Fix bug where floating keyboard jitters when dragging with multi-touch

When you use multiple fingers to drag the keyboard around, the events
for these get sent to the event filter sequentially. Check for a
pointer ID (which is unique per touch point) and include it in the
active drag descriptor. Ignore non-matching pointer events.

Bug: 802992
Change-Id: I5a3948719e5c103ee1aa618afc3fe36939567326
Reviewed-on: https://chromium-review.googlesource.com/979739Reviewed-by: Yuichiro Hanada <yhanada@chromium.org>
Commit-Queue: Blake O'Hare <blakeo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#549424}

ui/keyboard/container_floating_behavior.cc

@@ -4,6 +4,7 @@
 
 #include "ui/keyboard/container_floating_behavior.h"
 
+#include "ui/events/event.h"
 #include "ui/gfx/geometry/point.h"
 #include "ui/gfx/geometry/rect.h"
 #include "ui/gfx/geometry/size.h"
@@ -194,6 +195,12 @@ bool ContainerFloatingBehavior::HandlePointerEvent(
   if (keyboard_bounds.height() <= 0)
     return false;
 
+  ui::PointerId pointer_id = -1;
+  if (event.IsTouchEvent()) {
+    const ui::TouchEvent* te = event.AsTouchEvent();
+    pointer_id = te->pointer_details().id;
+  }
+
   bool handled = false;
 
   const ui::EventType type = event.type();
@@ -210,8 +217,9 @@ bool ContainerFloatingBehavior::HandlePointerEvent(
       } else if (!drag_descriptor_) {
         // If there is no active drag descriptor, start a new one.
         bool drag_started_by_touch = (type == ui::ET_TOUCH_PRESSED);
-        drag_descriptor_.reset(new DragDescriptor(
-            keyboard_bounds.origin(), kb_offset, drag_started_by_touch));
+        drag_descriptor_.reset(
+            new DragDescriptor(keyboard_bounds.origin(), kb_offset,
+                               drag_started_by_touch, pointer_id));
         handled = true;
       }
       break;
@@ -225,6 +233,8 @@ bool ContainerFloatingBehavior::HandlePointerEvent(
         // If the event isn't of the same type that started the drag, end the
         // drag to prevent confusion.
         drag_descriptor_ = nullptr;
+      } else if (drag_descriptor_->pointer_id() != pointer_id) {
+        // do nothing.
       } else {
         // Drag continues.
         // If there is an active drag, use it to determine the new location

ui/keyboard/drag_descriptor.cc

@@ -4,6 +4,7 @@
 
 #include "ui/keyboard/drag_descriptor.h"
 
+#include "ui/events/event.h"
 #include "ui/gfx/geometry/point.h"
 #include "ui/gfx/geometry/vector2d.h"
 
@@ -11,9 +12,11 @@ namespace keyboard {
 
 DragDescriptor::DragDescriptor(const gfx::Point& keyboard_location,
                                const gfx::Vector2d& click_offset,
-                               bool is_touch_drag)
+                               bool is_touch_drag,
+                               ui::PointerId pointer_id)
     : original_keyboard_location_(keyboard_location),
       original_click_offset_(click_offset),
-      is_touch_drag_(is_touch_drag) {}
+      is_touch_drag_(is_touch_drag),
+      pointer_id_(pointer_id) {}
 
 }  // namespace keyboard

ui/keyboard/drag_descriptor.h

@@ -5,6 +5,7 @@
 #ifndef UI_KEYBOARD_DRAG_DESCRIPTOR_H_
 #define UI_KEYBOARD_DRAG_DESCRIPTOR_H_
 
+#include "ui/events/event.h"
 #include "ui/gfx/geometry/point.h"
 #include "ui/gfx/geometry/vector2d.h"
 
@@ -19,13 +20,15 @@ class DragDescriptor {
  public:
   DragDescriptor(const gfx::Point& keyboard_location,
                  const gfx::Vector2d& click_offset,
-                 bool is_touch_drag);
+                 bool is_touch_drag,
+                 ui::PointerId pointer_id);
 
   gfx::Point original_keyboard_location() const {
     return original_keyboard_location_;
   }
   gfx::Vector2d original_click_offset() const { return original_click_offset_; }
   bool is_touch_drag() { return is_touch_drag_; }
+  ui::PointerId pointer_id() { return pointer_id_; }
 
  private:
   const gfx::Point original_keyboard_location_;
@@ -34,6 +37,10 @@ class DragDescriptor {
   // Distinguish whether the current drag is from a touch event or mouse event,
   // so drag/move events can be filtered accordingly
   const bool is_touch_drag_;
+
+  // The pointer ID provided by the touch event to disambiguate multiple
+  // touch points. If this is a mouse event, then this value is -1.
+  const ui::PointerId pointer_id_;
 };
 
 }  // namespace keyboard