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/*
* Copyright (C) 2012 Google Inc. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are
* met:
*
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above
* copyright notice, this list of conditions and the following disclaimer
* in the documentation and/or other materials provided with the
* distribution.
* * Neither the name of Google Inc. nor the names of its
* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include "third_party/blink/renderer/core/page/touch_disambiguation.h"
#include <algorithm>
#include <cmath>
#include "third_party/blink/renderer/core/dom/document.h"
#include "third_party/blink/renderer/core/dom/element.h"
#include "third_party/blink/renderer/core/dom/node_traversal.h"
#include "third_party/blink/renderer/core/frame/local_frame.h"
#include "third_party/blink/renderer/core/frame/local_frame_view.h"
#include "third_party/blink/renderer/core/html/html_html_element.h"
#include "third_party/blink/renderer/core/input/event_handler.h"
#include "third_party/blink/renderer/core/layout/hit_test_result.h"
#include "third_party/blink/renderer/core/layout/layout_block.h"
namespace blink {
static IntRect BoundingBoxForEventNodes(Node* event_node) {
if (!event_node->GetDocument().View())
return IntRect();
IntRect result;
Node* node = event_node;
while (node) {
// Skip the whole sub-tree if the node doesn't propagate events.
if (node != event_node && node->WillRespondToMouseClickEvents()) {
node = NodeTraversal::NextSkippingChildren(*node, event_node);
continue;
}
result.Unite(node->PixelSnappedBoundingBox());
node = NodeTraversal::Next(*node, event_node);
}
return event_node->GetDocument().View()->ContentsToRootFrame(result);
}
static float ScoreTouchTarget(IntPoint touch_point,
int padding,
IntRect bounding_box) {
if (bounding_box.IsEmpty())
return 0;
float reciprocal_padding = 1.f / padding;
float score = 1;
IntSize distance = bounding_box.DifferenceToPoint(touch_point);
score *=
std::max((padding - abs(distance.Width())) * reciprocal_padding, 0.f);
score *=
std::max((padding - abs(distance.Height())) * reciprocal_padding, 0.f);
return score;
}
struct TouchTargetData {
IntRect window_bounding_box;
float score;
};
void FindGoodTouchTargets(const IntRect& touch_box_in_root_frame,
LocalFrame* main_frame,
Vector<IntRect>& good_targets,
HeapVector<Member<Node>>& highlight_nodes) {
good_targets.clear();
int touch_point_padding = ceil(std::max(touch_box_in_root_frame.Width(),
touch_box_in_root_frame.Height()) *
0.5);
IntPoint touch_point = touch_box_in_root_frame.Center();
IntPoint contents_point =
main_frame->View()->RootFrameToContents(touch_point);
HitTestResult result = main_frame->GetEventHandler().HitTestResultAtPoint(
contents_point,
HitTestRequest::kReadOnly | HitTestRequest::kActive |
HitTestRequest::kListBased,
LayoutRectOutsets(touch_point_padding, touch_point_padding,
touch_point_padding, touch_point_padding));
const HeapListHashSet<Member<Node>>& hit_results =
result.ListBasedTestResult();
// Blacklist nodes that are container of disambiguated nodes.
// It is not uncommon to have a clickable <div> that contains other clickable
// objects. This heuristic avoids excessive disambiguation in that case.
HeapHashSet<Member<Node>> black_list;
for (const auto& hit_result : hit_results) {
// Ignore any Nodes that can't be clicked on.
LayoutObject* layout_object = hit_result.Get()->GetLayoutObject();
if (!layout_object || !hit_result.Get()->WillRespondToMouseClickEvents())
continue;
// Blacklist all of the Node's containers.
for (LayoutBlock* container = layout_object->ContainingBlock(); container;
container = container->ContainingBlock()) {
Node* container_node = container->GetNode();
if (!container_node)
continue;
if (!black_list.insert(container_node).is_new_entry)
break;
}
}
HeapHashMap<Member<Node>, TouchTargetData> touch_targets;
float best_score = 0;
for (const auto& hit_result : hit_results) {
if (!hit_result)
continue;
for (Node& node : NodeTraversal::InclusiveAncestorsOf(*hit_result)) {
if (black_list.Contains(&node))
continue;
if (node.IsDocumentNode() || IsHTMLHtmlElement(node) ||
IsHTMLBodyElement(node))
break;
if (node.WillRespondToMouseClickEvents()) {
TouchTargetData& target_data =
touch_targets.insert(&node, TouchTargetData()).stored_value->value;
target_data.window_bounding_box = BoundingBoxForEventNodes(&node);
target_data.score = ScoreTouchTarget(touch_point, touch_point_padding,
target_data.window_bounding_box);
best_score = std::max(best_score, target_data.score);
break;
}
}
}
// The scoring function uses the overlap area with the fat point as the score.
// We ignore the candidates that have less than this (empirically tuned)
// fraction of overlap than the best candidate to avoid excessive popups.
//
// If this value were 1, then the disambiguation feature would only be seen
// when two nodes have precisely the same overlap with the touch radius. If
// it were 0, then any miniscule overlap with the edge of another node would
// trigger it.
const float kRelativeAmbiguityThreshold = 0.75f;
for (const auto& touch_target : touch_targets) {
if (touch_target.value.score < best_score * kRelativeAmbiguityThreshold)
continue;
good_targets.push_back(touch_target.value.window_bounding_box);
highlight_nodes.push_back(touch_target.key);
}
}
} // namespace blink
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