feat(panes): desktop host — real windows and the system tray

Registers a `desktop` pane host at priority 20, above the browser pop-up
host (10) and the dock (0), whenever the Electron bridge exposes
feedBackDesktop.panes. A popped-out pane then gets a real BrowserWindow:
it remembers where you put it, can float above everything, minimizes to
the system tray, and appears in the tray's menu.

In a plain browser — or on an older desktop build that predates the
bridge — this file registers nothing and the browser pop-up host handles
detach exactly as before. Nothing else in the pane system changes. That
is what the host registry is for.

Two things only this realm can decide, so it owns them:

- The user closed a pane window (or it crashed). Close the pane, or the
  dialog its pop-out chip hid never comes back and the user is left with
  no way to reach their own UI.
- The tray asked to toggle a pane it has no window for. Main cannot know
  what opening one means — the pane might belong in the dock — so it asks.

Unlike a browser pop-up, this host needs no user gesture, so it sets
autoRestore: true — a pane you left popped out comes back popped out,
where you left it, on the next launch.

Pairs with got-feedback/feedBack-desktop#103.

Signed-off-by: topkoa <topkoa@gmail.com>

static/panes/pane-desktop-host.js

@@ -0,0 +1,108 @@
+/*
+ * fee[dB]ack — the desktop pane host.
+ *
+ * When running inside the desktop app, a popped-out pane gets a real
+ * BrowserWindow instead of a browser pop-up: it remembers where you put it, it
+ * can float above everything, it minimizes to the system tray, and the tray
+ * lists every pane you have.
+ *
+ * Registers as the `desktop` host at priority 20 — above `window` (10, the
+ * browser pop-up) and `dock` (0) — so `panes.detach()` picks it whenever the
+ * desktop bridge is present. In a plain browser this file registers nothing and
+ * the browser pop-up host takes over. Nothing else in the pane system changes;
+ * that is what the host registry is for.
+ *
+ * The renderer stays the authority on what a pane IS. The main process only owns
+ * the window. So this file pushes the pane registry up to the tray, and answers
+ * the tray when it asks for a pane to be toggled.
+ */
+(function () {
+    'use strict';
+
+    const panes = window.feedBack && window.feedBack.panes;
+    const bus = window.feedBack;
+    // `feedBackDesktop.panes` is absent in a browser, and also in an OLDER
+    // desktop build that predates this feature — in both cases we simply don't
+    // register, and the browser pop-out host handles detach as before.
+    const desktop = window.feedBackDesktop && window.feedBackDesktop.panes;
+    if (!panes || !bus || !desktop) return;
+
+    const open = new Set();
+
+    function mount(spec) {
+        const url = new URL(window.location.origin + '/pane');
+        url.searchParams.set('pane', spec.id);
+        url.searchParams.set('script', spec.script);
+
+        open.add(spec.id);
+        // Fire-and-forget: the pane's contents arrive over BroadcastChannel from
+        // pane-hub.js, not through this call. All the main process does is put a
+        // window on screen pointing at our own origin.
+        desktop.open({
+            paneId: spec.id,
+            url: url.toString(),
+            title: spec.title,
+            width: spec.width,
+            height: spec.height,
+        }).then((ok) => {
+            if (ok) return;
+            console.error('[panes] desktop refused to open a window for', spec.id);
+            open.delete(spec.id);
+            panes.close(spec.id);
+        }).catch((err) => {
+            console.error('[panes] desktop pane open failed', spec.id, err);
+            open.delete(spec.id);
+            panes.close(spec.id);
+        });
+
+        return { paneId: spec.id };   // an opaque handle; the manager only checks it's truthy
+    }
+
+    function unmount(id) {
+        open.delete(id);
+        desktop.close(id).catch(() => { /* window already gone */ });
+    }
+
+    panes.registerHost({
+        id: 'desktop',
+        priority: 20,
+        remote: true,
+        // Unlike a browser pop-up, this needs no user gesture — so a pane the user
+        // left popped out comes back popped out, where they left it, on next launch.
+        autoRestore: true,
+        available: () => typeof BroadcastChannel === 'function',
+        // A pane with no `script` is only a closure in this realm and cannot
+        // honestly cross a window boundary; the router falls back to the dock.
+        canHost: (spec) => !!spec.script,
+        mount,
+        unmount,
+        focus: (id) => { desktop.focus(id).catch(() => { /* window already gone */ }); },
+    });
+
+    // The user closed the pane window (or it crashed). Close the pane, so the
+    // dialog its pop-out chip hid comes back — otherwise the user's own UI is
+    // hidden with no way to reach it.
+    desktop.onClosed((paneId) => {
+        if (!open.has(paneId)) return;
+        open.delete(paneId);
+        panes.close(paneId);
+    });
+
+    // The tray asked to toggle a pane it has no window for. Only this realm knows
+    // what opening one means.
+    desktop.onToggle((paneId) => {
+        if (panes.isOpen(paneId)) panes.close(paneId);
+        else panes.detach(paneId);
+    });
+
+    // Keep the tray's menu in step with the registry. Cheap and rare — panes are
+    // registered at load and toggled by hand, never on a playback path.
+    function sync() {
+        desktop.sync(panes.list().map((p) => ({ id: p.id, title: p.title, icon: p.icon, open: p.open })));
+    }
+    bus.on('panes:registered', sync);
+    bus.on('panes:unregistered', sync);
+    bus.on('panes:opened', sync);
+    bus.on('panes:closed', sync);
+    sync();
+})();

static/v3/index.html

@@ -1327,6 +1327,10 @@
     <script defer src="/static/panes/pane-manager.js"></script>
     <script defer src="/static/panes/pane-dock.js"></script>
     <script defer src="/static/panes/pane-window-host.js"></script>
+    <!-- Desktop host: registers above the browser pop-up host when the Electron
+         bridge is present (real BrowserWindow + system tray), and registers
+         nothing at all in a browser. -->
+    <script defer src="/static/panes/pane-desktop-host.js"></script>
     <script defer src="/static/panes/pane-hub.js"></script>
     <script defer src="/static/panes/pane-chip.js"></script>
     <script defer src="/static/panes/pane-launcher.js"></script>