| # Introduction |
| |
| Subset preprocessing is a mechanism which can significantly speed up font subsetting operations. |
| It works by prepopulating datastructures from the source font which can be used in later subsetting |
| operations to more quickly produce the subset. Preprocessing is useful in cases where multiple subsets |
| will be cut from the same source font. |
| |
| # Usage |
| |
| ```c++ |
| hb_face_t* preprocessed = hb_subset_preprocess (source_face); |
| |
| ... |
| |
| hb_face_t* subset = hb_subset_or_fail (preprocessed, subset_input); |
| ``` |
| |
| # Additional Details |
| |
| * A subset produced from a preprocessed face should be identical to a subset produced from only the |
| original face. The preprocessor does not change the functionality of the subsetter, just speeds |
| things up. |
| |
| * The preprocessing operation may take longer than the time it takes to produce a subset from the |
| source font. Thus the main performance gains are made when a preprocessed face is reused for |
| multiple subsetting operations. |
| |
| * Currently the largest performance gains are seen when using a preprocessed face for CFF subsetting. |
| |
| * The preprocessed face may contain references to the memory backing the source face. If this memory |
| is fully owned by a harfbuzz hb_blob_t* then it will automatically be kept alive for the lifetime |
| of the preprocessed face. However, if this memory is not fully owned by a harfbuzz hb_blob_t* then |
| it is necessary to ensure that the memory is kept alive for the lifetime of the preprocessed face. |
| |
| |
| # Performance Improvements |
| |
| Here is the performance difference of producing a subset with a preprocessed face vs producing |
| a subset with the source face: |
| |
| Benchmark | Delta Time (%) |
| ----------|----------------- |
| BM_subset/subset_glyphs/Roboto-Regular.ttf/10_median|-56% |
| BM_subset/subset_glyphs/Roboto-Regular.ttf/64_median|-33% |
| BM_subset/subset_glyphs/Roboto-Regular.ttf/512_median|-28% |
| BM_subset/subset_glyphs/Roboto-Regular.ttf/1000_median|-11% |
| BM_subset/subset_glyphs/Roboto-Regular.ttf/nohinting/10_median|-56% |
| BM_subset/subset_glyphs/Roboto-Regular.ttf/nohinting/64_median|-33% |
| BM_subset/subset_glyphs/Roboto-Regular.ttf/nohinting/512_median|-21% |
| BM_subset/subset_glyphs/Roboto-Regular.ttf/nohinting/1000_median|-9% |
| BM_subset/subset_glyphs/Amiri-Regular.ttf/10_median|-67% |
| BM_subset/subset_glyphs/Amiri-Regular.ttf/64_median|-48% |
| BM_subset/subset_glyphs/Amiri-Regular.ttf/512_median|-21% |
| BM_subset/subset_glyphs/Amiri-Regular.ttf/4096_median|-9% |
| BM_subset/subset_glyphs/Amiri-Regular.ttf/nohinting/10_median|-66% |
| BM_subset/subset_glyphs/Amiri-Regular.ttf/nohinting/64_median|-50% |
| BM_subset/subset_glyphs/Amiri-Regular.ttf/nohinting/512_median|-8% |
| BM_subset/subset_glyphs/Amiri-Regular.ttf/nohinting/4096_median|-9% |
| BM_subset/subset_glyphs/NotoNastaliqUrdu-Regular.ttf/10_median|-85% |
| BM_subset/subset_glyphs/NotoNastaliqUrdu-Regular.ttf/64_median|-71% |
| BM_subset/subset_glyphs/NotoNastaliqUrdu-Regular.ttf/512_median|-3% |
| BM_subset/subset_glyphs/NotoNastaliqUrdu-Regular.ttf/1400_median|4% |
| BM_subset/subset_glyphs/NotoNastaliqUrdu-Regular.ttf/nohinting/10_median|-84% |
| BM_subset/subset_glyphs/NotoNastaliqUrdu-Regular.ttf/nohinting/64_median|-72% |
| BM_subset/subset_glyphs/NotoNastaliqUrdu-Regular.ttf/nohinting/512_median|0% |
| BM_subset/subset_glyphs/NotoNastaliqUrdu-Regular.ttf/nohinting/1400_median|0% |
| BM_subset/subset_glyphs/NotoSansDevanagari-Regular.ttf/10_median|-30% |
| BM_subset/subset_glyphs/NotoSansDevanagari-Regular.ttf/64_median|-24% |
| BM_subset/subset_glyphs/NotoSansDevanagari-Regular.ttf/512_median|-3% |
| BM_subset/subset_glyphs/NotoSansDevanagari-Regular.ttf/1000_median|-3% |
| BM_subset/subset_glyphs/NotoSansDevanagari-Regular.ttf/nohinting/10_median|-30% |
| BM_subset/subset_glyphs/NotoSansDevanagari-Regular.ttf/nohinting/64_median|-24% |
| BM_subset/subset_glyphs/NotoSansDevanagari-Regular.ttf/nohinting/512_median|-3% |
| BM_subset/subset_glyphs/NotoSansDevanagari-Regular.ttf/nohinting/1000_median|-5% |
| BM_subset/subset_glyphs/Mplus1p-Regular.ttf/10_median|-96% |
| BM_subset/subset_glyphs/Mplus1p-Regular.ttf/64_median|-90% |
| BM_subset/subset_glyphs/Mplus1p-Regular.ttf/512_median|-74% |
| BM_subset/subset_glyphs/Mplus1p-Regular.ttf/4096_median|-25% |
| BM_subset/subset_glyphs/Mplus1p-Regular.ttf/10000_median|-23% |
| BM_subset/subset_glyphs/Mplus1p-Regular.ttf/nohinting/10_median|-95% |
| BM_subset/subset_glyphs/Mplus1p-Regular.ttf/nohinting/64_median|-90% |
| BM_subset/subset_glyphs/Mplus1p-Regular.ttf/nohinting/512_median|-73% |
| BM_subset/subset_glyphs/Mplus1p-Regular.ttf/nohinting/4096_median|-24% |
| BM_subset/subset_glyphs/Mplus1p-Regular.ttf/nohinting/10000_median|-11% |
| BM_subset/subset_glyphs/SourceHanSans-Regular_subset.otf/10_median|-84% |
| BM_subset/subset_glyphs/SourceHanSans-Regular_subset.otf/64_median|-77% |
| BM_subset/subset_glyphs/SourceHanSans-Regular_subset.otf/512_median|-70% |
| BM_subset/subset_glyphs/SourceHanSans-Regular_subset.otf/4096_median|-80% |
| BM_subset/subset_glyphs/SourceHanSans-Regular_subset.otf/10000_median|-86% |
| BM_subset/subset_glyphs/SourceHanSans-Regular_subset.otf/nohinting/10_median|-84% |
| BM_subset/subset_glyphs/SourceHanSans-Regular_subset.otf/nohinting/64_median|-78% |
| BM_subset/subset_glyphs/SourceHanSans-Regular_subset.otf/nohinting/512_median|-71% |
| BM_subset/subset_glyphs/SourceHanSans-Regular_subset.otf/nohinting/4096_median|-86% |
| BM_subset/subset_glyphs/SourceHanSans-Regular_subset.otf/nohinting/10000_median|-88% |
| BM_subset/subset_glyphs/SourceSansPro-Regular.otf/10_median|-59% |
| BM_subset/subset_glyphs/SourceSansPro-Regular.otf/64_median|-55% |
| BM_subset/subset_glyphs/SourceSansPro-Regular.otf/512_median|-67% |
| BM_subset/subset_glyphs/SourceSansPro-Regular.otf/2000_median|-68% |
| BM_subset/subset_glyphs/SourceSansPro-Regular.otf/nohinting/10_median|-60% |
| BM_subset/subset_glyphs/SourceSansPro-Regular.otf/nohinting/64_median|-58% |
| BM_subset/subset_glyphs/SourceSansPro-Regular.otf/nohinting/512_median|-72% |
| BM_subset/subset_glyphs/SourceSansPro-Regular.otf/nohinting/2000_median|-71% |
| BM_subset/subset_glyphs/AdobeVFPrototype.otf/10_median|-70% |
| BM_subset/subset_glyphs/AdobeVFPrototype.otf/64_median|-64% |
| BM_subset/subset_glyphs/AdobeVFPrototype.otf/300_median|-73% |
| BM_subset/subset_glyphs/AdobeVFPrototype.otf/nohinting/10_median|-71% |
| BM_subset/subset_glyphs/AdobeVFPrototype.otf/nohinting/64_median|-68% |
| BM_subset/subset_glyphs/AdobeVFPrototype.otf/nohinting/300_median|-72% |
| BM_subset/subset_glyphs/MPLUS1-Variable.ttf/10_median|-90% |
| BM_subset/subset_glyphs/MPLUS1-Variable.ttf/64_median|-82% |
| BM_subset/subset_glyphs/MPLUS1-Variable.ttf/512_median|-31% |
| BM_subset/subset_glyphs/MPLUS1-Variable.ttf/4096_median|-9% |
| BM_subset/subset_glyphs/MPLUS1-Variable.ttf/6000_median|-22% |
| BM_subset/subset_glyphs/MPLUS1-Variable.ttf/nohinting/10_median|-88% |
| BM_subset/subset_glyphs/MPLUS1-Variable.ttf/nohinting/64_median|-83% |
| BM_subset/subset_glyphs/MPLUS1-Variable.ttf/nohinting/512_median|-31% |
| BM_subset/subset_glyphs/MPLUS1-Variable.ttf/nohinting/4096_median|-16% |
| BM_subset/subset_glyphs/MPLUS1-Variable.ttf/nohinting/6000_median|-18% |
| BM_subset/subset_glyphs/RobotoFlex-Variable.ttf/10_median|-44% |
| BM_subset/subset_glyphs/RobotoFlex-Variable.ttf/64_median|-18% |
| BM_subset/subset_glyphs/RobotoFlex-Variable.ttf/512_median|-2% |
| BM_subset/subset_glyphs/RobotoFlex-Variable.ttf/900_median|-6% |
| BM_subset/subset_glyphs/RobotoFlex-Variable.ttf/nohinting/10_median|-45% |
| BM_subset/subset_glyphs/RobotoFlex-Variable.ttf/nohinting/64_median|-17% |
| BM_subset/subset_glyphs/RobotoFlex-Variable.ttf/nohinting/512_median|-15% |
| BM_subset/subset_glyphs/RobotoFlex-Variable.ttf/nohinting/900_median|-3% |
| BM_subset/subset_codepoints/Roboto-Regular.ttf/10_median|-20% |
| BM_subset/subset_codepoints/Roboto-Regular.ttf/64_median|-16% |
| BM_subset/subset_codepoints/Roboto-Regular.ttf/512_median|-12% |
| BM_subset/subset_codepoints/Roboto-Regular.ttf/1000_median|-10% |
| BM_subset/subset_codepoints/Roboto-Regular.ttf/nohinting/10_median|-24% |
| BM_subset/subset_codepoints/Roboto-Regular.ttf/nohinting/64_median|-14% |
| BM_subset/subset_codepoints/Roboto-Regular.ttf/nohinting/512_median|-15% |
| BM_subset/subset_codepoints/Roboto-Regular.ttf/nohinting/1000_median|-9% |
| BM_subset/subset_codepoints/Amiri-Regular.ttf/10_median|-51% |
| BM_subset/subset_codepoints/Amiri-Regular.ttf/64_median|-37% |
| BM_subset/subset_codepoints/Amiri-Regular.ttf/512_median|-12% |
| BM_subset/subset_codepoints/Amiri-Regular.ttf/4096_median|-1% |
| BM_subset/subset_codepoints/Amiri-Regular.ttf/nohinting/10_median|-49% |
| BM_subset/subset_codepoints/Amiri-Regular.ttf/nohinting/64_median|-35% |
| BM_subset/subset_codepoints/Amiri-Regular.ttf/nohinting/512_median|-6% |
| BM_subset/subset_codepoints/Amiri-Regular.ttf/nohinting/4096_median|-1% |
| BM_subset/subset_codepoints/NotoNastaliqUrdu-Regular.ttf/10_median|-82% |
| BM_subset/subset_codepoints/NotoNastaliqUrdu-Regular.ttf/64_median|-9% |
| BM_subset/subset_codepoints/NotoNastaliqUrdu-Regular.ttf/512_median|0% |
| BM_subset/subset_codepoints/NotoNastaliqUrdu-Regular.ttf/1400_median|0% |
| BM_subset/subset_codepoints/NotoNastaliqUrdu-Regular.ttf/nohinting/10_median|-82% |
| BM_subset/subset_codepoints/NotoNastaliqUrdu-Regular.ttf/nohinting/64_median|-13% |
| BM_subset/subset_codepoints/NotoNastaliqUrdu-Regular.ttf/nohinting/512_median|-3% |
| BM_subset/subset_codepoints/NotoNastaliqUrdu-Regular.ttf/nohinting/1400_median|2% |
| BM_subset/subset_codepoints/NotoSansDevanagari-Regular.ttf/10_median|-40% |
| BM_subset/subset_codepoints/NotoSansDevanagari-Regular.ttf/64_median|-26% |
| BM_subset/subset_codepoints/NotoSansDevanagari-Regular.ttf/512_median|-5% |
| BM_subset/subset_codepoints/NotoSansDevanagari-Regular.ttf/1000_median|3% |
| BM_subset/subset_codepoints/NotoSansDevanagari-Regular.ttf/nohinting/10_median|-43% |
| BM_subset/subset_codepoints/NotoSansDevanagari-Regular.ttf/nohinting/64_median|-24% |
| BM_subset/subset_codepoints/NotoSansDevanagari-Regular.ttf/nohinting/512_median|-2% |
| BM_subset/subset_codepoints/NotoSansDevanagari-Regular.ttf/nohinting/1000_median|2% |
| BM_subset/subset_codepoints/Mplus1p-Regular.ttf/10_median|-83% |
| BM_subset/subset_codepoints/Mplus1p-Regular.ttf/64_median|-67% |
| BM_subset/subset_codepoints/Mplus1p-Regular.ttf/512_median|-39% |
| BM_subset/subset_codepoints/Mplus1p-Regular.ttf/4096_median|-20% |
| BM_subset/subset_codepoints/Mplus1p-Regular.ttf/10000_median|-25% |
| BM_subset/subset_codepoints/Mplus1p-Regular.ttf/nohinting/10_median|-83% |
| BM_subset/subset_codepoints/Mplus1p-Regular.ttf/nohinting/64_median|-65% |
| BM_subset/subset_codepoints/Mplus1p-Regular.ttf/nohinting/512_median|-42% |
| BM_subset/subset_codepoints/Mplus1p-Regular.ttf/nohinting/4096_median|-34% |
| BM_subset/subset_codepoints/Mplus1p-Regular.ttf/nohinting/10000_median|-21% |
| BM_subset/subset_codepoints/SourceHanSans-Regular_subset.otf/10_median|-69% |
| BM_subset/subset_codepoints/SourceHanSans-Regular_subset.otf/64_median|-69% |
| BM_subset/subset_codepoints/SourceHanSans-Regular_subset.otf/512_median|-70% |
| BM_subset/subset_codepoints/SourceHanSans-Regular_subset.otf/4096_median|-84% |
| BM_subset/subset_codepoints/SourceHanSans-Regular_subset.otf/10000_median|-83% |
| BM_subset/subset_codepoints/SourceHanSans-Regular_subset.otf/nohinting/10_median|-71% |
| BM_subset/subset_codepoints/SourceHanSans-Regular_subset.otf/nohinting/64_median|-68% |
| BM_subset/subset_codepoints/SourceHanSans-Regular_subset.otf/nohinting/512_median|-70% |
| BM_subset/subset_codepoints/SourceHanSans-Regular_subset.otf/nohinting/4096_median|-86% |
| BM_subset/subset_codepoints/SourceHanSans-Regular_subset.otf/nohinting/10000_median|-88% |
| BM_subset/subset_codepoints/SourceSansPro-Regular.otf/10_median|-45% |
| BM_subset/subset_codepoints/SourceSansPro-Regular.otf/64_median|-48% |
| BM_subset/subset_codepoints/SourceSansPro-Regular.otf/512_median|-57% |
| BM_subset/subset_codepoints/SourceSansPro-Regular.otf/2000_median|-66% |
| BM_subset/subset_codepoints/SourceSansPro-Regular.otf/nohinting/10_median|-43% |
| BM_subset/subset_codepoints/SourceSansPro-Regular.otf/nohinting/64_median|-50% |
| BM_subset/subset_codepoints/SourceSansPro-Regular.otf/nohinting/512_median|-63% |
| BM_subset/subset_codepoints/SourceSansPro-Regular.otf/nohinting/2000_median|-72% |
| BM_subset/subset_codepoints/AdobeVFPrototype.otf/10_median|-69% |
| BM_subset/subset_codepoints/AdobeVFPrototype.otf/64_median|-66% |
| BM_subset/subset_codepoints/AdobeVFPrototype.otf/300_median|-74% |
| BM_subset/subset_codepoints/AdobeVFPrototype.otf/nohinting/10_median|-70% |
| BM_subset/subset_codepoints/AdobeVFPrototype.otf/nohinting/64_median|-71% |
| BM_subset/subset_codepoints/AdobeVFPrototype.otf/nohinting/300_median|-75% |
| BM_subset/subset_codepoints/MPLUS1-Variable.ttf/10_median|-66% |
| BM_subset/subset_codepoints/MPLUS1-Variable.ttf/64_median|-46% |
| BM_subset/subset_codepoints/MPLUS1-Variable.ttf/512_median|-15% |
| BM_subset/subset_codepoints/MPLUS1-Variable.ttf/4096_median|-5% |
| BM_subset/subset_codepoints/MPLUS1-Variable.ttf/6000_median|-16% |
| BM_subset/subset_codepoints/MPLUS1-Variable.ttf/nohinting/10_median|-66% |
| BM_subset/subset_codepoints/MPLUS1-Variable.ttf/nohinting/64_median|-45% |
| BM_subset/subset_codepoints/MPLUS1-Variable.ttf/nohinting/512_median|-14% |
| BM_subset/subset_codepoints/MPLUS1-Variable.ttf/nohinting/4096_median|-11% |
| BM_subset/subset_codepoints/MPLUS1-Variable.ttf/nohinting/6000_median|-27% |
| BM_subset/subset_codepoints/RobotoFlex-Variable.ttf/10_median|-38% |
| BM_subset/subset_codepoints/RobotoFlex-Variable.ttf/64_median|-9% |
| BM_subset/subset_codepoints/RobotoFlex-Variable.ttf/512_median|-3% |
| BM_subset/subset_codepoints/RobotoFlex-Variable.ttf/900_median|-16% |
| BM_subset/subset_codepoints/RobotoFlex-Variable.ttf/nohinting/10_median|-39% |
| BM_subset/subset_codepoints/RobotoFlex-Variable.ttf/nohinting/64_median|-12% |
| BM_subset/subset_codepoints/RobotoFlex-Variable.ttf/nohinting/512_median|-4% |
| BM_subset/subset_codepoints/RobotoFlex-Variable.ttf/nohinting/900_median|-2% |
| BM_subset/instance/MPLUS1-Variable.ttf/10_median|-68% |
| BM_subset/instance/MPLUS1-Variable.ttf/64_median|-45% |
| BM_subset/instance/MPLUS1-Variable.ttf/512_median|-18% |
| BM_subset/instance/MPLUS1-Variable.ttf/4096_median|-2% |
| BM_subset/instance/MPLUS1-Variable.ttf/6000_median|4% |
| BM_subset/instance/MPLUS1-Variable.ttf/nohinting/10_median|-69% |
| BM_subset/instance/MPLUS1-Variable.ttf/nohinting/64_median|-46% |
| BM_subset/instance/MPLUS1-Variable.ttf/nohinting/512_median|-11% |
| BM_subset/instance/MPLUS1-Variable.ttf/nohinting/4096_median|4% |
| BM_subset/instance/MPLUS1-Variable.ttf/nohinting/6000_median|-5% |
| BM_subset/instance/RobotoFlex-Variable.ttf/10_median|-34% |
| BM_subset/instance/RobotoFlex-Variable.ttf/64_median|-12% |
| BM_subset/instance/RobotoFlex-Variable.ttf/512_median|6% |
| BM_subset/instance/RobotoFlex-Variable.ttf/900_median|-6% |
| BM_subset/instance/RobotoFlex-Variable.ttf/nohinting/10_median|-33% |
| BM_subset/instance/RobotoFlex-Variable.ttf/nohinting/64_median|-11% |
| BM_subset/instance/RobotoFlex-Variable.ttf/nohinting/512_median|3% |
| BM_subset/instance/RobotoFlex-Variable.ttf/nohinting/900_median|0% |
