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Allow users to extend a longpress-triggered selection by dragging their finger continuously after the longpress. Enabled using the "--enable-longpress-drag-selection" flag on Android. BUG=466749 Review URL: https://codereview.chromium.org/1087893003 Cr-Commit-Position: refs/heads/master@{#332439}
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,141 @@ | ||
| // Copyright 2015 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. | ||
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| #include "ui/touch_selection/longpress_drag_selector.h" | ||
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| #include "base/auto_reset.h" | ||
| #include "ui/events/gesture_detection/motion_event.h" | ||
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| namespace ui { | ||
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| LongPressDragSelector::LongPressDragSelector( | ||
| LongPressDragSelectorClient* client) | ||
| : client_(client), | ||
| state_(INACTIVE), | ||
| has_longpress_drag_start_anchor_(false) { | ||
| } | ||
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| LongPressDragSelector::~LongPressDragSelector() { | ||
| } | ||
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| 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(LONGPRESS_PENDING); | ||
| return false; | ||
|
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| case MotionEvent::ACTION_UP: | ||
| case MotionEvent::ACTION_CANCEL: | ||
| SetState(INACTIVE); | ||
| return false; | ||
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| case MotionEvent::ACTION_MOVE: | ||
| break; | ||
|
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| default: | ||
| return false; | ||
| } | ||
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| if (state_ != DRAG_PENDING && state_ != DRAGGING) | ||
| return false; | ||
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| 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; | ||
| } | ||
|
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| // 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; | ||
| } | ||
|
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| // Allow an additional slop affordance after the longpress occurs. | ||
| gfx::Vector2dF delta = position - longpress_drag_start_anchor_; | ||
| if (client_->IsWithinTapSlop(delta)) | ||
| return true; | ||
|
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| 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. | ||
| // 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 - position; | ||
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| // The vectors must be normalized to make dot product comparison meaningful. | ||
| if (!start_delta.IsZero()) | ||
| start_delta.Scale(1.f / start_delta.Length()); | ||
| gfx::Vector2dF end_delta = selection_end - position; | ||
| if (!end_delta.IsZero()) | ||
| end_delta.Scale(1.f / start_delta.Length()); | ||
|
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| // The larger the dot product the more similar the direction. | ||
| extend_selection_start = | ||
| gfx::DotProduct(start_delta, delta) > gfx::DotProduct(end_delta, delta); | ||
| } | ||
|
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| gfx::PointF extent = extend_selection_start ? selection_start : selection_end; | ||
| longpress_drag_selection_offset_ = extent - position; | ||
| client_->OnDragBegin(*this, extent); | ||
| SetState(DRAGGING); | ||
| return true; | ||
| } | ||
|
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| bool LongPressDragSelector::IsActive() const { | ||
| return state_ != INACTIVE && state_ != LONGPRESS_PENDING; | ||
| } | ||
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| 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_ == LONGPRESS_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::TimeDelta::FromMicroseconds(10)) && | ||
| client_->IsWithinTapSlop(touch_down_position_ - position)) { | ||
| SetState(SELECTION_PENDING); | ||
| } | ||
| } | ||
|
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| void LongPressDragSelector::OnSelectionActivated() { | ||
| if (state_ == SELECTION_PENDING) | ||
| SetState(DRAG_PENDING); | ||
| } | ||
|
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| void LongPressDragSelector::OnSelectionDeactivated() { | ||
| SetState(INACTIVE); | ||
| } | ||
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| void LongPressDragSelector::SetState(SelectionState state) { | ||
| if (state_ == state) | ||
| return; | ||
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| const bool was_dragging = state_ == DRAGGING; | ||
| const bool was_active = IsActive(); | ||
| state_ = state; | ||
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| // TODO(jdduke): Add UMA for tracking relative longpress drag frequency. | ||
| if (was_dragging) | ||
| client_->OnDragEnd(*this); | ||
|
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| if (was_active != IsActive()) | ||
| client_->OnLongPressDragActiveStateChanged(); | ||
| } | ||
|
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| } // namespace ui |
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