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Issue 2403083002: Revert of Turned on SkSL->GLSL compiler (Closed)
Patch Set: Created 4 years, 2 months ago
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1 Overview
2 ========
3
4 SkSL ("Skia Shading Language") is a variant of GLSL which is used as Skia's
5 internal shading language. SkSL is, at its heart, a single standardized version
6 of GLSL which avoids all of the various version and dialect differences found
7 in GLSL "in the wild", but it does bring a few of its own changes to the table.
8
9 Skia uses the SkSL compiler to convert SkSL code to GLSL, GLSL ES, or SPIR-V
10 before handing it over to the graphics driver.
11
12 Differences from GLSL
13 =====================
14
15 SkSL is based on GLSL 4.5. For the most part, write SkSL exactly as you would
16 desktop GLSL, and the SkSL compiler will take care of version and dialect
17 differences (for instance, you always use "in" and "out", and skslc will handle
18 translating them to "varying" and "attribute" as appropriate). Be aware of the
19 following differences between SkSL and GLSL:
20
21 * no #version or "precision" statement is required, and they will be ignored if
22 present
23 * the output color is sk_FragColor (do not declare it)
24 * lowp, mediump, and highp are always permitted (but will only be respected if
25 you run on a GLES device)
26 * you do not need to include ".0" to make a number a float (meaning that
27 "vec2(x, y) * 4" is perfectly legal in SkSL, unlike GLSL where it would often
28 have to be expressed "vec2(x, y) * 4.0". There is no performance penalty for
29 this, as the number is converted to a float at compile time)
30 * type suffixes on numbers (1.0f, 0xFFu) are both unnecessary and unsupported
31 * some built-in functions and one or two rarely-used language features are not
32 yet supported (sorry!)
33
34 SkSL is still under development, and is expected to diverge further from GLSL
35 over time.
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