Bug 1578947 - Add onFirstContentfulPaint() to GeckoView#ContentDelegate r=geckoview-reviewers,smaug,agi,snorp

Differential Revision: https://phabricator.services.mozilla.com/D46230

--HG--
extra : moz-landing-system : lando

layout/base/nsPresContext.cpp

@@ -10,6 +10,9 @@
 #include "nsPresContextInlines.h"
 
 #include "mozilla/ArrayUtils.h"
+#if defined(MOZ_WIDGET_ANDROID)
+#  include "mozilla/AsyncEventDispatcher.h"
+#endif
 #include "mozilla/DebugOnly.h"
 #include "mozilla/Encoding.h"
 #include "mozilla/EventDispatcher.h"
@@ -2361,6 +2364,11 @@ void nsPresContext::NotifyContentfulPaint() {
       if (nsRootPresContext* rootPresContext = GetRootPresContext()) {
         mFirstContentfulPaintTransactionId =
             Some(rootPresContext->mRefreshDriver->LastTransactionId().Next());
+#if defined(MOZ_WIDGET_ANDROID)
+        (new AsyncEventDispatcher(mDocument,
+            NS_LITERAL_STRING("MozFirstContentfulPaint"), CanBubble::eYes,
+            ChromeOnlyDispatch::eYes))->PostDOMEvent();
+#endif
       }
     }
   }

mobile/android/chrome/geckoview/GeckoViewContentChild.js

@@ -91,6 +91,7 @@ class GeckoViewContentChild extends GeckoViewChildModule {
     addEventListener("MozDOMFullscreen:Request", this, false);
     addEventListener("contextmenu", this, { capture: true });
     addEventListener("DOMContentLoaded", this, false);
+    addEventListener("MozFirstContentfulPaint", this, false);
   }
 
   onDisable() {
@@ -104,6 +105,7 @@ class GeckoViewContentChild extends GeckoViewChildModule {
     removeEventListener("MozDOMFullscreen:Request", this);
     removeEventListener("contextmenu", this, { capture: true });
     removeEventListener("DOMContentLoaded", this);
+    removeEventListener("MozFirstContentfulPaint", this);
   }
 
   collectSessionState() {
@@ -480,7 +482,13 @@ class GeckoViewContentChild extends GeckoViewChildModule {
             });
           }
         });
+        break;
       }
+      case "MozFirstContentfulPaint":
+        this.eventDispatcher.sendRequest({
+          type: "GeckoView:FirstContentfulPaint",
+        });
+        break;
     }
   }
 

mobile/android/geckoview/api.txt

@@ -578,6 +578,7 @@ package org.mozilla.geckoview {
     method @UiThread default public void onCrash(@NonNull GeckoSession);
     method @UiThread default public void onExternalResponse(@NonNull GeckoSession, @NonNull GeckoSession.WebResponseInfo);
     method @UiThread default public void onFirstComposite(@NonNull GeckoSession);
+    method @UiThread default public void onFirstContentfulPaint(@NonNull GeckoSession);
     method @UiThread default public void onFocusRequest(@NonNull GeckoSession);
     method @UiThread default public void onFullScreen(@NonNull GeckoSession, boolean);
     method @UiThread default public void onKill(@NonNull GeckoSession);

mobile/android/geckoview/src/androidTest/java/org/mozilla/geckoview/test/ContentDelegateTest.kt

@@ -847,6 +847,16 @@ class ContentDelegateTest : BaseSessionTest() {
         mainSession.releaseDisplay(display)
     }
 
+    @WithDisplay(width = 10, height = 10)
+    @Test fun firstContentfulPaint() {
+        mainSession.loadTestPath(HELLO_HTML_PATH)
+        sessionRule.waitUntilCalled(object : Callbacks.ContentDelegate {
+            @AssertCalled(count = 1)
+            override fun onFirstContentfulPaint(session: GeckoSession) {
+            }
+        })
+    }
+
     @Test fun webAppManifest() {
         mainSession.loadTestPath(HELLO_HTML_PATH)
         mainSession.waitUntilCalled(object : Callbacks.All {

mobile/android/geckoview/src/main/java/org/mozilla/geckoview/GeckoSession.java

@@ -453,6 +453,7 @@ public class GeckoSession implements Parcelable {
                 "GeckoView:FullScreenEnter",
                 "GeckoView:FullScreenExit",
                 "GeckoView:WebAppManifest",
+                "GeckoView:FirstContentfulPaint",
             }
         ) {
             @Override
@@ -505,6 +506,8 @@ public class GeckoSession implements Parcelable {
                     } catch (JSONException e) {
                         Log.e(LOGTAG, "Failed to convert web app manifest to JSON", e);
                     }
+                } else if ("GeckoView:FirstContentfulPaint".equals(event)) {
+                    delegate.onFirstContentfulPaint(GeckoSession.this);
                 }
             }
         };
@@ -3109,6 +3112,20 @@ public class GeckoSession implements Parcelable {
         @UiThread
         default void onFirstComposite(@NonNull GeckoSession session) {}
 
+        /**
+         * Notification that the first content paint has occurred.
+         * This callback is invoked for the first content paint after
+         * a page has been loaded. The function {@link #onFirstComposite(GeckoSession)}
+         * will be called once the compositor has started rendering. However, it is
+         * possible for the compositor to start rendering before there is any content to render.
+         * onFirstContentfulPaint() is called once some content has been rendered. It may be nothing
+         * more than the page background color. It is not an indication that the whole page has
+         * been rendered.
+         * @param session The GeckoSession that had a first paint event.
+         */
+        @UiThread
+        default void onFirstContentfulPaint(@NonNull GeckoSession session) {}
+
         /**
          * This is fired when the loaded document has a valid Web App Manifest present.
          *

mobile/android/geckoview/src/main/java/org/mozilla/geckoview/doc-files/CHANGELOG.md

@@ -31,7 +31,7 @@ exclude: true
   ([bug 1511033]({{bugzilla}}1511033))
 - Added ['GeckoRuntimeSettings.Builder#aboutConfigEnabled'][71.11] to control whether or
   not `about:config` should be available.
-
+- Added [`GeckoSession.ContentDelegate.onFirstContentfulPaint()`][71.12]
 [71.1]: {{javadoc_uri}}/RuntimeTelemetry.Delegate.html#onBooleanScalar-org.mozilla.geckoview.RuntimeTelemetry.Metric-
 [71.2]: {{javadoc_uri}}/RuntimeTelemetry.Delegate.html#onLongScalar-org.mozilla.geckoview.RuntimeTelemetry.Metric-
 [71.3]: {{javadoc_uri}}/RuntimeTelemetry.Delegate.html#onStringScalar-org.mozilla.geckoview.RuntimeTelemetry.Metric-
@@ -43,6 +43,7 @@ exclude: true
 [71.9]: {{javadoc_uri}}/GeckoRuntime.ServiceWorkerDelegate.html
 [71.10]: {{javadoc_uri}}/GeckoRuntime#setServiceWorkerDelegate-org.mozilla.geckoview.GeckoRuntime.ServiceWorkerDelegate-
 [71.11]: {{javadoc_uri}}/GeckoRuntimeSettings.Builder.html#aboutConfigEnabled-boolean-
+[71.12]: {{javadoc_uri}}/GeckoSession.ContentDelegate.html#onFirstContentfulPaint-org.mozilla.geckoview.GeckoSession-
 
 ## v70
 - Added API for session context assignment
@@ -365,4 +366,4 @@ exclude: true
 [65.24]: {{javadoc_uri}}/CrashReporter.html#sendCrashReport-android.content.Context-android.os.Bundle-java.lang.String-
 [65.25]: {{javadoc_uri}}/GeckoResult.html
 
-[api-version]: 16e050b1d50a9909b936c740a94220eaff4115a3
+[api-version]: 40441c6fcd77218d1d32b468894558141d8ccad9