[Android] Add a native pull-to-refresh overscroll effect

content/browser/android/overscroll_controller_android.cc

Index: content/browser/android/overscroll_controller_android.cc
diff --git a/content/browser/android/overscroll_controller_android.cc b/content/browser/android/overscroll_controller_android.cc
new file mode 100644
index 0000000000000000000000000000000000000000..cb18e66a64ca2a8fd7c2cfa4398ba729ba73469b
--- /dev/null
+++ b/content/browser/android/overscroll_controller_android.cc
@@ -0,0 +1,221 @@
+// Copyright 2014 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.
+
+#include "content/browser/android/overscroll_controller_android.h"
+
+#include "base/android/build_info.h"
+#include "cc/layers/layer.h"
+#include "cc/output/compositor_frame_metadata.h"
+#include "content/browser/android/content_view_core_impl.h"
+#include "content/browser/android/edge_effect.h"
+#include "content/browser/android/edge_effect_l.h"
+#include "content/common/input/did_overscroll_params.h"
+#include "ui/base/android/window_android.h"
+#include "ui/base/android/window_android_compositor.h"
+
+namespace content {
+namespace {
+
+// Used for conditional creation of EdgeEffect types for the overscroll glow.
+const int kAndroidLSDKVersion = 21;
+
+ui::SystemUIResourceManager* GetSystemUIResourceManager(
+    ContentViewCore* content_view_core) {
+  ui::WindowAndroid* window = content_view_core->GetWindowAndroid();
+  DCHECK(window);
+  ui::WindowAndroidCompositor* compositor = window->GetCompositor();
+  DCHECK(compositor);
+  return &compositor->GetSystemUIResourceManager();
+}
+
+scoped_ptr<EdgeEffectBase> CreateGlowEdgeEffect(
+    ui::SystemUIResourceManager* resource_manager,
+    float dpi_scale) {
+  DCHECK(resource_manager);
+  static bool use_l_flavoured_effect =
+      base::android::BuildInfo::GetInstance()->sdk_int() >= kAndroidLSDKVersion;
+  if (use_l_flavoured_effect)
+    return scoped_ptr<EdgeEffectBase>(new EdgeEffectL(resource_manager));
+
+  return scoped_ptr<EdgeEffectBase>(
+      new EdgeEffect(resource_manager, dpi_scale));
+}
+
+}  // namespace
+
+OverscrollControllerAndroid::OverscrollControllerAndroid(
+    ContentViewCoreImpl* content_view_core)
+    : WebContentsObserver(content_view_core->GetWebContents()),
+      content_view_core_(content_view_core),
+      enabled_(true),
+      glow_effect_(base::Bind(&CreateGlowEdgeEffect,
+                              GetSystemUIResourceManager(content_view_core),
+                              content_view_core->GetDpiScale())),
+      refresh_effect_(GetSystemUIResourceManager(content_view_core), this),
+      triggered_refresh_active_(false) {
+}
+
+OverscrollControllerAndroid::~OverscrollControllerAndroid() {
+}
+
+bool OverscrollControllerAndroid::WillHandleGestureEvent(
+    const blink::WebGestureEvent& event) {
+  if (!enabled_)
+    return false;
+
+  bool handled = false;
+  bool maybe_needs_animate = false;
+  switch (event.type) {
+    case blink::WebInputEvent::GestureScrollBegin:
+      refresh_effect_.OnScrollBegin();
+      break;
+
+    case blink::WebInputEvent::GestureScrollUpdate: {
+      gfx::Vector2dF scroll_delta(event.data.scrollUpdate.deltaX,
+                                  event.data.scrollUpdate.deltaY);
+      scroll_delta.Scale(GetDpiScale());
+      maybe_needs_animate = true;
+      handled = refresh_effect_.WillHandleScrollUpdate(scroll_delta);
+    } break;
+
+    case blink::WebInputEvent::GestureScrollEnd:
+      refresh_effect_.OnScrollEnd(gfx::Vector2dF());
+      maybe_needs_animate = true;
+      break;
+
+    case blink::WebInputEvent::GestureFlingStart: {
+      gfx::Vector2dF scroll_velocity(event.data.flingStart.velocityX,
+                                     event.data.flingStart.velocityY);
+      scroll_velocity.Scale(GetDpiScale());
+      refresh_effect_.OnScrollEnd(scroll_velocity);
+      if (refresh_effect_.IsActive()) {
+        // TODO(jdduke): Figure out a cleaner way of suppressing a fling.

[aelias_OOO_until_Jul13, 2014/10/30 03:53:21]

What would happen if we just let flings always go through to the renderer?

[jdduke (slow), 2014/10/30 15:19:02]

That's the behavior I had originally, and it's certainly not a problem for
"upward" flings, as they immediately terminate.  However, Ted pointed out that
allowing a "downward" fling felt weird, and I agree with him. Perhaps it's
because we consume the downward touch scroll, so the fling motion at the end
feels discontinuous?

I almost rewired the whole |FilterInputEvent| chain to take an event pointer and
allow mutation, but that's just asking for trouble and I'd really prefer not to
open that up =/

+        // It's important that the any downstream code sees a scroll-ending
+        // event (in this case GestureFlingStart) if it has seen a scroll begin.
+        // Thus, we cannot simply consume the fling. Changing the event type to
+        // a GestureScrollEnd might work in practice, but could lead to
+        // unexpected results. For now, simply truncate the fling velocity, but
+        // not to zero as downstream code may not expect a zero-velocity fling.
+        blink::WebGestureEvent& modified_event =
+            const_cast<blink::WebGestureEvent&>(event);
+        modified_event.data.flingStart.velocityX = .01f;
+        modified_event.data.flingStart.velocityY = .01f;
+      }
+      maybe_needs_animate = true;
+    } break;
+
+    default:
+      break;
+  }
+
+  if (maybe_needs_animate && refresh_effect_.IsActive())
+    content_view_core_->SetNeedsAnimate();

[Ted C, 2014/10/31 23:52:05]

I wonder if we should just make GetRenderWidgetHostViewAndroid public in
ContentViewCore to avoid having to add this method there.

[jdduke (slow), 2014/11/06 00:10:37]

Your call, don't have a strong opinion here. It's nice not to depend on RWHVA
here, but maybe not as nice as not having to add the animate bridge... =/

[Ted C, 2014/11/06 19:25:40]

I have a slight preference for exposing RWHVA.  Maybe we can stem the tide that
is the growth of the beast that is CVC.

[jdduke (slow), 2014/11/07 18:33:44]

I did us all a favor and removed all of the ContentViewCore/RWHVA dependencies.
Instead we take a WebContents, a WindowAndroidCompositor and a DPI scale.

+
+  return handled;
+}
+
+void OverscrollControllerAndroid::OnGestureEventAck(
+    const blink::WebGestureEvent& event,
+    InputEventAckState ack_result) {
+  if (!enabled_)
+    return;
+
+  if (event.type == blink::WebInputEvent::GestureScrollUpdate) {
+    bool consumed = ack_result == INPUT_EVENT_ACK_STATE_CONSUMED;
+    refresh_effect_.OnScrollUpdateAck(consumed);
+  }
+}
+
+void OverscrollControllerAndroid::OnOverscrolled(
+    const DidOverscrollParams& params) {
+  if (!enabled_)
+    return;
+
+  if (refresh_effect_.IsActive() ||
+      refresh_effect_.IsPendingScrollUpdateAck()) {
+    // An active (or potentially active) refresh effect should always pre-empt
+    // the passive glow effect.
+    return;
+  }
+
+  const float dpi_scale = GetDpiScale();
+  if (glow_effect_.OnOverscrolled(
+          base::TimeTicks::Now(),
+          gfx::ScaleVector2d(params.accumulated_overscroll, dpi_scale),
+          gfx::ScaleVector2d(params.latest_overscroll_delta, dpi_scale),
+          gfx::ScaleVector2d(params.current_fling_velocity, dpi_scale),
+          gfx::ScaleVector2d(
+              params.causal_event_viewport_point.OffsetFromOrigin(),
+              dpi_scale))) {
+    content_view_core_->SetNeedsAnimate();
+  }
+}
+
+bool OverscrollControllerAndroid::Animate(base::TimeTicks current_time) {
+  if (!enabled_)
+    return false;
+
+  scoped_refptr<cc::Layer> parent = content_view_core_->GetLayer();
+  bool needs_animate = refresh_effect_.Animate(current_time, parent.get());
+  needs_animate |= glow_effect_.Animate(current_time, parent.get());
+  return needs_animate;
+}
+
+void OverscrollControllerAndroid::OnFrameMetadataUpdated(
+    const cc::CompositorFrameMetadata& frame_metadata) {
+  const float scale_factor =
+      frame_metadata.page_scale_factor * frame_metadata.device_scale_factor;
+  gfx::SizeF viewport_size =
+      gfx::ScaleSize(frame_metadata.scrollable_viewport_size, scale_factor);
+  gfx::SizeF content_size =
+      gfx::ScaleSize(frame_metadata.root_layer_size, scale_factor);
+  gfx::Vector2dF content_scroll_offset =
+      gfx::ScaleVector2d(frame_metadata.root_scroll_offset, scale_factor);
+
+  refresh_effect_.UpdateDisplay(viewport_size, content_scroll_offset);
+  glow_effect_.UpdateDisplay(
+      viewport_size, content_size, content_scroll_offset);
+}
+
+void OverscrollControllerAndroid::Enable() {
+  enabled_ = true;
+}
+
+void OverscrollControllerAndroid::Disable() {
+  if (!enabled_)
+    return;
+  enabled_ = false;
+  if (!enabled_) {
+    refresh_effect_.Reset();
+    glow_effect_.Reset();
+  }
+}
+
+void OverscrollControllerAndroid::DidNavigateMainFrame(
+    const LoadCommittedDetails& details,
+    const FrameNavigateParams& params) {
+  // Once the main frame has navigated, there's little need to further animate
+  // the reload effect. Note that the effect will naturally time out should the
+  // reload be interruped for any reason.
+  triggered_refresh_active_ = false;
+}
+
+void OverscrollControllerAndroid::TriggerRefresh() {
+  triggered_refresh_active_ = false;
+  WebContents* web_contents = content_view_core_->GetWebContents();
+  if (web_contents) {
+    triggered_refresh_active_ = true;
+    web_contents->ReloadFocusedFrame(false);
+  }
+}
+
+bool OverscrollControllerAndroid::IsTriggeredRefreshActive() const {
+  return triggered_refresh_active_;
+}
+
+float OverscrollControllerAndroid::GetDpiScale() const {
+  return content_view_core_->GetDpiScale();
+}
+
+}  // namespace content