punctuation therefore moved hyphens, colons, dots, quotes and other punctuation into the margin in order to achieve a more even look for the right and left margin. Scribus follows pdfTeX and moves punctuation only partially into the margins. Other characters are moved into the right margins using some heuristic kerning.

Checkout [1.3.4 sample file] to see how Scribus 1.3.4 does in comparison (left column: old Scribus justification, right column: Scribus 1.3.4 with minimal wordspacing 50%, glyph extension 97%-103%, optical margins on).

Read [Hermann Zapf's article] about microtypography. That article shows a similar example comparing regular justification with Hermann Zapf's hz-program.

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