layout/mathml/nsMathMLmfracFrame.h

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
   3 /* This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 #ifndef nsMathMLmfracFrame_h___
   8 #define nsMathMLmfracFrame_h___
   9
  10 #include "mozilla/Attributes.h"
  11 #include "nsMathMLContainerFrame.h"
  12
  13 namespace mozilla {
  14 class PresShell;
  15 }  // namespace mozilla
  16
  17 //
  18 // <mfrac> -- form a fraction from two subexpressions
  19 //
  20
  21 /*
  22 The MathML REC describes:
  23
  24 The <mfrac> element is used for fractions. It can also be used to mark up
  25 fraction-like objects such as binomial coefficients and Legendre symbols.
  26 The syntax for <mfrac> is:
  27   <mfrac> numerator denominator </mfrac>
  28
  29 Attributes of <mfrac>:
  30      Name                      values                     default
  31   linethickness  number [ v-unit ] | thin | medium | thick  1
  32
  33 E.g.,
  34 linethickness=2 actually means that linethickness=2*DEFAULT_THICKNESS
  35 (DEFAULT_THICKNESS is not specified by MathML, see below.)
  36
  37 The linethickness attribute indicates the thickness of the horizontal
  38 "fraction bar", or "rule", typically used to render fractions. A fraction
  39 with linethickness="0" renders without the bar, and might be used within
  40 binomial coefficients. A linethickness greater than one might be used with
  41 nested fractions.
  42
  43 In general, the value of linethickness can be a number, as a multiplier
  44 of the default thickness of the fraction bar (the default thickness is
  45 not specified by MathML), or a number with a unit of vertical length (see
  46 Section 2.3.3), or one of the keywords medium (same as 1), thin (thinner
  47 than 1, otherwise up to the renderer), or thick (thicker than 1, otherwise
  48 up to the renderer).
  49
  50 The <mfrac> element sets displaystyle to "false", or if it was already
  51 false increments scriptlevel by 1, within numerator and denominator.
  52 These attributes are inherited by every element from its rendering
  53 environment, but can be set explicitly only on the <mstyle>
  54 element.
  55 */
  56
  57 class nsMathMLmfracFrame final : public nsMathMLContainerFrame {
  58  public:
  59   NS_DECL_FRAMEARENA_HELPERS(nsMathMLmfracFrame)
  60
  61   friend nsIFrame* NS_NewMathMLmfracFrame(mozilla::PresShell* aPresShell,
  62                                           ComputedStyle* aStyle);
  63
  64   virtual eMathMLFrameType GetMathMLFrameType() override;
  65
  66   virtual nsresult MeasureForWidth(DrawTarget* aDrawTarget,
  67                                    ReflowOutput& aDesiredSize) override;
  68
  69   virtual nsresult Place(DrawTarget* aDrawTarget, bool aPlaceOrigin,
  70                          ReflowOutput& aDesiredSize) override;
  71
  72   virtual void BuildDisplayList(nsDisplayListBuilder* aBuilder,
  73                                 const nsDisplayListSet& aLists) override;
  74
  75   virtual nsresult AttributeChanged(int32_t aNameSpaceID, nsAtom* aAttribute,
  76                                     int32_t aModType) override;
  77
  78   NS_IMETHOD
  79   TransmitAutomaticData() override;
  80
  81   // override the base method so that we can deal with the fraction line
  82   virtual nscoord FixInterFrameSpacing(ReflowOutput& aDesiredSize) override;
  83
  84   // helper to translate the thickness attribute into a usable form
  85   nscoord CalcLineThickness(nsPresContext* aPresContext,
  86                             ComputedStyle* aComputedStyle,
  87                             nsString& aThicknessAttribute, nscoord onePixel,
  88                             nscoord aDefaultRuleThickness,
  89                             float aFontSizeInflation);
  90
  91   uint8_t ScriptIncrement(nsIFrame* aFrame) override;
  92
  93  protected:
  94   explicit nsMathMLmfracFrame(ComputedStyle* aStyle,
  95                               nsPresContext* aPresContext)
  96       : nsMathMLContainerFrame(aStyle, aPresContext, kClassID),
  97         mSlashChar(nullptr),
  98         mLineThickness(0) {}
  99   virtual ~nsMathMLmfracFrame();
 100
 101   nsresult PlaceInternal(DrawTarget* aDrawTarget, bool aPlaceOrigin,
 102                          ReflowOutput& aDesiredSize, bool aWidthOnly);
 103
 104   // Display a slash
 105   void DisplaySlash(nsDisplayListBuilder* aBuilder, const nsRect& aRect,
 106                     nscoord aThickness, const nsDisplayListSet& aLists);
 107
 108   nsRect mLineRect;
 109   nsMathMLChar* mSlashChar;
 110   nscoord mLineThickness;
 111 };
 112
 113 #endif /* nsMathMLmfracFrame_h___ */