1 files changed, 137 insertions, 0 deletions
diff --git a/mobile/android/geckoview/src/main/java/org/mozilla/gecko/MagnifiableSurfaceView.java b/mobile/android/geckoview/src/main/java/org/mozilla/gecko/MagnifiableSurfaceView.java
new file mode 100644
index 0000000000..2003abcc6f
--- /dev/null
+++ b/mobile/android/geckoview/src/main/java/org/mozilla/gecko/MagnifiableSurfaceView.java
@@ -0,0 +1,137 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+package org.mozilla.gecko;
+
+import android.content.Context;
+import android.graphics.Canvas;
+import android.graphics.Rect;
+import android.view.Surface;
+import android.view.SurfaceHolder;
+import android.view.SurfaceView;
+
+/**
+ * A {@link android.view.SurfaceView} which allows a {@link android.widget.Magnifier} widget to
+ * magnify a custom {@link android.view.Surface} rather than the SurfaceView's default Surface.
+ */
+public class MagnifiableSurfaceView extends SurfaceView {
+  private static final String LOGTAG = "MagnifiableSurfaceView";
+
+  private SurfaceHolderWrapper mHolder;
+
+  public MagnifiableSurfaceView(final Context context) {
+    super(context);
+  }
+
+  @Override
+  public SurfaceHolder getHolder() {
+    if (mHolder != null) {
+      // Only return our custom holder if we are being called from the Magnifier class.
+      // Throwable.getStackTrace() is faster than Thread.getStackTrace(), but still has a cost,
+      // hence why we only check the caller if we have set an override Surface.
+      final StackTraceElement[] stackTrace = new Throwable().getStackTrace();
+      if (stackTrace.length >= 2
+          && stackTrace[1].getClassName().equals("android.widget.Magnifier")) {
+        return mHolder;
+      }
+    }
+    return super.getHolder();
+  }
+
+  /**
+   * Sets the Surface that should be magnified by a Magnifier widget.
+   *
+   * <p>This should be set immediately before calling {@link android.widget.Magnifier#show()} or
+   * {@link android.widget.Magnifier#update()}, and unset immediately afterwards.
+   *
+   * @param surface The Surface to be magnified. If null, the SurfaceView's default Surface will be
+   *     used.
+   */
+  public void setMagnifierSurface(final Surface surface) {
+    if (surface != null) {
+      mHolder = new SurfaceHolderWrapper(getHolder(), surface);
+    } else {
+      mHolder = null;
+    }
+  }
+
+  /**
+   * A {@link android.view.SurfaceHolder} implementation that simply forwards all methods to a
+   * provided SurfaceHolder instance, except for getSurface() which returns a custom Surface.
+   */
+  private class SurfaceHolderWrapper implements SurfaceHolder {
+    private final SurfaceHolder mHolder;
+    private final Surface mSurface;
+
+    public SurfaceHolderWrapper(final SurfaceHolder holder, final Surface surface) {
+      mHolder = holder;
+      mSurface = surface;
+    }
+
+    @Override
+    public void addCallback(final Callback callback) {
+      mHolder.addCallback(callback);
+    }
+
+    @Override
+    public void removeCallback(final Callback callback) {
+      mHolder.removeCallback(callback);
+    }
+
+    @Override
+    public boolean isCreating() {
+      return mHolder.isCreating();
+    }
+
+    @Override
+    public void setType(final int type) {
+      mHolder.setType(type);
+    }
+
+    @Override
+    public void setFixedSize(final int width, final int height) {
+      mHolder.setFixedSize(width, height);
+    }
+
+    @Override
+    public void setSizeFromLayout() {
+      mHolder.setSizeFromLayout();
+    }
+
+    @Override
+    public void setFormat(final int format) {
+      mHolder.setFormat(format);
+    }
+
+    @Override
+    public void setKeepScreenOn(final boolean screenOn) {
+      mHolder.setKeepScreenOn(screenOn);
+    }
+
+    @Override
+    public Canvas lockCanvas() {
+      return mHolder.lockCanvas();
+    }
+
+    @Override
+    public Canvas lockCanvas(final Rect dirty) {
+      return mHolder.lockCanvas(dirty);
+    }
+
+    @Override
+    public void unlockCanvasAndPost(final Canvas canvas) {
+      mHolder.unlockCanvasAndPost(canvas);
+    }
+
+    @Override
+    public Rect getSurfaceFrame() {
+      return mHolder.getSurfaceFrame();
+    }
+
+    @Override
+    public Surface getSurface() {
+      return mSurface;
+    }
+  }
+}