[SB Refactor] Add content descriptions for the mobile triangle.

This mirrors `SignalController#getContentDescription`, which is called
from `MobileSignalController#notifyListeners`.

Bug: 238425913
Test: manual: Verified content description updates correctly using demo
mode
Test: atest MobileIconViewModelTest

Change-Id: I2f1f603fd6b0d1257d90fb6addb1403847438415

packages/SystemUI/src/com/android/systemui/statusbar/pipeline/mobile/ui/binder/MobileIconBinder.kt

@@ -29,6 +29,7 @@ import androidx.lifecycle.Lifecycle
 import androidx.lifecycle.repeatOnLifecycle
 import com.android.settingslib.graph.SignalDrawable
 import com.android.systemui.R
+import com.android.systemui.common.ui.binder.ContentDescriptionViewBinder
 import com.android.systemui.common.ui.binder.IconViewBinder
 import com.android.systemui.lifecycle.repeatWhenAttached
 import com.android.systemui.statusbar.StatusBarIconView
@@ -97,6 +98,12 @@ object MobileIconBinder {
                     }
                 }
 
+                launch {
+                    viewModel.contentDescription.distinctUntilChanged().collect {
+                        ContentDescriptionViewBinder.bind(it, view)
+                    }
+                }
+
                 // Set the network type icon
                 launch {
                     viewModel.networkTypeIcon.distinctUntilChanged().collect { dataTypeId ->

packages/SystemUI/src/com/android/systemui/statusbar/pipeline/mobile/ui/viewmodel/MobileIconViewModel.kt

@@ -16,6 +16,8 @@
 
 package com.android.systemui.statusbar.pipeline.mobile.ui.viewmodel
 
+import com.android.settingslib.AccessibilityContentDescriptions.PHONE_SIGNAL_STRENGTH
+import com.android.settingslib.AccessibilityContentDescriptions.PHONE_SIGNAL_STRENGTH_NONE
 import com.android.settingslib.graph.SignalDrawable
 import com.android.systemui.common.shared.model.ContentDescription
 import com.android.systemui.common.shared.model.Icon
@@ -43,6 +45,7 @@ interface MobileIconViewModelCommon {
     val subscriptionId: Int
     /** An int consumable by [SignalDrawable] for display */
     val iconId: Flow<Int>
+    val contentDescription: Flow<ContentDescription>
     val roaming: Flow<Boolean>
     /** The RAT icon (LTE, 3G, 5G, etc) to be displayed. Null if we shouldn't show anything */
     val networkTypeIcon: Flow<Icon?>
@@ -102,6 +105,23 @@ constructor(
             .stateIn(scope, SharingStarted.WhileSubscribed(), initial)
     }
 
+    override val contentDescription: Flow<ContentDescription> = run {
+        val initial = ContentDescription.Resource(PHONE_SIGNAL_STRENGTH_NONE)
+        combine(
+                iconInteractor.level,
+                iconInteractor.isInService,
+            ) { level, isInService ->
+                val resId =
+                    when {
+                        isInService -> PHONE_SIGNAL_STRENGTH[level]
+                        else -> PHONE_SIGNAL_STRENGTH_NONE
+                    }
+                ContentDescription.Resource(resId)
+            }
+            .distinctUntilChanged()
+            .stateIn(scope, SharingStarted.WhileSubscribed(), initial)
+    }
+
     private val showNetworkTypeIcon: Flow<Boolean> =
         combine(
             iconInteractor.isDataConnected,

packages/SystemUI/tests/src/com/android/systemui/statusbar/pipeline/mobile/ui/viewmodel/MobileIconViewModelTest.kt

@@ -17,6 +17,8 @@
 package com.android.systemui.statusbar.pipeline.mobile.ui.viewmodel
 
 import androidx.test.filters.SmallTest
+import com.android.settingslib.AccessibilityContentDescriptions.PHONE_SIGNAL_STRENGTH
+import com.android.settingslib.AccessibilityContentDescriptions.PHONE_SIGNAL_STRENGTH_NONE
 import com.android.settingslib.graph.SignalDrawable
 import com.android.settingslib.mobile.TelephonyIcons.THREE_G
 import com.android.systemui.SysuiTestCase
@@ -121,6 +123,39 @@ class MobileIconViewModelTest : SysuiTestCase() {
             job.cancel()
         }
 
+    @Test
+    fun contentDescription_notInService_usesNoPhone() =
+        testScope.runTest {
+            var latest: ContentDescription? = null
+            val job = underTest.contentDescription.onEach { latest = it }.launchIn(this)
+
+            interactor.isInService.value = false
+
+            assertThat((latest as ContentDescription.Resource).res)
+                .isEqualTo(PHONE_SIGNAL_STRENGTH_NONE)
+
+            job.cancel()
+        }
+
+    @Test
+    fun contentDescription_inService_usesLevel() =
+        testScope.runTest {
+            var latest: ContentDescription? = null
+            val job = underTest.contentDescription.onEach { latest = it }.launchIn(this)
+
+            interactor.isInService.value = true
+
+            interactor.level.value = 2
+            assertThat((latest as ContentDescription.Resource).res)
+                .isEqualTo(PHONE_SIGNAL_STRENGTH[2])
+
+            interactor.level.value = 0
+            assertThat((latest as ContentDescription.Resource).res)
+                .isEqualTo(PHONE_SIGNAL_STRENGTH[0])
+
+            job.cancel()
+        }
+
     @Test
     fun networkType_dataEnabled_groupIsRepresented() =
         testScope.runTest {