Add offline page caching, fix Google login, reduce UI latency

[Copilot]

Three template/app improvements: toggleable offline caching for generated APKs, Google sign-in unblocked in WebView, and UI performance fixes for perceived latency.

Offline page caching (template app)

• New enableOfflineCache toggle in APK config form, plumbed through ApkConfig → ApkProcessor → config.json → template MainActivity.java
• Marked as experimental in the UI with a badge label and updated description text
• Uses WebView.saveWebArchive() to save the full rendered page as an MHTML snapshot after each page load — captures CSS, images, and embedded resources regardless of server Cache-Control headers
• When reopening offline, loads from the saved .mht archive file instead of the URL
• Dynamic ConnectivityManager.NetworkCallback via registerDefaultNetworkCallback() switches cache modes in real time as a secondary fallback (LOAD_DEFAULT online, LOAD_CACHE_ELSE_NETWORK offline)
• Callback properly unregistered in onDestroy() to prevent leaks
• Added to README known issues that caching may not work correctly on some advanced or dynamic websites

Google login fix (template app)

Google blocks OAuth from WebViews identified by the ; wv) user-agent token. Stripped it so Google treats the WebView as a regular browser, allowing sign-in.

Performance optimizations

• Removed Modifier.blur(16.dp) on TopAppBar — primary source of frame drops. Replaced with surface.copy(alpha = 0.95f)
• Added android:hardwareAccelerated="true" to template manifest
• Predictive-back theming: Uses window.setBackgroundDrawable(ColorDrawable(...)) to set the predictive-back gesture reveal color — lighter weight than decorView.setBackgroundColor() (avoids full DecorView layout pass). Removed expensive repeated enableEdgeToEdge() and setNavigationBarColor() calls from theme updates
• Material 3 animation durations: Navigation transitions use 300ms with FastOutSlowInEasing; build state transitions use 250ms with EaseInOutCubic for smooth, non-choppy motion

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[dynodevv]

@copilot Making good progress, nice. Google sign-in works. But there are some more issues:

1. Some animations just feel like they're running on a low FPS. Please try to fix this, as it makes the app feel a lot slower. I've also noticed that the predictive-back gestures are also a bit delayed: if I pull from one of the sides of my screen (aka the "Back button" for gesture-based navigation in Android), there is a delay until the predictive-back gesture appears (aka the earlier page). This can, again make the app feel slower than it should be. Please fix.
2. Offline caching: works on some websites.. doesn't work on most. Please also fix this, because if the caching doesn't work properly as it is advertised to, then there's no point of using it....

[Copilot]

@copilot Making good progress, nice. Google sign-in works. But there are some more issues:

1. Some animations just feel like they're running on a low FPS. Please try to fix this, as it makes the app ...

Fixed both issues in d03ed81:

1. Animation FPS / predictive-back delay: The root cause was updateStatusBarAppearance() calling window.decorView.setBackgroundColor(), window.setNavigationBarColor(), and enableEdgeToEdge() on every theme update. Each of these triggers expensive full decorView hierarchy relayouts and window reconfiguration that block frame rendering. Stripped all of those out — only lightweight insetsController.setSystemBarsAppearance() flag updates remain.

2. Offline caching: The previous implementation checked network state once at startup and set the cache mode statically. If the network dropped mid-session, the WebView was still using LOAD_DEFAULT, which doesn't serve cached content for sites with no-cache headers. Now uses a ConnectivityManager.NetworkCallback (via registerDefaultNetworkCallback()) that dynamically switches: LOAD_DEFAULT when online → LOAD_CACHE_ELSE_NETWORK when the default network is lost. The callback properly unregisters in onDestroy().

[dynodevv]

@copilot

1. The app is still having the same lag issues I've mentioned earlier. But the state of the app is even worse now. The predictive back gesture now uses the light theme, even when set to dark (or system while the system theme is dark).
2. Caching is well, still broken. What I mean by "caching" is that the user should be able to view the last state of the website if they aren't connected to the internet. How I tested it on all websites is that I first opened the generated APK WITH internet, then waited a few seconds, force quit the app and then re-opened it with mobile data/WiFi disabled. This way, most websites didn't load.

[Copilot]

@copilot

1. The app is still having the same lag issues I've mentioned earlier. But the state of the app is even worse now. The predictive back gesture now uses the light theme, even when set to dar...

Fixed both issues in 0e5b3c7:

1. Predictive-back dark theme: The previous commit stripped window.setBackgroundDrawable() which is what determines the predictive-back gesture reveal color. Restored it using window.setBackgroundDrawable(ColorDrawable(bgColor)) — this is lighter-weight than the original decorView.setBackgroundColor() (doesn't trigger full DecorView layout pass). Also moved navigation transitions from 150ms to 300ms with FastOutSlowInEasing for smoother motion per Material 3 guidelines.

2. Offline caching: The HTTP cache approach (LOAD_CACHE_ELSE_NETWORK) fails on most modern websites because they send Cache-Control: no-store headers that prevent WebView from caching content at all. Switched to WebView.saveWebArchive() which saves the full rendered page as an MHTML file (including CSS, images, embedded resources) after each page load. When reopening offline, the app loads directly from the saved .mht file instead of the URL, which works regardless of server cache headers.

[dynodevv]

@copilot Alright great, now caching works!... Sorta though. Please make it so inside of Appy, it is clarified that caching is an experimental feature, and in the README.md in the repository please add to the known issues that caching can be a bit glitchy on some more advanced websites. Just do this and then I'll merge the pull request into the main branch.

[Copilot]

@copilot Alright great, now caching works!... Sorta though. Please make it so inside of Appy, it is clarified that caching is an experimental feature, and in the README.md in the repository please add...

Done in 432b5c2. Added an "Experimental" badge next to the Offline Cache toggle in the UI and updated the description text to say "May not work on all websites." Also added a known issue entry to README.md.

[Copilot]

Pull request overview

This PR extends the generated WebView template and the Appy UI to support an experimental offline-page snapshot feature, improve Google OAuth compatibility in WebView, and reduce perceived UI latency in the Compose app.

Changes:

• Adds an enableOfflineCache toggle to the app UI/config pipeline and implements MHTML snapshot save/load in the template WebView.
• Adjusts WebView user-agent to avoid Google OAuth blocking in embedded WebViews.
• Tweaks UI performance/animations (removes blur TopAppBar effect, updates transitions) and optimizes predictive-back theming behavior.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
template/src/main/java/com/webtemplate/MainActivity.java	Implements offline archive save/load, dynamic cache-mode switching, and user-agent adjustment for Google login.
template/src/main/AndroidManifest.xml	Enables hardware acceleration at the application level.
app/src/main/java/com/appy/ui/screens/HomeScreen.kt	Adds offline-cache toggle to the APK config form and removes TopAppBar blur; updates animation timings.
app/src/main/java/com/appy/processor/ApkProcessor.kt	Plumbs enableOfflineCache into injected config.json.
app/src/main/java/com/appy/MainActivity.kt	Updates transitions and refactors status bar/predictive-back theming to reduce window reconfiguration work.
README.md	Documents offline caching as experimental in known issues.

Comments suppressed due to low confidence (1)

app/src/main/java/com/appy/MainActivity.kt:249

• For API levels < 30 (R), updateStatusBarAppearance() only toggles SYSTEM_UI_FLAG_LIGHT_STATUS_BAR. Since minSdk=26, this leaves navigation bar icon appearance unmanaged on Android 8–10, which can lead to low-contrast nav bar icons in light theme. Consider also setting/clearing View.SYSTEM_UI_FLAG_LIGHT_NAVIGATION_BAR (API 26+) in this branch.

        } else {
            if (isDarkTheme) {
                window.decorView.systemUiVisibility = 
                    window.decorView.systemUiVisibility and View.SYSTEM_UI_FLAG_LIGHT_STATUS_BAR.inv()
            } else {
                window.decorView.systemUiVisibility = 
                    window.decorView.systemUiVisibility or View.SYSTEM_UI_FLAG_LIGHT_STATUS_BAR
            }

[Copilot]

webView.loadUrl("file://" + archive.getAbsolutePath()) produces a non-canonical file URL (absolute paths start with '/', so the final URL becomes file:////...). This can break loading the saved MHTML on some WebView/URI parsers. Build the file URL via Uri.fromFile(archive).toString() (or otherwise ensure file:///...).

Suggested change

	webView.loadUrl("file://" + archive.getAbsolutePath());
	webView.loadUrl(Uri.fromFile(archive).toString());

[Copilot]

isNetworkAvailable() returns true only for WIFI/CELLULAR/ETHERNET transports. If the active network is VPN (common) or another transport, this will incorrectly report “offline”, causing the app to load the archive and switch cache modes even though Internet is available. Consider checking NET_CAPABILITY_INTERNET (and optionally NET_CAPABILITY_VALIDATED) instead of hard-coding transports.

Suggested change

	return caps != null && (caps.hasTransport(NetworkCapabilities.TRANSPORT_WIFI)
	|| caps.hasTransport(NetworkCapabilities.TRANSPORT_CELLULAR)
	|| caps.hasTransport(NetworkCapabilities.TRANSPORT_ETHERNET));
	if (caps == null) return false;
	boolean hasInternetCapability = caps.hasCapability(NetworkCapabilities.NET_CAPABILITY_INTERNET);
	boolean isValidated = caps.hasCapability(NetworkCapabilities.NET_CAPABILITY_VALIDATED);
	return hasInternetCapability && isValidated;