Docs: reply to the gpui-mobile#30 review

docs/upstream/replies/gpui-mobile-30.md

@@ -1,49 +1,62 @@
 # Reply to huacnlee's review of longbridge/gpui-mobile#30
 
 Draft, to be posted by hand. The review (12 Oct, CHANGES_REQUESTED) was on
-c62c318. The force-push later that day to
-[ec5c89d](https://github.com/longbridge/gpui-mobile/pull/30/commits/ec5c89dfe3ab399bcc90a01f03cf89873cb750b2)
-only rebased the PR onto main after #29 merged: `HOST_ASSETS` now gets its
-AssetManager from the `HOST_APPLICATION` context this PR keeps, instead of
-calling `getApplicationContext()` a second time. `host.rs` and `platform.rs` are
-unchanged apart from line offsets. **None of the review points are addressed
-yet.** So this reply says that and lays out the plan. It should be rewritten
-once the fixes are pushed.
+c62c318. The force-push that day (ec5c89d) was only a rebase onto #29. All
+review points are addressed in
+[fa0075b](https://github.com/longbridge/gpui-mobile/pull/30/commits/fa0075b137437b34daeaf6a0d8d4a33686423384),
+pushed on top of ec5c89d as a separate commit.
 
 ---
 
-Thanks for the careful review! One thing to clear up first: the force-push on
-12 Oct was only a rebase onto main after #29 merged. It now shares the
-application context that #29's `HOST_ASSETS` needs, and nothing else changed.
-It does not address your points yet. Sorry it looked like a response. Here is
-what I plan to do for each one:
-
-1. **android-activity path starts Light.** You're right. `window_appearance()`
-   now reports the real mode, but nothing on the `InitWindow` path sets the
-   window's own appearance, so the two disagree until a `ConfigChanged`. Fixed
-   by item 2.
-2. **Sync in the shared code.** I'll move the initial `sync_appearance` into
-   `AndroidPlatform::open_window` and after `init_window`, so both entry points
-   go through it, and remove the call-site copies in `host.rs` that this makes
-   redundant. I'll keep the one in `resumed`.
-3. **App-local night mode.** Agreed. I'll read `uiMode` from the current host
-   Activity's Resources instead of the application context, so
-   `AppCompatDelegate.setDefaultNightMode` is respected. `HOST_APPLICATION`
-   stays only for the AssetManager.
-4. **Order of config changes.** I'll change the signature to
-   `host::configuration_changed(ui_mode: i32)` and have the host pass
-   `newConfig.uiMode`, so nothing re-reads a configuration that may not be
-   updated yet. The host docs will show the call.
-
-On the non-blocking points, I'll do all three in the same push:
-
-- `window_appearance()` will return the value last stored by `sync_appearance`
-  instead of querying over JNI or building an `AConfiguration` on every call.
-- The `ConfigurationChanged` handler will work out the appearance once and call
-  `set_appearance` on each window.
-- A failed `host_ui_mode` will log a `warn!` instead of quietly meaning Light.
-  (Today only a failed `getApplicationContext()` in `set_host_activity` logs.)
-
-I'll reply again with the commit once it's pushed. None of this has been
-verified on a device yet. I'll test a cold start in dark mode on both paths, and
-an in-app night-mode toggle, before asking for another look.
+Thanks for the review, and sorry for the silent force-push on the 12th: that
+was only a rebase onto #29 and did not address anything. The fixes are in
+fa0075b, on top of it:
+
+1. **android-activity path starts Light.** Fixed by item 2. On a cold start in
+   dark mode, `cx.window_appearance()` and `window.appearance()` both say Dark
+   on the first frame now. Before, the window said Light.
+2. **Sync in the shared code.** `AndroidPlatform::open_window` applies the night
+   mode, and so does a new `AndroidPlatform::reinit_window`, which both
+   `InitWindow` and the host's reattach now use instead of calling
+   `init_window` directly. The call-site syncs in `host.rs` are gone. Only
+   `resumed` still re-reads it, in case it changed while another app was in
+   front.
+3. **App-local night mode.** `uiMode` now comes from the current host Activity's
+   Resources, so `AppCompatDelegate.setDefaultNightMode` counts. With the
+   application context no longer needed for night mode, I dropped the global
+   this PR had added. The AssetManager is fetched as on main again.
+4. **Order of config changes.** It's now `host::configuration_changed(ui_mode: i32)`,
+   and the host passes `newConfig.uiMode`. Nothing re-reads a configuration in
+   that path. The module docs show the call.
+
+Non-blocking:
+
+- The platform stores the appearance it last applied, and
+  `window_appearance()` just returns it, with no JNI call or `AConfiguration`.
+  It has its own small lock rather than living in the platform state, because
+  GPUI reads it from main-thread tasks, and `flush_main_thread_tasks()` runs
+  those with the state locked. My first version stored it in the state and
+  deadlocked on the first night-mode change on the android-activity path.
+  The device test below caught it.
+- `ConfigurationChanged` reads the night mode once and applies it to every
+  window (`AndroidPlatform::set_appearance`).
+- A failed `uiMode` read logs a `warn!`. The read also runs in a local frame
+  now, since the render thread never returns to Java.
+
+Tested on a OnePlus with Android 16, switching with `cmd uimode night`:
+
+- host path (Bombatomica64/Gpui-android, Diagnostics screen): cold start in
+  dark mode, a live toggle to light (the Activity handles `uiMode`), back to
+  dark while in the background then resumed, and a light system with the
+  Activity forced to dark the way AppCompat does it. All four show the right
+  appearance.
+- android-activity path (this repo's example, with a log in an
+  `observe_window_appearance` callback): a cold start in dark mode logs
+  `platform=Dark window=Dark` (ec5c89d logged `platform=Dark window=Light`), and
+  toggling light and back fires the observer each time with both values
+  agreeing.
+
+![Cold start dark, live toggle to light, app-local dark on a light system](https://raw.githubusercontent.com/Bombatomica64/Gpui-android/main/docs/demos/android-night-mode-review.png)
+
+One API change for hosts: `configuration_changed` now takes the `uiMode`
+argument.