layout/style/nsMediaFeatures.h

   1 /* vim: set shiftwidth=4 tabstop=8 autoindent cindent expandtab: */
   2 /* This Source Code Form is subject to the terms of the Mozilla Public
   3  * License, v. 2.0. If a copy of the MPL was not distributed with this
   4  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   5
   6 /* the features that media queries can test */
   7
   8 #ifndef nsMediaFeatures_h_
   9 #define nsMediaFeatures_h_
  10
  11 #include "nsCSSProps.h"
  12
  13 class nsIAtom;
  14 class nsPresContext;
  15 class nsCSSValue;
  16
  17 struct nsMediaFeature;
  18 typedef nsresult
  19 (* nsMediaFeatureValueGetter)(nsPresContext* aPresContext,
  20                               const nsMediaFeature* aFeature,
  21                               nsCSSValue& aResult);
  22
  23 struct nsMediaFeature {
  24     nsIAtom **mName; // extra indirection to point to nsGkAtoms members
  25
  26     enum RangeType { eMinMaxAllowed, eMinMaxNotAllowed };
  27     RangeType mRangeType;
  28
  29     enum ValueType {
  30         // All value types allow eCSSUnit_Null to indicate that no value
  31         // was given (in addition to the types listed below).
  32         eLength,     // values are such that nsCSSValue::IsLengthUnit() is true
  33         eInteger,    // values are eCSSUnit_Integer
  34         eFloat,      // values are eCSSUnit_Number
  35         eBoolInteger,// values are eCSSUnit_Integer (0, -0, or 1 only)
  36         eIntRatio,   // values are eCSSUnit_Array of two eCSSUnit_Integer
  37         eResolution, // values are in eCSSUnit_Inch (for dpi),
  38                      //   eCSSUnit_Pixel (for dppx), or
  39                      //   eCSSUnit_Centimeter (for dpcm)
  40         eEnumerated, // values are eCSSUnit_Enumerated (uses keyword table)
  41         eIdent       // values are eCSSUnit_Ident
  42         // Note that a number of pieces of code (both for parsing and
  43         // for matching of valueless expressions) assume that all numeric
  44         // value types cannot be negative.  The parsing code also does
  45         // not allow zeros in eIntRatio types.
  46     };
  47     ValueType mValueType;
  48
  49     union {
  50       // In static arrays, it's the first member that's initialized.  We
  51       // need that to be void* so we can initialize both other types.
  52       // This member should never be accessed by name.
  53       const void* mInitializer_;
  54       // If mValueType == eEnumerated:  const int32_t*: keyword table in
  55       //   the same format as the keyword tables in nsCSSProps.
  56       const nsCSSProps::KTableValue* mKeywordTable;
  57       // If mGetter == GetSystemMetric (which implies mValueType ==
  58       //   eBoolInteger): nsIAtom * const *, for the system metric.
  59       nsIAtom * const * mMetric;
  60     } mData;
  61
  62     // A function that returns the current value for this feature for a
  63     // given presentation.  If it returns eCSSUnit_Null, the feature is
  64     // not present.
  65     nsMediaFeatureValueGetter mGetter;
  66 };
  67
  68 class nsMediaFeatures {
  69 public:
  70     // Terminated with an entry whose mName is null.
  71     static const nsMediaFeature features[];
  72 };
  73
  74 #endif /* !defined(nsMediaFeatures_h_) */