66 lines
2.1 KiB
C++
66 lines
2.1 KiB
C++
#pragma once
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#include <cstdint>
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#include <vector>
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namespace ThaiShaper {
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/**
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* Represents a positioned glyph within a Thai cluster.
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*
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* Thai clusters consist of a base consonant with optional:
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* - Leading vowel (displayed before base but stored after in Unicode)
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* - Above vowel/marks (stacked above base)
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* - Below vowel (positioned below base)
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* - Tone mark (stacked above vowels)
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* - Follow vowel (displayed after base)
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*/
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struct PositionedGlyph {
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uint32_t codepoint; // Unicode codepoint to render
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int8_t xOffset; // X offset from cluster origin (in font units fraction)
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int8_t yOffset; // Y offset from baseline (negative = up, positive = down)
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bool zeroAdvance; // If true, this glyph doesn't advance the cursor
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};
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/**
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* A Thai grapheme cluster - the minimal unit for proper rendering.
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*
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* A cluster typically contains:
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* - 0-1 leading vowel (displayed first)
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* - 1 base consonant
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* - 0-1 above vowel
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* - 0-1 below vowel
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* - 0-1 tone mark
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* - 0-1 follow vowel
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* - 0-1 thanthakhat/yamakkan
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*/
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struct ThaiCluster {
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std::vector<PositionedGlyph> glyphs;
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int totalAdvance; // Total width of cluster in font advanceX units
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ThaiCluster() : totalAdvance(0) {}
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};
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/**
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* Y-offset constants for Thai mark positioning.
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* These are relative adjustments based on typical Thai font metrics.
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* Values are in "font units" where the typical em-height is ~1.0
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* Negative values move UP, positive move DOWN.
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*/
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namespace ThaiOffset {
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// Above marks (relative to baseline, scaled by font size)
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constexpr int8_t ABOVE_VOWEL = -2; // Base above-vowel position
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constexpr int8_t TONE_MARK = -4; // Tone mark above vowel
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constexpr int8_t TONE_MARK_ALONE =
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-2; // Tone mark when no above vowel (sits lower at same position as above vowel would)
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// Below marks
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constexpr int8_t BELOW_VOWEL = 3; // Below-vowel position
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// X-offset for ascender consonants (tall consonants like ป ฝ ฟ)
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// When these have above marks, the marks may need to shift
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constexpr int8_t ASCENDER_X_SHIFT = 0; // No shift needed in most fonts
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} // namespace ThaiOffset
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} // namespace ThaiShaper
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