feat(terminal): draw herdr-core panes with libghostty, Kitty graphics pictures included, behind a Settings toggle

DESIGN.md

@@ -3184,7 +3184,8 @@ Alert rows of the table above from the `--droplet-*` roles in `src/styles.css`.
   `composerPasteSend`), and on a touch screen the suggestion chip (off by default); then
   **Quick replies**; then **File viewer**: wrap long lines, Markdown width, Diff layout), **Terminal** (font size, font family, wheel
   speed, input mode, Key bar, Clipboard from a pane, Pictures in the terminal (off by default, the
-  device setting `terminalImages`), Use alongside herdr's own window, Follow
+  device setting `terminalImages`), Draw with libghostty (off by default, the device setting
+  `terminalGhostty`), Use alongside herdr's own window, Follow
   herdr's focus), **Alerts**, **Voice input**, **Agents**,
   **Shortcuts** (the platform-resolved global bindings), **Phone & devices** (Connect a phone,
   Keep screen on, Install; then Portal, where the server offers it; then paired devices; then Access),
@@ -3483,6 +3484,13 @@ Alert rows of the table above from the `--droplet-*` roles in `src/styles.css`.
   ordered change set, so Retry resends the current change, never an old request body.
 
 ### Terminal host, key bar and drawer
+- **Draw with libghostty** (Settings > Terminal, off by default, herdr-core only): libghostty-vt draws the
+  pane's text, cursor and Kitty graphics pictures in a layer over xterm's screen, at xterm's cell size;
+  xterm's own text and cursor are hidden under it and xterm keeps input, selection, links, search and
+  scrolling. It follows Ghostty's own split of a terminal core (libghostty-vt) from the renderer an app
+  draws with, rather than a second terminal widget: everything built on xterm keeps working while the
+  drawing moves. The layer takes no pointer events; pictures keep the layer Kitty gave them (below
+  the text, or above it).
 - **Find in terminal** in the header's More menu and Mod+Shift+F opens a find bar above the
   grid. It uses the existing input and icon-button primitives: a query, match ordinal,
   previous/next and close controls, with a dim note that scrolling is shared by all clients.

THIRD_PARTY_NOTICES.md

@@ -1518,6 +1518,105 @@ FROM, OUT OF THE USE OR INABILITY TO USE THE FONT SOFTWARE OR FROM
 OTHER DEALINGS IN THE FONT SOFTWARE.
 ```
 
+## libghostty-vt
+
+`src/lib/ghostty/ghostty-vt.wasm` is libghostty-vt from [Ghostty](https://github.com/ghostty-org/ghostty) at
+commit e95bed6, built for wasm32 by `scripts/ghostty-vt/build.sh` with the small change in
+`scripts/ghostty-vt/kitty-on-wasm.patch` (Kitty graphics on, file media off). It draws a terminal when
+Settings > Terminal > Draw with libghostty is on, under the MIT License below. The module links two
+packages Ghostty's build brings in: [Wuffs](https://github.com/google/wuffs) 0.4.0-alpha.10, which decodes
+Kitty PNG pictures, under the MIT License (it is offered under MIT or Apache-2.0), and
+[uucode](https://github.com/jacobsandlund/uucode) 0.2.0, Unicode tables, under the MIT License.
+
+```
+MIT License
+
+Copyright (c) 2024 Mitchell Hashimoto, Ghostty contributors
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
+```
+
+Wuffs:
+
+```
+Copyright 2023 The Wuffs Authors
+
+Permission is hereby granted, free of charge, to any
+person obtaining a copy of this software and associated
+documentation files (the "Software"), to deal in the
+Software without restriction, including without
+limitation the rights to use, copy, modify, merge,
+publish, distribute, sublicense, and/or sell copies of
+the Software, and to permit persons to whom the Software
+is furnished to do so, subject to the following
+conditions:
+
+The above copyright notice and this permission notice
+shall be included in all copies or substantial portions
+of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF
+ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED
+TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
+PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT
+SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR
+IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+DEALINGS IN THE SOFTWARE.
+```
+
+uucode:
+
+```
+# uucode license
+
+MIT License
+
+Copyright (c) 2026 Jacob Sandlund
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of
+this software and associated documentation files (the "Software"), to deal in
+the Software without restriction, including without limitation the rights to
+use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
+of the Software, and to permit persons to whom the Software is furnished to do
+so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
+
+## Other licenses
+
+See [./licenses](./licenses) for licenses of code being used in the repo:
+
+* [LICENSE_Bjoern_Hoehrmann](./licenses/LICENSE_Bjoern_Hoehrmann)
+* [LICENSE_unicode](./licenses/LICENSE_unicode)
+```
+
 ## JetBrains Mono
 
 `src/fonts/JetBrainsMono-Regular.woff2` and `src/fonts/JetBrainsMono-Bold.woff2` are

changelog.d/terminal-ghostty-renderer.md

@@ -0,0 +1,5 @@
+### Added
+- Settings > Terminal > Draw with libghostty (off by default) draws a pane with libghostty, the
+  terminal engine of Ghostty, on a PC that runs herdr-core, as the desktop app does, with the pictures
+  a program sends with the Kitty graphics protocol (kitty icat, timg, chafa). Typing, selection,
+  links and search still go through xterm.js underneath.

docs/development.md

@@ -268,6 +268,7 @@ bun scripts/pane-input-focus-demo-regression.ts # the input focus shortcut again
 bun scripts/mirror-scroll-demo-regression.ts # fixed mirror wheel/touch, native history, no guessed program input, observe guards
 bun scripts/terminal-images-demo-regression.ts # Settings -> Pictures in the terminal: a picture is drawn, goes while off, and on again the next one is drawn only where it was printed
 bun scripts/core-history-scroll-demo-regression.ts # a herdr-core server's history kept in xterm: wheel and swipe scroll it, a replay erases the last one, nothing typed; herdr's own keeps none (#2663)
+bun scripts/terminal-ghostty-demo-regression.ts # Settings -> Draw with libghostty: a herdr-core pane drawn from its first byte, a Kitty picture placed and deleted, typing still through xterm; herdr's own and off stay xterm without fetching the module
 bun scripts/mirror-fold-demo-regression.ts # a mirror, or an attached pane a phone watches at a wider grid, folded whole (portrait, landscape), Original width from the pane menu, driving phones and desktops unfolded
 bun scripts/shortcut-exact-modifiers-demo-regression.ts # recording exact-modifier chords: confirm, refusals, dispatch
 bun scripts/output-browser-qa.ts # terminal output flow control end to end

scripts/ci-browser.sh

@@ -80,6 +80,7 @@ run_script scripts/omo-question-wheel-regression.ts
 run_script scripts/mirror-scroll-demo-regression.ts
 run_script scripts/core-history-scroll-demo-regression.ts
 run_script scripts/terminal-images-demo-regression.ts
+run_script scripts/terminal-ghostty-demo-regression.ts
 run_script scripts/mirror-fold-demo-regression.ts
 run_script scripts/chat-no-rewind-demo-regression.ts
 run_script scripts/terminal-cjk-punctuation-regression.ts

scripts/compressed-assets.ts

@@ -9,7 +9,7 @@ const brotli = promisify(brotliCompress), gz = promisify(gzip);
 export function compressedAssets(): Plugin {
   return { name: "compressed-static-assets", async writeBundle(options, bundle) {
     if (!options.dir) return;
-    await Promise.all(Object.values(bundle).filter(asset => /\.(?:js|css)$/.test(asset.fileName)).map(async asset => {
+    await Promise.all(Object.values(bundle).filter(asset => /\.(?:js|css|wasm)$/.test(asset.fileName)).map(async asset => {
       const source = asset.type === "chunk" ? asset.code : asset.source;
       const bytes = typeof source === "string" ? Buffer.from(source) : Buffer.from(source);
       const [br, gzip] = await Promise.all([brotli(bytes, { params: { [constants.BROTLI_PARAM_QUALITY]: 5 } }), gz(bytes, { level: 9 })]);

scripts/ghostty-vt/build.sh

@@ -0,0 +1,25 @@
+#!/usr/bin/env bash
+# Rebuilds src/lib/ghostty/ghostty-vt.wasm: libghostty-vt from ghostty (MIT) at a pinned commit, with
+# kitty-on-wasm.patch, which turns the Kitty graphics protocol on for wasm32-freestanding (upstream
+# leaves it off there: no file medium and no PNG decoder). The patch refuses the file, temporary
+# file and shared memory media, which have no meaning in a browser, and links ghostty's bundled
+# wuffs PNG decoder, so a PNG a program sends is decoded inside the module.
+#
+#   ZIG=/path/to/zig-0.17.1/zig scripts/ghostty-vt/build.sh
+#
+# Expected output sha256 (zig 0.17.1, x86_64-linux):
+#   b8e8d0f8dd4e84718002198f80d5399005d6d42f2d419b31644343d5703a1444
+set -euo pipefail
+GHOSTTY_COMMIT=e95bed6
+here="$(cd "$(dirname "$0")" && pwd)"
+repo="$(cd "$here/../.." && pwd)"
+zig="${ZIG:-zig}"
+work="$(mktemp -d)"
+trap 'rm -rf "$work"' EXIT
+git -C "$work" init -q ghostty
+git -C "$work/ghostty" fetch -q --depth 1 https://github.com/ghostty-org/ghostty "$GHOSTTY_COMMIT"
+git -C "$work/ghostty" checkout -q FETCH_HEAD
+git -C "$work/ghostty" apply "$here/kitty-on-wasm.patch"
+(cd "$work/ghostty" && "$zig" build -Demit-lib-vt -Dtarget=wasm32-freestanding -Doptimize=ReleaseSmall --prefix "$work/out")
+cp "$work/out/bin/ghostty-vt.wasm" "$repo/src/lib/ghostty/ghostty-vt.wasm"
+sha256sum "$repo/src/lib/ghostty/ghostty-vt.wasm"

scripts/ghostty-vt/kitty-on-wasm.patch

@@ -0,0 +1,40 @@
+diff --git a/src/terminal/build_options.zig b/src/terminal/build_options.zig
+index 628ecbd..1542c32 100644
+--- a/src/terminal/build_options.zig
++++ b/src/terminal/build_options.zig
+@@ -272,7 +272,7 @@ pub const Options = struct {
+     /// targets, so it is always disabled there regardless of the
+     /// feature setting.
+     pub fn kittyGraphics(self: Options, target: std.Target) bool {
+-        if (target.os.tag == .freestanding) return false;
++        _ = target;
+         return self.features.kitty_graphics;
+     }
+
+diff --git a/src/terminal/kitty/graphics_image.zig b/src/terminal/kitty/graphics_image.zig
+index 281bb02..cba04a5 100644
+--- a/src/terminal/kitty/graphics_image.zig
++++ b/src/terminal/kitty/graphics_image.zig
+@@ -182,6 +182,9 @@ pub const LoadingImage = struct {
+             }
+         }
+
++        // Freestanding (wasm) has no filesystem: only direct payloads.
++        if (comptime builtin.target.os.tag == .freestanding) return error.UnsupportedMedium;
++
+         // Depending on the medium, load the data from the path.
+         switch (t.medium) {
+             .direct => unreachable, // handled above
+diff --git a/src/terminal/sys.zig b/src/terminal/sys.zig
+index 3f6b501..712a754 100644
+--- a/src/terminal/sys.zig
++++ b/src/terminal/sys.zig
+@@ -16,7 +16,7 @@ const build_options = @import("terminal_options");
+ /// and the exact semantics are up to callers. For example, the Kitty Graphics
+ /// Protocol will work but cannot accept PNG images.
+ pub var decode_png: ?DecodePngFn = png: {
+-    if (build_options.artifact == .lib) break :png null;
++    if (build_options.artifact == .lib and @import("builtin").target.os.tag != .freestanding) break :png null;
+     break :png &decodePngWuffs;
+ };
+