Class: Fontisan::Stitcher::PartitionStrategy::Base

Inherits:
Object
  • Object
show all
Defined in:
lib/fontisan/stitcher/partition_strategy/base.rb

Overview

Abstract base. Concrete partitioners (ByPlane, ByBlock, …) implement #call and return a Blueprint.

Direct Known Subclasses

ByBlock, ByPlane, ByScript

Constant Summary collapse

NOTDEF_RESERVED =

Glyph-cap headroom below the format's hard cap (GlyphLimit::TTF_GLYPH_CAP / OTF_GLYPH_CAP = 65,535). The partitioner must keep each partition's codepoint count low enough that compile-time glyph expansion still fits under the hard cap.

Reserved slots:

- .notdef (1 slot, mandated by OpenType — every font has it
at GID 0 even when no codepoint binds to it)
- composite expansion: compiling adds composites (ligatures,
decomposable glyphs, variant attachments) on top of the
source codepoint count. Empirically ~5% of typical BMP
size for CJK-heavy fonts (≈2,500 composites on a 50k-cp
BMP font). 5,534 slots covers that with margin.
1
COMPOSITE_HEADROOM = 
5_534
DEFAULT_CAP =

Default cap for the most common format (TTF, where the glyph cap equals 65,535). Use cap_for when partitioning for a different format.

cap_for(:ttf)

Class Method Summary collapse

Instance Method Summary collapse

Class Method Details

.cap_for(format) ⇒ Integer

Derive the partition cap from a format's hard glyph limit. Mirrors GlyphLimit so a future bump (e.g. CFF2 card24 INDEX counts) cascades automatically — no second magic number to keep in sync.

Parameters:

  • format (Symbol) —

    :ttf, :otf, or :otf2

Returns:

  • (Integer) 


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# File 'lib/fontisan/stitcher/partition_strategy/base.rb', line 33

def self.cap_for(format)
  GlyphLimit.for_format(format) - NOTDEF_RESERVED - COMPOSITE_HEADROOM
end

Instance Method Details

#call(cp_map, cap: DEFAULT_CAP) ⇒ Blueprint

Parameters:

  • cp_map (Hash{Integer=>Object}) —

    codepoint → donor label

  • cap (Integer) (defaults to: DEFAULT_CAP) —

    max codepoints per partition

Returns:

Raises:

  • (NotImplementedError) 


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# File 'lib/fontisan/stitcher/partition_strategy/base.rb', line 45

def call(cp_map, cap: DEFAULT_CAP)
  raise NotImplementedError,
        "#{self.class} must implement #call"
end