nsMathMLmfracFrame.h (3897B)
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 "nsMathMLContainerFrame.h" 11 12 namespace mozilla { 13 class PresShell; 14 } // namespace mozilla 15 16 // 17 // <mfrac> -- form a fraction from two subexpressions 18 // 19 20 /* 21 The MathML REC describes: 22 23 The <mfrac> element is used for fractions. It can also be used to mark up 24 fraction-like objects such as binomial coefficients and Legendre symbols. 25 The syntax for <mfrac> is: 26 <mfrac> numerator denominator </mfrac> 27 28 Attributes of <mfrac>: 29 Name values default 30 linethickness number [ v-unit ] | thin | medium | thick 1 31 32 E.g., 33 linethickness=2 actually means that linethickness=2*DEFAULT_THICKNESS 34 (DEFAULT_THICKNESS is not specified by MathML, see below.) 35 36 The linethickness attribute indicates the thickness of the horizontal 37 "fraction bar", or "rule", typically used to render fractions. A fraction 38 with linethickness="0" renders without the bar, and might be used within 39 binomial coefficients. A linethickness greater than one might be used with 40 nested fractions. 41 42 In general, the value of linethickness can be a number, as a multiplier 43 of the default thickness of the fraction bar (the default thickness is 44 not specified by MathML), or a number with a unit of vertical length (see 45 Section 2.3.3), or one of the keywords medium (same as 1), thin (thinner 46 than 1, otherwise up to the renderer), or thick (thicker than 1, otherwise 47 up to the renderer). 48 49 The <mfrac> element sets displaystyle to "false", or if it was already 50 false increments scriptlevel by 1, within numerator and denominator. 51 These attributes are inherited by every element from its rendering 52 environment, but can be set explicitly only on the <mstyle> 53 element. 54 */ 55 56 class nsMathMLmfracFrame final : public nsMathMLContainerFrame { 57 public: 58 NS_DECL_FRAMEARENA_HELPERS(nsMathMLmfracFrame) 59 60 friend nsIFrame* NS_NewMathMLmfracFrame(mozilla::PresShell* aPresShell, 61 ComputedStyle* aStyle); 62 63 MathMLFrameType GetMathMLFrameType() override; 64 65 void Place(DrawTarget* aDrawTarget, const PlaceFlags& aFlags, 66 ReflowOutput& aDesiredSize) override; 67 68 void BuildDisplayList(nsDisplayListBuilder* aBuilder, 69 const nsDisplayListSet& aLists) override; 70 71 nsresult AttributeChanged(int32_t aNameSpaceID, nsAtom* aAttribute, 72 AttrModType aModType) override; 73 74 NS_IMETHOD 75 TransmitAutomaticData() override; 76 77 // override the base method so that we can deal with the fraction line 78 nscoord FixInterFrameSpacing(ReflowOutput& aDesiredSize) override; 79 80 // helper to translate the thickness attribute into a usable form 81 nscoord CalcLineThickness(nsString& aThicknessAttribute, nscoord onePixel, 82 nscoord aDefaultRuleThickness, 83 float aFontSizeInflation); 84 85 uint8_t ScriptIncrement(nsIFrame* aFrame) override; 86 87 protected: 88 explicit nsMathMLmfracFrame(ComputedStyle* aStyle, 89 nsPresContext* aPresContext) 90 : nsMathMLContainerFrame(aStyle, aPresContext, kClassID), 91 mSlashChar(nullptr), 92 mLineThickness(0) {} 93 virtual ~nsMathMLmfracFrame(); 94 95 bool IsMathContentBoxHorizontallyCentered() const final { return true; } 96 97 // Display a slash 98 void DisplaySlash(nsDisplayListBuilder* aBuilder, const nsRect& aRect, 99 nscoord aThickness, const nsDisplayListSet& aLists); 100 101 nsRect mLineRect; 102 nsMathMLChar* mSlashChar; 103 nscoord mLineThickness; 104 }; 105 106 #endif /* nsMathMLmfracFrame_h___ */