Improve TrueType specificiation compliance for generated fonts #124
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From the TrueType font specification section about the cmap table: > No character code should be mapped to glyph index -1 (0xFFFF), which is a special value reserved in processing to indicate the position of a glyph deleted from the glyph stream. ref #123
...before calculating the head table checksum. Per the head table specification: > checkSumAdjustment: To compute set it to 0, calculate the checksum for the 'head' table and put it in the table directory, sum the entire font as a uint32_t, then store 0xB1B0AFBA - sum. (The checksum for the 'head' table will be wrong as a result. That is OK; do not reset it.) ref #123
The number of tables in the font may change when generating a font file. Because the font header is dependent on the number of tables the values need to be recalculated. ref #123
Per the spec: > Table checksums are the unsigned sum of the longs in a table.
Per the spec: > The length of any table is a multiple of four bytes, or that tables are padded with zero to four byte-aligned offsets. Actual table lengths recorded in the TableDirectory should not include padding. fixes #119
Before this change when the font loca table was using the short format (glyph size / 2), an odd-numbered glyph byte length would be incorrectly record. To prevent this issue, when writing a font we will padd glyphs to align with a 4-byte boundary. Note: Official guidance needed. The 4-byte boundary is based on table requirements, as well as being a multiple of 2.
Most name strings should be encoded with UTF-16BE per the spec, but there are situations where other encodings are required or acceptable. This change only addresses a subset of potential encodings. fixes #70
A font with a format 2 cmap table will still re-encode with a format 4 cmap table. relates to #123
This librarry relies on Unicode data for a number of functions (namely font re-encoding). Without a Unicode-encoded cmap table those functions do not work as expected.
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