1 files changed, 246 insertions, 0 deletions
diff --git a/mobile/android/geckoview/src/main/java/org/mozilla/geckoview/OverscrollEdgeEffect.java b/mobile/android/geckoview/src/main/java/org/mozilla/geckoview/OverscrollEdgeEffect.java
new file mode 100644
index 0000000000..efd8061c98
--- /dev/null
+++ b/mobile/android/geckoview/src/main/java/org/mozilla/geckoview/OverscrollEdgeEffect.java
@@ -0,0 +1,246 @@
+/* -*- Mode: Java; c-basic-offset: 4; tab-width: 20; indent-tabs-mode: nil; -*-
+ * 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.geckoview;
+
+import android.annotation.SuppressLint;
+import android.content.Context;
+import android.graphics.BlendMode;
+import android.graphics.Canvas;
+import android.graphics.Paint;
+import android.graphics.PorterDuff;
+import android.graphics.PorterDuffXfermode;
+import android.graphics.Rect;
+import android.os.Build;
+import android.widget.EdgeEffect;
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
+import androidx.annotation.UiThread;
+import java.lang.reflect.Field;
+import org.mozilla.gecko.util.ThreadUtils;
+
+@UiThread
+public final class OverscrollEdgeEffect {
+  // Used to index particular edges in the edges array
+  private static final int TOP = 0;
+  private static final int BOTTOM = 1;
+  private static final int LEFT = 2;
+  private static final int RIGHT = 3;
+
+  /* package */ static final int AXIS_X = 0;
+  /* package */ static final int AXIS_Y = 1;
+
+  // All four edges of the screen
+  private final EdgeEffect[] mEdges = new EdgeEffect[4];
+
+  private GeckoSession mSession;
+  private Runnable mInvalidationCallback;
+  private int mWidth;
+  private int mHeight;
+
+  /* package */ OverscrollEdgeEffect() {}
+
+  private static Field sPaintField;
+
+  @SuppressLint("DiscouragedPrivateApi")
+  private void setBlendMode(final EdgeEffect edgeEffect) {
+    if (Build.VERSION.SDK_INT < 29) {
+      // setBlendMode is only supported on SDK_INT >= 29 and above.
+
+      if (sPaintField == null) {
+        try {
+          sPaintField = EdgeEffect.class.getDeclaredField("mPaint");
+          sPaintField.setAccessible(true);
+        } catch (final NoSuchFieldException e) {
+          // Cannot get the field, nothing we can do here
+          return;
+        }
+      }
+
+      try {
+        final Paint paint = (Paint) sPaintField.get(edgeEffect);
+        final PorterDuffXfermode mode = new PorterDuffXfermode(PorterDuff.Mode.SRC);
+        paint.setXfermode(mode);
+      } catch (final IllegalAccessException ex) {
+        // Nothing we can do
+      }
+
+      return;
+    }
+
+    edgeEffect.setBlendMode(BlendMode.SRC);
+  }
+
+  /**
+   * Set the theme to use for overscroll from a given Context.
+   *
+   * @param context Context to use for the overscroll theme.
+   */
+  public void setTheme(final @NonNull Context context) {
+    ThreadUtils.assertOnUiThread();
+
+    for (int i = 0; i < mEdges.length; i++) {
+      final EdgeEffect edgeEffect = new EdgeEffect(context);
+      if (mWidth != 0 || mHeight != 0) {
+        edgeEffect.setSize(mWidth, mHeight);
+      }
+      setBlendMode(edgeEffect);
+      mEdges[i] = edgeEffect;
+    }
+  }
+
+  /* package */ void setSession(final @Nullable GeckoSession session) {
+    mSession = session;
+  }
+
+  /**
+   * Set a Runnable that acts as a callback to invalidate the overscroll effect (for example, as a
+   * response to user fling for example). The Runnbale should schedule a future call to {@link
+   * #draw(Canvas)} as a result of the invalidation.
+   *
+   * @param runnable Invalidation Runnable.
+   * @see #getInvalidationCallback()
+   */
+  public void setInvalidationCallback(final @Nullable Runnable runnable) {
+    ThreadUtils.assertOnUiThread();
+    mInvalidationCallback = runnable;
+  }
+
+  /**
+   * Get the current invalidatation Runnable.
+   *
+   * @return Invalidation Runnable.
+   * @see #setInvalidationCallback(Runnable)
+   */
+  public @Nullable Runnable getInvalidationCallback() {
+    ThreadUtils.assertOnUiThread();
+    return mInvalidationCallback;
+  }
+
+  /* package */ void setSize(final int width, final int height) {
+    mEdges[LEFT].setSize(height, width);
+    mEdges[RIGHT].setSize(height, width);
+    mEdges[TOP].setSize(width, height);
+    mEdges[BOTTOM].setSize(width, height);
+
+    mWidth = width;
+    mHeight = height;
+  }
+
+  private EdgeEffect getEdgeForAxisAndSide(final int axis, final float side) {
+    if (axis == AXIS_Y) {
+      if (side < 0) {
+        return mEdges[TOP];
+      } else {
+        return mEdges[BOTTOM];
+      }
+    } else {
+      if (side < 0) {
+        return mEdges[LEFT];
+      } else {
+        return mEdges[RIGHT];
+      }
+    }
+  }
+
+  /* package */ void setVelocity(final float velocity, final int axis) {
+    if (velocity == 0.0f) {
+      if (axis == AXIS_Y) {
+        mEdges[TOP].onRelease();
+        mEdges[BOTTOM].onRelease();
+      } else {
+        mEdges[LEFT].onRelease();
+        mEdges[RIGHT].onRelease();
+      }
+
+      if (mInvalidationCallback != null) {
+        mInvalidationCallback.run();
+      }
+      return;
+    }
+
+    final EdgeEffect edge = getEdgeForAxisAndSide(axis, velocity);
+
+    // If we're showing overscroll already, start fading it out.
+    if (!edge.isFinished()) {
+      edge.onRelease();
+    } else {
+      // Otherwise, show an absorb effect
+      edge.onAbsorb((int) velocity);
+    }
+
+    if (mInvalidationCallback != null) {
+      mInvalidationCallback.run();
+    }
+  }
+
+  /* package */ void setDistance(final float distance, final int axis) {
+    // The first overscroll event often has zero distance. Throw it out
+    if (distance == 0.0f) {
+      return;
+    }
+
+    final EdgeEffect edge = getEdgeForAxisAndSide(axis, (int) distance);
+    edge.onPull(distance / (axis == AXIS_X ? mWidth : mHeight));
+
+    if (mInvalidationCallback != null) {
+      mInvalidationCallback.run();
+    }
+  }
+
+  /**
+   * Draw the overscroll effect on a Canvas.
+   *
+   * @param canvas Canvas to draw on.
+   */
+  public void draw(final @NonNull Canvas canvas) {
+    ThreadUtils.assertOnUiThread();
+
+    if (mSession == null) {
+      return;
+    }
+
+    final Rect pageRect = new Rect();
+    mSession.getSurfaceBounds(pageRect);
+
+    // If we're pulling an edge, or fading it out, draw!
+    boolean invalidate = false;
+    if (!mEdges[TOP].isFinished()) {
+      invalidate |= draw(mEdges[TOP], canvas, pageRect.left, pageRect.top, 0);
+    }
+
+    if (!mEdges[BOTTOM].isFinished()) {
+      invalidate |= draw(mEdges[BOTTOM], canvas, pageRect.right, pageRect.bottom, 180);
+    }
+
+    if (!mEdges[LEFT].isFinished()) {
+      invalidate |= draw(mEdges[LEFT], canvas, pageRect.left, pageRect.bottom, 270);
+    }
+
+    if (!mEdges[RIGHT].isFinished()) {
+      invalidate |= draw(mEdges[RIGHT], canvas, pageRect.right, pageRect.top, 90);
+    }
+
+    // If the edge effect is animating off screen, invalidate.
+    if (invalidate && mInvalidationCallback != null) {
+      mInvalidationCallback.run();
+    }
+  }
+
+  private static boolean draw(
+      final EdgeEffect edge,
+      final Canvas canvas,
+      final float translateX,
+      final float translateY,
+      final float rotation) {
+    final int state = canvas.save();
+    canvas.translate(translateX, translateY);
+    canvas.rotate(rotation);
+    final boolean invalidate = edge.draw(canvas);
+    canvas.restoreToCount(state);
+
+    return invalidate;
+  }
+}