feat(imaging): add pure-Rust Skia backend (#112)

ci/ci-coverage.json

@@ -13,6 +13,7 @@
     "minimal-features",
     "jpeg2000",
     "rust-j2k",
+    "rust-skia",
     "skia-binary",
     "program-offline-smoke",
     "clippy",
@@ -104,8 +105,8 @@
       "workflow": "skia.yml",
       "responsibility": "Default and Skia feature tests plus package listing",
       "destination": "required",
-      "checks": ["skia-binary", "workspace-tests"],
-      "rationale": "The required gate proves the exact ARM64 GNU archive is installed and forbids source compilation."
+      "checks": ["rust-skia", "skia-binary", "workspace-tests"],
+      "rationale": "A dedicated dependency-free job tests the Rust-only codec graph, while the required gate proves the exact ARM64 GNU archive is installed and forbids source compilation."
     },
     {
       "workflow": "supply-chain.yml",

ci/dependency-policy.json

@@ -2,7 +2,7 @@
   "schema": 1,
   "msrv": "1.96.0",
   "current": "stable",
-  "reviewed_on": "2026-08-12",
+  "reviewed_on": "2026-08-13",
   "review_by": "2026-11-11",
   "direct": [
     { "name": "base64", "versions": ["0.22.1"], "purpose": "LLSD, login, asset, and protocol base64 encoding", "maintenance": "active", "transitive_cost": "low", "native": false, "rewrite_anchor": "`base64`" },
@@ -15,6 +15,7 @@
     { "name": "getrandom", "versions": ["0.4.3"], "purpose": "Operating-system entropy for protocol identifiers", "maintenance": "active", "transitive_cost": "low", "native": false, "rewrite_anchor": "`getrandom`" },
     { "name": "goblin", "versions": ["0.10.5"], "purpose": "Cross-platform ELF, PE, and Mach-O release artifact inspection", "maintenance": "active", "transitive_cost": "low", "native": false, "rewrite_anchor": "`goblin`" },
     { "name": "hound", "versions": ["3.5.1"], "purpose": "Bounded PCM WAV parsing for WebRTC playback", "maintenance": "stable", "transitive_cost": "low", "native": false, "rewrite_anchor": "`hound`" },
+    { "name": "image-webp", "versions": ["0.2.4"], "purpose": "Opt-in pure-Rust bounded WebP image decoding", "maintenance": "active", "transitive_cost": "low", "native": false, "rewrite_anchor": "`image-webp`" },
     { "name": "j2k", "versions": ["0.8.1"], "purpose": "Opt-in pure-Rust bounded JPEG 2000 and JP2 encoding and decoding", "maintenance": "active", "transitive_cost": "medium", "native": false, "rewrite_anchor": "`j2k`" },
     { "name": "mac_address2", "versions": ["2.0.2"], "purpose": "Cross-platform machine identity compatibility input", "maintenance": "active", "transitive_cost": "low", "native": false, "rewrite_anchor": "`mac_address2`" },
     { "name": "md-5", "versions": ["0.10.6"], "purpose": "Legacy protocol checksum compatibility", "maintenance": "active", "transitive_cost": "low", "native": false, "rewrite_anchor": "`md-5`" },
@@ -29,6 +30,7 @@
     { "name": "sha1", "versions": ["0.10.7"], "purpose": "Legacy protocol hash compatibility", "maintenance": "active", "transitive_cost": "low", "native": false, "rewrite_anchor": "`sha1`" },
     { "name": "sha2", "versions": ["0.11.0"], "purpose": "Manifest integrity and protocol hashing", "maintenance": "active", "transitive_cost": "low", "native": false, "rewrite_anchor": "`sha2`" },
     { "name": "skia-safe", "versions": ["0.99.0"], "purpose": "Opt-in cross-platform Skia image decoding", "maintenance": "monitored-native", "transitive_cost": "high", "native": true, "rewrite_anchor": "`skia-safe`" },
+    { "name": "skia-rs-codec", "versions": ["0.3.0"], "purpose": "Opt-in pure-Rust BMP, GIF, ICO, JPEG, PNG, and WBMP image decoding", "maintenance": "active", "transitive_cost": "high", "native": false, "rewrite_anchor": "`skia-rs-codec`" },
     { "name": "stats_alloc", "versions": ["0.1.10"], "purpose": "Allocation-budget compatibility tests, concurrency leak audits, and reproducible performance evidence", "maintenance": "stable", "transitive_cost": "low", "native": false, "rewrite_anchor": "`stats_alloc`" },
     { "name": "str0m", "versions": ["0.22.0"], "purpose": "Native Rust ICE, DTLS, SRTP, RTP, and SCTP WebRTC transport", "maintenance": "active", "transitive_cost": "high", "native": false, "rewrite_anchor": "`str0m`" },
     { "name": "syn", "versions": ["2.0.119"], "purpose": "Syntax validation for generated Rust sources", "maintenance": "active", "transitive_cost": "medium", "native": false, "rewrite_anchor": "`syn`" },
@@ -40,6 +42,8 @@
     { "name": "vorbis_rs", "versions": ["0.5.6"], "purpose": "Opt-in Ogg Vorbis asset encoding", "maintenance": "monitored-native", "transitive_cost": "medium", "native": true, "rewrite_anchor": "`vorbis_rs`" }
   ],
   "approved_duplicates": [
+    { "name": "bit-vec", "versions": ["0.8.0", "0.9.1"], "reason": "The pinned skia-rs shader parser and current WebRTC certificate stack require adjacent bit-vector API lines." },
+    { "name": "bitflags", "versions": ["1.3.2", "2.13.1"], "reason": "The pinned pure-Rust PNG codec remains on bitflags 1 while the rest of the workspace uses bitflags 2." },
     { "name": "block-buffer", "versions": ["0.10.4", "0.12.1"], "reason": "RustCrypto digest 0.10 and 0.11 consumers have not unified their block-buffer major version." },
     { "name": "cfg_aliases", "versions": ["0.1.1", "0.2.2"], "reason": "The target-specific native stacks use different nix-generation build helpers." },
     { "name": "chacha20", "versions": ["0.9.1", "0.10.1"], "reason": "The WebRTC crypto and current random-number stacks require different RustCrypto generations." },
@@ -48,12 +52,14 @@
     { "name": "crypto-common", "versions": ["0.1.7", "0.2.2"], "reason": "Legacy protocol hashes and current SHA-2 intentionally span RustCrypto digest generations." },
     { "name": "digest", "versions": ["0.10.7", "0.11.3"], "reason": "MD5, SHA-1, and WebRTC use digest 0.10 while manifest SHA-2 uses the audited 0.11 API." },
     { "name": "getrandom", "versions": ["0.2.17", "0.3.4", "0.4.3"], "reason": "WebRTC crypto, transitive rand, and direct UUID entropy consumers span three compatible APIs." },
+    { "name": "hashbrown", "versions": ["0.16.1", "0.17.1"], "reason": "The pinned skia-rs geometry and shader dependencies have not unified their hash table minor line." },
     { "name": "jni-sys", "versions": ["0.3.1", "0.4.1"], "reason": "CPAL Android NDK support and rustls Android certificate verification require different JNI bindings." },
     { "name": "nix", "versions": ["0.28.0", "0.31.3"], "reason": "Machine-address and operating-system reporting crates have not unified their Unix API generation." },
     { "name": "nom", "versions": ["7.1.3", "8.0.0"], "reason": "Skia bindgen tooling remains on nom 7 while the native WebRTC stack uses nom 8." },
     { "name": "r-efi", "versions": ["5.3.0", "6.0.0"], "reason": "The three resolved getrandom generations require two WASI EFI interface generations." },
     { "name": "rand", "versions": ["0.9.5", "0.10.2"], "reason": "WebRTC protocol crates use rand 0.9 while target-specific dependencies have adopted rand 0.10." },
     { "name": "rand_core", "versions": ["0.6.4", "0.9.5", "0.10.1"], "reason": "DTLS elliptic curves and the two resolved rand generations require distinct rand_core APIs." },
+    { "name": "rustc-hash", "versions": ["1.1.0", "2.1.3"], "reason": "The pinned skia-rs shader parser remains on rustc-hash 1 while existing workspace parsers use version 2." },
     { "name": "sha2", "versions": ["0.10.9", "0.11.0"], "reason": "WebRTC crypto still requires SHA-2 0.10 while MetaCrate integrity code directly uses 0.11." },
     { "name": "shlex", "versions": ["1.3.0", "2.0.1"], "reason": "Skia bindgen and current native C compilation helpers use different shell-token parsers." },
     { "name": "syn", "versions": ["2.0.119", "3.0.3"], "reason": "MetaCrate code generation uses syn 2 while current derive macro dependencies use syn 3." },

ci/release-matrix.json

@@ -42,12 +42,12 @@
       "execution": "native",
       "toolchain": "1.96.0",
       "target": "x86_64-unknown-linux-gnu",
-      "feature_sets": ["no-default-features", "rust-j2k"],
+      "feature_sets": ["no-default-features", "rust-j2k", "rust-skia"],
       "prerequisites": ["libopus-1.3"],
       "commands": [
         {
           "label": "Compile the portable public crates on the declared MSRV",
-          "args": ["check", "--locked", "-j", "1", "--all-targets", "--no-default-features", "--features", "libremetaverse-imaging/rust-j2k", "-p", "libremetaverse-types", "-p", "libremetaverse-structured-data", "-p", "libremetaverse-imaging", "-p", "libremetaverse-imaging-skia", "-p", "libremetaverse-prim-mesher", "-p", "libremetaverse-lsl-tools", "-p", "libremetaverse-rlv", "-p", "metacrate-ci-matrix"]
+          "args": ["check", "--locked", "-j", "1", "--all-targets", "--no-default-features", "--features", "libremetaverse-imaging/rust-j2k,libremetaverse-imaging-skia/rust-skia", "-p", "libremetaverse-types", "-p", "libremetaverse-structured-data", "-p", "libremetaverse-imaging", "-p", "libremetaverse-imaging-skia", "-p", "libremetaverse-prim-mesher", "-p", "libremetaverse-lsl-tools", "-p", "libremetaverse-rlv", "-p", "metacrate-ci-matrix"]
         },
         {
           "label": "Compile the safe native Opus boundary and WebRTC voice on the declared MSRV",
@@ -106,7 +106,7 @@
       "execution": "native",
       "toolchain": "stable",
       "target": "x86_64-unknown-linux-gnu",
-      "feature_sets": ["all-features", "dds-bc67", "jpeg2000", "rust-j2k", "skia", "vorbis", "real-audio", "tests"],
+      "feature_sets": ["all-features", "dds-bc67", "jpeg2000", "rust-j2k", "rust-skia", "skia", "vorbis", "real-audio", "tests"],
       "prerequisites": ["openjpeg-2.5.4", "skia-safe-0.99.0", "libopus-1.3", "alsa-1.2", "vorbis-rs-0.5.6"],
       "commands": [
         {
@@ -125,10 +125,18 @@
           "label": "Test OpenJPEG and pure-Rust JPEG 2000 interoperability",
           "args": ["test", "-p", "libremetaverse-imaging", "--no-default-features", "--features", "jpeg2000,rust-j2k", "--locked", "-j", "1"]
         },
+        {
+          "label": "Test the pure-Rust Skia-compatible feature independently",
+          "args": ["test", "-p", "libremetaverse-imaging-skia", "--no-default-features", "--features", "rust-skia", "--locked", "-j", "1"]
+        },
         {
           "label": "Test the Skia feature independently",
           "args": ["test", "-p", "libremetaverse-imaging-skia", "--no-default-features", "--features", "skia", "--locked", "-j", "1"]
         },
+        {
+          "label": "Test native Skia and pure-Rust codec interoperability",
+          "args": ["test", "-p", "libremetaverse-imaging-skia", "--no-default-features", "--features", "skia,rust-skia", "--locked", "-j", "1"]
+        },
         {
           "label": "Test the Vorbis feature independently",
           "args": ["test", "-p", "libremetaverse", "--no-default-features", "--features", "vorbis", "--lib", "--locked", "-j", "1", "--", "asset_pipeline_semantics"]
@@ -170,12 +178,12 @@
       "execution": "cross",
       "toolchain": "stable",
       "target": "x86_64-pc-windows-gnu",
-      "feature_sets": ["no-default-features", "dds-bc67", "rust-j2k"],
+      "feature_sets": ["no-default-features", "dds-bc67", "rust-j2k", "rust-skia"],
       "prerequisites": [],
       "commands": [
         {
           "label": "Cross-check portable crates for Windows GNU",
-          "args": ["check", "--locked", "-j", "1", "--target", "x86_64-pc-windows-gnu", "--all-targets", "--no-default-features", "--features", "libremetaverse-imaging/rust-j2k", "-p", "libremetaverse-types", "-p", "libremetaverse-structured-data", "-p", "libremetaverse-imaging", "-p", "libremetaverse-imaging-skia", "-p", "libremetaverse-prim-mesher", "-p", "libremetaverse-lsl-tools", "-p", "libremetaverse-rlv", "-p", "metacrate-ci-matrix"]
+          "args": ["check", "--locked", "-j", "1", "--target", "x86_64-pc-windows-gnu", "--all-targets", "--no-default-features", "--features", "libremetaverse-imaging/rust-j2k,libremetaverse-imaging-skia/rust-skia", "-p", "libremetaverse-types", "-p", "libremetaverse-structured-data", "-p", "libremetaverse-imaging", "-p", "libremetaverse-imaging-skia", "-p", "libremetaverse-prim-mesher", "-p", "libremetaverse-lsl-tools", "-p", "libremetaverse-rlv", "-p", "metacrate-ci-matrix"]
         }
       ]
     },
@@ -186,12 +194,12 @@
       "execution": "cross",
       "toolchain": "stable",
       "target": "x86_64-apple-darwin",
-      "feature_sets": ["no-default-features", "dds-bc67", "rust-j2k"],
+      "feature_sets": ["no-default-features", "dds-bc67", "rust-j2k", "rust-skia"],
       "prerequisites": [],
       "commands": [
         {
           "label": "Cross-check portable crates for macOS",
-          "args": ["check", "--locked", "-j", "1", "--target", "x86_64-apple-darwin", "--all-targets", "--no-default-features", "--features", "libremetaverse-imaging/rust-j2k", "-p", "libremetaverse-types", "-p", "libremetaverse-structured-data", "-p", "libremetaverse-imaging", "-p", "libremetaverse-imaging-skia", "-p", "libremetaverse-prim-mesher", "-p", "libremetaverse-lsl-tools", "-p", "libremetaverse-rlv", "-p", "metacrate-ci-matrix"]
+          "args": ["check", "--locked", "-j", "1", "--target", "x86_64-apple-darwin", "--all-targets", "--no-default-features", "--features", "libremetaverse-imaging/rust-j2k,libremetaverse-imaging-skia/rust-skia", "-p", "libremetaverse-types", "-p", "libremetaverse-structured-data", "-p", "libremetaverse-imaging", "-p", "libremetaverse-imaging-skia", "-p", "libremetaverse-prim-mesher", "-p", "libremetaverse-lsl-tools", "-p", "libremetaverse-rlv", "-p", "metacrate-ci-matrix"]
         }
       ]
     }