M13.1: ScriptUI frontend (dialogs, palettes, dockable panels), script menus, example plug-in, docs

- ui-egui: scriptui_view draws script windows at engine layout bounds; PanelKind::ScriptPanel; File ▸ Scripts and Window menu list scripts/panels (egui + native menus)
- examples/plugins/posterize-bands (WebAssembly, API v1); host plug-in tests; desktop loads <config>/Plug-ins
- MCP: script_ui and history tools; docs/plugins.md, agents.md, parity, architecture, ATTRIBUTION

Co-Authored-By: Claude Opus 5.5 <[email protected]>

examples/plugins/posterize-bands/Cargo.lock

@@ -0,0 +1,7 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 4
+
+[[package]]
+name = "posterize-bands"
+version = "1.0.0"

examples/plugins/posterize-bands/Cargo.toml

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+[package]
+name = "posterize-bands"
+description = "Example EffectCraft effect plug-in (WebAssembly, plug-in API v1): posterizes luminance into tinted bands"
+version = "1.0.0"
+edition = "2024"
+license = "MIT OR Apache-2.0"
+publish = false
+
+# Standalone: build with `cargo build --release --target wasm32-unknown-unknown` in this folder.
+[workspace]
+
+[lib]
+crate-type = ["cdylib"]
+
+[profile.release]
+opt-level = "s"
+lto = true
+panic = "abort"

examples/plugins/posterize-bands/src/lib.rs

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+//! Posterize Bands: an example EffectCraft effect plug-in (plug-in API v1, see
+//! `docs/plugins.md`). It quantizes each pixel's luminance into `levels` bands and mixes a tint
+//! colour in by `mix` percent, optionally only above a `threshold`.
+//!
+//! Build: `cargo build --release --target wasm32-unknown-unknown`, then load
+//! `target/wasm32-unknown-unknown/release/posterize_bands.wasm` with Effect ▸ Load Effect Plug-in
+//! (or `effect.plugins.load {"path": …}`), or drop it in the settings folder's `Plug-ins`.
+
+use std::cell::RefCell;
+
+/// The manifest: id, name, Effects & Presets category, parameters (flattened in this order:
+/// levels, mix, tint r g b a, invert).
+const MANIFEST: &str = r#"{
+  "api": 1,
+  "id": "org.effectcraft.example.posterize-bands",
+  "name": "Posterize Bands",
+  "category": "Stylize",
+  "version": "1.0.0",
+  "author": "EffectCraft contributors",
+  "description": "Quantizes luminance into tinted bands.",
+  "params": [
+    {"id": "levels", "name": "Levels", "type": "slider", "default": 4, "min": 2, "max": 64, "sliderMax": 16, "decimals": 0},
+    {"id": "mix", "name": "Tint Amount", "type": "slider", "default": 50, "min": 0, "max": 100, "decimals": 1},
+    {"id": "tint", "name": "Tint", "type": "color", "default": [1.0, 0.55, 0.2, 1.0]},
+    {"id": "invert", "name": "Invert Bands", "type": "checkbox", "default": false}
+  ]
+}"#;
+
+thread_local! {
+    static BUF: RefCell<Vec<u64>> = const { RefCell::new(Vec::new()) };
+}
+
+#[unsafe(no_mangle)]
+pub extern "C" fn ec_api_version() -> i32 {
+    1
+}
+
+#[unsafe(no_mangle)]
+pub extern "C" fn ec_manifest_ptr() -> i32 {
+    MANIFEST.as_ptr() as i32
+}
+
+#[unsafe(no_mangle)]
+pub extern "C" fn ec_manifest_len() -> i32 {
+    MANIFEST.len() as i32
+}
+
+/// One reusable, 8-byte-aligned buffer for the parameters and pixels.
+#[unsafe(no_mangle)]
+pub extern "C" fn ec_alloc(bytes: i32) -> i32 {
+    BUF.with(|b| {
+        let mut b = b.borrow_mut();
+        let words = (bytes.max(0) as usize).div_ceil(8);
+        if b.len() < words {
+            b.resize(words, 0);
+        }
+        b.as_mut_ptr() as i32
+    })
+}
+
+/// # Safety
+/// The host passes pointers into the buffer `ec_alloc` returned.
+#[unsafe(no_mangle)]
+pub unsafe extern "C" fn ec_render(pixels: i32, width: i32, height: i32, params: i32, nparams: i32, _time: f64, _scale: f64) -> i32 {
+    if nparams < 7 {
+        return 1;
+    }
+    let p = unsafe { std::slice::from_raw_parts(params as *const f64, nparams as usize) };
+    let px = unsafe { std::slice::from_raw_parts_mut(pixels as *mut [f32; 4], (width.max(0) * height.max(0)) as usize) };
+    let levels = p[0].round().max(2.0) as f32;
+    let mix = (p[1] / 100.0).clamp(0.0, 1.0) as f32;
+    let tint = [p[2] as f32, p[3] as f32, p[4] as f32];
+    let invert = p[6] != 0.0;
+    for c in px.iter_mut() {
+        let a = c[3];
+        if a <= 0.0 {
+            continue;
+        }
+        // Un-premultiply, band the luminance, re-premultiply.
+        let (r, g, b) = (c[0] / a, c[1] / a, c[2] / a);
+        let y = 0.2126 * r + 0.7152 * g + 0.0722 * b;
+        let mut band = (y * levels).floor().min(levels - 1.0) / (levels - 1.0);
+        if invert {
+            band = 1.0 - band;
+        }
+        for (i, ch) in [r, g, b].into_iter().enumerate() {
+            let banded = if y > 0.0 { ch * band / y.max(1e-6) } else { band };
+            let v = banded * (1.0 - mix) + band * tint[i] * mix;
+            c[i] = v.max(0.0) * a;
+        }
+    }
+    0
+}