fix: 终端延迟到容器有尺寸后再 open（零尺寸初始化崩溃，WKWebView 底部面板展开后终端空白，#25）

src/client/TerminalView.tsx

@@ -24,6 +24,7 @@ import { Terminal, type ITheme } from 'xterm'
 import { FitAddon } from '@xterm/addon-fit'
 import 'xterm/css/xterm.css'
 import { t } from './locales.ts'
+import { openWhenSized } from './open-when-sized.ts'
 import type { SessionScope } from './api.ts'
 import { agentUuidOf, isAgentTabId, type SidebarStore } from './state.ts'
 import { isDarkScheme, subscribeColorScheme, tokenValue } from './theme.ts'
@@ -97,8 +98,6 @@ export function TerminalView(props: { scope: SessionScope; tabId: string; store:
     })
     const fit = new FitAddon()
     term.loadAddon(fit)
-    term.open(host)
-    fit.fit()
     // Re-theme in place when the app's scheme flips (tokens + palette).
     const applyTheme = (): void => {
       term.options.theme = xtermTheme()
@@ -208,9 +207,30 @@ export function TerminalView(props: { scope: SessionScope; tabId: string; store:
       }
     })
 
+    // The terminal must not be opened in a zero-size container: xterm's
+    // renderer creation fails there and the next Viewport refresh crashes
+    // reading `.dimensions` off the undefined renderer (blank terminal on
+    // WKWebView when the bottom panel's expand slide leaves the host at
+    // height 0; any display:none-hidden ancestor does the same). Defer
+    // open+fit until the host has a real size — writes arriving meanwhile
+    // are buffered by xterm's WriteBuffer and render once open, and
+    // FitAddon.fit() is a safe no-op before open. sendResize() here covers
+    // the deferred path where the socket may already be open with the
+    // default 80x24 dims.
+    const cancelOpen = openWhenSized(host, () => {
+      try {
+        term.open(host)
+        fit.fit()
+        sendResize()
+      } catch (error) {
+        console.error('[dsh-better-sidebar] xterm open failed:', error)
+      }
+    })
+
     connect()
     return () => {
       closed = true
+      cancelOpen()
       window.clearTimeout(retry)
       observer.disconnect()
       fontSub()

src/client/open-when-sized.ts

@@ -0,0 +1,43 @@
+/**
+ * Deferred one-shot open for hosts that may not have a real size yet.
+ *
+ * xterm's `Terminal.open()` must not run in a zero-size container: the
+ * renderer creation fails there (the DomRenderer is built from the host's
+ * dimensions), leaving the render service's renderer `undefined`, and the
+ * next Viewport refresh crashes reading `.dimensions` off it. WebKit-based
+ * hosts (WKWebView) reliably report zero while the bottom panel's expand
+ * slide is in flight; any `display:none`-hidden ancestor does the same.
+ *
+ * The caller's `open` callback (open + fit + resize) is invoked exactly
+ * once, on the first frame where the host reports a real size. While the
+ * host stays zero-sized the polling continues every frame; it stops when
+ * the host leaves the document (`isConnected`), so a pending open never
+ * fires after unmount. The returned cancel function drops a pending frame
+ * immediately (idempotent).
+ *
+ * `raf`/`caf` are injectable so tests can drive the polling deterministically.
+ */
+export function openWhenSized(
+  host: HTMLElement,
+  open: () => void,
+  raf: (cb: FrameRequestCallback) => number = requestAnimationFrame,
+  caf: (id: number) => void = cancelAnimationFrame,
+): () => void {
+  let frame: number | null = null
+  const step = (): void => {
+    frame = null
+    if (!host.isConnected) return
+    if (host.clientWidth > 0 && host.clientHeight > 0) {
+      open()
+      return
+    }
+    frame = raf(step)
+  }
+  frame = raf(step)
+  return () => {
+    if (frame !== null) {
+      caf(frame)
+      frame = null
+    }
+  }
+}