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// Copyright 2015 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "ui/touch_selection/longpress_drag_selector.h"
#include "ui/events/velocity_tracker/motion_event.h"
namespace ui {
namespace {
gfx::Vector2dF SafeNormalize(const gfx::Vector2dF& v) {
return v.IsZero() ? v : ScaleVector2d(v, 1.f / v.Length());
}
} // namespace
LongPressDragSelector::LongPressDragSelector(
LongPressDragSelectorClient* client)
: client_(client),
state_(INACTIVE),
has_longpress_drag_start_anchor_(false) {
}
LongPressDragSelector::~LongPressDragSelector() {
}
bool LongPressDragSelector::WillHandleTouchEvent(const MotionEvent& event) {
switch (event.GetAction()) {
case MotionEvent::Action::DOWN:
touch_down_position_.SetPoint(event.GetX(), event.GetY());
touch_down_time_ = event.GetEventTime();
has_longpress_drag_start_anchor_ = false;
SetState(INITIATING_GESTURE_PENDING);
return false;
case MotionEvent::Action::UP:
case MotionEvent::Action::CANCEL:
SetState(INACTIVE);
return false;
case MotionEvent::Action::MOVE:
break;
default:
return false;
}
if (state_ != DRAG_PENDING && state_ != DRAGGING)
return false;
gfx::PointF position(event.GetX(), event.GetY());
if (state_ == DRAGGING) {
gfx::PointF drag_position = position + longpress_drag_selection_offset_;
client_->OnDragUpdate(*this, drag_position);
return true;
}
// We can't use |touch_down_position_| as the offset anchor, as
// showing the selection UI may have shifted the motion coordinates.
if (!has_longpress_drag_start_anchor_) {
has_longpress_drag_start_anchor_ = true;
longpress_drag_start_anchor_ = position;
return true;
}
// Allow an additional slop affordance after the longpress occurs.
gfx::Vector2dF delta = position - longpress_drag_start_anchor_;
if (client_->IsWithinTapSlop(delta))
return true;
gfx::PointF selection_start = client_->GetSelectionStart();
gfx::PointF selection_end = client_->GetSelectionEnd();
bool extend_selection_start = false;
if (std::abs(delta.y()) > std::abs(delta.x())) {
// If initial motion is up/down, extend the start/end selection bound.
extend_selection_start = delta.y() < 0;
} else {
// Otherwise extend the selection bound toward which we're moving, or
// the closest bound if motion is already away from both bounds.
// Note that, for mixed RTL text, or for multiline selections triggered
// by longpress, this may not pick the most suitable drag target
gfx::Vector2dF start_delta = selection_start - longpress_drag_start_anchor_;
gfx::Vector2dF end_delta = selection_end - longpress_drag_start_anchor_;
// The vectors must be normalized to make dot product comparison meaningful.
gfx::Vector2dF normalized_start_delta = SafeNormalize(start_delta);
gfx::Vector2dF normalized_end_delta = SafeNormalize(end_delta);
double start_dot_product = gfx::DotProduct(normalized_start_delta, delta);
double end_dot_product = gfx::DotProduct(normalized_end_delta, delta);
if (start_dot_product >= 0 || end_dot_product >= 0) {
// The greater the dot product the more similar the direction.
extend_selection_start = start_dot_product > end_dot_product;
} else {
// If we're already moving away from both endpoints, pick the closest.
extend_selection_start =
start_delta.LengthSquared() < end_delta.LengthSquared();
}
}
gfx::PointF extent = extend_selection_start ? selection_start : selection_end;
longpress_drag_selection_offset_ = extent - position;
client_->OnDragBegin(*this, extent);
SetState(DRAGGING);
return true;
}
bool LongPressDragSelector::IsActive() const {
return state_ == DRAG_PENDING || state_ == DRAGGING;
}
void LongPressDragSelector::OnLongPressEvent(base::TimeTicks event_time,
const gfx::PointF& position) {
// We have no guarantees that the current gesture stream is aligned with the
// observed touch stream. We only know that the gesture sequence is downstream
// from the touch sequence. Using a time/distance heuristic helps ensure that
// the observed longpress corresponds to the active touch sequence.
if (state_ == INITIATING_GESTURE_PENDING &&
// Ensure the down event occurs *before* the longpress event. Use a
// small time epsilon to account for floating point time conversion.
(touch_down_time_ < event_time + base::Microseconds(10)) &&
client_->IsWithinTapSlop(touch_down_position_ - position)) {
SetState(SELECTION_PENDING);
}
}
void LongPressDragSelector::OnDoublePressEvent(base::TimeTicks event_time,
const gfx::PointF& position) {
// Handle a double press the same way as a long press.
if (state_ == INITIATING_GESTURE_PENDING &&
// Check event time and position to ensure that the observed double
// press corresponds to the active touch sequence. It should be ok to
// check the exact times and positions here, since a tap down gesture
// event is created directly from the corresponding down motion event when
// the gesture is initially detected.
touch_down_time_ == event_time && touch_down_position_ == position) {
SetState(SELECTION_PENDING);
}
}
void LongPressDragSelector::OnScrollBeginEvent() {
SetState(INACTIVE);
}
void LongPressDragSelector::OnSelectionActivated() {
if (state_ == SELECTION_PENDING)
SetState(DRAG_PENDING);
}
void LongPressDragSelector::OnSelectionDeactivated() {
SetState(INACTIVE);
}
void LongPressDragSelector::SetState(SelectionState state) {
if (state_ == state)
return;
const bool was_dragging = state_ == DRAGGING;
const bool was_active = IsActive();
state_ = state;
// TODO(jdduke): Add UMA for tracking relative longpress drag frequency.
if (was_dragging)
client_->OnDragEnd(*this);
if (was_active != IsActive())
client_->OnLongPressDragActiveStateChanged();
}
} // namespace ui
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