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107 lines
3.5 KiB
C++
107 lines
3.5 KiB
C++
// Copyright 2014 The Chromium Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#include "ui/events/gesture_detection/snap_scroll_controller.h"
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#include <cmath>
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#include "ui/events/gesture_detection/motion_event.h"
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#include "ui/gfx/display.h"
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namespace ui {
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namespace {
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const int kSnapBound = 16;
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const float kMinSnapChannelDistance = kSnapBound;
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const float kMaxSnapChannelDistance = kMinSnapChannelDistance * 3.f;
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const float kSnapChannelDipsPerScreenDip = kMinSnapChannelDistance / 480.f;
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float CalculateChannelDistance(const gfx::Display& display) {
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if (display.bounds().IsEmpty())
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return kMinSnapChannelDistance;
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float screen_size =
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std::abs(hypot(static_cast<float>(display.bounds().width()),
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static_cast<float>(display.bounds().height())));
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float snap_channel_distance = screen_size * kSnapChannelDipsPerScreenDip;
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return std::max(kMinSnapChannelDistance,
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std::min(kMaxSnapChannelDistance, snap_channel_distance));
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}
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} // namespace
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SnapScrollController::SnapScrollController(const gfx::Display& display)
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: channel_distance_(CalculateChannelDistance(display)),
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snap_scroll_mode_(SNAP_NONE),
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first_touch_x_(-1),
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first_touch_y_(-1),
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distance_x_(0),
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distance_y_(0) {}
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SnapScrollController::~SnapScrollController() {}
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void SnapScrollController::UpdateSnapScrollMode(float distance_x,
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float distance_y) {
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if (snap_scroll_mode_ == SNAP_HORIZ || snap_scroll_mode_ == SNAP_VERT) {
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distance_x_ += std::abs(distance_x);
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distance_y_ += std::abs(distance_y);
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if (snap_scroll_mode_ == SNAP_HORIZ) {
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if (distance_y_ > channel_distance_) {
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snap_scroll_mode_ = SNAP_NONE;
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} else if (distance_x_ > channel_distance_) {
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distance_x_ = 0;
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distance_y_ = 0;
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}
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} else {
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if (distance_x_ > channel_distance_) {
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snap_scroll_mode_ = SNAP_NONE;
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} else if (distance_y_ > channel_distance_) {
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distance_x_ = 0;
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distance_y_ = 0;
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}
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}
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}
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}
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void SnapScrollController::SetSnapScrollingMode(
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const MotionEvent& event,
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bool is_scale_gesture_detection_in_progress) {
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switch (event.GetAction()) {
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case MotionEvent::ACTION_DOWN:
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snap_scroll_mode_ = SNAP_NONE;
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first_touch_x_ = event.GetX();
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first_touch_y_ = event.GetY();
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break;
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// Set scrolling mode to SNAP_X if scroll towards x-axis exceeds kSnapBound
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// and movement towards y-axis is trivial.
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// Set scrolling mode to SNAP_Y if scroll towards y-axis exceeds kSnapBound
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// and movement towards x-axis is trivial.
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// Scrolling mode will remain in SNAP_NONE for other conditions.
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case MotionEvent::ACTION_MOVE:
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if (!is_scale_gesture_detection_in_progress &&
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snap_scroll_mode_ == SNAP_NONE) {
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int x_diff = static_cast<int>(std::abs(event.GetX() - first_touch_x_));
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int y_diff = static_cast<int>(std::abs(event.GetY() - first_touch_y_));
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if (x_diff > kSnapBound && y_diff < kSnapBound) {
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snap_scroll_mode_ = SNAP_HORIZ;
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} else if (x_diff < kSnapBound && y_diff > kSnapBound) {
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snap_scroll_mode_ = SNAP_VERT;
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}
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}
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break;
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case MotionEvent::ACTION_UP:
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case MotionEvent::ACTION_CANCEL:
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first_touch_x_ = -1;
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first_touch_y_ = -1;
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distance_x_ = 0;
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distance_y_ = 0;
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break;
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default:
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break;
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}
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}
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} // namespace ui
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