Gestures are now possible using touch events with any ids

ui/aura/gestures/gesture_sequence.cc

Index: ui/aura/gestures/gesture_sequence.cc
diff --git a/ui/aura/gestures/gesture_sequence.cc b/ui/aura/gestures/gesture_sequence.cc
index 40dbb492b3482791f576890642f4a87b672fcb0b..f808919f9cdd26df9999e86d385256633bd87892 100644
--- a/ui/aura/gestures/gesture_sequence.cc
+++ b/ui/aura/gestures/gesture_sequence.cc
@@ -12,11 +12,6 @@
 #include "ui/aura/gestures/gesture_configuration.h"
 #include "ui/base/events.h"
 
-// TODO(sad): Pinch gestures currently always assume that the first two
-//            touch-points (i.e. at indices 0 and 1) are involved. This may not
-//            always be the case. This needs to be fixed eventually.
-//            http://crbug.com/113144
-
 namespace {
 
 // TODO(girard): Make these configurable in sync with this CL
@@ -99,18 +94,6 @@ enum EdgeStateSignatureType {
   GST_SCROLL_FIRST_CANCELLED =
       G(GS_SCROLL, 0, TS_CANCELLED, false),
 
-  GST_SCROLL_FIRST_PRESSED =
-      G(GS_SCROLL, 0, TS_PRESSED, false),
-
-  GST_SCROLL_SECOND_RELEASED =
-      G(GS_SCROLL, 1, TS_RELEASED, false),
-
-  GST_SCROLL_SECOND_MOVED =
-      G(GS_SCROLL, 1, TS_MOVED, false),
-
-  GST_SCROLL_SECOND_CANCELLED =
-      G(GS_SCROLL, 1, TS_CANCELLED, false),
-
   GST_SCROLL_SECOND_PRESSED =
       G(GS_SCROLL, 1, TS_PRESSED, false),
 
@@ -163,9 +146,6 @@ GestureSequence::GestureSequence()
       pinch_distance_current_(0.f),
       long_press_timer_(CreateTimer()),
       point_count_(0) {
-  for (int i = 0; i < kMaxGesturePoints; ++i) {
-    points_[i].set_touch_id(i);
-  }
 }
 
 GestureSequence::~GestureSequence() {
@@ -184,7 +164,13 @@ GestureSequence::Gestures* GestureSequence::ProcessTouchEventForGesture(
   if (event.type() == ui::ET_TOUCH_PRESSED) {
     if (point_count_ == kMaxGesturePoints)
       return NULL;
-    ++point_count_;
+    GesturePoint* new_point = &points_[event.touch_id()];
+    // We shouldn't be able to get two PRESSED events, without a RELEASE
+    DCHECK(!points_[event.touch_id()].in_use());
+    new_point->set_point_id(point_count_++);
+  } else {
+    // Make sure the point we're modifying was PRESSED at some point in the past
+    DCHECK(points_[event.touch_id()].in_use());
   }
 
   GestureState last_state = state_;
@@ -194,7 +180,8 @@ GestureSequence::Gestures* GestureSequence::ProcessTouchEventForGesture(
   GesturePoint& point = GesturePointForEvent(event);
   point.UpdateValues(event);
   flags_ = event.flags();
-  switch (Signature(state_, event.touch_id(), event.type(), false)) {
+  const int point_id = points_[event.touch_id()].point_id();
+  switch (Signature(state_, point_id, event.type(), false)) {
     case GST_NO_GESTURE_FIRST_PRESSED:
       TouchDown(event, point, gestures.get());
       set_state(GS_PENDING_SYNTHETIC_CLICK);
@@ -216,7 +203,6 @@ GestureSequence::Gestures* GestureSequence::ProcessTouchEventForGesture(
       NoGesture(event, point, gestures.get());
       break;
     case GST_SCROLL_FIRST_MOVED:
-    case GST_SCROLL_SECOND_MOVED:
       if (scroll_type_ == ST_VERTICAL ||
           scroll_type_ == ST_HORIZONTAL)
         BreakRailScroll(event, point, gestures.get());
@@ -225,12 +211,9 @@ GestureSequence::Gestures* GestureSequence::ProcessTouchEventForGesture(
       break;
     case GST_SCROLL_FIRST_RELEASED:
     case GST_SCROLL_FIRST_CANCELLED:
-    case GST_SCROLL_SECOND_RELEASED:
-    case GST_SCROLL_SECOND_CANCELLED:
       ScrollEnd(event, point, gestures.get());
       set_state(GS_NO_GESTURE);
       break;
-    case GST_SCROLL_FIRST_PRESSED:
     case GST_SCROLL_SECOND_PRESSED:
     case GST_PENDING_SYNTHETIC_CLICK_SECOND_PRESSED:
       PinchStart(event, point, gestures.get());
@@ -264,15 +247,27 @@ GestureSequence::Gestures* GestureSequence::ProcessTouchEventForGesture(
   if (last_state == GS_PENDING_SYNTHETIC_CLICK && state_ != last_state)
     long_press_timer_->Stop();
 
-  if (event.type() == ui::ET_TOUCH_RELEASED)
+  // The set of point_ids must be contiguous and include 0.

[rjkroege, 2012/02/24 19:11:29]

my understanding is that we at least admit the desired property here: i can
pinch, start a drag with one finger and then scroll with the other finger
without releasing the finger.

[sadrul, 2012/02/25 19:06:30]

Indeed. This is still possible with this change (Tim added a test for it too in
this CL!)

+  // When a touch point is released, all points with ids greater than the
+  // released point must have their ids decremented, or the set of point_ids
+  // could end up with gaps.
+  if (event.type() == ui::ET_TOUCH_RELEASED) {
+    GesturePoint& old_point = points_[event.touch_id()];
+    for (int i = 0; i < kMaxGesturePoints; ++i) {

[sadrul, 2012/02/24 17:52:24]

It should be OK to go only upto point_count_ here, right?

[tdresser, 2012/02/24 18:19:51]

GesturePoints which represent current touches are not always contiguous in
points_, as they are indexed by touch_id. If we knew that they were contiguous,
we could only go up to point_count, but because we don't have that guarantee, we
have to scan the whole list.

[sadrul, 2012/02/24 18:21:01]

Of course! My bad, I read it wrong.

+      GesturePoint& point = points_[i];
+      if (point.point_id() > old_point.point_id())
+        point.set_point_id(point.point_id() - 1);
+    }
+    old_point.Reset();
     --point_count_;
+  }
 
   return gestures.release();
 }
 
 void GestureSequence::Reset() {
   set_state(GS_NO_GESTURE);
-  for (int i = 0; i < point_count_; ++i)
+  for (int i = 0; i < kMaxGesturePoints; ++i)
     points_[i].Reset();
 }
 
@@ -291,6 +286,17 @@ GesturePoint& GestureSequence::GesturePointForEvent(
   return points_[event.touch_id()];
 }
 
+GesturePoint* GestureSequence::GetPointByPointId(int point_id) {
+  DCHECK(0 <= point_id && point_id < kMaxGesturePoints);
+  for (int i = 0; i < kMaxGesturePoints; ++i) {
+    GesturePoint& point = points_[i];
+    if (point.in_use() && point.point_id() == point_id)
+      return &point;
+  }
+  NOTREACHED();
+  return NULL;
+}
+
 void GestureSequence::AppendTapDownGestureEvent(const GesturePoint& point,
                                                 Gestures* gestures) {
   gestures->push_back(linked_ptr<GestureEvent>(new GestureEvent(
@@ -481,16 +487,15 @@ bool GestureSequence::TouchDown(const TouchEvent& event,
 }
 
 void GestureSequence::AppendLongPressGestureEvent() {
-  // TODO(tdresser) - this may not always be the first point
-  const GesturePoint& point = points_[0];
+  const GesturePoint* point = GetPointByPointId(0);
+  DCHECK(point);

[sadrul, 2012/02/24 17:52:24]

point being NULL will cause a crash in the next line anyway. In such cases,
CHECK/DCHECK's are seen as unnecessary.

[tdresser, 2012/02/24 18:19:51]

Done.

   GestureEvent* gesture = new GestureEvent(
       ui::ET_GESTURE_LONG_PRESS,
-      point.first_touch_position().x(),
-      point.first_touch_position().y(),
+      point->first_touch_position().x(),
+      point->first_touch_position().y(),
       flags_,
-      base::Time::FromDoubleT(point.last_touch_time()),
-      point.touch_id(), 0.f);
-
+      base::Time::FromDoubleT(point->last_touch_time()),
+      point->point_id(), 0.f);
   RootWindow::GetInstance()->DispatchGestureEvent(gesture);
 }
 
@@ -513,13 +518,16 @@ bool GestureSequence::PinchStart(const TouchEvent& event,
          state_ == GS_PENDING_SYNTHETIC_CLICK);
   AppendTapDownGestureEvent(point, gestures);
 
-  pinch_distance_current_ = points_[0].Distance(points_[1]);
+  const GesturePoint* point1 = GetPointByPointId(0);
+  const GesturePoint* point2 = GetPointByPointId(1);
+
+  pinch_distance_current_ = point1->Distance(*point2);
   pinch_distance_start_ = pinch_distance_current_;
-  AppendPinchGestureBegin(points_[0], points_[1], gestures);
+  AppendPinchGestureBegin(*point1, *point2, gestures);
 
   if (state_ == GS_PENDING_SYNTHETIC_CLICK) {
-    gfx::Point center = points_[0].last_touch_position().Middle(
-        points_[1].last_touch_position());
+    gfx::Point center = point1->last_touch_position().Middle(
+        point2->last_touch_position());
     AppendScrollGestureBegin(point, center, gestures);
   }
 
@@ -529,23 +537,27 @@ bool GestureSequence::PinchStart(const TouchEvent& event,
 bool GestureSequence::PinchUpdate(const TouchEvent& event,
     const GesturePoint& point, Gestures* gestures) {
   DCHECK(state_ == GS_PINCH);
-  float distance = points_[0].Distance(points_[1]);
+
+  const GesturePoint* point1 = GetPointByPointId(0);
+  const GesturePoint* point2 = GetPointByPointId(1);
+
+  float distance = point1->Distance(*point2);
   if (abs(distance - pinch_distance_current_) <
       GestureConfiguration::minimum_pinch_update_distance_in_pixels()) {
     // The fingers didn't move towards each other, or away from each other,
     // enough to constitute a pinch. But perhaps they moved enough in the same
     // direction to do a two-finger scroll.
-    if (!points_[0].DidScroll(event,
+    if (!point1->DidScroll(event,
         GestureConfiguration::minimum_distance_for_pinch_scroll_in_pixels()) ||
-        !points_[1].DidScroll(event,
+        !point2->DidScroll(event,
         GestureConfiguration::minimum_distance_for_pinch_scroll_in_pixels()))
       return false;
 
-    gfx::Point center = points_[0].last_touch_position().Middle(
-                        points_[1].last_touch_position());
+    gfx::Point center = point1->last_touch_position().Middle(
+                        point2->last_touch_position());
     AppendScrollGestureUpdate(point, center, gestures);
   } else {
-    AppendPinchGestureUpdate(points_[0], points_[1],
+    AppendPinchGestureUpdate(*point1, *point2,
         distance / pinch_distance_current_, gestures);
     pinch_distance_current_ = distance;
   }
@@ -555,8 +567,12 @@ bool GestureSequence::PinchUpdate(const TouchEvent& event,
 bool GestureSequence::PinchEnd(const TouchEvent& event,
     const GesturePoint& point, Gestures* gestures) {
   DCHECK(state_ == GS_PINCH);
-  float distance = points_[0].Distance(points_[1]);
-  AppendPinchGestureEnd(points_[0], points_[1],
+
+  const GesturePoint* point1 = GetPointByPointId(0);
+  const GesturePoint* point2 = GetPointByPointId(1);
+
+  float distance = point1->Distance(*point2);
+  AppendPinchGestureEnd(*point1, *point2,
       distance / pinch_distance_start_, gestures);
 
   pinch_distance_start_ = 0;