Support "display": "fullscreen" for sites added to the home screen.

chrome/android/java/src/org/chromium/chrome/browser/webapps/WebappActivity.java

Index: chrome/android/java/src/org/chromium/chrome/browser/webapps/WebappActivity.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/webapps/WebappActivity.java b/chrome/android/java/src/org/chromium/chrome/browser/webapps/WebappActivity.java
index 7a35c67a8ce7a90cbdfc875aec890b77f31d55d4..6bf1d00e947f63da1fdb8d1abdf120b398ccf2cf 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/webapps/WebappActivity.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/webapps/WebappActivity.java
@@ -9,12 +9,14 @@ import android.graphics.Bitmap;
 import android.graphics.Color;
 import android.graphics.drawable.Drawable;
 import android.net.Uri;
+import android.os.Build;
 import android.os.Bundle;
 import android.os.StrictMode;
 import android.os.SystemClock;
 import android.text.TextUtils;
 import android.view.LayoutInflater;
 import android.view.View;
+import android.view.View.OnSystemUiVisibilityChangeListener;
 import android.view.ViewGroup;
 import android.widget.FrameLayout;
 import android.widget.ImageView;
@@ -54,6 +56,17 @@ public class WebappActivity extends FullScreenActivity {
     private static final String TAG = "WebappActivity";
     private static final long MS_BEFORE_NAVIGATING_BACK_FROM_INTERSTITIAL = 1000;
 
+    private static final int ENTER_IMMERSIVE_MODE_DELAY_MILLIS = 300;
+    private static final int RESTORE_IMMERSIVE_MODE_DELAY_MILLIS = 3000;
+    private static final int IMMERSIVE_MODE_UI_FLAGS =
+            View.SYSTEM_UI_FLAG_LAYOUT_STABLE
+                | View.SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN

[Ted C, 2017/02/07 18:35:17]

I think this line and the following need to be indented +4 more

[Leo, 2017/02/13 10:00:03]

Acknowledged.

+                | View.SYSTEM_UI_FLAG_LAYOUT_HIDE_NAVIGATION
+                | View.SYSTEM_UI_FLAG_HIDE_NAVIGATION // hide nav bar
+                | View.SYSTEM_UI_FLAG_FULLSCREEN // hide status bar
+                | View.SYSTEM_UI_FLAG_LOW_PROFILE
+                | View.SYSTEM_UI_FLAG_IMMERSIVE;
+
     private final WebappDirectoryManager mDirectoryManager;
 
     protected WebappInfo mWebappInfo;
@@ -68,6 +81,8 @@ public class WebappActivity extends FullScreenActivity {
 
     private Bitmap mLargestFavicon;
 
+    private Runnable mSetImmersiveRunnable;
+
     /**
      * Construct all the variables that shouldn't change.  We do it here both to clarify when the
      * objects are created and to ensure that they exist throughout the parallelized initialization
@@ -92,8 +107,6 @@ public class WebappActivity extends FullScreenActivity {
             mWebappInfo = newWebappInfo;
             resetSavedInstanceState();
             if (mIsInitialized) initializeUI(null);
-            // TODO(dominickn): send the web app into fullscreen if mDisplayMode is
-            // WebDisplayMode.Fullscreen. See crbug.com/581522
         }
     }
 
@@ -118,9 +131,10 @@ public class WebappActivity extends FullScreenActivity {
 
         getActivityTab().addObserver(createTabObserver());
         getActivityTab().getTabWebContentsDelegateAndroid().setDisplayMode(
-                WebDisplayMode.Standalone);
-        // TODO(dominickn): send the web app into fullscreen if mDisplayMode is
-        // WebDisplayMode.Fullscreen. See crbug.com/581522
+                mWebappInfo.displayMode());
+        if (mWebappInfo.displayMode() == WebDisplayMode.Fullscreen) {
+            enterImmersiveMode();
+        }
     }
 
     @Override
@@ -203,6 +217,65 @@ public class WebappActivity extends FullScreenActivity {
     }
 
     @Override
+    public void onWindowFocusChanged(boolean hasFocus) {
+        super.onWindowFocusChanged(hasFocus);
+
+        // Re-enter immersive mode after users switch back to this Activity.
+        if (hasFocus) {
+            asyncSetImmersive(ENTER_IMMERSIVE_MODE_DELAY_MILLIS);
+        }
+    }
+
+    /**
+     * Sets activity's decor view into an immersive mode.
+     * If immersive mode is not supported, this method no-ops.
+     */
+    private void enterImmersiveMode() {
+        // Immersive mode is only supported in API 19+.
+        if (Build.VERSION.SDK_INT < Build.VERSION_CODES.KITKAT) return;

[Ted C, 2017/02/07 18:35:17]

any reason why this is the case?  our other fullscreen stuff supports all
versions of android (albeit using non system visibility to do it)

Also, how does this feature behave with html5 fullscreen?  If you have a webapp
that points to something that uses those features, will FullscreenHtmlApiHandler
start clobbering these bits?

Do we need to do anything to prevent them from stomping on each others toes? 
How about fullscreen video?  Is that a different path?

[Leo, 2017/02/13 10:00:03]

I have another CL to add the support for pre-K versions. The reason I didn't add
them to this CL is to keep this CL simple and safe. AFAIK, old devices may have
very different Navi buttons (soft or physical) and UI flags settings, which
requires much more cases or scenarios to be tested. So hopefully we introduce
that complexity in another single CL.
Thanks for your insight, I didn't realize HTML5 Fullscreen implementation sets
the same bits until you pointed it out. It took my some time to build the proper
demos so I can understand these features' details.
In my testings, some use cases in PWA did cause some UX issues. I wrote them
down in the docs below.
https://docs.google.com/a/chromium.org/document/d/189N6GboVg09Fwm7Gmw3rOyGj4p...

And seems some issue has existed from PWA standalone mode. Looks we need a
code-refact to unify all fullscreen api.

+
+        if (mSetImmersiveRunnable == null) {
+
+            final View decor = getWindow().getDecorView();
+
+            mSetImmersiveRunnable = new Runnable() {
+                @Override
+                public void run() {
+                    int currentFlags = decor.getSystemUiVisibility();
+                    int desiredFlags = currentFlags | IMMERSIVE_MODE_UI_FLAGS;
+                    if (currentFlags != desiredFlags) {
+                        decor.setSystemUiVisibility(desiredFlags);
+                    }
+                }
+            };
+
+            // When we enter immersive mode for the first time, register a
+            // SystemUiVisibilityChangeListener that restores immersive mode. This is necessary
+            // because user actions like focusing a keyboard will break out of immersive mode.
+            decor.setOnSystemUiVisibilityChangeListener(new OnSystemUiVisibilityChangeListener() {
+                @Override
+                public void onSystemUiVisibilityChange(int newFlags) {
+                    if ((newFlags & View.SYSTEM_UI_FLAG_FULLSCREEN) == 0) {
+                        asyncSetImmersive(RESTORE_IMMERSIVE_MODE_DELAY_MILLIS);
+                    }
+                }
+            });
+        }
+
+        asyncSetImmersive(ENTER_IMMERSIVE_MODE_DELAY_MILLIS);
+    }
+
+    /**
+     * This method no-ops before {@link enterImmersiveMode()) is called explicitly.
+     */
+    private void asyncSetImmersive(int delayInMills) {
+        if (mSetImmersiveRunnable == null) return;
+
+        mHandler.removeCallbacks(mSetImmersiveRunnable);
+        mHandler.postDelayed(mSetImmersiveRunnable, delayInMills);
+    }
+
+    @Override
     public void onResume() {
         if (!isFinishing()) {
             if (getIntent() != null) {