layout/mathml/nsMathMLmfracFrame.h

   1 /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   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 #ifndef nsMathMLmfracFrame_h___
   7 #define nsMathMLmfracFrame_h___
   8
   9 #include "mozilla/Attributes.h"
  10 #include "nsMathMLContainerFrame.h"
  11
  12 //
  13 // <mfrac> -- form a fraction from two subexpressions
  14 //
  15
  16 /*
  17 The MathML REC describes:
  18
  19 The <mfrac> element is used for fractions. It can also be used to mark up
  20 fraction-like objects such as binomial coefficients and Legendre symbols.
  21 The syntax for <mfrac> is:
  22   <mfrac> numerator denominator </mfrac>
  23
  24 Attributes of <mfrac>:
  25      Name                      values                     default
  26   linethickness  number [ v-unit ] | thin | medium | thick  1
  27
  28 E.g.,
  29 linethickness=2 actually means that linethickness=2*DEFAULT_THICKNESS
  30 (DEFAULT_THICKNESS is not specified by MathML, see below.)
  31
  32 The linethickness attribute indicates the thickness of the horizontal
  33 "fraction bar", or "rule", typically used to render fractions. A fraction
  34 with linethickness="0" renders without the bar, and might be used within
  35 binomial coefficients. A linethickness greater than one might be used with
  36 nested fractions.
  37
  38 In general, the value of linethickness can be a number, as a multiplier
  39 of the default thickness of the fraction bar (the default thickness is
  40 not specified by MathML), or a number with a unit of vertical length (see
  41 Section 2.3.3), or one of the keywords medium (same as 1), thin (thinner
  42 than 1, otherwise up to the renderer), or thick (thicker than 1, otherwise
  43 up to the renderer).
  44
  45 The <mfrac> element sets displaystyle to "false", or if it was already
  46 false increments scriptlevel by 1, within numerator and denominator.
  47 These attributes are inherited by every element from its rendering
  48 environment, but can be set explicitly only on the <mstyle>
  49 element.
  50 */
  51
  52 class nsMathMLmfracFrame : public nsMathMLContainerFrame {
  53 public:
  54   NS_DECL_FRAMEARENA_HELPERS
  55
  56   friend nsIFrame* NS_NewMathMLmfracFrame(nsIPresShell* aPresShell, nsStyleContext* aContext);
  57
  58   virtual eMathMLFrameType GetMathMLFrameType() MOZ_OVERRIDE;
  59
  60   virtual nsresult
  61   MeasureForWidth(nsRenderingContext& aRenderingContext,
  62                   nsHTMLReflowMetrics& aDesiredSize) MOZ_OVERRIDE;
  63
  64   virtual nsresult
  65   Place(nsRenderingContext& aRenderingContext,
  66         bool                 aPlaceOrigin,
  67         nsHTMLReflowMetrics& aDesiredSize) MOZ_OVERRIDE;
  68
  69   virtual void BuildDisplayList(nsDisplayListBuilder*   aBuilder,
  70                                 const nsRect&           aDirtyRect,
  71                                 const nsDisplayListSet& aLists) MOZ_OVERRIDE;
  72
  73   NS_IMETHOD
  74   TransmitAutomaticData() MOZ_OVERRIDE;
  75
  76   // override the base method so that we can deal with the fraction line
  77   virtual nscoord
  78   FixInterFrameSpacing(nsHTMLReflowMetrics& aDesiredSize) MOZ_OVERRIDE;
  79
  80   // helper to translate the thickness attribute into a usable form
  81   static nscoord
  82   CalcLineThickness(nsPresContext*  aPresContext,
  83                     nsStyleContext*  aStyleContext,
  84                     nsString&        aThicknessAttribute,
  85                     nscoord          onePixel,
  86                     nscoord          aDefaultRuleThickness);
  87
  88   uint8_t
  89   ScriptIncrement(nsIFrame* aFrame) MOZ_OVERRIDE;
  90
  91 protected:
  92   nsMathMLmfracFrame(nsStyleContext* aContext) : nsMathMLContainerFrame(aContext) {}
  93   virtual ~nsMathMLmfracFrame();
  94
  95   nsresult PlaceInternal(nsRenderingContext& aRenderingContext,
  96                          bool                 aPlaceOrigin,
  97                          nsHTMLReflowMetrics& aDesiredSize,
  98                          bool                 aWidthOnly);
  99
 100   // Display a slash
 101   void DisplaySlash(nsDisplayListBuilder* aBuilder,
 102                     nsIFrame* aFrame, const nsRect& aRect,
 103                     nscoord aThickness,
 104                     const nsDisplayListSet& aLists);
 105
 106   nsRect        mLineRect;
 107   nsMathMLChar* mSlashChar;
 108   nscoord       mLineThickness;
 109   bool          mIsBevelled;
 110 };
 111
 112 #endif /* nsMathMLmfracFrame_h___ */