Fix #4460: Add Wiki documentation for adding the spotlight experience…

… to any element (#4943)

<!-- READ ME FIRST: Please fill in the explanation section below and
check off every point from the Essential Checklist! -->
## Explanation
<!--
- Explain what your PR does. If this PR fixes an existing bug, please
include
- "Fixes #bugnum:" in the explanation so that GitHub can auto-close the
issue
  - when this PR is merged.
  -->

Fixes #4460 
This PR adds a new page to the Wiki explaining how Spotlights should be
used, how new ones should be added and how should they be tested.


## Essential Checklist
<!-- Please tick the relevant boxes by putting an "x" in them. -->
- [x] The PR title and explanation each start with "Fix #bugnum: " (If
this PR fixes part of an issue, prefix the title with "Fix part of
#bugnum: ...".)
- [x] Any changes to
[scripts/assets](https://github.com/oppia/oppia-android/tree/develop/scripts/assets)
files have their rationale included in the PR explanation.
- [x] The PR follows the [style
guide](https://github.com/oppia/oppia-android/wiki/Coding-style-guide).
- [x] The PR does not contain any unnecessary code changes from Android
Studio
([reference](https://github.com/oppia/oppia-android/wiki/Guidance-on-submitting-a-PR#undo-unnecessary-changes)).
- [x] The PR is made from a branch that's **not** called "develop" and
is up-to-date with "develop".
- [x] The PR is **assigned** to the appropriate reviewers
([reference](https://github.com/oppia/oppia-android/wiki/Guidance-on-submitting-a-PR#clarification-regarding-assignees-and-reviewers-section)).

wiki/Spotlight-Guide.md

@@ -0,0 +1,146 @@
+Feature Spotlights
+# Introduction
+
+Spotlight is a visual tool that highlights and brings a user’s focus to an element on the screen. We use them to communicate the purpose of a specific screen element to the user, which they might otherwise miss. Spotlighting involves dimming the other areas on the screen and lighting the element to bring the user’s focus onto it, and explaining what/how that feature should be used. For example, this is a spotlight on the home screen spotlighting a story:
+
+![image](https://user-images.githubusercontent.com/64526117/233807103-0bb76f92-8821-47cc-a8ac-8222e71214b4.png)
+
+# Creating a new spotlight
+
+The [SpotlightFragment](https://github.com/oppia/oppia-android/blob/d2c37dc547f3e5d12dfe62fa97b9b16fbf0fed6e/app/src/main/java/org/oppia/android/app/spotlight/SpotlightFragment.kt#L44) contains APIs to call spotlights for any in-app screen element. To create a spotlight, call one of these functions:
+- [requestSpotlight](https://github.com/oppia/oppia-android/blob/d2c37dc547f3e5d12dfe62fa97b9b16fbf0fed6e/app/src/main/java/org/oppia/android/app/spotlight/SpotlightManager.kt#L26)
+- [requestSpotlightWithDelayedLayout](https://github.com/oppia/oppia-android/blob/d2c37dc547f3e5d12dfe62fa97b9b16fbf0fed6e/app/src/main/java/org/oppia/android/app/spotlight/SpotlightManager.kt#L13)
+
+Both these functions expect a parameter, [SpotlightTarget](https://github.com/oppia/oppia-android/blob/d2c37dc547f3e5d12dfe62fa97b9b16fbf0fed6e/app/src/main/java/org/oppia/android/app/spotlight/SpotlightTarget.kt#L14). The spotlight target is a holder for the necessary information to show a spotlight. 
+
+The spotlight target binds these fields together:
+- anchor: The view that should be spotlit.
+- hint: The helpful text that should appear along the spotlight to describe the element being spotlit.
+- shape: The preferred shape of the spotlight highlight. Can be either a circle or a rounded rectangle, based on whichever shape best fits the area being highlighted.
+- feature: The specific app feature that the spotlight is tied to. It’s used to track whether this specific spotlight has been seen.
+
+In order to start spotlighting an element in the UI, three high-level things need to be done:
+- The feature’s spotlight needs to be defined.
+- The new spotlight needs to be hooked up for persistent storage.
+- The spotlight needs to be hooked up to be shown in the UI.
+
+## Registering a new feature
+
+In the file [spotlight.proto](https://github.com/oppia/oppia-android/blob/d2c37dc547f3e5d12dfe62fa97b9b16fbf0fed6e/model/src/main/proto/spotlight.proto#L1), two things need to be added.
+
+A new feature (in the [Spotlight](https://github.com/oppia/oppia-android/blob/d2c37dc547f3e5d12dfe62fa97b9b16fbf0fed6e/model/src/main/proto/spotlight.proto#L10) proto):
+```proto
+message Spotlight {
+  // Determines the UI element being spotlit.
+  oneof feature {
+    // Corresponds to the onboarding screen's next button.
+    SpotlightViewState onboarding_next_button = 1;
+
+    // Corresponds to the topic fragment's lessons tab.
+    SpotlightViewState topic_lesson_tab = 2;
+
+    // Corresponds to the topic fragment's revision tab.
+    SpotlightViewState topic_revision_tab = 3;
+
+    // Add and describe your new spotlit feature here.
+    SpotlightViewState your_feature_name = <next_available_index>;
+}
+```
+
+And somewhere to store it (in [SpotlightStateDatabase](https://github.com/oppia/oppia-android/blob/d2c37dc547f3e5d12dfe62fa97b9b16fbf0fed6e/model/src/main/proto/spotlight.proto#L53)):
+```proto
+message SpotlightStateDatabase {
+  // Corresponds to the onboarding screen's next button.
+  SpotlightViewState onboarding_next_button = 1;
+
+  // Corresponds to the topic fragment's lessons tab.
+  SpotlightViewState topic_lesson_tab = 2;
+
+  // Corresponds to the topic fragment's revision tab.
+  SpotlightViewState topic_revision_tab = 3;
+
+  // Similarly, add storage for your new feature here.
+  SpotlightViewState your_feature_name = <next_available_index>;
+}
+```
+
+The new spotlight feature also needs to be added to the [SpotlightStateController](https://github.com/oppia/oppia-android/blob/d2c37dc547f3e5d12dfe62fa97b9b16fbf0fed6e/domain/src/main/java/org/oppia/android/domain/spotlight/SpotlightStateController.kt#L3). In the [retrieveSpotlightViewState](https://github.com/oppia/oppia-android/blob/d2c37dc547f3e5d12dfe62fa97b9b16fbf0fed6e/domain/src/main/java/org/oppia/android/domain/spotlight/SpotlightStateController.kt#L80) and the [recordSpotlightStateAsync](https://github.com/oppia/oppia-android/blob/d2c37dc547f3e5d12dfe62fa97b9b16fbf0fed6e/domain/src/main/java/org/oppia/android/domain/spotlight/SpotlightStateController.kt#L110) methods, add the feature to the switch case as so:
+```kotlin
+fun retrieveSpotlightViewState(
+    profileId: ProfileId,
+    feature: Spotlight.FeatureCase,
+  ): DataProvider<SpotlightViewState> {
+    return retrieveCacheStore(profileId)
+      .transformAsync(
+        RETRIEVE_SPOTLIGHT_CHECKPOINT_DATA_PROVIDER_ID
+      ) {
+        val viewState = when (feature) {
+          ONBOARDING_NEXT_BUTTON -> it.onboardingNextButton
+          TOPIC_LESSON_TAB -> it.topicLessonTab
+          TOPIC_REVISION_TAB -> it.topicRevisionTab
+          YOUR_FEATURE_NAME -> it.yourFeatureName
+```
+
+Similarly for the [recordSpotlightStateAsync](https://github.com/oppia/oppia-android/blob/d2c37dc547f3e5d12dfe62fa97b9b16fbf0fed6e/domain/src/main/java/org/oppia/android/domain/spotlight/SpotlightStateController.kt#L110) method.
+
+## Hooking up the spotlight
+In order to request a spotlight in the UI, use [SpotlightManager](https://github.com/oppia/oppia-android/blob/d2c37dc547f3e5d12dfe62fa97b9b16fbf0fed6e/app/src/main/java/org/oppia/android/app/spotlight/SpotlightManager.kt#L4):
+
+```kotlin
+checkNotNull(getSpotlightManager()).requestSpotlight(
+  SpotlightTarget(
+    binding.yourFeatureName,
+    R.string.your_feature_string_string_resource,
+    SpotlightShape.RoundedRectangle,
+    Spotlight.FeatureCase.YOUR_FEATURE_NAME
+  )
+)
+
+private fun getSpotlightManager(): SpotlightManager? {
+  return fragment.requireActivity().supportFragmentManager.findFragmentByTag(
+    SpotlightManager.SPOTLIGHT_FRAGMENT_TAG
+  ) as? SpotlightManager
+}
+```
+
+For views that are laid out late in the lifecycle (such as recycler views loaded after a data provider call, view pagers, or elements that show up after an enter animation), use [requestSpotlightWithDelayedLayout](https://github.com/oppia/oppia-android/blob/d2c37dc547f3e5d12dfe62fa97b9b16fbf0fed6e/app/src/main/java/org/oppia/android/app/spotlight/SpotlightManager.kt#L13) instead.
+
+# Testing spotlights
+Spotlights are tested by checking if the expected hint is shown on the screen or not.
+
+```kotlin
+  @Test
+  fun testPromotedStorySpotlight_setToShowOnSecondLogin_notSeenBefore_checkSpotlightShown() {
+    logIntoUserTwice()
+    launch<HomeActivity>(createHomeActivityIntent(internalProfileId1)).use {
+      testCoroutineDispatchers.runCurrent()
+      onView(withText(R.string.promoted_story_spotlight_hint))
+        .check(matches(isDisplayed()))
+      // Or, use check(doesNotExist()) to verify it is not being shown.
+    }
+  }
+```
+
+In order to bypass a spotlight without any UI interaction, the ``SpotlightStateController`` should be used to mark the spotlights as seen. A helper function can be introduced and used to mark one or more spotlights as seen. 
+
+```kotlin
+  private fun markAllSpotlightsSeen() {
+    val profileId = ProfileId.newBuilder().setInternalId(internalProfileId).build()
+    spotlightStateController.markSpotlightViewed(profileId, TOPIC_LESSON_TAB)  
+    spotlightStateController.markSpotlightViewed(profileId, TOPIC_REVISION_TAB) 
+    spotlightStateController.markSpotlightViewed(profileId, YOUR_FEATURE_NAME)
+    testCoroutineDispatchers.runCurrent()
+  }
+```
+
+## Disabling the spotlights
+If the spotlights need to be disabled, the platform parameter value should be set:
+
+### In tests
+If the spotlights need to be disabled in the tests, use the ``TestPlatformParameterModule`` to turn off the [enableSpotlightUi](https://github.com/oppia/oppia-android/blob/d2c37dc547f3e5d12dfe62fa97b9b16fbf0fed6e/utility/src/main/java/org/oppia/android/util/platformparameter/PlatformParameterConstants.kt#L218) platform parameter.
+
+```kotlin
+TestPlatformParameterModule.forceEnableSpotlightUi(false)
+```
+###  In production
+In order to do it in production, turn the value of ``ENABLE_SPOTLIGHT_UI_DEFAULT_VALUE`` to ``false``.

wiki/_Sidebar.md

@@ -48,6 +48,7 @@
   * [Work Manager](https://github.com/oppia/oppia-android/wiki/Work-Manager)
   * [Dependency Injection](https://github.com/oppia/oppia-android/wiki/Dependency-Injection) with [Dagger](https://github.com/oppia/oppia-android/wiki/Dagger)
   * [Revert & regression policy](https://github.com/oppia/oppia-android/wiki/Revert-&-regression-policy)
+  * [Spotlight Guide](https://github.com/oppia/oppia-android/wiki/Spotlight-Guide)
   * Bazel
     * [Gradle Bazel Migration Best Practices and FAQ](https://github.com/oppia/oppia-android/wiki/Gradle--Bazel-Migration-Best-Practices-and-FAQ)    
     * [Updating Maven Dependencies](https://github.com/oppia/oppia-android/wiki/Updating-Maven-Dependencies)