Merge #6844

6844: For #6757 - Adds firstContentfulPaint callback to SessionState r=pocmo a=ekager
Co-authored-by: ekager <ekager@mozilla.com>

components/browser/engine-gecko-beta/src/main/java/mozilla/components/browser/engine/gecko/GeckoEngineView.kt

@@ -7,6 +7,7 @@ package mozilla.components.browser.engine.gecko
 import android.content.Context
 import android.graphics.Bitmap
 import android.util.AttributeSet
+import android.view.View
 import android.widget.FrameLayout
 import androidx.annotation.VisibleForTesting
 import androidx.core.view.ViewCompat
@@ -67,6 +68,10 @@ class GeckoEngineView @JvmOverloads constructor(
             rebind()
         }
 
+        override fun onFirstContentfulPaint() {
+            visibility = View.VISIBLE
+        }
+
         override fun onAppPermissionRequest(permissionRequest: PermissionRequest) = Unit
         override fun onContentPermissionRequest(permissionRequest: PermissionRequest) = Unit
     }

components/browser/engine-gecko-nightly/src/main/java/mozilla/components/browser/engine/gecko/GeckoEngineSession.kt

@@ -600,6 +600,7 @@ class GeckoEngineSession(
 
         override fun onFirstContentfulPaint(session: GeckoSession) {
             firstContentfulPaint = true
+            notifyObservers { onFirstContentfulPaint() }
         }
 
         override fun onContextMenu(

components/browser/engine-gecko-nightly/src/main/java/mozilla/components/browser/engine/gecko/GeckoEngineView.kt

@@ -7,6 +7,7 @@ package mozilla.components.browser.engine.gecko
 import android.content.Context
 import android.graphics.Bitmap
 import android.util.AttributeSet
+import android.view.View
 import android.widget.FrameLayout
 import androidx.annotation.VisibleForTesting
 import androidx.core.view.ViewCompat
@@ -67,6 +68,10 @@ class GeckoEngineView @JvmOverloads constructor(
             rebind()
         }
 
+        override fun onFirstContentfulPaint() {
+            visibility = View.VISIBLE
+        }
+
         override fun onAppPermissionRequest(permissionRequest: PermissionRequest) = Unit
         override fun onContentPermissionRequest(permissionRequest: PermissionRequest) = Unit
     }

components/browser/engine-gecko/src/main/java/mozilla/components/browser/engine/gecko/GeckoEngineView.kt

@@ -7,6 +7,7 @@ package mozilla.components.browser.engine.gecko
 import android.content.Context
 import android.graphics.Bitmap
 import android.util.AttributeSet
+import android.view.View
 import android.widget.FrameLayout
 import androidx.annotation.VisibleForTesting
 import androidx.core.view.ViewCompat
@@ -67,6 +68,10 @@ class GeckoEngineView @JvmOverloads constructor(
             rebind()
         }
 
+        override fun onFirstContentfulPaint() {
+            visibility = View.VISIBLE
+        }
+
         override fun onAppPermissionRequest(permissionRequest: PermissionRequest) = Unit
         override fun onContentPermissionRequest(permissionRequest: PermissionRequest) = Unit
     }

components/browser/session/src/main/java/mozilla/components/browser/session/engine/EngineObserver.kt

@@ -46,6 +46,10 @@ internal class EngineObserver(
         session.searchTerms = ""
     }
 
+    override fun onFirstContentfulPaint() {
+        store?.dispatch(ContentAction.UpdateFirstContentfulPaintStateAction(session.id, true))
+    }
+
     override fun onLocationChange(url: String) {
         if (!isUrlSame(session.url, url)) {
             session.title = ""

components/browser/session/src/test/java/mozilla/components/browser/session/engine/EngineObserverTest.kt

@@ -500,6 +500,20 @@ class EngineObserverTest {
         ))
     }
 
+    @Test
+    fun engineObserverHandlesFirstContentfulPaint() {
+        val session = Session("")
+        val store = mock(BrowserStore::class.java)
+        whenever(store.state).thenReturn(mock())
+        val observer = EngineObserver(session, store)
+
+        observer.onFirstContentfulPaint()
+        verify(store).dispatch(ContentAction.UpdateFirstContentfulPaintStateAction(
+            session.id,
+            true
+        ))
+    }
+
     @Test
     fun `onMediaAdded will subscribe to media and add it to store`() {
         val store = BrowserStore()

components/browser/state/src/main/java/mozilla/components/browser/state/action/BrowserAction.kt

@@ -266,6 +266,14 @@ sealed class ContentAction : BrowserAction() {
      */
     data class UpdateBackNavigationStateAction(val sessionId: String, val canGoBack: Boolean) : ContentAction()
 
+    /**
+     * Updates the [ContentState] of the given [sessionId] to indicate whether the first contentful paint has happened.
+     */
+    data class UpdateFirstContentfulPaintStateAction(
+        val sessionId: String,
+        val firstContentfulPaint: Boolean
+    ) : ContentAction()
+
     /**
      * Updates the [ContentState] of the given [sessionId] to indicate whether or not a forward navigation is possible.
      */

components/browser/state/src/main/java/mozilla/components/browser/state/reducer/ContentStateReducer.kt

@@ -117,6 +117,9 @@ internal object ContentStateReducer {
             is ContentAction.RemoveWebAppManifestAction -> updateContentState(state, action.sessionId) {
                 it.copy(webAppManifest = null)
             }
+            is ContentAction.UpdateFirstContentfulPaintStateAction -> updateContentState(state, action.sessionId) {
+                it.copy(firstContentfulPaint = action.firstContentfulPaint)
+            }
         }
     }
 }

components/browser/state/src/main/java/mozilla/components/browser/state/state/ContentState.kt

@@ -39,6 +39,7 @@ import mozilla.components.concept.engine.window.WindowRequest
  * @property canGoBack whether or not there's an history item to navigate back to.
  * @property canGoForward whether or not there's an history item to navigate forward to.
  * @property webAppManifest the Web App Manifest for the currently visited page (or null).
+ * @property firstContentfulPaint whether or not the first contentful paint has happened.
  */
 data class ContentState(
     val url: String,
@@ -60,5 +61,6 @@ data class ContentState(
     val layoutInDisplayCutoutMode: Int = 0,
     val canGoBack: Boolean = false,
     val canGoForward: Boolean = false,
-    val webAppManifest: WebAppManifest? = null
+    val webAppManifest: WebAppManifest? = null,
+    val firstContentfulPaint: Boolean = false
 )

components/concept/engine/src/main/java/mozilla/components/concept/engine/EngineSession.kt

@@ -49,6 +49,10 @@ abstract class EngineSession(
          */
         fun onExcludedOnTrackingProtectionChange(excluded: Boolean) = Unit
 
+        /**
+         * Event to indicate that this session has had it's first engine contentful paint of page content.
+         */
+        fun onFirstContentfulPaint() = Unit
         fun onLongPress(hitResult: HitResult) = Unit
         fun onDesktopModeChange(enabled: Boolean) = Unit
         fun onFind(text: String) = Unit

docs/changelog.md

@@ -12,6 +12,9 @@ permalink: /changelog/
 * [Gecko](https://github.com/mozilla-mobile/android-components/blob/master/buildSrc/src/main/java/Gecko.kt)
 * [Configuration](https://github.com/mozilla-mobile/android-components/blob/master/buildSrc/src/main/java/Config.kt)
 
+* **browser-state**
+  * Adds `firstContentfulPaint` to `ContentState` to know if first contentful paint has happened.
+
 * **service-glean**
   * ⚠️ **This is a breaking change**: Glean's configuration now requires explicitly setting an http client. Users need to pass one at construction.
     A default `lib-fetch-httpurlconnection` implementation is available.