feat: verify webview version and prevent loading blank screen

Author: Fandroid745

AnkiDroid/src/main/java/com/ichi2/anki/pages/PageFragment.kt

@@ -26,10 +26,12 @@ import androidx.core.net.toUri
 import androidx.fragment.app.Fragment
 import com.google.android.material.appbar.MaterialToolbar
 import com.google.android.material.progressindicator.CircularProgressIndicator
+import com.ichi2.anki.AnkiActivity
 import com.ichi2.anki.R
 import com.ichi2.anki.workarounds.OnWebViewRecreatedListener
 import com.ichi2.anki.workarounds.SafeWebViewLayout
 import com.ichi2.themes.Themes
+import com.ichi2.utils.checkWebviewVersion
 import timber.log.Timber
 
 /**
@@ -100,6 +102,12 @@ abstract class PageFragment(
         view: View,
         savedInstanceState: Bundle?,
     ) {
+        val ankiActivity = requireActivity() as AnkiActivity
+        if (checkWebviewVersion(ankiActivity)) {
+            Timber.w("Aborting PageFragement load: WebView is outdated")
+            ankiActivity.onBackPressedDispatcher.onBackPressed()
+            return
+        }
         server = AnkiServer(this).also { it.start() }
         webViewLayout = view.findViewById(R.id.webview_layout)
 

AnkiDroid/src/main/java/com/ichi2/utils/WebViewUtils.kt

@@ -34,14 +34,14 @@ import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.withContext
 import timber.log.Timber
 
-internal const val OLDEST_WORKING_WEBVIEW_VERSION_CODE = 418306960L
-internal const val OLDEST_WORKING_WEBVIEW_VERSION = 85
+internal const val OLDEST_WORKING_WEBVIEW_VERSION_CODE = 443000000L
+internal const val OLDEST_WORKING_WEBVIEW_VERSION = 90
 
 /**
  * Shows a dialog if the current WebView version is older than the last supported version.
  */
-fun checkWebviewVersion(activity: AnkiActivity) {
-    val userVisibleCode = getChromeLikeWebViewVersionIfOutdated(activity) ?: return
+fun checkWebviewVersion(activity: AnkiActivity): Boolean {
+    val userVisibleCode = getChromeLikeWebViewVersionIfOutdated(activity) ?: return false
 
     // Provide guidance to the user if the WebView is outdated
     val webviewPackageInfo = getAndroidSystemWebViewPackageInfo(activity.packageManager)
@@ -54,6 +54,7 @@ fun checkWebviewVersion(activity: AnkiActivity) {
         Timber.w("WebView is outdated. %s: %s", webviewPackageInfo?.packageName, webviewPackageInfo?.versionName)
         showOutdatedWebViewDialog(activity, userVisibleCode, R.string.link_webview_update)
     }
+    return true
 }
 
 @MainThread
@@ -96,33 +97,33 @@ fun checkWebViewVersionComponents(
     versionCode: Long,
     userAgent: String?,
 ): Int? {
-    // Checking the version code works for most webview packages
-    if (versionCode >= OLDEST_WORKING_WEBVIEW_VERSION_CODE) {
-        Timber.d(
-            "WebView is up to date. %s: %s(%s)",
-            packageName,
-            webviewVersion,
-            versionCode.toString(),
-        )
-        return null
-    }
-
     // Sometimes the webview version code appears too old, and the package name does as well,
     // but it's a webview that advertises modern capabilities via User-Agent in "Chrome" section
     // Our warning is purely advisory, so, let's let those through if User-Agent looks okay
     userAgent?.let {
         val chromeRegex = """Chrome/(\d+)""".toRegex()
         val matchResult = chromeRegex.find(userAgent)?.groupValues?.get(1)
         matchResult?.toInt()?.let {
-            if (it < OLDEST_WORKING_WEBVIEW_VERSION) {
-                // If we got here, even the User-Agent says it's incompatible, return something
-                // potentially useful to the user as a browser version
+            if (it >= OLDEST_WORKING_WEBVIEW_VERSION) {
+                // If the User-Agent says we are modern, trust it and skip further checks.
+                return null
+            } else {
+                // If the User-Agent is explicitly below the floor, return it immediately.
                 return it
             }
         }
     }
-
-    return null
+    // Checking the version code works for most webview packages
+    if (versionCode >= OLDEST_WORKING_WEBVIEW_VERSION_CODE) {
+        Timber.d(
+            "WebView is up to date. %s: %s(%s)",
+            packageName,
+            webviewVersion,
+            versionCode.toString(),
+        )
+        return null
+    }
+    return webviewVersion.split('.').firstOrNull()?.toIntOrNull()
 }
 
 data class WebViewInfo(