content/renderer/disambiguation_popup_helper.cc

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "content/renderer/disambiguation_popup_helper.h"
   6
   7 #include "third_party/WebKit/Source/WebKit/chromium/public/platform/WebRect.h"
   8 #include "ui/gfx/size_conversions.h"
   9
  10 using WebKit::WebRect;
  11 using WebKit::WebVector;
  12
  13 namespace {
  14
  15 // The amount of padding to add to the disambiguation popup to show
  16 // content around the possible elements, adding some context.
  17 const int kDisambiguationPopupPadding = 8;
  18
  19 // Constants used for fitting the disambiguation popup inside the bounds of
  20 // the view. Note that there are mirror constants in PopupZoomer.java.
  21 const int kDisambiguationPopupBoundsMargin = 25;
  22
  23 // The smallest allowable touch target used for disambiguation popup.
  24 // This value is used to determine the minimum amount we need to scale to
  25 // make all targets touchable.
  26 const int kDisambiguationPopupMinimumTouchSize = 40;
  27 const float kDisambiguationPopupMaxScale = 5.0;
  28 const float kDisambiguationPopupMinScale = 2.0;
  29
  30 // Compute the scaling factor to ensure the smallest touch candidate reaches
  31 // a certain clickable size after zooming
  32 float FindOptimalScaleFactor(const WebVector<WebRect>& target_rects) {
  33   using std::min;
  34   using std::max;
  35   if (!target_rects.size()) // shall never reach
  36     return kDisambiguationPopupMinScale;
  37   int smallest_target = min(target_rects[0].width, target_rects[0].height);
  38   for (size_t i = 1; i < target_rects.size(); i++) {
  39     smallest_target = min(smallest_target, target_rects[i].width);
  40     smallest_target = min(smallest_target, target_rects[i].height);
  41   }
  42   smallest_target = max(smallest_target, 1);
  43   return min(kDisambiguationPopupMaxScale, max(kDisambiguationPopupMinScale,
  44       static_cast<float>(kDisambiguationPopupMinimumTouchSize)
  45           / smallest_target));
  46 }
  47
  48 void TrimEdges(int *e1, int *e2, int max_combined) {
  49   if (*e1 + *e2 <= max_combined)
  50     return;
  51
  52   if (std::min(*e1, *e2) * 2 >= max_combined)
  53     *e1 = *e2 = max_combined / 2;
  54   else if (*e1 > *e2)
  55     *e1 = max_combined - *e2;
  56   else
  57     *e2 = max_combined - *e1;
  58 }
  59
  60 // Ensure the disambiguation popup fits inside the screen,
  61 // clip the edges farthest to the touch point if needed.
  62 gfx::Rect CropZoomArea(const gfx::Rect& zoom_rect,
  63                        const gfx::Size& viewport_size,
  64                        const gfx::Point& touch_point,
  65                        float scale) {
  66   gfx::Size max_size = viewport_size;
  67   max_size.Enlarge(-2 * kDisambiguationPopupBoundsMargin,
  68                    -2 * kDisambiguationPopupBoundsMargin);
  69   max_size = ToCeiledSize(ScaleSize(max_size, 1.0 / scale));
  70
  71   int left = touch_point.x() - zoom_rect.x();
  72   int right = zoom_rect.right() - touch_point.x();
  73   int top = touch_point.y() - zoom_rect.y();
  74   int bottom = zoom_rect.bottom() - touch_point.y();
  75   TrimEdges(&left, &right, max_size.width());
  76   TrimEdges(&top, &bottom, max_size.height());
  77
  78   return gfx::Rect(touch_point.x() - left,
  79                    touch_point.y() - top,
  80                    left + right,
  81                    top + bottom);
  82 }
  83
  84 } // unnamed namespace
  85
  86 namespace content {
  87
  88 float DisambiguationPopupHelper::ComputeZoomAreaAndScaleFactor(
  89     const gfx::Rect& tap_rect,
  90     const WebVector<WebRect>& target_rects,
  91     const gfx::Size& viewport_size,
  92     gfx::Rect* zoom_rect) {
  93   *zoom_rect = tap_rect;
  94   for (size_t i = 0; i < target_rects.size(); i++)
  95     zoom_rect->Union(gfx::Rect(target_rects[i]));
  96   zoom_rect->Inset(-kDisambiguationPopupPadding, -kDisambiguationPopupPadding);
  97   zoom_rect->Intersect(gfx::Rect(viewport_size));
  98
  99   float scale = FindOptimalScaleFactor(target_rects);
 100   *zoom_rect = CropZoomArea(
 101       *zoom_rect, viewport_size, tap_rect.CenterPoint(), scale);
 102
 103   return scale;
 104 }
 105
 106 } // namespace content