C bindings for Skia (chrome/m142)

A flat C API (sk_capi.h / sk_capi.cpp) over Skia, built as a self-contained library for embedding in non-C++ projects via a stable C ABI. Note that these have been tailored to the needs of my specific projects and may not be suitable for anyone else.

Source baseline

Component	Pin
Skia branch	chrome/m142
Depot Tools commit	488d7480e234ccbca59a49eadf9d23cd7aa02c31

Both pins are set in tandem in build.sh to keep a consistent set of sources.

See the file skia/skia/RELEASE_NOTES.txt for changes made to skia.

Platforms & artifacts

build.sh detects the host OS and architecture and produces a single library named skia_<os>_<arch>:

OS	Architectures	Output
macOS (darwin)	amd64, arm64	libskia_darwin_<arch>.a (static)
Linux	amd64, arm64	libskia_linux_<arch>.a (static)
Windows	amd64, arm64	skia_windows_<arch>.dll (shared)

• macOS targets a minimum deployment of macOS 11.
• Windows is built as a component (DLL) build using LLVM/clang; symbols are exported via SKIA_C_DLL / __declspec(dllexport).
• The build emits the public header sk_capi.h and the library into dist/, and (when a sibling ../unison tree is present) also copies them into unison/internal/skia.

Build configuration highlights

Enabled in this release:

• PDF document output (skia_enable_pdf).
• SkShaper text shaping (skia_enable_skshaper).
• GPU: Ganesh OpenGL backend (skia_use_gl, discrete GPU support).
• Image codecs via wuffs and bundled libjpeg-turbo / libpng / libwebp / zlib.
• XML/SVG support via bundled expat.
• Platform font hosting: CoreText on macOS, FreeType + fontconfig on Linux, GDI on Windows.

Deliberately disabled to keep the library lean and portable: ANGLE, Dawn, Vulkan, Metal, EGL, HarfBuzz, ICU, DNG SDK, PIEX, Lua, Skottie, and the build tools. The corresponding third-party dependencies are also pruned from DEPS before syncing.

API surface

The C API exposes the following Skia areas (see sk_capi.h for full signatures):

• Geometry & types — points, rects, sizes, matrices, colors, image info, sampling options, blend/blur/clip modes.
• Canvas — transforms, clipping, save/restore layers, and draw operations for rects, ovals, arcs, circles, round rects, paths, points, lines, images (incl. nine-patch and rect), text, and text blobs.
• Paint — style, stroke parameters, color, antialias/dither, and attachment of shaders, color filters, mask filters, image filters, and path effects.
• Paths & path ops — construction (lines, curves, arcs, primitives), SVG path string parse/emit, transforms, queries, boolean ops, simplify, and an op builder.
• Shaders — solid color, blend, linear/radial/sweep/two-point conical gradients, and Perlin noise (fractal & turbulence).
• Filters — color filters (matrix, compose, high contrast, lighting, luma, blend mode), mask filters (blur, clip, gamma, shader, table), and a broad set of image filters (blur, dilate/erode, drop shadow, lighting, displacement, magnifier, matrix convolution, arithmetic, merge, offset, tile, image source, and more).
• Text — fonts, font managers/style sets, font styles, typefaces, font metrics, glyph/measurement helpers, and text blob building.
• Images — raster and encoded image creation, pixel reads, shaders from images, and GPU texture images.
• Image encoding — JPEG, PNG, and WebP encoders.
• Surfaces — raster surfaces, GPU backend render-target surfaces, snapshots, and surface properties.
• GPU context — Ganesh GrDirectContext over a native or assembled GL interface, with backend render targets.
• Documents — PDF document creation with metadata, page begin/end, and stream output.
• Streams — dynamic-memory and file write streams.
• Strings & data — sk_string_t and sk_data_t helpers.
• Codecs — register_image_codecs() to register the built-in image decoders.