1/*
2 * Copyright (C) 2012 Google Inc. All rights reserved.
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions are
6 * met:
7 *
8 *     * Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 *     * Redistributions in binary form must reproduce the above
11 * copyright notice, this list of conditions and the following disclaimer
12 * in the documentation and/or other materials provided with the
13 * distribution.
14 *     * Neither the name of Google Inc. nor the names of its
15 * contributors may be used to endorse or promote products derived from
16 * this software without specific prior written permission.
17 *
18 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
19 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
20 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
21 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
22 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
23 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
24 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
25 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
26 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
27 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
28 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
29 */
30
31#include "config.h"
32
33#include "TouchDisambiguation.h"
34
35#include "Document.h"
36#include "Element.h"
37#include "Frame.h"
38#include "FrameView.h"
39#include "HTMLNames.h"
40#include "HitTestResult.h"
41#include "NodeTraversal.h"
42#include "RenderBlock.h"
43#include <algorithm>
44#include <cmath>
45
46using namespace std;
47
48namespace WebCore {
49
50static IntRect boundingBoxForEventNodes(Node* eventNode)
51{
52    if (!eventNode->document()->view())
53        return IntRect();
54
55    IntRect result;
56    Node* node = eventNode;
57    while (node) {
58        // Skip the whole sub-tree if the node doesn't propagate events.
59        if (node != eventNode && node->willRespondToMouseClickEvents()) {
60            node = NodeTraversal::nextSkippingChildren(node, eventNode);
61            continue;
62        }
63        result.unite(node->pixelSnappedBoundingBox());
64        node = NodeTraversal::next(node, eventNode);
65    }
66    return eventNode->document()->view()->contentsToWindow(result);
67}
68
69static float scoreTouchTarget(IntPoint touchPoint, int padding, IntRect boundingBox)
70{
71    if (boundingBox.isEmpty())
72        return 0;
73
74    float reciprocalPadding = 1.f / padding;
75    float score = 1;
76
77    IntSize distance = boundingBox.differenceToPoint(touchPoint);
78    score *= max((padding - abs(distance.width())) * reciprocalPadding, 0.f);
79    score *= max((padding - abs(distance.height())) * reciprocalPadding, 0.f);
80
81    return score;
82}
83
84struct TouchTargetData {
85    IntRect windowBoundingBox;
86    float score;
87};
88
89void findGoodTouchTargets(const IntRect& touchBox, Frame* mainFrame, Vector<IntRect>& goodTargets)
90{
91    goodTargets.clear();
92
93    int touchPointPadding = ceil(max(touchBox.width(), touchBox.height()) * 0.5);
94    // FIXME: Rect-based hit test doesn't transform the touch point size.
95    //        We have to pre-apply frame scale factor here.
96    int padding = ceil(touchPointPadding / mainFrame->frameScaleFactor());
97
98    IntPoint touchPoint = touchBox.center();
99    IntPoint contentsPoint = mainFrame->view()->windowToContents(touchPoint);
100
101    HitTestResult result = mainFrame->eventHandler()->hitTestResultAtPoint(contentsPoint, HitTestRequest::ReadOnly | HitTestRequest::Active | HitTestRequest::DisallowShadowContent, IntSize(padding, padding));
102    const ListHashSet<RefPtr<Node> >& hitResults = result.rectBasedTestResult();
103
104    // Blacklist nodes that are container of disambiguated nodes.
105    // It is not uncommon to have a clickable <div> that contains other clickable objects.
106    // This heuristic avoids excessive disambiguation in that case.
107    HashSet<Node*> blackList;
108    for (ListHashSet<RefPtr<Node> >::const_iterator it = hitResults.begin(); it != hitResults.end(); ++it) {
109        // Ignore any Nodes that can't be clicked on.
110        RenderObject* renderer = it->get()->renderer();
111        if (!renderer || !it->get()->willRespondToMouseClickEvents())
112            continue;
113
114        // Blacklist all of the Node's containers.
115        for (RenderBlock* container = renderer->containingBlock(); container; container = container->containingBlock()) {
116            Node* containerNode = container->node();
117            if (!containerNode)
118                continue;
119            if (!blackList.add(containerNode).isNewEntry)
120                break;
121        }
122    }
123
124    HashMap<Node*, TouchTargetData> touchTargets;
125    float bestScore = 0;
126    for (ListHashSet<RefPtr<Node> >::const_iterator it = hitResults.begin(); it != hitResults.end(); ++it) {
127        for (Node* node = it->get(); node; node = node->parentNode()) {
128            if (blackList.contains(node))
129                continue;
130            if (node->isDocumentNode() || node->hasTagName(HTMLNames::htmlTag) || node->hasTagName(HTMLNames::bodyTag))
131                break;
132            if (node->willRespondToMouseClickEvents()) {
133                TouchTargetData& targetData = touchTargets.add(node, TouchTargetData()).iterator->value;
134                targetData.windowBoundingBox = boundingBoxForEventNodes(node);
135                targetData.score = scoreTouchTarget(touchPoint, touchPointPadding, targetData.windowBoundingBox);
136                bestScore = max(bestScore, targetData.score);
137                break;
138            }
139        }
140    }
141
142    for (HashMap<Node*, TouchTargetData>::iterator it = touchTargets.begin(); it != touchTargets.end(); ++it) {
143        // Currently the scoring function uses the overlap area with the fat point as the score.
144        // We ignore the candidates that has less than 1/2 overlap (we consider not really ambiguous enough) than the best candidate to avoid excessive popups.
145        if (it->value.score < bestScore * 0.5)
146            continue;
147        goodTargets.append(it->value.windowBoundingBox);
148    }
149}
150
151} // namespace WebCore
152