app/src/main/kotlin/io/flamenet/messenger/app/NotificationSection.kt

@@ -1,5 +1,10 @@
 package io.flamenet.messenger.app
 
+import android.provider.Settings
+import android.os.Build
+import android.net.Uri
+import android.content.Intent
+import android.app.NotificationManager
 import androidx.compose.foundation.layout.ColumnScope
 import androidx.compose.foundation.layout.Row
 import androidx.compose.foundation.layout.Spacer
@@ -75,6 +80,49 @@ fun ColumnScope.NotificationSection() {
 
     Spacer(Modifier.height(Space.xs))
 
+    // A ringing call needs a permission the manifest cannot grant itself.
+    //
+    // Since Android 14, USE_FULL_SCREEN_INTENT is auto-granted only to apps the
+    // system already treats as calling apps. Declared and not granted, an
+    // incoming call is demoted to an ordinary heads-up: it shows for about two
+    // seconds and collapses, which reads as the call notification being broken.
+    // The system refuses silently, so the only way anybody learns is here.
+    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.UPSIDE_DOWN_CAKE) {
+        val manager = context.getSystemService(NotificationManager::class.java)
+        if (manager?.canUseFullScreenIntent() == false) {
+            Spacer(Modifier.height(Space.sm))
+            Text(
+                "Calls will not ring full screen",
+                style = MaterialTheme.typography.titleSmall,
+                modifier = Modifier.testTag("notify-fsi-title"),
+            )
+            Text(
+                "Android is holding back the permission that lets an incoming call " +
+                    "take over the screen, so a call shows as a banner for a couple of " +
+                    "seconds and then goes. Grant it and calls ring properly.",
+                fontSize = 12.sp,
+                color = Palette.SecondaryText,
+            )
+            Spacer(Modifier.height(Space.xs))
+            KitSecondaryButton(
+                text = "Let calls ring",
+                onClick = {
+                    runCatching {
+                        context.startActivity(
+                            Intent(
+                                Settings.ACTION_MANAGE_APP_USE_FULL_SCREEN_INTENT,
+                                Uri.fromParts("package", context.packageName, null),
+                            ).addFlags(Intent.FLAG_ACTIVITY_NEW_TASK),
+                        )
+                    }
+                },
+                tag = "notify-fsi-grant",
+            )
+        }
+    }
+
+    Spacer(Modifier.height(Space.xs))
+
     // Says what turning it on costs, and does not pretend the default is merely
     // cautious.
     Text(