LilyPond's Feta and Parmesan fonts ================================== [The name `feta' is based on a non-translatable Dutch pun (`font-en-tja'). Given that it is the name of a cheese type, the font for old music symbols is called `parmesan', and the OpenType font that merges these two fonts is called `emmentaler'.] This is a font of music symbols. All MetaFont sources are original. Most of the documentation is in comments in the MetaFont code. Non-square pixels are not supported; with other words, the horizontal and vertical resolution of the output device must be the same. Conversion from MetaFont to PostScript -------------------------------------- The MetaFont code gets directly converted to PostScript Type 1 font with a tool called `mf2pt1', which in turn calls `FontForge' to postprocess the output (mainly to remove outline overlaps and to add hints). The recommended calling sequence of mf2pt1 is mf2pt1 --rounding=0.0001 You need mf2pt1 version 2.1 or newer. Here some guidelines to assure a clean conversion. . Never use `---'. Replace it with `--' together with explicit path directions (if necessary). . Don't use self-intersecting outlines in general since they can confuse mf2pt1's algorithm to get the orientation of a closed path. Note that MetaPost's implementation of the `turningnumber' primitive (which would immediately give the orientation of a path) is severely broken before version 1.0 of MetaPost, thus some hand-made code in mf2pt1.mp is used to work around this bug. . If outlines intersect, avoid grazing intersections. In case two outlines intersect in an explicitly defined point, include this point in both intersecting paths to avoid problems due to rounding errors. . Don't use `draw' with a polygonal pen but for straight lines (consisting of exactly two points). In most cases it is quite easy to emulate `draw' with an explicit definition of the outline or with `penstroke'. . Don't apply transformations after calling `fill' -- for example, don't mirror `currentpicture'. Instead, transform the path and call `fill' afterwards. This ensures that mf2pt1 gets the correct outline directions, which is a necessary prerequisite for FontForge's algorithm to remove overlaps. Glyph name rules ---------------- . Most glyph names have the form ., where is defined with the `fet_begingroup' command, and is given with `fet_beginchar' (within a `fet_begingroup' block). Example: `clefs.vaticana.fa'. . Sometimes it would be sensible to use negative numbers in glyph names. However, the `-' character shouldn't be used in a glyph name. Replace it with `M'. For example, write `rests.M3mensural' instead of `rests.-3mensural'. . Glyphs that exist in both an `up' and `down' version should start the part with either `u' or `d', respectively. Example: `flags.d3', `flags.u3'. Glyphs that are neutral w.r.t. the direction, and where members of the glyph group exist that have `up' and `down' versions, should start with an `s'. Example: `noteheads.s0re'. Design rules ------------ . Always use smooth curve transitions. Since this is difficult to see in MetaFont proof sheets (which don't show the tangents) I recommend to call mf2pt1 like this FONTFORGE=foo mf2pt1 ... (`foo' should be a non-existent program; this avoids the default postprocessing). Then call FontForge to inspect the outlines. . Use rounded corners. Hints for stem attachment ------------------------- . Stem attachment of glyphs is controlled by two special variables called `charwx' and `charwy'. Stems can be regarded as (very oblonged) rectangles with slightly rounded corners. For stems pointing upwards the lower right corner of this rectangle is attached to the glyph at position (charwx, charwy). For stems pointing downwards it works analogously but with the upper left corner, where the position of the attachment point is additionally reflected horizontally about the center of the glyph -- this ensures that in most cases `charwx' and `charwy' can be set to the same values for up and down stems even though these are attached at the right/left end of the note, respectively. To make this more precise, the upper left corner of a down stem is attached at position (charwd/2 - charwx, charwy) , where `charwd' is an internal MetaFont variable representing the glyph width as specified by the `set_char_box' command. . In case different stem attachments for upward and downward pointing stems are needed, two separate glyphs must be defined in the MetaFont file; of course, this also applies if two entirely different shapes are needed. These have the same name but are prefixed by `u' and `d', respectively (for `up' and `down', obviously). In each of these glyphs the variables `charwx' and `charwy' must be set accordingly. If, on the other hand, the attachment point is the `same' for both directions (with the abovementioned horizontal reflection taken into account), then the prefix `s' (for `symmetric') should be used. See the existing files for examples. The numbers in the glyph names refer to the duration of the note; e.g., `s0cross' in feta-noteheads.mf defines the notehead for a whole cross-shaped note (similarly, `s1cross' and `s2cross' are for half and quarter notes, respectively). Proofing -------- The proofing tool for MetaFont to inspect its output is `gftodvi', converting a font in MetaFont's native GF font format to a DVI document, which can then be viewed with DVI viewers like `xdvi'. The `gftodvi' program needs two special fonts, `gray' and `black'. Assuming that you are using TeXLive, say mktextfm gray mktextfm black on the command line to generate the needed metric files (from its source files), which are then stored within your local TEXMF tree. Here is a shell script that you can use to produce two DVI files, `foo.proof.dvi' and `foo.ljfour.dvi', showing the glyphs of font `foo.mf' in proofing mode and a 600dpi rasterization for a LaserJet IV printer. #!/bin/sh mf "\mode:=proof; input $1" gftodvi $1.2602gf && mv $1.dvi $1.proof.dvi mf "\mode:=ljfour; input $1" echo "grayfont black " | gftodvi $1.600gf/ \ && mv $1.dvi $1.ljfour.dvi Assuming that you name this script `makefeta.sh', you can call it with e.g. sh makefeta.sh feta23 The main importance of the proofing DVI output is to show points marked in the MetaFont source code with the macros `penlabels' and `labels'. In most cases, those points are used for constructing the shapes only and are thus not present in the output after the conversion with mf2pt1. Rasterization ------------- Finally, some rules to assure that rasterization at low resolutions (produced directly with MetaFont) gives good results. Today, this is a minor issue, but in some cases it might show design flaws. . Use `define_whole_pixels' and friends where appropriate. . Use `hround' and `vround' consistently. A lot of auxiliary macros are defined in feta-macros.mf. . If a path element is duplicated or shifted, use an integer value for the offset. . Add `eps' for mirrored paths to assure correct MetaFont rasterization. See the comment and the variables at the end of `feta-params.mf' for details how vertical symmetry should be achieved.