Skia Analyst — Analysis Instructions

Read this before starting any analysis. It covers both lenses — changelog (what shipped) and gap analysis (what's missing) — because every finding needs both.

Input Flexibility

The user may specify:

• Nothing → full scan (all milestones, everything)
• One milestone → "what's new since m133" (windowed from that milestone to current)
• Two milestones → "between m133 and m147" (windowed range)
• One git ref → "what changed since v3.119.4" (diff from ref to HEAD)
• Two git refs → "diff v3.119.4..origin/main" (explicit range)
• Vague → "scan for new stuff" (full scan)

Infer the scan mode from context. If unclear, ask.

Data Sources

1. Skia Release Notes

Fetch from: https://raw.githubusercontent.com/google/skia/main/RELEASE_NOTES.md Extract features per milestone. For windowed/diff mode, focus on the relevant range but still scan a few milestones beyond.

2. C++ Header Scan (Hidden API Discovery)

For types SkiaSharp already binds, fetch upstream C++ headers from google/skia and compare against what SkiaSharp exposes:

• Upstream C++ headers: fetch from GitHub (owner=google, repo=skia, path=include/core/SkImage.h)
• SkiaSharp C API: grep binding/SkiaSharp/SkiaApi.generated.cs for sk_* / gr_* P/Invoke externs. This reflects the full C API surface even if externals/skia/include/c/ isn't checked out.
• SkiaSharp C# wrappers: binding/SkiaSharp/*.cs

High-value headers to scan:

C#	C API prefix	C++ header
SKCanvas	sk_canvas_*	include/core/SkCanvas.h
SKImage	sk_image_*	include/core/SkImage.h
SKPath	sk_path_*	include/core/SkPath.h
SKPathBuilder	sk_pathbuilder_*	include/core/SkPathBuilder.h
SKShader	sk_shader_*	include/core/SkShader.h
SKImageFilter	sk_imagefilter_*	include/effects/SkImageFilters.h
SKColorFilter	sk_colorfilter_*	include/core/SkColorFilter.h
SKCodec	sk_codec_*	include/codec/SkCodec.h
SKFont	sk_font_*	include/core/SkFont.h
SKTypeface	sk_typeface_*	include/core/SkTypeface.h
SKSurface	sk_surface_*	include/core/SkSurface.h
SKColorSpace	sk_colorspace_*	include/core/SkColorSpace.h

3. Git Diff (when refs provided)

• C API diff: git diff REF1..REF2 -- externals/skia/include/c/ externals/skia/src/c/
• C# binding diff: git diff REF1..REF2 -- binding/ ':!*.generated.cs'
• Git log: git log REF1..REF2 --oneline
• Build/deps: git diff REF1..REF2 -- native/ externals/skia/DEPS cgmanifest.json

Classification: Both Lenses

Every finding needs BOTH a changelog classification AND a gap classification.

Changelog lens (what happened)

changeType:

Value	Criteria
added	New API, class, method, capability
changed	Modified behavior or signature
fixed	Bug fix
deprecated	New [Obsolete] marker
removed	Removed API or feature
dependency	Dependency version bump
platform	New platform, build flag change
upstream	Benefit from Skia engine upgrade (automatic, no API change)

importance:

Value	Criteria
breaking	Existing code may fail to compile or behave differently
major	New user-facing capability, significant feature
minor	Enhancement, quality improvement
patch	Bug fix, internal improvement

Gap lens (what to do about it)

bindingStatus:

Value	Description
full	C API + C# wrapper both exist
partial	C API exists but C# wrapper missing (quick win)
missing	Neither C API nor C# wrapper
action_needed	SkiaSharp wraps deprecated/removed Skia API
correctly_absent	Skia removed; SkiaSharp never wrapped
not_applicable	Doesn't need a binding (internal, auto-available)

impact:

Value	Decision guide
transformative	"Does this unlock a new category of app?"
significant	"Would a user see the difference or gain a major capability?"
moderate	"Is this useful but not exciting?"
minor	Default for small helpers

priority:

Value	Criteria
critical	Will break on next Skia bump
high	Major new capability or highly requested
medium	Useful addition, quality improvement
low	Minor utility, internal concern

What to Include vs Exclude

Include:

• New classes, APIs, capabilities
• Codec/format support (AVIF, JPEG XL, HDR)
• Shader capabilities, image filter additions
• Color types, color spaces
• Performance improvements
• Behavior changes
• Deprecations and removals
• Security hardening, dependency updates
• Platform expansion

Exclude:

• Internal refactoring (header moves)
• Graphite-only changes (SkiaSharp uses Ganesh)
• Dawn backend changes
• Build system internals (GN flags)
• Version bump commits
• CI/docs/skill-only changes

Upstream Benefits (changeType: "upstream")

When a Skia bump is in the diff, extract "invisible benefits" — things users get automatically:

• Rendering quality (mipmap sharpening, noise rotation, backdrop tiling)
• Performance (noise raster speedup, canvas preallocation)
• Color accuracy (kRec709 BT.1886, kHLG/kPQ corrections)
• Codec improvements (Exif orientation, high bit-depth detection)
• Reliability (Vulkan device-lost, SkSL validation)

For upstream findings: bindingStatus = not_applicable, impact and priority based on user value.

Optional Enrichment Fields

For findings with importance of major or higher, include a slideBullet — a one-line marketing bullet for downstream tooling (e.g., blog post drafts). Not rendered in the Markdown report but captured in the JSON for other tools to use.

For importance: "breaking" findings, include a migrationGuide with before/after code.

For changeType: "dependency" findings, include dependencyName, dependencyFrom, dependencyTo.

Accuracy Tips

• Don't confuse enum values with full support
• Check the actual C# method, not just the class
• Verify C# wrappers call the right C API
• Check SkiaApi.generated.cs for hidden plumbing
• milestone fields must be integers (133 not "m133")