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GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2288033003 Review-Url: https://codereview.chromium.org/2288033003
35 lines
1.6 KiB
Plaintext
35 lines
1.6 KiB
Plaintext
Overview
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========
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SkSL ("Skia Shading Language") is a variant of GLSL which is used as Skia's
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internal shading language. SkSL is, at its heart, a single standardized version
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of GLSL which avoids all of the various version and dialect differences found
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in GLSL "in the wild", but it does bring a few of its own changes to the table.
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Skia uses the SkSL compiler to convert SkSL code to GLSL, GLSL ES, or SPIR-V
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before handing it over to the graphics driver.
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Differences from GLSL
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=====================
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SkSL is based on GLSL 4.5. For the most part, write SkSL exactly as you would
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desktop GLSL, and the SkSL compiler will take care of version and dialect
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differences (for instance, you always use "in" and "out", and skslc will handle
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translating them to "varying" and "attribute" as appropriate). Be aware of the
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following differences between SkSL and GLSL:
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* no #version or "precision" statement is required, and they will be ignored if
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present
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* the output color is sk_FragColor (do not declare it)
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* lowp, mediump, and highp are always permitted (but will only be respected if
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you run on a GLES device)
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* you do not need to include ".0" to make a number a float (meaning that
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"vec2(x, y) * 4" is perfectly legal in SkSL, unlike GLSL where it would have
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to be expressed "vec2(x, y) * 4.0". There is no performance penalty for this,
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as the number is converted to a float at compile time)
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* some built-in functions and one or two rarely-used language features are not
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yet supported (sorry!)
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SkSL is still under development, and is expected to diverge further from GLSL
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over time.
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