From 3443c1c65e9f1753e1e656b35d08416c1fa298f2 Mon Sep 17 00:00:00 2001
From: godosa <godosa@godosa.eu>
Date: Wed, 7 Oct 2026 00:14:38 +0200
Subject: worldmap-viewer: initial public history

---
 viewer/js/layers.js | 84 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 84 insertions(+)
 create mode 100644 viewer/js/layers.js

(limited to 'viewer/js/layers.js')

diff --git a/viewer/js/layers.js b/viewer/js/layers.js
new file mode 100644
index 0000000..c0ab662
--- /dev/null
+++ b/viewer/js/layers.js
@@ -0,0 +1,84 @@
+// layers.js — layer textures (fetched on first use, a few kept on the GPU)
+import * as THREE from 'three';
+import { el } from './ui.js';
+
+const KEEP = 4;   // base + over-layer + 2 recent; an 8192×4096 texture is ≈180 MB of GPU memory with mipmaps
+
+export class LayerStore {
+  constructor(layers, maxTextureSize, anisotropy = 1, load = null) {
+    this.layers = layers;
+    this.loadImpl = load;              // tests inject a loader; the browser uses #load
+    this.pinned = new Set();           // ids wanted right now (base + over): never evicted
+    this.shown = new Set();            // ids drawn right now (may lag the wanted ones while they load): never evicted
+    this.max = maxTextureSize;
+    this.anisotropy = anisotropy;
+    this.cache = new Map();   // id → Promise<THREE.Texture>, least recently used first
+  }
+
+  get(id) {
+    return this.layers.find(l => l.id === id);
+  }
+
+  pin(ids) {
+    this.pinned = new Set(ids.filter(Boolean));
+  }
+
+  showing(ids) {
+    this.shown = new Set(ids.filter(Boolean));
+  }
+
+  dispose(keep = []) {   // another era's store took over: free the GPU memory, except textures still drawn
+    for (const q of this.cache.values()) q.then(t => { if (!keep.includes(t)) t.dispose(); }, () => {});
+    this.cache.clear();
+  }
+
+  texture(id) {
+    let p = this.cache.get(id);
+    if (p) this.cache.delete(id);
+    else p = (this.loadImpl ?? (l => this.#load(l)))(this.get(id)).catch(e => { this.cache.delete(id); throw e; });
+    this.cache.set(id, p);
+    for (const [old, q] of [...this.cache]) {   // oldest first; textures on screen stay
+      if (this.cache.size <= KEEP) break;
+      if (this.pinned.has(old) || this.shown.has(old) || old === id) continue;
+      this.cache.delete(old);
+      q.then(t => t.dispose(), () => {});
+    }
+    return p;
+  }
+
+  async #load(layer) {
+    const img = await new THREE.ImageLoader().loadAsync(layer.file)
+      .catch(() => { throw new Error(`could not load ${layer.file}`); });
+    let src = img;
+    if (img.width > this.max) {                      // GPU limit: downsample to 4096 wide
+      const w = Math.min(4096, this.max);
+      src = document.createElement('canvas');
+      src.width = w;
+      src.height = w / 2;
+      src.getContext('2d').drawImage(img, 0, 0, w, w / 2);
+    }
+    const tex = new THREE.Texture(src);
+    tex.colorSpace = THREE.NoColorSpace;             // shaders pass the JPEG's sRGB bytes straight through
+    tex.anisotropy = this.anisotropy;
+    tex.needsUpdate = true;
+    return tex;
+  }
+}
+
+const UNIT_LABEL = { degC: '°C' };   // layers.json keeps the build's unit codes
+const fmtTick = v => (Math.abs(v) >= 100 ? Math.round(v).toLocaleString('en-US') : String(+v.toFixed(2)));
+
+export function renderLegend(box, layer) {
+  const L = layer.legend;
+  box.hidden = !L;
+  if (!L) return box.replaceChildren();
+  const title = el('div', { class: 'muted' }, layer.name);
+  if (L.type === 'categorical') {
+    return box.replaceChildren(title, ...L.items.map(it =>
+      el('div', {}, el('span', { class: 'sw', style: `background:${it.color}` }), it.name)));
+  }
+  const lo = L.stops[0][0], hi = L.stops.at(-1)[0];
+  const grad = L.stops.map(([v, c]) => `${c} ${(((v - lo) / (hi - lo)) * 100).toFixed(1)}%`).join(', ');
+  box.replaceChildren(title, el('div', { class: 'bar', style: `background: linear-gradient(to right, ${grad})` }),
+    el('div', { class: 'ticks' }, el('span', {}, fmtTick(lo)), el('span', {}, UNIT_LABEL[L.unit] ?? L.unit), el('span', {}, fmtTick(hi))));
+}
-- 
cgit