How to adjust Line space in Fontlab 7 ?

Hello everybody,
i want to know how to adjust the space between lines in Fontlab 7 . 
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  • John HudsonJohn Hudson Posts: 1,987
    I suggest asking FontLab-specific questions in the FontLab Forum.
  • The font height boundaries are a critical and fundamental part of fonts. They are unsigned Win Ascent and unsigned Win Descent. When rendered, the values will be rounded (half away from zero) to get the rendered font height boundaries. Like how fonts rely on the horizontal spacing to work, they also rely on the vertical spacing, so the design will be built around the font height boundaries and any change of font height boundaries will require redesigning the entire font to optically match. Also, unlike the advance width, the font height boundaries are fundamental boundaries where any content placed beyond font height boundaries will be clipped. This ensures each scanline belongs to exactly one line of text as a fundamental of text rendering. When making variable fonts, it can be more difficult to ensure no glyph exceeds vertical boundaries in any of the masters. When doing manual hinting, the cvts should be made in such a way as to not lead to exceeding vertical boundaries.
  • Thomas PhinneyThomas Phinney Posts: 1,929
    edited December 2020
    Most typographically savvy apps simply use the point size of the font, plus a percentage or number of points, to set the line spacing. For those apps, to get more line spacing, you need to either scale all your glyphs smaller on the em, or increase the size of the em while leaving all else constant.

    However, SOME apps (mostly on Windows) use the font BBOX or usWinAscent/usWinDescent, plus some percentage, to determine their default line spacing. In FontLab 7, you set this with: File > Font Info > Family Dimensions, Safe Top and Safe Bottom.
  • Most typographically savvy apps simply use the point size of the font, plus a percentage or number of points, to set the line spacing. For those apps, to get more line spacing, you need to either scale all your glyphs smaller on the em, or increase the size of the em while leaving all else constant.

    However, SOME apps (mostly on Windows) use the font BBOX or usWinAscent/usWinDescent, plus some percentage, to determine their default line spacing. In FontLab 7, you set this with: File > Font Info > Family Dimensions, Safe Top and Safe Bottom.
    Thank you soooo much ♥
  • Just to be clear, that latter method will only affect some Windows apps, mostly the less typographically savvy ones!

    Note that Safe Top and Safe Bottom are usually set to the highest and lowest extent in the font (font BBOX). As far as I know, making them a bit larger will have no untoward side effects other than increasing line spacing (and perhaps trivially memory usage).

    Good luck!
  • Just to be clear, that latter method will only affect some Windows apps, mostly the less typographically savvy ones!

    Note that Safe Top and Safe Bottom are usually set to the highest and lowest extent in the font (font BBOX). As far as I know, making them a bit larger will have no untoward side effects other than increasing line spacing (and perhaps trivially memory usage).

    Good luck!
    In my renderer called TD renderer I only ever use unsigned Win Ascent and unsigned Win Descent for the font height boundaries (the line spacing is equivalent to the font height). I would rather think of the font height boundaries the other way around, they are set in a way that makes the design, positioning and spacing optically correct and the type designer avoids exceeding vertical boundaries.
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