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

content/browser/android/overscroll_controller_android.cc

+// 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 "base/bind.h"
+#include "cc/layers/layer.h"
+#include "cc/output/compositor_frame_metadata.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 "content/public/browser/web_contents.h"
+#include "third_party/WebKit/public/web/WebInputEvent.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;
+
+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(
+    WebContents* web_contents,
+    ui::WindowAndroidCompositor* compositor,
+    float dpi_scale)
+    : WebContentsObserver(web_contents),
+      compositor_(compositor),
+      dpi_scale_(dpi_scale),
+      enabled_(true),
+      glow_effect_(base::Bind(&CreateGlowEdgeEffect,
+                              &compositor->GetSystemUIResourceManager(),
+                              dpi_scale_)),
+      refresh_effect_(&compositor->GetSystemUIResourceManager(), this),
+      triggered_refresh_active_(false) {
+  DCHECK(web_contents);
+}
+
+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(dpi_scale_);
+      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(dpi_scale_);
+      refresh_effect_.OnScrollEnd(scroll_velocity);
+      if (refresh_effect_.IsActive()) {
+        // TODO(jdduke): Figure out a cleaner way of suppressing a fling.
+        // 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())
+    SetNeedsAnimate();
+
+  return handled;
+}
+
+void OverscrollControllerAndroid::OnGestureEventAck(
+    const blink::WebGestureEvent& event,
+    InputEventAckState ack_result) {
+  if (!enabled_)
+    return;
+
+  // The overscroll effect requires an explicit release signal that may not be
+  // sent from the renderer compositor.
+  if (event.type == blink::WebInputEvent::GestureScrollEnd ||
+      event.type == blink::WebInputEvent::GestureFlingStart) {
+    OnOverscrolled(DidOverscrollParams());
+  }
+
+  if (event.type == blink::WebInputEvent::GestureScrollUpdate) {
+    // The effect should only be allowed if both the causal touch events go
+    // unconsumed and the generated scroll events go unconsumed.
+    // TODO(jdduke): Prevent activation if the first touchmove was consumed,
+    // i.e., the first GSU was prevented.
+    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_.IsAwaitingScrollUpdateAck()) {
+    // An active (or potentially active) refresh effect should always pre-empt
+    // the passive glow effect.
+    return;
+  }
+
+  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_))) {
+    SetNeedsAnimate();
+  }
+}
+
+bool OverscrollControllerAndroid::Animate(base::TimeTicks current_time,
+                                          cc::Layer* parent_layer) {
+  DCHECK(parent_layer);
+  if (!enabled_)
+    return false;
+
+  bool needs_animate = refresh_effect_.Animate(current_time, parent_layer);
+  needs_animate |= glow_effect_.Animate(current_time, parent_layer);
+  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;
+  if (!web_contents())
+    return;
+
+  triggered_refresh_active_ = true;
+  web_contents()->ReloadFocusedFrame(false);
+}
+
+bool OverscrollControllerAndroid::IsStillRefreshing() const {
+  return triggered_refresh_active_;
+}
+
+void OverscrollControllerAndroid::SetNeedsAnimate() {
+  compositor_->SetNeedsAnimate();
+}
+
+}  // namespace content