52 lines
2.5 KiB
Markdown
52 lines
2.5 KiB
Markdown
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# Configuring HarfBuzz
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Most of the time you will not need any custom configuration. The configuration
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options provided by `configure` or `cmake` should be enough. In particular,
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if you just want HarfBuzz library plus hb-shape / hb-view utilities, make sure
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FreeType and Cairo are available and found during configuration.
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If you are building for distribution, you should more carefully consider whether
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you need Glib, ICU, Graphite2, as well as CoreText / Uniscribe / DWrite. Make
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sure the relevant ones are enabled.
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If you are building for custom environment (embedded, downloadable app, etc)
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where you mostly just want to call `hb_shape()` and the binary size of the
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resulting library is very important to you, the rest of this file guides you
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through your options to disable features you may not need, in exchange for
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binary size savings.
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## Compiler Options
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Make sure you build with your compiler's "optimize for size" option. On `gcc`
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this is `-Os`, and can be enabled by passing `CXXFLAGS=-Os` either to `configure`
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(sticky) or to `make` (non-sticky). On clang there is an even more extreme flag,
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`-Oz`.
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HarfBuzz heavily uses inline functions and the optimize-size flag can make the
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library smaller by 20% or more. Moreover, sometimes, based on the target CPU,
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the optimize-size builds perform *faster* as well, thanks to lower code
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footprint and caching effects. So, definitely try that even if size is not
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extremely tight but you have a huge application. For example, Chrome does
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that. Note that this configuration also automatically enables certain internal
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optimizations. Search for `HB_OPTIMIZE_SIZE` for details, if you are using
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other compilers, or continue reading.
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Another compiler option to consider is "link-time optimization", also known as
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'lto'. To enable that, with `gcc` or `clang`, add `-flto` to both `CXXFLAGS`
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and `LDFLAGS`, either on `configure` invocation (sticky) or on `make` (non-sticky).
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This, also, can have a huge impact on the final size, 20% or more.
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Finally, if you are making a static library build or otherwise linking the
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library into your app, make sure your linker removes unused functions. This
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can be tricky and differ from environment to environment, but you definitely
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want to make sure this happens. Otherwise, every unused public function will
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be adding unneeded bytes to your binary.
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Combining the above three build options should already shrink your library a lot.
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The rest of this file shows you ways to shrink the library even further at the
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expense of removing functionality (that may not be needed).
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## Custom configuration
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TODO
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