dom/base/nsViewportInfo.h

   1 /* This Source Code Form is subject to the terms of the Mozilla Public
   2  * License, v. 2.0. If a copy of the MPL was not distributed with this
   3  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   4
   5 #ifndef nsViewportInfo_h___
   6 #define nsViewportInfo_h___
   7
   8 #include <algorithm>
   9 #include <stdint.h>
  10 #include "mozilla/Attributes.h"
  11 #include "mozilla/StaticPrefs_apz.h"
  12 #include "Units.h"
  13
  14 namespace mozilla::dom {
  15 enum class ViewportFitType : uint8_t {
  16   Auto,
  17   Contain,
  18   Cover,
  19 };
  20 }  // namespace mozilla::dom
  21
  22 /**
  23  * Default values for the nsViewportInfo class.
  24  */
  25 static const mozilla::CSSIntSize kViewportMinSize(200, 40);
  26 static const mozilla::CSSIntSize kViewportMaxSize(10000, 10000);
  27
  28 inline mozilla::LayoutDeviceToScreenScale ViewportMinScale() {
  29   return mozilla::LayoutDeviceToScreenScale(
  30       std::max(mozilla::StaticPrefs::apz_min_zoom(), 0.1f));
  31 }
  32
  33 inline mozilla::LayoutDeviceToScreenScale ViewportMaxScale() {
  34   return mozilla::LayoutDeviceToScreenScale(
  35       std::min(mozilla::StaticPrefs::apz_max_zoom(), 100.0f));
  36 }
  37
  38 /**
  39  * Information retrieved from the <meta name="viewport"> tag. See
  40  * Document::GetViewportInfo for more information on this functionality.
  41  */
  42 class MOZ_STACK_CLASS nsViewportInfo {
  43  public:
  44   enum class AutoSizeFlag {
  45     AutoSize,
  46     FixedSize,
  47   };
  48   enum class AutoScaleFlag {
  49     AutoScale,
  50     FixedScale,
  51   };
  52   enum class ZoomFlag {
  53     AllowZoom,
  54     DisallowZoom,
  55   };
  56   enum class ZoomBehaviour {
  57     Mobile,
  58     Desktop,  // disallows zooming out past default zoom
  59   };
  60   nsViewportInfo(const mozilla::ScreenIntSize& aDisplaySize,
  61                  const mozilla::CSSToScreenScale& aDefaultZoom,
  62                  ZoomFlag aZoomFlag, ZoomBehaviour aBehaviour,
  63                  AutoScaleFlag aAutoScaleFlag = AutoScaleFlag::FixedScale)
  64       : mDefaultZoom(aDefaultZoom),
  65         mViewportFit(mozilla::dom::ViewportFitType::Auto),
  66         mDefaultZoomValid(aAutoScaleFlag != AutoScaleFlag::AutoScale),
  67         mAutoSize(true),
  68         mAllowZoom(aZoomFlag == ZoomFlag::AllowZoom) {
  69     mSize = mozilla::ScreenSize(aDisplaySize) / mDefaultZoom;
  70     mozilla::CSSToLayoutDeviceScale pixelRatio(1.0f);
  71     if (aBehaviour == ZoomBehaviour::Desktop) {
  72       mMinZoom = aDefaultZoom;
  73     } else {
  74       mMinZoom = pixelRatio * ViewportMinScale();
  75     }
  76     mMaxZoom = pixelRatio * ViewportMaxScale();
  77     ConstrainViewportValues();
  78   }
  79
  80   nsViewportInfo(const mozilla::CSSToScreenScale& aDefaultZoom,
  81                  const mozilla::CSSToScreenScale& aMinZoom,
  82                  const mozilla::CSSToScreenScale& aMaxZoom,
  83                  const mozilla::CSSSize& aSize, AutoSizeFlag aAutoSizeFlag,
  84                  AutoScaleFlag aAutoScaleFlag, ZoomFlag aZoomFlag,
  85                  mozilla::dom::ViewportFitType aViewportFit)
  86       : mDefaultZoom(aDefaultZoom),
  87         mMinZoom(aMinZoom),
  88         mMaxZoom(aMaxZoom),
  89         mSize(aSize),
  90         mViewportFit(aViewportFit),
  91         mDefaultZoomValid(aAutoScaleFlag != AutoScaleFlag::AutoScale),
  92         mAutoSize(aAutoSizeFlag == AutoSizeFlag::AutoSize),
  93         mAllowZoom(aZoomFlag == ZoomFlag::AllowZoom) {
  94     ConstrainViewportValues();
  95   }
  96
  97   bool IsDefaultZoomValid() const { return mDefaultZoomValid; }
  98   mozilla::CSSToScreenScale GetDefaultZoom() const { return mDefaultZoom; }
  99   mozilla::CSSToScreenScale GetMinZoom() const { return mMinZoom; }
 100   mozilla::CSSToScreenScale GetMaxZoom() const { return mMaxZoom; }
 101
 102   mozilla::CSSSize GetSize() const { return mSize; }
 103
 104   bool IsAutoSizeEnabled() const { return mAutoSize; }
 105   bool IsZoomAllowed() const { return mAllowZoom; }
 106
 107   mozilla::dom::ViewportFitType GetViewportFit() const { return mViewportFit; }
 108
 109   static constexpr float kAuto = -1.0f;
 110   static constexpr float kExtendToZoom = -2.0f;
 111   static constexpr float kDeviceSize =
 112       -3.0f;  // for device-width or device-height
 113
 114   // MIN/MAX computations where one of the arguments is auto resolve to the
 115   // other argument. For instance, MIN(0.25, auto) = 0.25, and
 116   // MAX(5, auto) = 5.
 117   // https://drafts.csswg.org/css-device-adapt/#constraining-defs
 118   static const float& Max(const float& aA, const float& aB);
 119   static const float& Min(const float& aA, const float& aB);
 120
 121  private:
 122   /**
 123    * Constrain the viewport calculations from the
 124    * Document::GetViewportInfo() function in order to always return
 125    * sane minimum/maximum values.
 126    */
 127   void ConstrainViewportValues();
 128
 129   // Default zoom indicates the level at which the display is 'zoomed in'
 130   // initially for the user, upon loading of the page.
 131   mozilla::CSSToScreenScale mDefaultZoom;
 132
 133   // The minimum zoom level permitted by the page.
 134   mozilla::CSSToScreenScale mMinZoom;
 135
 136   // The maximum zoom level permitted by the page.
 137   mozilla::CSSToScreenScale mMaxZoom;
 138
 139   // The size of the viewport, specified by the <meta name="viewport"> tag.
 140   mozilla::CSSSize mSize;
 141
 142   // The value of the viewport-fit.
 143   mozilla::dom::ViewportFitType mViewportFit;
 144
 145   // If the default zoom was specified and was between the min and max
 146   // zoom values.
 147   // FIXME: Bug 1504362 - Unify this and mDefaultZoom into
 148   // Maybe<CSSToScreenScale>.
 149   bool mDefaultZoomValid;
 150
 151   // Whether or not we should automatically size the viewport to the device's
 152   // width. This is true if the document has been optimized for mobile, and
 153   // the width property of a specified <meta name="viewport"> tag is either
 154   // not specified, or is set to the special value 'device-width'.
 155   bool mAutoSize;
 156
 157   // Whether or not the user can zoom in and out on the page. Default is true.
 158   bool mAllowZoom;
 159 };
 160
 161 #endif