AndroidOverlay implementation using Dialog.

content/public/android/java/src/org/chromium/content/browser/androidoverlay/DialogOverlayCore.java

+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package org.chromium.content.browser.androidoverlay;
+
+import android.annotation.SuppressLint;
+import android.app.Dialog;
+import android.os.IBinder;
+import android.view.Gravity;
+import android.view.Surface;
+import android.view.SurfaceHolder;
+import android.view.WindowManager;
+
+import org.chromium.gfx.mojom.Rect;
+import org.chromium.media.mojom.AndroidOverlayConfig;
+
+/**
+ * Core class for control of a single Dialog-based AndroidOverlay instance.  Everything runs on the
+ * overlay-ui thread, which is not the Browser UI thread.
+ *
+ * Note that this does not implement AndroidOverlay; we assume that, and the associated thread-
+ * hopping, is handled elsewhere (DialogOverlayImpl).
+ */
+class DialogOverlayCore {
+    private static final String TAG = "DSCore";
+
+    // Host interface, since we're on the wrong thread to talk to mojo, or anything else, really.
+    public interface Host {
+        // Notify the host that we have a surface.
+        void onSurfaceReady(Surface surface);
+
+        // Notify the host that we have failed to get a surface or the surface was destroyed.
+        void onOverlayDestroyed();
+
+        // Wait until the host has been told to clean up.  We are allowed to let surfaceDestroyed
+        // proceed once this happens.
+        void waitForCleanup();
+    }
+
+    Host mHost;
+
+    // When initialized via Init, we'll create mDialog.  We'll clear it when we send
+    // onOverlayDestroyed to the host.  In general, when this is null, either we haven't been
+    // initialized yet, or we've been torn down.  It shouldn't be the case that anything calls
+    // methods after construction but before |initialize()|, though.
+    private Dialog mDialog;
+
+    private Callbacks mDialogCallbacks;
+
+    // Most recent layout parameters.
+    private WindowManager.LayoutParams mLayoutParams;
+
+    /**
+     * Construction may be called from a random thread, for simplicity.  Call initialize from the
+     * proper thread before doing anything else.
+     */
+    public DialogOverlayCore() {}
+
+    /**
+     * Finish init on the proper thread.  We'll use this thread for the Dialog Looper thread.
+     * @param dialog the dialog, which uses our current thread as the UI thread.
+     * @param config initial config.
+     * @param host host interface, for sending messages that (probably) need to thread hop.
+     */
+    public void initialize(Dialog dialog, AndroidOverlayConfig config, Host host) {
+        mHost = host;
+        mLayoutParams = createLayoutParams(config.secure);
+        layoutSurface(config.rect);
+
+        // Set this after calling layoutSurface(), so that it doesn't try to use it.  We haven't
+        // shown |dialog| yet!
+        mDialog = dialog;
+    }
+
+    /**
+     * Release the underlying surface, and generally clean up, in response to
+     * the client releasing the AndroidOverlay.
+     */
+    public void release() {
+        // If we've not released the dialog yet, then do so.
+        if (mDialog != null) {
+            if (mDialog.isShowing()) mDialog.dismiss();
+            mDialog = null;
+            mDialogCallbacks = null;
+        }
+
+        mLayoutParams.token = null;
+
+        // We don't bother to notify |mHost| that we've been destroyed; it told us.
+        mHost = null;
+    }
+
+    /**
+     * Layout the AndroidOverlay.  If we don't have a token, then we ignore it, since a well-behaved
+     * client shouldn't call us before getting the surface anyway.
+     */
+    public void layoutSurface(final Rect rect) {
+        if (mDialog == null || mLayoutParams.token == null) return;
+
+        // TODO(liberato): adjust for CompositorView screen location here if we want to support
+        // non-full screen use cases.
+        mLayoutParams.x = rect.x;
+        mLayoutParams.y = rect.y;
+        mLayoutParams.width = rect.width;
+        mLayoutParams.height = rect.height;
+
+        mDialog.getWindow().setAttributes(mLayoutParams);
+    }
+
+    /**
+     * Callbacks for finding out about the Dialog's Surface.
+     * These happen on the looper thread.
+     */
+    private class Callbacks implements SurfaceHolder.Callback2 {
+        @Override
+        public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {}
+
+        @Override
+        public void surfaceCreated(SurfaceHolder holder) {
+            // Make sure that we haven't torn down the dialog yet.
+            if (mDialog == null) return;
+
+            if (mHost != null) mHost.onSurfaceReady(holder.getSurface());
+        }
+
+        @Override
+        public void surfaceDestroyed(SurfaceHolder holder) {
+            if (mDialog == null || mHost == null) return;
+
+            // Notify the host that we've been destroyed, and wait for it to clean up.
+            mHost.onOverlayDestroyed();
+            mHost.waitForCleanup();
+            mHost = null;
+        }
+
+        @Override
+        public void surfaceRedrawNeeded(SurfaceHolder holder) {}
+    }
+
+    public void onWindowToken(IBinder token) {
+        if (mDialog == null || mHost == null) return;
+
+        if (token == null || (mLayoutParams.token != null && token != mLayoutParams.token)) {
+            // We've lost the token, if we had one, or we got a new one.
+            // Notify the client.
+            mHost.onOverlayDestroyed();
+            mHost = null;
+            if (mDialog.isShowing()) mDialog.dismiss();
+            return;
+        }
+
+        if (mLayoutParams.token == token) {
+            // Same token, do nothing.
+            return;
+        }
+
+        // We have a token, so layout the dialog.
+        mLayoutParams.token = token;
+        mDialog.getWindow().setAttributes(mLayoutParams);
+        mDialogCallbacks = new Callbacks();
+        mDialog.getWindow().takeSurface(mDialogCallbacks);
+        mDialog.show();
+
+        // We don't notify the client here.  We'll wait until the Android Surface is created.
+    }
+
+    @SuppressLint("RtlHardcoded")
+    private WindowManager.LayoutParams createLayoutParams(boolean secure) {
+        // Rather than using getAttributes, we just create them from scratch.
+        // The default dialog attributes aren't what we want.
+        WindowManager.LayoutParams layoutParams = new WindowManager.LayoutParams();
+
+        // NOTE: we really do want LEFT here, since we're dealing in compositor
+        // coordinates.  Those are always from the left.
+        layoutParams.gravity = Gravity.TOP | Gravity.LEFT;
+
+        // Use a media surface, which is what SurfaceView uses by default.  For
+        // debugging overlay drawing, consider using TYPE_APPLICATION_PANEL to
+        // move the dialog over the CompositorView.
+        layoutParams.type = WindowManager.LayoutParams.TYPE_APPLICATION_MEDIA;
+
+        layoutParams.flags = WindowManager.LayoutParams.FLAG_NOT_TOUCH_MODAL
+                | WindowManager.LayoutParams.FLAG_NOT_TOUCHABLE
+                | WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE
+                | WindowManager.LayoutParams.FLAG_LAYOUT_NO_LIMITS;
+
+        if (secure) {
+            layoutParams.flags |= WindowManager.LayoutParams.FLAG_SECURE;
+        }
+
+        // Don't set FLAG_SCALED.  in addition to not being sure what it does
+        // (SV uses it), it also causes a crash in WindowManager when we hide
+        // (not dismiss), navigate, and/or exit the app without hide/dismiss.
+        // There's a missing null check in WindowManagerService.java@3170
+        // on M MR2.  To repro, change dimiss() to hide(), bring up a SV, and
+        // navigate away or press home.
+
+        // Turn off the position animation, so that it doesn't animate from one
+        // position to the next.  Ignore errors.
+        // 0x40 is PRIVATE_FLAG_NO_MOVE_ANIMATION.
+        try {
+            int currentFlags =
+                    (Integer) layoutParams.getClass().getField("privateFlags").get(layoutParams);

[boliu, 2017/03/30 22:42:03]

arrr, same comment as last time about reflection..

[liberato (no reviews please), 2017/04/04 17:49:29]

my apologies, i meant to have an offline conversation with you about this but i
forgot.

+            layoutParams.getClass()
+                    .getField("privateFlags")
+                    .set(layoutParams, currentFlags | 0x00000040);
+            // It would be nice to just catch Exception, but findbugs doesn't
+            // allow it.  If we cannot set the flag, then that's okay too.
+        } catch (NoSuchFieldException e) {
+        } catch (NullPointerException e) {
+        } catch (SecurityException e) {
+        } catch (IllegalAccessException e) {
+        } catch (IllegalArgumentException e) {
+        } catch (ExceptionInInitializerError e) {
+        }
+
+        return layoutParams;
+    }
+}