layout/style/nsMediaFeatures.h

   1 /* vim: set shiftwidth=4 tabstop=8 autoindent cindent expandtab: */
   2 /* ***** BEGIN LICENSE BLOCK *****
   3  * Version: MPL 1.1/GPL 2.0/LGPL 2.1
   4  *
   5  * The contents of this file are subject to the Mozilla Public License Version
   6  * 1.1 (the "License"); you may not use this file except in compliance with
   7  * the License. You may obtain a copy of the License at
   8  * http://www.mozilla.org/MPL/
   9  *
  10  * Software distributed under the License is distributed on an "AS IS" basis,
  11  * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
  12  * for the specific language governing rights and limitations under the
  13  * License.
  14  *
  15  * The Original Code is nsMediaFeatures.
  16  *
  17  * The Initial Developer of the Original Code is the Mozilla Foundation.
  18  * Portions created by the Initial Developer are Copyright (C) 2008
  19  * the Initial Developer. All Rights Reserved.
  20  *
  21  * Contributor(s):
  22  *   L. David Baron <dbaron@dbaron.org>, Mozilla Corporation (original author)
  23  *
  24  * Alternatively, the contents of this file may be used under the terms of
  25  * either the GNU General Public License Version 2 or later (the "GPL"), or
  26  * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
  27  * in which case the provisions of the GPL or the LGPL are applicable instead
  28  * of those above. If you wish to allow use of your version of this file only
  29  * under the terms of either the GPL or the LGPL, and not to allow others to
  30  * use your version of this file under the terms of the MPL, indicate your
  31  * decision by deleting the provisions above and replace them with the notice
  32  * and other provisions required by the GPL or the LGPL. If you do not delete
  33  * the provisions above, a recipient may use your version of this file under
  34  * the terms of any one of the MPL, the GPL or the LGPL.
  35  *
  36  * ***** END LICENSE BLOCK ***** */
  37
  38 /* the features that media queries can test */
  39
  40 #ifndef nsMediaFeatures_h_
  41 #define nsMediaFeatures_h_
  42
  43 #include "nscore.h"
  44
  45 class nsIAtom;
  46 class nsPresContext;
  47 class nsCSSValue;
  48
  49 struct nsMediaFeature;
  50 typedef nsresult
  51 (* nsMediaFeatureValueGetter)(nsPresContext* aPresContext,
  52                               const nsMediaFeature* aFeature,
  53                               nsCSSValue& aResult);
  54
  55 struct nsMediaFeature {
  56     nsIAtom **mName; // extra indirection to point to nsGkAtoms members
  57
  58     enum RangeType { eMinMaxAllowed, eMinMaxNotAllowed };
  59     RangeType mRangeType;
  60
  61     enum ValueType {
  62         // All value types allow eCSSUnit_Null to indicate that no value
  63         // was given (in addition to the types listed below).
  64         eLength,     // values are such that nsCSSValue::IsLengthUnit() is true
  65         eInteger,    // values are eCSSUnit_Integer
  66         eFloat,      // values are eCSSUnit_Number
  67         eBoolInteger,// values are eCSSUnit_Integer (0, -0, or 1 only)
  68         eIntRatio,   // values are eCSSUnit_Array of two eCSSUnit_Integer
  69         eResolution, // values are in eCSSUnit_Inch (for dpi) or
  70                      //   eCSSUnit_Centimeter (for dpcm)
  71         eEnumerated, // values are eCSSUnit_Enumerated (uses keyword table)
  72         eIdent       // values are eCSSUnit_Ident
  73         // Note that a number of pieces of code (both for parsing and
  74         // for matching of valueless expressions) assume that all numeric
  75         // value types cannot be negative.  The parsing code also does
  76         // not allow zeros in eIntRatio types.
  77     };
  78     ValueType mValueType;
  79
  80     union {
  81       // In static arrays, it's the first member that's initialized.  We
  82       // need that to be void* so we can initialize both other types.
  83       // This member should never be accessed by name.
  84       const void* mInitializer_;
  85       // If mValueType == eEnumerated:  const PRInt32*: keyword table in
  86       //   the same format as the keyword tables in nsCSSProps.
  87       const PRInt32* mKeywordTable;
  88       // If mGetter == GetSystemMetric (which implies mValueType ==
  89       //   eBoolInteger): nsIAtom * const *, for the system metric.
  90       nsIAtom * const * mMetric;
  91     } mData;
  92
  93     // A function that returns the current value for this feature for a
  94     // given presentation.  If it returns eCSSUnit_Null, the feature is
  95     // not present.
  96     nsMediaFeatureValueGetter mGetter;
  97 };
  98
  99 class nsMediaFeatures {
 100 public:
 101     // Terminated with an entry whose mName is null.
 102     static const nsMediaFeature features[];
 103 };
 104
 105 #endif /* !defined(nsMediaFeatures_h_) */