[CRD iOS] Injecting scroll events w/ fling animation

remoting/client/ui/gesture_interpreter.cc

Index: remoting/client/ui/gesture_interpreter.cc
diff --git a/remoting/client/ui/gesture_interpreter.cc b/remoting/client/ui/gesture_interpreter.cc
index fda5560790bc13bef34a69478b6f4b26089b21c4..7cc6b3476bc010bdc3a4219284b2035836ee5e87 100644
--- a/remoting/client/ui/gesture_interpreter.cc
+++ b/remoting/client/ui/gesture_interpreter.cc
@@ -13,6 +13,7 @@
 namespace {
 
 const float kOneFingerFlingTimeConstant = 325.f;
+const float kScrollFlingTimeConstant = 120.f;
 
 }  // namespace
 
@@ -23,7 +24,11 @@ GestureInterpreter::GestureInterpreter(RendererProxy* renderer,
       input_stub_(input_stub),
       pan_animation_(kOneFingerFlingTimeConstant,
                      base::Bind(&GestureInterpreter::PanWithoutAbortAnimations,
-                                base::Unretained(this))) {
+                                base::Unretained(this))),
+      scroll_animation_(
+          kScrollFlingTimeConstant,
+          base::Bind(&GestureInterpreter::ScrollWithoutAbortAnimations,
+                     base::Unretained(this))) {
   viewport_.RegisterOnTransformationChangedCallback(
       base::Bind(&RendererProxy::SetTransformation,
                  base::Unretained(renderer_)),
@@ -87,10 +92,34 @@ void GestureInterpreter::OneFingerFling(float velocity_x, float velocity_y) {
   pan_animation_.Tick();
 }
 
+void GestureInterpreter::Scroll(float x, float y, float dx, float dy) {
+  AbortAnimations();
+
+  ViewMatrix::Point cursor_position = TrackAndGetPosition(x, y);
+
+  // Inject the cursor position to the host so that scrolling can happen on the
+  // right place.
+  input_stub_->SendMouseEvent(cursor_position.x, cursor_position.y,
+                              protocol::MouseEvent_MouseButton_BUTTON_UNDEFINED,
+                              false);
+
+  ScrollWithoutAbortAnimations(dx, dy);
+}
+
+void GestureInterpreter::ScrollFling(float velocity_x, float velocity_y) {
+  AbortAnimations();
+
+  scroll_animation_.SetVelocity(velocity_x, velocity_y);
+  scroll_animation_.Tick();
+}
+
 void GestureInterpreter::ProcessAnimations() {
   if (pan_animation_.IsAnimationInProgress()) {
     pan_animation_.Tick();
   }
+  if (scroll_animation_.IsAnimationInProgress()) {

[nicholss, 2017/05/16 18:13:10]

Does it hurt to call Tick without checking IsAnimationInProgress externally and
instead check internally to the class? What is the side effect of calling tick
with no animation happening?

[Yuwei, 2017/05/17 05:42:20]

Done.

TBH nope. Just the negligible overhead of opening new stack frame O_o

+    scroll_animation_.Tick();
+  }
 }
 
 void GestureInterpreter::OnSurfaceSizeChanged(int width, int height) {
@@ -108,6 +137,12 @@ void GestureInterpreter::PanWithoutAbortAnimations(float translation_x,
   SetCursorPositionOnRenderer();
 }
 
+void GestureInterpreter::ScrollWithoutAbortAnimations(float dx, float dy) {
+  ViewMatrix::Point desktopDelta =
+      input_strategy_->MapScrollVector({dx, dy}, viewport_);
+  input_stub_->SendMouseWheelEvent(desktopDelta.x, desktopDelta.y);
+}
+
 void GestureInterpreter::AbortAnimations() {
   pan_animation_.Abort();
 }