Results

Read the result of a subset before writing it: which requested characters the font could not map, how many glyphs stayed, and what the subsetter had to change. The numbers come from the SubsetResult that Font::subset() returns.

List the characters the font cannot map

A requested character absent from the source is dropped without a warning. When every character is required, check before subsetting:

<?php

$missing = [];
foreach ($characters as $codepoint) {
    if (null === $font->glyphIdForCodepoint($codepoint)) {
        $missing[] = sprintf('U+%04X', $codepoint);
    }
}

if ([] !== $missing) {
    throw new RuntimeException('Characters missing from the font: '.implode(', ', $missing));
}

After subsetting, $result->mappedCodepointCount is the number of requested codepoints that were found; compare it with count($characters).

Read the counts

• mappedCodepointCount counts the requested codepoints found in the character map.
• retainedGlyphCount counts the glyphs kept: the mapped ones, .notdef, compound components, and the glyphs reachable through preserved substitutions.
• originalGlyphCount counts the glyph slots in the source.
• sfntSize is the size of the uncompressed result in bytes, before WOFF or WOFF2 compression.

For ALTO Font 0123456789 on the bundled Inter Latin sample, 19 characters are mapped and 104 glyphs stay. The grid shows which of A to Z and 0 to 9 remain mapped:

With the default GlyphIdPolicy::Preserve, the new font keeps all 518 slots and empties the unused ones, so $result->font->face()->glyphCount is still 518; retainedGlyphCount is the number to report. Glyph counts details each count and the effect of the policies.

Read the warnings

$result->warnings lists what the subsetter transformed or could not keep:

<?php

foreach ($result->warnings as $warning) {
    fwrite(STDERR, $warning."\n");
}

Read them before distributing the output. They do not list missing characters; the check above does.

Measure the output

sfntSize is the uncompressed size. The size that matters for a web font is the written file: call filesize() on the WOFF or WOFF2 output, and compare the complete font and the subset in the same container. Sizes lists measured sizes for the bundled sample.

Use the new font

$result->font is a regular Font: read its metadata and metrics, resolve glyphs, or pass it to a writer. With compact numbering, glyph identifiers differ from the source; resolve them from the new font, never from the old one.