fix #1063: give each terminal its own WebGL texture atlas (disable cross-terminal sharing) (#1071)

Root cause of the persistent split-view 花屏: xterm's WebGL addon shares
ONE TextureAtlas across terminal instances with equal config (font / size
/ theme / DPR) — acquireTextureAtlas does `if (configEquals) { ownedBy.push;
return atlas }`. Two split panes then share an atlas, so the
clearTextureAtlas calls netcatty makes to recover from glyph corruption
(on resize / DPR / font change / tab show, from #1049 and #1066) clobber
the *other* pane's rendering. That's why the earlier redraw/clear-based
recovery attempts didn't help and only bounced the garble between panes.

Disable the sharing: remove the "reuse a matching atlas" loop so every
terminal creates its own atlas. The published bundle is minified, so this
is done with a small idempotent postinstall script (a patch-package patch
would be a ~550KB unreadable blob of the whole minified line). It
string-replaces the exact loop in the CJS + ESM builds, runs after
patch-package, and warns without failing if @xterm/addon-webgl changes.

Verified: split-view WebGL no longer garbles; script is idempotent
(patched=2 → already=2) and the production build is unaffected.

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

package.json

@@ -28,7 +28,7 @@
     "pack:linux": "npm run build && cross-env NODE_OPTIONS=--disable-warning=DEP0190 electron-builder --config electron-builder.config.cjs --linux --publish=never",
     "pack:linux-x64": "npm run build && cross-env npm_config_arch=x64 NODE_OPTIONS=--disable-warning=DEP0190 electron-builder --config electron-builder.config.cjs --linux --x64 --publish=never",
     "pack:linux-arm64": "npm run build && cross-env npm_config_arch=arm64 NODE_OPTIONS=--disable-warning=DEP0190 electron-builder --config electron-builder.config.cjs --linux --arm64 --publish=never",
-    "postinstall": "electron-builder install-app-deps && patch-package",
+    "postinstall": "electron-builder install-app-deps && patch-package && node scripts/patch-xterm-webgl-atlas.cjs",
     "rebuild": "electron-builder install-app-deps",
     "tool:cli": "node electron/cli/netcatty-tool-cli.cjs",
     "lint": "eslint .",

scripts/patch-xterm-webgl-atlas.cjs

@@ -0,0 +1,74 @@
+#!/usr/bin/env node
+/**
+ * Disable @xterm/addon-webgl's cross-terminal texture-atlas sharing.
+ *
+ * xterm's WebGL addon shares ONE TextureAtlas across terminal instances whose
+ * config (font / size / theme / device-pixel-ratio) is equal — see
+ * `acquireTextureAtlas`, which does `if (configEquals) { ownedBy.push; return
+ * atlas }`. In a split workspace two panes then share an atlas, so clearing or
+ * rebuilding it for one pane (which netcatty does on resize / DPR change / font
+ * change / tab show to recover from glyph corruption) corrupts the OTHER pane's
+ * rendering — the persistent "花屏 / garbled" report in issue #1063, most
+ * visible in split view where both panes stay on screen.
+ *
+ * Fix: give every terminal its own atlas by removing the "reuse a matching
+ * atlas" loop, so each terminal falls through to creating its own. The published
+ * package is minified, so we string-replace the exact loop in both the CJS and
+ * ESM builds. This runs from `postinstall` (after patch-package).
+ *
+ * Idempotent. If the upstream code changes (e.g. an @xterm/addon-webgl upgrade)
+ * the loop won't be found; we warn loudly but do not fail the install, and the
+ * strings below must then be refreshed for the new version.
+ */
+"use strict";
+const fs = require("node:fs");
+const path = require("node:path");
+
+const MARKER = "/*netcatty:#1063 atlas-isolation*/";
+
+// Exact (minified) "reuse a shared atlas" loop, per @xterm/addon-webgl@0.19.0.
+const TARGETS = [
+  {
+    file: "node_modules/@xterm/addon-webgl/lib/addon-webgl.mjs",
+    loop: "for(let h=0;h<le.length;h++){let f=le[h];if(Mi(f.config,u))return f.ownedBy.push(i),f.atlas}",
+  },
+  {
+    file: "node_modules/@xterm/addon-webgl/lib/addon-webgl.js",
+    loop: "for(let t=0;t<r.length;t++){const i=r[t];if((0,n.configEquals)(i.config,d))return i.ownedBy.push(e),i.atlas}",
+  },
+];
+
+let patched = 0;
+let already = 0;
+let missing = 0;
+
+for (const { file, loop } of TARGETS) {
+  const abs = path.resolve(process.cwd(), file);
+  let src;
+  try {
+    src = fs.readFileSync(abs, "utf8");
+  } catch {
+    console.warn(`[patch-xterm-webgl-atlas] skip (not found): ${file}`);
+    missing++;
+    continue;
+  }
+  if (src.includes(MARKER)) {
+    already++;
+    continue;
+  }
+  if (!src.includes(loop)) {
+    console.warn(
+      `[patch-xterm-webgl-atlas] WARNING: atlas-sharing loop not found in ${file}. ` +
+        "@xterm/addon-webgl likely changed — split-view WebGL may garble again (#1063). " +
+        "Refresh the minified target strings in scripts/patch-xterm-webgl-atlas.cjs.",
+    );
+    missing++;
+    continue;
+  }
+  fs.writeFileSync(abs, src.replace(loop, MARKER));
+  patched++;
+}
+
+console.log(
+  `[patch-xterm-webgl-atlas] atlas isolation: patched=${patched} already=${already} missing=${missing}`,
+);