Page zoom improvements

content/public/common/page_zoom.cc

+// Copyright (c) 2011 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.
+
+#include <cmath>
+
+#include "content/public/common/page_zoom.h"
+#include "third_party/WebKit/Source/WebKit/chromium/public/WebView.h"
+
+namespace content {
+
+const double kMinimumZoomFactor = 0.25;
+const double kMaximumZoomFactor = 5.0;
+
+const double kPresetZoomFactors[] = { 0.25, 0.333, 0.5, 0.666, 0.75, 0.9, 1.0,
+                                      1.1, 1.25, 1.5, 1.75, 2.0, 2.5, 3.0, 4.0,
+                                      5.0 };
+
+std::vector<double> PageZoomHelpers::PresetFactorsWithCustomValue(
+    double custom_factor) {
+  return PresetValuesWithCustomValue(PAGE_ZOOM_VALUE_TYPE_FACTOR,
+                                     custom_factor);
+}
+
+std::vector<double> PageZoomHelpers::PresetLevelsWithCustomValue(
+    double custom_level) {
+  return PresetValuesWithCustomValue(
+      PageZoomHelpers::PAGE_ZOOM_VALUE_TYPE_LEVEL, custom_level);
+}
+
+std::vector<double> PageZoomHelpers::PresetValuesWithCustomValue(
+    PageZoomHelpers::PageZoomValueType value_type, double custom_value) {
+  // Generate a vector of zoom values from an array of known preset
+  // factors. The values in content::kPresetZoomFactors will already be in
+  // sorted order.
+  std::vector<double> zoom_values;
+  bool found_default = false;
+  for (size_t i = 0; i < arraysize(kPresetZoomFactors); i++) {
+    double zoom_value = content::kPresetZoomFactors[i];
+    if (value_type == PageZoomHelpers::PAGE_ZOOM_VALUE_TYPE_LEVEL)
+      zoom_value = WebKit::WebView::zoomFactorToZoomLevel(zoom_value);
+    if (ZoomValuesEqual(zoom_value, custom_value))
+      found_default = true;
+    zoom_values.push_back(zoom_value);
+  }
+  // If the preset array did not contain the custom value, append it to the
+  // vector and then sort.
+  if (!found_default) {
+    zoom_values.push_back(custom_value);
+    std::sort(zoom_values.begin(), zoom_values.end());
+  }
+  return zoom_values;
+}
+
+bool PageZoomHelpers::ZoomValuesEqual(double value_a, double value_b) {
+  // Epsilon value for comparing two floating-point zoom values. We don't use
+  // std::numeric_limits<> because it is too precise for zoom values. Zoom
+  // values loose precision due to factor/level conversions. A value of 0.001
+  // is precise enough for zoom value comparisons.
+  const double epsilon = 0.001;
+
+  return (std::fabs(value_a - value_b) <= epsilon);
+}
+
+}  // namespace content
+